350z/G35/////brembo vs STD

[Q45tech]

http://www.zeckhausen.com/testing_brakes.htm

Nice read that until multiple [6-8] 100 mph stops there was no difference in stopping distances.

http://www.stoptech.com/techni...t.htm

The 90-96 Q front pressure at the breakpoint is 1067 psi when rear is 750+ and C caliper deflection might be 3-4 times more than a good 4 piston set up say 75-100/1,000th vs 25/1,000th.

[PalmerWMD]

Wow, those Brembo Rotors are expensive$2000 for a set of four, I hope they last a bit.

Great read, pretty much cemeted what I suspected all along.

The stopping distances are basically the same ,except the Brembo package will offer more fade resistance.(and it looks real cool:drooling)

Fred...

[AZhitman]

Keep in mind the G35 SEDAN stops from 60 mph in 111 feet (3 feet shorter than the 2004 Z-06).

And that's WITHOUT the Brembo brakes and bigger rotors!

[PalmerWMD]

Keep in mind the G35 SEDAN stops from 60 mph in 111 feet (3 feet shorter than the 2004 Z-06).

And that's WITHOUT the Brembo brakes and bigger rotors!

yes, the only advantage the Brembos offer is greater fade resistance ,as they cant improve on those stopping numbers.

Fred...

[Mayhem_J30]

,as they cant improve on those stopping numbers.

Fred...

Sure they could. Put on stickier tires.

[AZhitman]

And really soft pads (softer than what's already on there, which would be roughly the equivalent of steel wool...)

[Q45tech]

Steel has a very bad coefficient of friction worse than cast iron rotors."Asperities, which are microscopic projections from the "average surface," play a major role in determining the coefficient of friction between materials. The friction depends on the asperities of the surfaces in contact. The pressure on an asperity is greater than the normal force, that it may deform the contact area "plastically" (asperities can weld together). Therefore, frictional resistance arises from sliding objects breaking and creating bonds created by asperities. "

The Brembo greater thickness means the walls of the rotor are thicker by at least 25% each and so is the venting air space! This probably doubles the mileage to warping.

With grippier tires [than the Pilots] the ABS would need to be reprogrammed to get below 100 feet [60 to zero].

The[tire/road friction coefficient would need to go to 1.21 vs 1.08 currently.http://hyperphysics.phy-astr.g....html

[EWT]

yes, the only advantage the Brembos offer is greater fade resistance ,as they cant improve on those stopping numbers.

Fred...

And better pad wear under hard use. 2 piston sliding calipers taper pads like crazy if they're used hard due to caliper flex.. I've seen pads that came off a Z06 that were down to the backing plate on one end of the pad, and had >50% material left on the other end. A good 4 piston caliper feels firmer at the pedal too due to the flex issue.

Eric

[Mayhem_J30]

Q45Tech,How is a CofF value assigned for a certain tire on an ABS system? On different surfaces wouldn't the CofF be significantly different ie; pavement, concrete, wet, snow...

When ABS systems distribute their assistance is how they apply braking forces always the same? In other words, does ABS always apply the same force, duration of force and time between force pulses?

Now once CofF is increased, both on the software level and the ACTUAL CofF, what actually changes in the way ABS is applied? Is duration of force increased?

I'm going to start googling for more tech docs, but I figured I would go ahead and ask here.

Steel has a very bad coefficient of friction worse than cast iron rotors."Asperities, which are microscopic projections from the "average surface," play a major role in determining the coefficient of friction between materials. The friction depends on the asperities of the surfaces in contact. The pressure on an asperity is greater than the normal force, that it may deform the contact area "plastically" (asperities can weld together). Therefore, frictional resistance arises from sliding objects breaking and creating bonds created by asperities. "

The Brembo greater thickness means the walls of the rotor are thicker by at least 25% each and so is the venting air space! This probably doubles the mileage to warping.

With grippier tires [than the Pilots] the ABS would need to be reprogrammed to get below 100 feet [60 to zero].

The[tire/road friction coefficient would need to go to 1.21 vs 1.08 currently.http://hyperphysics.phy-astr.g....html

[Mayhem_J30]

OK. I found a good article that may have helped answer some of my questions, but I still would like some verification.http://academic.csuohio.edu/ae...0.pdf

Page 4 of the article might answer my questions.

