Im using a 350z as a donor car for my 240sx build, and one of the components I plan on bringing over is the brakes.

I know the weight distribution is 53/47 for both cars, so bias should not be an issue. My car will weigh about 2500-2600 pounds when done.

The brakes I have are from the base model, and I'm wondering if they will stand up to hard track use, or if I will have to upgrade them in some way.

Do you guys think that new pads with the stock calipers would be a sufficient upgrade? Im worried about brake fade... im wondering if you guys know if there are larger discs available that have the same thickness, and where i could get them. The disc offset from the hub could probably vary a bit from stock, as the calipers are going to require custom brackets anyways...

I will definately be upgrading the lines and fluid... might as well do it right the first time.

fireslave wrote:I know the weight distribution is 53/47 for both cars, so bias should not be an issue. My car will weigh about 2500-2600 pounds when done.

You're planning on changing the master cylinder I hope. Your post makes it sound like you expect to just change calipers & rotors because the two cars share similar weight distributions.

Brake bias isn't determined by the balance of the vehicle. Just because two vehicle share the same balance does not mean you can swap out brakes from one to the other with no other modifications and expect the system to function properly.

Brake Bias 101

Neither the stock or the Brembo brakes found on the 350Z can handle "hard track use".

Again, think about what HARD track use means.

I recently tracked my 350Z with little N/A mods and had BIG problems with the brakes. So, here's what you need to do...

Decide HOW MUCH track use and HOW MUCH money you're willing to put into it. I will discuss brakes first:

First: get the best brake fluid you can find. It will help to keep temp down so when it does finally boil, it takes longer. I tracked for 20 minute segments and at the end, the fluid was boiling and the car had little if not braking left.

Second: get the brake pads. Hawk or whatever company you choose. Just make sure they're not the "street" version. I ran that and had problems. Find the best "track-suited" brake pads. Hawk and others make them.

Third: get bigger discs and braided lines. The lines are inexpensive but don't prove THAT much when it comes to HARD track use. If you didn't do them until now, it's time. Bigger discs that can accomodate the stock calipers are good because they will allow heat to disperse faster and thus allowing you to push the car further.

Again, this is all for HARD track use... i.e. ENDURANCE.. more than 10-20 minute segments.

Fourth: get the BBK. If you still have brake problems with the STOCK ENGINE and its HP, so you ARE doing endurance 12hour or 24hour Le Mans' style racing, get the biggest baddest big brake kit you can find. Wilwood, AP, StopTech, Greddy are just some. Find some 14" or bigger rotors, slotted/drilled, 6 to 12 pistons per caliper and brake till you drop.

Finally, leaving brakes aside, if you are planning to hit the track HARD with the 350z-powered 240sx you will face bigger problems than the brakes. Tires, camber, suspension, all can potentially (and most probabily will) fail on the track. If you push the car, it will push back. Get the best suspension, alter it for use with the [bigger or less] front weight of the new eninge, find some sort of camber alignment kit that WORKS in extreme conditions (like being pushed on the track). And I can go on.

However, if by "hard track use" you mean 10-20 minutes of putting about a small track (not F1 circuit, circa 4+ kilometers of actual CURVES and not straights), you'll be fine with stock... everything.

spitalul2bad wrote:Neither the stock or the Brembo brakes found on the 350Z can handle "hard track use".

I think you just had a bad experience. I have tracked my Z for 2 days at a time. Running for about 25 mins and maybe 6 or 7 runs a day and my brakes did great. And don't think im an armature and don't know how to brake. I can keep up with 4S and E46 M3s. I think with some good track pads and good fluid the brakes should be fine.

spitalul2bad wrote:Fourth: get the BBK. If you still have brake problems with the STOCK ENGINE and its HP, so you ARE doing endurance 12hour or 24hour Le Mans' style racing, get the biggest baddest big brake kit you can find. Wilwood, AP, StopTech, Greddy are just some. Find some 14" or bigger rotors, slotted/drilled, 6 to 12 pistons per caliper and brake till you drop.

4 piston is all you need. Anything more is just over kill. and anyone running a track car would not have drilled rotors. Its all about slotted. And I dont know that many people that do the 24 hour type races. Most of us here in the states do the track events where they are 30min runs. Am I wrong here?

yea, 350z master cylinder is part of the plan too. I plan on swapping pretty much all the mechanicals/electronics except of course the suspension.

I'm also going to have the same width tires, front and rear. Im doing this for handling balance, but should be good for brake balance too, considering the stock brakes on stock cars are usually front biased a little bit more than is ideal. Probably wont have a huge effect though, you guys think? (I know the 350z tires are a bit skinner up front, reducing their braking ability compared to the rears)

And when I said hard track use, im talking about 20-30 mins, not hours.

Unfortunately, I have the non-brembos. Im going to assume that the're 2 piston fronts and 1 piston out back, but I actually have no clue... you guys know?

I'm not really concerned with taking a few feet off my braking distance when the brakes are cold, so I was kinda hoping that the stock calipers would suffice, maybe with bigger discs. Cant go too big, though, as my rims are going to be 17's.
Modified by fireslave at 2:37 PM 4/17/2009

You didn't tell us the intended purpose of this car? Track? AutoX?

If I remember correctly the front and rear are both single piston floating calipers which are worthless for anything more than commuting.

If your tracking your car there are no race pads avaialble for them. You will need the Brembo's at a minimum.

autocross mostly, just because its more available, but i'd like to take it to an actual track when possible...

are the master cylinders the same for the brembos and non-brembos?

I also heard that replacement discs are like 500 bucks each! is this true? Are there any similar discs (same thickness, similar diameter, similar offset) that you guys have found to work for cheaper? Since I am doing custom mounts anyways, they wouldnt have to be identical...

Also need to fit them behind 17's...

I would just go with Z32 brakes with the Z32 master cyl the 350 brakes are ok but the car is something like a 100 hp less than a TT Z and Z32 brakes are not that expensive plus finding the brake lines for the 350 brakes to the 240 which you can do for the Z32 ones

and if you get the Z32 brake as a upgrade make sure to find TT aluminum ones the disapate heat better also the R32 GTST brakes are the same

sean8564 wrote:350 brakes are ok but the car is something like a 100 hp less than a TT Z

I don't think so

last 350 is saw on the dyno made 218 and my 300 TT mostly stock makes around 290 so not too far off i do not think

If your tracking your car there are no race pads avaialble for them. You will need the Brembo's at a minimum.

Not true, Nismo makes R-Tune non brembo replacement pads.

sean8564 wrote:last 350 is saw on the dyno made 218 and my 300 TT mostly stock makes around 290 so not too far off i do not think

Yeah you gotta pay more attention. 218 whp maybe, most see closer to 240 whp. At the crank the VQ35DE makes 287hp and the VQ35HR makes 306. They are comparable to a stock TT Z.

R-Tune replacement pads, eh? neato.

I guess I'll try the 350z brakes, and see how they work. They're free after all...

Do you guys know if there are bigger rotors available for those brakes? I'll have to get my wheels on first, to get an idea of how much clearance there is.

Do you guys have any idea as to brake fade front vs. rear? I never hear anyone talk about it, but im going to assume that even with the bigger rotors, the front brakes fade first... I might try ducting some air towards them if there's enough room after all the other crap I plan to install...

NFSP 350 wrote:Not true, Nismo makes R-Tune non brembo replacement pads.

The R-Tune NISMO pads are hardly a track compound pad. I don't care what pads you put in the OEM standard brakes they are an extremely poor choice for the track.

aris_unlimited wrote:
Yeah you gotta pay more attention. 218 whp maybe, most see closer to 240 whp. At the crank the VQ35DE makes 287hp and the VQ35HR makes 306. They are comparable to a stock TT Z.

Plus the only stock one i saw on the dyno was auto that might have a lot to do with the numbers as well

JETPILOT wrote: The R-Tune NISMO pads are hardly a track compound pad. I don't care what pads you put in the OEM standard brakes they are an extremely poor choice for the track.

Based on what? Consider the vehicle this is going on. It weighs a good deal less than the 350Z. Depending on trim, perhaps more than 600 lbs of difference. The Z33 brakes are significantly bigger than the 10" or so brakes that the 240sx comes with. Quite a bit thicker as well. Plenty of 240sx guys used Z32 brakes which are only about 11 inches in diameter and just over an inch in thickness (26mm version). I was one of them. I ran OE pads on it at the track with these brakes. Mine was also turbocharged mildly putting about 230 at the wheels so it was accelerating at least as fast as a stock 350Z. Never had an issue with fade. The 350Z brakes (any of them) are likely overkill for a stockish 240sx. It should be able to an mildly boosted 240sx just fine as well.

JETPILOT wrote:If I remember correctly the front and rear are both single piston floating calipers which are worthless for anything more than commuting.

Single piston floating calipers don't have an inherent inability to clamp down on a rotor. Nor are they inherently unsuitable for track use. They can feel slightly spongier than multi-piston fixed calipers (though if the early G35 sedan's brakes are any indication, they can also be quite grabby) and can exhibit more leading edge pad wear, but it can provide every bit as much stopping power. The S2000 uses a single piston caliper up front and it has been regarded by plenty of magazines as having one of the best braking systems ever from an OE. Coincidentally, the S2000 uses a rotor that is only 0.1 inch larger in diameter than the non-Brembo Z (03-04). The width is 24mm which is just shy of 0.95 inches which is the thickness of the Z's rotors.

I would agree that the choices in available pads might not be great, but its likely that he has much more brake than he needs and thus would see much less heat in the rotors, even if the car was lapping at the same lap times as a stock 350Z. If the 240 starts getting faster than that, at some point it might necessitate better pads or a brake upgrade, but for a near stock 240 or even a mildly boosted one, I've have no reservations about putting those brakes to use in this particular application...

The OEM standard brake calipers don't have enough mass or the ability to dissipate heat nearly as well as the Brembo's. They will stop as well as the best braking system on earth the first time. You have a situation of diminishing returns for every stop thereafter. If this guy uses his brakes as he should on a road course which he likely will by the end of the day of instruction then he will need something far better.