"To make the estimation less sensitive to noisy peaks, the deceleration rate limit is defined as the slope between the peak and the start point of ABS (point 1), rather than the slope between two adjacent peaks. To accommodate potential changes in road surface condition and the overall nonlinearly curve of vehicle deceleration, the rate limit R is set to be increasing at a fixed rated, BUT NEVER EXCEEDS THE MAXIMAL DECELERATION."

I believe this is telling us that there is a limit in deceleration programmed into the ABS ECU that *could* be surpassed with superior tires. BUT it is typically programmed with a lesser decel value because typically consumers are not running heated, R-compound tires on a dry road course. If a greater R value was used on lesser tires, braking distance could be increased when ABS is applied using different wheel velocity changes. Is this correct?

It seems the value 'R' is key.

[HeavyDuty]

The Cool Stop pads that come with Brembo's street GT kits are essentially for good stopping power from cold to warm. If the car sees any track time, a Porterfield or Hawk can be "prescribed". The trade off there is the more aggressive pads wear the rotor more quickly, don't stop as well when cold & dust like MAD!

Having spent 5 months in a Brembo GT equipped vehicle, my opinion is that once you drive a car with them, you'll be spoiled with anything but.

[Q45tech]

It the tires don't slip the ABS never applies therefore there is 100% pressure 100% of the time from application till the vehicle stops.

ABS actually lengthens a straight stop [in dry] when less than optimum tires are fitted.Because owners won't buy race tires that only last a few thousand miles, nor do most have the vehicle sensitivity nor precision of mind body control in panic situations the ABS dsoes better.

http://www-nrd.nhtsa.dot.gov/vrtc/ca/lvabs.htm

http://www.edccorp.com/whatsnew/abssae.htmlDownload pdf 0033 at bottom

http://www.edccorp.com/library.htmlhttp ... chref.html

You will see that the cycle time is variable and the time delay is a function of ABS distance from each brake caliper rear vs front left right.

The ABS contains its own microprocessor and learns, it tries a release cycle [from memory] and watches what happens and fine tunes depending on the friction between the tire and road. It takes 5-6 cycles to zero in on the optimum but obviously that continuously changes as the tires are heating up.......it gets closer but never perfect.............if the cycle times are 0.2 seconds it has 15-20 tries to get it right...........but right is a moving target.

I know members don't want to take responsibility for braking distances because they would need to pay for superior tires and not be able to blame the wreck on themselves or the other guy.

But as the tirerack test show between tires there is a 15-20 foot difference in only 50 to zero dry braking with ABS on!!!!!!!!!!!!!!!!

The differences get amplified in wet braking.

You can't trust marketing because the Gyear Aquatread 3 [even Michelin hydroedge] is one of the worst wet brakers in all the test at 108 [105 for hydroedge] feet vs my lowly recommended Pilot H4 at 99 feet.................the Michelin Pilot A/S is 98 feet in wet

[Mayhem_J30]

The 2nd article is great. I haven't got to the last two yet. I have a question about calculating Slip.Using:S= (Vr - Omega_w * R)/Vr

How is Omega_w calculated? Or what is its' units. In order to keep the values within equal units it would have to be a measure of distance if it's multiplied by R (a distance) to give a 'distance per time' unit.Then the article defines Omega_w = Wheel spin velocity. This can't be because velocity is more than just a distance.

Once I figure this out I can figure out the ill effects of a larger radius wheel/tire combo. Using what the computers thinks SLIP is at vs. what SLIP is actually at. This keeping ABS out of optimal operating preventing maximum threshold pressure from being applied at the appropriate time, maximum wheel acceleration threshold.

[AGM]

My experiance with a Q45 Brake upgrade, is that it does more than just resist brake fade. It definatley pulls up quicker. You can still brake gently and it retains the Limo feel, but if you hit the brake pedal hard, you will get seatbelt bruising. The stopping power of my upgrade is actually quite exhilarating. I never realised how much fun it was stopping really quick, even if it is just for the sake of it.

With Chally's help I will attach an old pic. Please not the Impul bodykit was not fitted at this stage. The rims are only 17" and have been replaced by 19".

If anyone wants the pdf pic, drop me an email.

Regards

AGM

[Chally]

Here it is.