This is not speculation. This is experience. Take the NISMO pads out of their heat range and they will fail.

A buddy of mine who used his Brembo's and the R NISMO pads and they were history by lunch. I watched him as he went off the track onto the runoff area in front of me at the end of a braking zone. His pedal went soft and went right to the floor. The heat goes right into the fluid and it boils.

I realize the 240 is much lighter than the Z. I still don'ty think the OEM standard calipers are even close to being up to the task of lapping a road course by anyone but a novice and novices don;t stay novices for long.

It's my experience the OP is setting himself up for dissapointment.

I should have to explain this to you or are you just looking for an argument? You want the trophy for the person with the most knowledge?

JETPILOT wrote:
A buddy of mine who used his Brembo's and the R NISMO pads and they were history by lunch. I watched him as he went off the track onto the runoff area in front of me at the end of a braking zone. His pedal went soft and went right to the floor. The heat goes right into the fluid and it boils.

The EXACT same thing happened to me, while on an F1 track. Lost any braking, pedal went to the floor with little if no braking. Managed to limp back to the pit lane. Waited 30 minutes. Rinse and repeat... until it failed miserably and ended with a fully blown motor.

spitalul2bad wrote:
The EXACT same thing happened to me, while on an F1 track. Lost any braking, pedal went to the floor with little if no braking. Managed to limp back to the pit lane. Waited 30 minutes. Rinse and repeat... until it failed miserably and ended with a fully blown motor.

Just trying to clarify here. Please tell me you are not trying to connect overheating brake systems with a blown motor?

no, 'course not.engine failure was due to some bad ECU tuning (I suspect), and ended up in a piston melting and finding its way to the oil pan, two holes in the block and some split rods I think. Nicely enough, Nissan is replacing the motor under warranty.

I was running the Brembo brakes with HAWK brake pads and NEW fluids and it was still 20-30 minute runs at MOST. If I had enough money, I would get a BBK, even though 90% of the forum thinks it's overkill. However, staying out a couple of hours on an F1 track (Hungaroring, google it) is just too much for street brakes.

p.s. my car is N/A. just small N/A mods added. so it's not like I was running a 400whp or more car, which would be too much stress on the stock brakes.

JETPILOT wrote:The OEM standard brake calipers don't have enough mass or the ability to dissipate heat nearly as well as the Brembo's. They will stop as well as the best braking system on earth the first time. You have a situation of diminishing returns for every stop thereafter. If this guy uses his brakes as he should on a road course which he likely will by the end of the day of instruction then he will need something far better.

This is not speculation. This is experience. Take the NISMO pads out of their heat range and they will fail.

A buddy of mine who used his Brembo's and the R NISMO pads and they were history by lunch. I watched him as he went off the track onto the runoff area in front of me at the end of a braking zone. His pedal went soft and went right to the floor. The heat goes right into the fluid and it boils.

I realize the 240 is much lighter than the Z. I still don'ty think the OEM standard calipers are even close to being up to the task of lapping a road course by anyone but a novice and novices don;t stay novices for long.

It's my experience the OP is setting himself up for dissapointment.

Look at this from an energy perspective. Ultimately, that is what is it is. The mechanical energy produced by the motor accelerates the car's mass to a certain speed. The brakes then convert that energy into heat. The heat is absorbed primarily by the rotors.

In the case of a 240sx, its mechanical energy is lower as the motor is less powerful. The car's mass is lower so at a given speed, its kinetic energy is lower. Since energy can not be created or destroyed, the amount of kinetic energy converted into heat energy can only be as high as the amount of kinetic energy available.

A rotor, being the primary heat sink, absorbs most of this heat energy. The temperatures the rotor will reach will be related to the amount of energy, the mass of the rotor and the specific heat of the rotor. Since rotor materials are generally the same or very similar the specific heat of the rotor will not be a significant factor. Since we are assuming a certain amount of kinetic energy is converted to heat, then that remains equal. So all that is left is rotor mass. That said, if we apply the given heat energy to a large mass and a small mass, the smaller mass will see a higher peak temperature than the larger mass.

Conversely, if we had to slow a car of light mass and a car of heavier mass from the same speed, the car with the heavier mass would generate more heat energy. So for a given rotor mass, the heavier car will cause higher rotor temperatures.

Now, you mention heat dissipation from the caliper. This is really a non-issue. Calipers transfer very little heat to the air compared to rotors (which have specific design aspects that dissipate heat; vanes). Calipers on the other hand are generally designed to slow heat transfer. Typically, the pistons are stainless steel, which have slower heat transfer properties than aluminum, iron and steel. Also, they are shaped as hollow cylinders, which reduce the contact area to the back of the brake pad. This acts effectively as a heat dam. The other side of a sliding caliper is not as well protected from heat, but since the heat has to travel through a significant amount of metal to get to the brake fluid, its not that big of a deal. Its contact area on the outboard side is also kept relatively low as well.

However, if you also wanted to consider a typical sliding caliper to an aluminum fixed caliper, consider that aluminum will reach a higher temperature for a given amount of heat energy. While aluminum has better heat transfer properties, which could mean it can dissapate heat a bit faster, few calipers actually have any design aspects that would promote better heat dissipation. And more importantly, if you are suggesting that the caliper is supposed to try and dissapate any significant amount of heat, consider the the temperatures your rotors will reach on a given track day. Hell, even on the street. Then take a look at the boiling temperature of any available fluid. If there was any intent to try and use the caliper to dissapate heat, no fluid we have access to could be kept from boiling.

JETPILOT wrote:I should have to explain this to you or are you just looking for an argument? You want the trophy for the person with the most knowledge?

Since when is providing fact an indication that I want my ego stroked? A lot of people respect you here. And I'm not trying to take that away from you. But suggesting this is beneath you. If you feel I am wrong, provide facts to back it up. In this case, I feel you are wrong ans I am simply backing that up with evidence. Last I checked, that was the best way to present an argument.

C-Kwik wrote:
Based on what? Consider the vehicle this is going on. It weighs a good deal less than the 350Z. Depending on trim, perhaps more than 600 lbs of difference. The Z33 brakes are significantly bigger than the 10" or so brakes that the 240sx comes with. Quite a bit thicker as well. Plenty of 240sx guys used Z32 brakes which are only about 11 inches in diameter and just over an inch in thickness (26mm version). I was one of them. I ran OE pads on it at the track with these brakes. Mine was also turbocharged mildly putting about 230 at the wheels so it was accelerating at least as fast as a stock 350Z. Never had an issue with fade. The 350Z brakes (any of them) are likely overkill for a stockish 240sx. It should be able to an mildly boosted 240sx just fine as well.

Single piston floating calipers don't have an inherent inability to clamp down on a rotor. Nor are they inherently unsuitable for track use. They can feel slightly spongier than multi-piston fixed calipers (though if the early G35 sedan's brakes are any indication, they can also be quite grabby) and can exhibit more leading edge pad wear, but it can provide every bit as much stopping power. The S2000 uses a single piston caliper up front and it has been regarded by plenty of magazines as having one of the best braking systems ever from an OE. Coincidentally, the S2000 uses a rotor that is only 0.1 inch larger in diameter than the non-Brembo Z (03-04). The width is 24mm which is just shy of 0.95 inches which is the thickness of the Z's rotors.

I would agree that the choices in available pads might not be great, but its likely that he has much more brake than he needs and thus would see much less heat in the rotors, even if the car was lapping at the same lap times as a stock 350Z. If the 240 starts getting faster than that, at some point it might necessitate better pads or a brake upgrade, but for a near stock 240 or even a mildly boosted one, I've have no reservations about putting those brakes to use in this particular application...

C-Kwik, I understand what you're saying about the S2000's brakes. I've raced two different S2000s and found their brakes to be great. However, the S2000 is a much lighter car than the 350z. With that said, I think the base 350z brakes on a 240sx will work just fine, the only limit you'll have is brake pads. A more aggressive will do wonders for improved braking and initial bite.

I'm sure if you took the S2000's brakes and put them on 350z, including the same pads, you'd get much different results.

For heavier cars, multiple piston calipers work better than single piston calipers. The dual-piston floating caliper has several advantages over its single piston counterpart. The most obvious advantage is that with increased piston area, the caliper is able to generate more torque. More torque means more stopping power. Also, by using the floating caliper design instead of an opposing piston design, engineers are able to avoid wheel clearance issues and other robust design features of the floating caliper.

With a single-piston caliper, the footprint of pad is limited in some ways to the diameter of the piston. The diameter can only grow so large in relation to the rotor and brake pads. If the pad is too long, it flexes. When the pad flexes, it creates an uneven friction coupling on the rotor’s face. The uneven friction can create unwanted noise. If the flexing is severe enough, the friction material can separate from the backing plate. An example of this is the early Chrysler Neon. Also, there is a direct relationship between the diameter of the rotor and the diameter of the single piston caliper.

With dual- or twin-piston brake pads, the pads can be larger with even pressure distribution. A larger brake pad has several benefits. First, a larger pad will absorb more initial heat (less thermal shock). Second, a larger brake pad will have better wear characteristics and a longer life due to even pressure distribution. Third, a larger pad is able to absorb more unwanted noise and vibration because it is able to cover more of the rotor.

Another advantage is in the area of drag and fuel savings. With dual- or twin pistons, it is possible to have more aggressive piston seals that can pull back the pads more effectively after the driver removes his foot from the brake pedal.

ldstang50 wrote:C-Kwik, I understand what you're saying about the S2000's brakes. I've raced two different S2000s and found their brakes to be great. However, the S2000 is a much lighter car than the 350z. With that said, I think the base 350z brakes on a 240sx will work just fine, the only limit you'll have is brake pads. A more aggressive will do wonders for improved braking and initial bite.

No disagreements on this here. The argument being that the base 350Z brakes are likely adequate for this particular application...

ldstang50 wrote:I'm sure if you took the S2000's brakes and put them on 350z, including the same pads, you'd get much different results.