[Q45tech]

The early Q ABS system is limited to 10 interventions per second so say up to 30 in a 60 mph to 3mph stop [ABS stops working at 3 mph].Each ABS system is modeled then fine tuned exhaustively using the oem tires to extract the fewest number of interventions considering: dry, wet, ice, variable mu [right wheels in gravel/on ice, etc].

The length of each intervention may cause the number of pressure return cycles to lengthen from 10>5.

What one wants is as few ABS cycles as possible. This is where the tire/road interface friction comes in to play.

Oscillations around the critical slip point. Lyapunof stability and Robustness is derived using Ricatti equation solutions to optimize the systems.

http://www.fuzzytech.com/e/e_a_sie.html ... te...n.pdf

http://wwwradig.informatik.tu-...7.pdf

http://www-nrd.nhtsa.dot.gov/vrtc/ca/CApubs.htm

http://www-nrd.nhtsa.dot.gov/v...8.pdfh ... /v...1.pdf

After you read a few thousand pages we can discuss further! When ever I post a link I read it first before deciding to subject members.

The Q ABS is rather gross [wide] in its tolerance of tire sizes say 5% [but less on the rear axle in systems with a single tone wheel on the rear diff] say 24.7 to 27.3 [unloaded diameter] all around as long as they are the same tire.

[AGM]

Chally, thanks for posting the pic!

Q45tech, as always I truly value your input and this site would not be the same without you.

In this instance, I just wish you could drive this car so that you would be able to actually compare my brake mods to stock.

With great respect to yourself, the true test is always an actual roadtest.

To be honest, I thought your comments in the second last paragraph were unnecessary.

Regards

AGM

[Q45tech]

I'm a mathematical kid of guy as the current simulation software is so advanced and accurate..........my feet/body/ mind are not calibrated as well as even cheap test equipment. A stopwatch and a 150 foot measuring tape.

Therefore I always am sceptical of unscientific comparisons.

Having worked with dynos [I probably done a 1,000 runs] I take every one posted on the forum as an inaccurate feel good print out designed to get the owners money and get them to return frequently and bring their friends.

Many brake improvements seem so good because the previous brake system was so bad from lack of maintenance or changed parts [pads, rotors].

Sorry I offended you ["read a few thousand pages we can discuss further"] but the body of published knowledge [just on ABS alone] is enormous as there are thousands of engineers working world wide on this narrow field.

I have hundreds of SAE papers [tens of thousands of pages] that cannot be scanned [they would sue me over copyright].

I try not to diseminate false or ambiguous info...........that's why I link so much, finding the links takes hours each day.

[AGM]

Q45tech,

Could you please explain (in layman's terms if possible) why larger disc brakes, larger calipers and softer brake pads offer absolutley NO improvement to braking performance to a Q45.

Are you saying the ABS program is designed to match the OEM set up and moving away from the OEM set up will be of no benefit, due to the ABS program not being matched to the altered brake set up.

Also, do touring cars (race versions of production cars) have a different ABS program to their production car equivelant, so they have a different ABS program to match the bigger brakes ect.

Regards

AGM

[maxnix]

Not to usurp Q45tech's privileges, but one thing he has maintained (and is supported by empirical evidence) is that the stock Q45 (as in new OEM specifications) can stop the car once as well as any car of its weight given the factory tires with the specified strong carcass and soft compound (160 wear rating).

After that, all bets are off if sufficient cool down time is not permitted. Bigger brakes (rotors) with larger pads (swept area) with correct pad compounds (soft street, hard racing/pursuit) will extend the envelope of performance beyond the OEM set-up in rapidly repeated intense decelerations, but will not necessarily stop the car more quickly on the initial application.

[Q45tech]

As long as the brakes can lock the tires [with ABS turned off] bigger brakes cannot lock the tires more.......locked is locked and tire sliding is tire sliding.

Larger diameter rotor just multiply the foot pedal force more, larger rotor weigh more, so they can sink more heat with a lower temperature rise, larger diameter rotors have more surface area so they can radiate what heat there is faster.

Normal pads need 20-40 pounds on the brake pedal, as the pads heat up [above 500- 600F] it takes more and more pedal pressure to maintain the same level of friction..............it can take 100 pounds with the pads at 800-1000F, it can take 200 pounds at 1300F.