Likely. My point had more to do with heat capacity and rotor temperature though.

ldstang50 wrote:For heavier cars, multiple piston calipers work better than single piston calipers. The dual-piston floating caliper has several advantages over its single piston counterpart. The most obvious advantage is that with increased piston area, the caliper is able to generate more torque. More torque means more stopping power. Also, by using the floating caliper design instead of an opposing piston design, engineers are able to avoid wheel clearance issues and other robust design features of the floating caliper.

No doubt multi-piston has advantages. But piston area is actually dependent on the piston area the manufacturer decides to use. A single piston caliper and a dual-piston caliper that has the same total piston area will exhibit the same hydraulic clamping force.

ldstang50 wrote:With a single-piston caliper, the footprint of pad is limited in some ways to the diameter of the piston. The diameter can only grow so large in relation to the rotor and brake pads. If the pad is too long, it flexes. When the pad flexes, it creates an uneven friction coupling on the rotor’s face. The uneven friction can create unwanted noise. If the flexing is severe enough, the friction material can separate from the backing plate. An example of this is the early Chrysler Neon. Also, there is a direct relationship between the diameter of the rotor and the diameter of the single piston caliper.

Certainly, there are dimensional problems. But we are discussing a pretty specific issue.

ldstang50 wrote:With dual- or twin-piston brake pads, the pads can be larger with even pressure distribution. A larger brake pad has several benefits. First, a larger pad will absorb more initial heat (less thermal shock). Second, a larger brake pad will have better wear characteristics and a longer life due to even pressure distribution. Third, a larger pad is able to absorb more unwanted noise and vibration because it is able to cover more of the rotor.

I agree on the first 2 aspects. Brake noise is a relatively complicated issue and can be attributed to so many factors, I don't know that such a blanket statement can exist. Since pad noise can generate from any point in which high frequency vibration in any of the brake component interfaces exist, its easily possible that a larger pad can cause more noise in certain situations.

ldstang50 wrote:Another advantage is in the area of drag and fuel savings. With dual- or twin pistons, it is possible to have more aggressive piston seals that can pull back the pads more effectively after the driver removes his foot from the brake pedal.

The negative pressure created when releasing the brake pedal is more than sufficient to release the pad. Any further withdrawal would cause the engagement point to be moved lower and reduce pedal response. A condition called pad knockback is already something people running large brakes have to deal with. Let alone any active method for withdrawing the pad from the rotor.

This has been a helpful discussion, guys...

Regardless of caliper design, if you slow a car down from 80 to 50 in 2 seconds, for example, you are going to put a certian amount of heat into the rotors. Two piston calipers will heat up the rots the same as a single piston caliper.

I realize that, for a given rotor temperature, a well-designed twin piston caliper will outperform a single-piston caliper (or in the case of cooler rotors, perform more-or-less the same)

So i guess the question is, if my rotors are 600 degrees and i have a single piston caliper, how will my fade compare to a twin piston caliper?

I plan on upgrading the fluid regardless, but i feel like if i had the choice between a single-piston with a slotted rotor, or a double piston with a standard rotor, the slotted rotor would show less fade.

do you guys agree?

fireslave wrote:This has been a helpful discussion, guys...

Regardless of caliper design, if you slow a car down from 80 to 50 in 2 seconds, for example, you are going to put a certian amount of heat into the rotors. Two piston calipers will heat up the rots the same as a single piston caliper.

fireslave wrote:I realize that, for a given rotor temperature, a well-designed twin piston caliper will outperform a single-piston caliper (or in the case of cooler rotors, perform more-or-less the same)

Depends on what aspect of performance you are measuring. And even then, it would likely be negligible. From a heat/fade standpoint, it would be unlikely that there would be a perceivable difference.

fireslave wrote:So i guess the question is, if my rotors are 600 degrees and i have a single piston caliper, how will my fade compare to a twin piston caliper?

While 600 degrees F probably won't induce any fade, there should be no difference in heat capacity simply from being a twin piston design or a single-piston design. The heat capacity of any braking cystem is primarily dictated by the rotor mass. Particularly in the section surrounding the hat.

fireslave wrote:I plan on upgrading the fluid regardless, but i feel like if i had the choice between a single-piston with a slotted rotor, or a double piston with a standard rotor, the slotted rotor would show less fade.

Slots in a rotor serve a primary purpose of wiping the pad. This helps with the initial bite. It doesn't offer very good firepath (allowing pad outgassing to escape) capabilities as it tends to be completely covered by the pad surface. Cross-drilling would do a better job of actually allowing pad vapors to escape, however, outgassing is really only a concern when you are running at the high end of the pad's temperature range. Running beyond it means you need to find a higher temp pad or upgrade the brakes. Cross-drilling will provide a bit of extra cooling as there is more surface area to ambient air, but you also lose some rotor mass which is what gives a rotor its heatsink properties. Cross-drilling also tends to weaken a rotor's structure.

Keep in mind, you are worrying about fade at this point without even knowing if fade is even an issue. The 350Z brakes are quite a bit larger (read heavier) than the 240sx brakes. As such, the rotor and pads should run much cooler and fade would be less likely. Fade also doesn't build with heat, but comes on as the temperature gets above a threshold point. At the low end of this, you'll feel some fade, but it might be managable and still provide some braking power. But as temperatures get higher than the threshold, fade will become much stronger. The key is to stay below the threshold as best you can. Rotors with more mass is key here.

Consider this. The stock 240 brakes are 10" by about 0.7 inches. If you considered the volume this creates, its about 55 cubic inches.

The brakes off a 300ZX are 11" by about 1" (26mm version). That comes out to about 95 cubic inches. The 30mm version works out to about 112 cubic inches.

The 350Z brakes in question are 11.7" by 0.95". This works out to about 102 cubic inches.

Now I realize this assumes quite a bit as it doesn't take into about the actual size of the contact surface and hat size, nor does it account for how thick the material in the rotors are between the contact surface and the vents. But this is merely a quick way to illustrate how significant the size differences actually are.

thermal capacity seems like it would be based on mass, but heat dissapation should be based more on surface area, and also the airflow over the surface area.

i hear people talking about brake fade as if it takes a half hour of driving to reach this point. I would figure that a rotor at 600 degrees would cool down to say, 300 degrees, fairly quickly. To me, it doesnt seem like there is enough thermal mass in the system that rotor temperatures could gradually rise over a half hour track session to the point where fade occours... (though it is possible that i over-estimate how quickly rotors dissapate heat) i would think that the rotors would be up to their max temperature (more or less) after maybe a dozen corners, not a hundred.

This makes me think that the caliper side of the equation has something to do with fade, as it would collect heat more gradually from the rotors. Say the rotor got to 600 and the caliper got to 200. if the rotor shed 300 degrees on a long strait, the caliper might only shed 50. After the next braking zone, the rotors might be 650, but the calipers could be 300.... does that make any sense?

I guess the reason i am worried about this is because i dont want to have in install an entire brake system, and then realize that its not up to the task. I intend to use high boiling point fluid right from the start when I install the stock 350z brakes.

Im not positive im going to get fade, but if i do, itd be nice to know that i could reslove it with something simple like pads or rotors, rather than calipers.

Thanks for the info on cross drilling vs. slotting. I thought the slots were designed for cooling, as they allow cool-ish air to move across the pad surface... but it makes sense now that cross drilling would do a much better job at that.

fireslave wrote:thermal capacity seems like it would be based on mass, but heat dissapation should be based more on surface area, and also the airflow over the surface area.

Heat dissapation is related to surface area. But the vanes going through the rotor will be responsible for a great majority of it as the vanes provide more overall surface area and pump and agitate the air.

As for thermal capacity, I am referring to the rotor's ability to store energy without heating up to the point the pads used are going to run too hot.

fireslave wrote:i hear people talking about brake fade as if it takes a half hour of driving to reach this point. I would figure that a rotor at 600 degrees would cool down to say, 300 degrees, fairly quickly. To me, it doesnt seem like there is enough thermal mass in the system that rotor temperatures could gradually rise over a half hour track session to the point where fade occours... (though it is possible that i over-estimate how quickly rotors dissapate heat) i would think that the rotors would be up to their max temperature (more or less) after maybe a dozen corners, not a hundred.

I can fade a set of brakes in a matter of a few minutes in most cars if I tried. But that takes repeated stops from high speed back to back. No race track is that brutal on the brakes. The full stops mean that there are times when the rotor will be pumping no air and times when it will be pumping relatively small amounts of air. Few race tracks I know of will drop you below a speed that would put you at less than 2nd gear. So there will always be a pretty good volume of air being pumped through the rotors. Not to mention, long turns that tend to cause contant speeds or slow acceleration provide some time for the rotors to transfer heat to the air. Of note, larger rotors tend to have more surface area both on the friction surfaces and through the vanes. For a given temperature gradient, thelarger rotor would move more heat energy out of the rotor more quickly.

fireslave wrote:This makes me think that the caliper side of the equation has something to do with fade, as it would collect heat more gradually from the rotors. Say the rotor got to 600 and the caliper got to 200. if the rotor shed 300 degrees on a long strait, the caliper might only shed 50. After the next braking zone, the rotors might be 650, but the calipers could be 300.... does that make any sense?

While I can't say the calipers don't absorb any heat, keep in mind that heat transfer is dependent on a temperature gradient. Basically it requires a difference in temperature from one object to another for heat to move from the hotter object to the cooler object. Or another way to look at it is that if everything in a physics system were the same temperature, then no heat transfer would occur within that system.

That said, I mentioned the heat dam effects of the pistons before. As there is a temperature gradient, heat would transfer to the pistons, but at a relatively slow rate. Think of it like water flowing from one container to another. The cross sectional area of the pipe that connects the two containers dictates how much water can flow. A large pipe would only allow water to flow fairly quickly, while a small pipe would allow less. The heat dam effects of the pistons work similarly. That is since the cross sectional area of the piston is small compared to the actual diameter of the piston, it provides a small path for heat to transfer.