Much of these large 13" rotors has to do with making it possible for a light race driver to be able to extert enough leg force and not exhaust him/herself in hours of racing........going from 11" to 13" reduces the pedal pressure reguired by 16% for exactly the same braking force with no other changes. PLUS the extra weight means the rotor is operating at at least 16% lower temperature and so are the pads [to a lesser degree], so you need less force.

Study the G35 stock vs Brembo single stop distances in even hot summer weather........measure the rotor rise in temperature from a single 80 mph stop......at worst the differences will be 75F say 350F vs 275F .

There is a theoretical maximum deceleration rate SET into ABS software based on factory test of worn oem tires on a very good road surface...........as the roads will always be less and the tires will be less [they might be new with full depth and squirmy].............you have to bound the equations to zero in on the optimum................lots of it depends on the road temperature and how the tires were aged.

[greg_atlanta]

I'm a believer in ABS again. Had a Town Car make a sudden left turn from the lane to the right of me (a phone queen driving move for sure). I slammed on the brakes and steered left and the ABS did it's thing and I stay out of trouble. I was certain was going to crush her. She deserved it... oh well!

Glad I wasn't in a FWD car.... would have nosedived right into her.

[Q45tech]

Members need to remember that the 1989 oem brake pads have changed for the worse due to complaints of dusting and fast wear..........the orginal U-90 pad has been replaced with a U91 or U93...........it appears [feels] like the new pads are less aggressive and for sure they last 50% longer and don't need changing every 17,000 miles..........many get 25,000-35,000 from the U91.

So Infinti changed the front pads without changing the ABS program

[greg_atlanta]

Are U91 and U93 about the same?

My first set of pads on my front powerstop rotors only lasted a year, but not sure what serial number they were. Current set of pads is still OK after 20 months, but part of that it me learning to brake less, esp. at highway speeds.

Maybe brand new powerstop rotors chew up the pads faster??

[Q45tech]

Of course drilled rotors wear the pads faster than no drilled/sloted...........slotted are the worst until the slots wear off.

TSB IBT94-005: 41060-66U91 -------------Jan 18,1994" These brake pads are intended to increase the effective service life, but it should be noted that they may experience a greater tendency fo brake noise"

The U93 are oem for later models 94-96Q where even more performance was sacrificed in the interest of luxury.

[HeavyDuty]

Not to jump into the fray to aggravate the situation, but just to clarify my comments were not related to any abs discussion, but rather normal driving/modulation. After driving my 91 Q on a short 120 mile road trip, (new oe pads, rotors, fluid, lines, and by happenstance struts) my brakes got worse by the mile during frequent rapid slow downs normally associated with heavy interstate traffic at Thanksgiving.

I'm not as interested in one-time panic stop data or even ABS type stops. If they both do equally as well in those situations, then ok.

I want repetitive motion confidence. I will have that with a Brembo setup with more leverage further from the center of the hub than stock, a floating rotor & a larger swept area. Before driving a car with them, I would have never made an argument for justifying a $2,000+ front only brake 'kit'.

[Q45tech]

The friction of each pad and each tire have one best temperature where the friction vs brake pedal pressure is the optimum.

Factory pads must work at 32F [for people who are ignorant of automobile technology] and thru 550-600F. Generally factory pads work best at 150-300F because that optimizes a single stop from 60-80 mph.

Dragging calipers or slightly warped rotors can heat the pads/rotors up in normal driving raising the UNBRAKED temperature.

New cars don't have dragging calipers or warped rotors [for the most part]...........used cars subjected to poor quality brake replacement work do.

The point is these discussions are meaningless unless members provide the rotor temperature [from which we can calculate the pad temperature].

Many times fading brakes can be traced to worn out water saturated [3%] low cost low quality brake fluid which has a 5-10 minute lag to peak temperature. {It is hotter 5 minutes after the braking].

The only cure for low speed temperature rise [in traffic where the air speed can't cool the rotors/pads is MORE MASS on the rotors.

Lexus [LS430] has embraced brakes and has 34 mm x 12" rotors with 4 piston calipers in front.........33% more weight* and Mass, not to mention real air deflectors, directing air towards calipers.

* when you add rotor, caliper, pad weights up vs even 2003 Q.