Now there are other ways heat transfers into the caliper from the rotor. Of note, is the convection through the air that is pumped through the rotors. This air contacts the caliper bridge which adds heat energy. But since the air that passes through the vbanes of the rotor remain for a very short period of time, the temperature of the air will be significantly lower than that of the rotor. And while all this is occuring, the caliper will be shedding heat as well. Especially while the car is moving. The air around the wheels and tires get thrashed around quite a bit. The caliper is not as efficient at shedding heat as the rotor, but its also not designed to try and absorbn heat either.

fireslave wrote:I guess the reason i am worried about this is because i dont want to have in install an entire brake system, and then realize that its not up to the task. I intend to use high boiling point fluid right from the start when I install the stock 350z brakes.

Considering your costs, I think its a very low risk to take. Free is much cheaper that a $2-3K BBK. And since its using OE parts, it can make replacement of parts cheaper. Bing a significan;ty larger rotor than stock, its likely that you won't be experiencing huge upward swings in temperature. That means if fade does occur, it will be gradual.

fireslave wrote:Im not positive im going to get fade, but if i do, itd be nice to know that i could reslove it with something simple like pads or rotors, rather than calipers.

Regardless, you'll be a whole lot better off from a heat capacity standpoint, but considering I've had many friends successfully run their 240's at the track with stock brakes (with maybe a higher temp pad), I think you'll be fine.

fireslave wrote:Thanks for the info on cross drilling vs. slotting. I thought the slots were designed for cooling, as they allow cool-ish air to move across the pad surface... but it makes sense now that cross drilling would do a much better job at that.

Slots could initially appear that way, but if air isn't pumping through it while the pad goes by, then the air in the slot will simply just heat up with the contact with the rotor and the pad face and not be able to provide any significant cooling. It would add some cooling, but its likely small enough to ignore.

C-Kwik wrote:
Look at this from an energy perspective. Ultimately, that is what is it is. The mechanical energy produced by the motor accelerates the car's mass to a certain speed. The brakes then convert that energy into heat. The heat is absorbed primarily by the rotors.

In the case of a 240sx, its mechanical energy is lower as the motor is less powerful. The car's mass is lower so at a given speed, its kinetic energy is lower. Since energy can not be created or destroyed, the amount of kinetic energy converted into heat energy can only be as high as the amount of kinetic energy available.

A rotor, being the primary heat sink, absorbs most of this heat energy. The temperatures the rotor will reach will be related to the amount of energy, the mass of the rotor and the specific heat of the rotor. Since rotor materials are generally the same or very similar the specific heat of the rotor will not be a significant factor. Since we are assuming a certain amount of kinetic energy is converted to heat, then that remains equal. So all that is left is rotor mass. That said, if we apply the given heat energy to a large mass and a small mass, the smaller mass will see a higher peak temperature than the larger mass.

Conversely, if we had to slow a car of light mass and a car of heavier mass from the same speed, the car with the heavier mass would generate more heat energy. So for a given rotor mass, the heavier car will cause higher rotor temperatures.

Now, you mention heat dissipation from the caliper. This is really a non-issue. Calipers transfer very little heat to the air compared to rotors (which have specific design aspects that dissipate heat; vanes). Calipers on the other hand are generally designed to slow heat transfer. Typically, the pistons are stainless steel, which have slower heat transfer properties than aluminum, iron and steel. Also, they are shaped as hollow cylinders, which reduce the contact area to the back of the brake pad. This acts effectively as a heat dam. The other side of a sliding caliper is not as well protected from heat, but since the heat has to travel through a significant amount of metal to get to the brake fluid, its not that big of a deal. Its contact area on the outboard side is also kept relatively low as well.

However, if you also wanted to consider a typical sliding caliper to an aluminum fixed caliper, consider that aluminum will reach a higher temperature for a given amount of heat energy. While aluminum has better heat transfer properties, which could mean it can dissapate heat a bit faster, few calipers actually have any design aspects that would promote better heat dissipation. And more importantly, if you are suggesting that the caliper is supposed to try and dissapate any significant amount of heat, consider the the temperatures your rotors will reach on a given track day. Hell, even on the street. Then take a look at the boiling temperature of any available fluid. If there was any intent to try and use the caliper to dissapate heat, no fluid we have access to could be kept from boiling.

Since when is providing fact an indication that I want my ego stroked? A lot of people respect you here. And I'm not trying to take that away from you. But suggesting this is beneath you. If you feel I am wrong, provide facts to back it up. In this case, I feel you are wrong ans I am simply backing that up with evidence. Last I checked, that was the best way to present an argument.

Your facts are based on what? All I see is speculation and alot of dialog based on assumption.

The real world facts are the Z calipers/rotors are wowefully inadequate in stopping the Z on the track without destroying the pads and boiling the fluid. There are no track compound pads for the OEM calipers I am aware of.

The OEM Z brakes will be only marginally more adequate in stopping a 400 lb lighter vehicle but still far short of being adequate.

I'm nto goign to get involved in a techical deiscussion of braking systems not because I'm not capable but because academic discussion is rendered useless in the face of real world results.

In my experience the best way to take time off a lap is in the braking zones. The later you can brake the faster you will be. There will be a weak link in your car. I wouldn't want that weakness to be in the one thing that can make me fast. You can outdrive any brake system on a track. The whole point is to drive within the cars limits. If the brakes are the weak link then you have to drive within those limits. But that's a pretty devestating weak link.
Modified by JETPILOT at 7:23 PM 5/6/2009

JETPILOT wrote:Your facts are based on what? All I see is speculation and alot of dialog based on assumption.

My facts are based on physics. Now, surely, I am making some assumptions as I don't have all the specific data that would be necessary to calculate all the capabilities. And even then, trying make all these calculations by hand would prove to be quite difficult, even for physicists and engineers. Computers are more heavily relied upon to get the most accurate data here. But the fact is the OP is asking about adding a significantly larger braking system to a relatively lightweight and low powered vehicle.

JETPILOT wrote:The real world facts are the Z calipers/rotors are wowefully inadequate in stopping the Z on the track without destroying the pads and boiling the fluid. There are no track compound pads for the OEM calipers I am aware of.

I am not disputing that the base model 350Z brakes are inadequate for a 350Z at a track. We are discussing using these brakes on a different application.

JETPILOT wrote:The OEM Z brakes will be only marginally more adequate in stopping a 400 lb lighter vehicle but still far short of being adequate.

How so? While I contend that 400 lbs would be a low estimate, I'll entertain it. 400 lbs is about 181 kg. Consider the equation:

KE = (1/2)mv^2

Where KE is Kinetic Energy in Joules, m is the mass in kg, and v is the velocity in meters per second. Assuming the 400 lbs is going 80 mph or 36 meters per second, we get:

KE = (1/2)(181kg)(36 m/s)^2

KE = 117,288 Joules.

Since braking takes the kinetic energy of a vehicle and converts it to heat, can assume this KE figure to be the heat energy that is transferred to the rotors. Now consider this equation:

Q = mcΔT

Where Q equals the heat energy in Joules, m is the mass of the object in g (in this case the rotor; lets assume a very generous 18 lbs or 8,165 g), c is the specific heat of the material (the specific heat of cast iron is 0.1298) and ΔT is the change in temperature in Celsius. Since there are 4 rotors and abias to the front, we will assume 70% goes to the front wheels and further split that into each rotor. So that comes out to 41050.8 J.

Rearrange the equation and we get:

ΔT = Q/(mc)

ΔT = 41050.8/(8,165 x 0.1298)

ΔT = 38.73 C.

That's 101.714 degrees in Fahrenheit.

To be fair, the weight of the rotor was based on the 300ZX 30mm rotor as it was all I could find, but I'd imagine its may not be too far off from the 350Z rotors. But 101 degrees at each of the front wheels is pretty significant, especially when you compound several stops. Keep in mind, this completely ignores the fact that the hat section of the rotor absorbs heat rather slowly so the initial temperature at the pad/rotor interface would likely be higher than this calculation. To be fair of course, there would also be some cooling occuring as the brakes are applied however, since the temperature increase would occur over a very short period of time (a matter of seconds), there would be little time for any significant heat shedding to occur. Lastly, I will also argue against myself that at a track, no turn requires all the kinetic energy to be dissapated so you would subtract the remaining kinetic energy, but this is merely a simple example of how much real heat is involved.

JETPILOT wrote:I'm nto goign to get involved in a techical deiscussion of braking systems not because I'm not capable but because academic discussion is rendered useless in the face of real world results.

I'll entertain that too...what experience do you have running the front base model 350Z brakes on a stockish 240sx? I'd say I have much closer experiences in that regard. As I stated before, I ran 300ZX brakes which probably have similar mass to the brakes we are discussing. And that car was actually about 100-200 lbs heavier than the OP's intended weight as mine was a 1998 model with all options, including a modest sound system. Not to mention, I later added the weight and power of a turbo kit which netted me higher speeds at the end of each straight and a bit of additional weight (more kinetic energy). Keep in mind I also ran OE pads (300ZX) on the track as well. So how is your experience more relevant than mine?

JETPILOT wrote:In my experience the best way to take time off a lap is in the braking zones. The later you can brake the faster you will be. There will be a weak link in your car. I wouldn't want that weakness to be in the one thing that can make me fast. You can outdrive any brake system on a track. The whole point is to drive within the cars limits. If the brakes are the weak link then you have to drive within those limits. But that's a pretty devestating weak link.

The maximum stopping potential of a car is ultimately dictated by how much grip there is at the tires. No amount of excess brake torque will allow a car to stop faster than the tires allow. That said, from a heat capacity standpoint, so long as the braking system doesn't actually get hot enough to induce fade (of any kind), there is no reason the tires can't be brought to the threshold of lock-up each and every time the brakes are applied. There is something to be said about the ability to modulate a braking system to hold a set of tires closer to and/or more consistently at the threshold of braking, but ultimately, if the speed at the braking zone is the same and the corner entry speed is the same, the same amount of energy is converted to heat in very close to the same time, which makes this negligible from a heat standpoint. And this part of your argument has more to do with being competetive in very small increments of time rather than if the brakes are adequate to be used on a race track. Could he be a bit faster with better brakes? Sure. But can he safely run 350Z brakes on his 240sx at the track? Well, I can't say with absolute certainty, but I'd say its quite likely.