Weight conscious Z brake upgrade

[cdlong]

I’ve always wanted to do a z32 swap on my car but I’ve helped a few guys do it on their cars and noticed that the rotors weigh a ton. I’m somewhat obsessed with weight so I didn’t want to add a lot to my car if I didn’t have to. The stock brakes are almost good enough, but I haven’t upgraded to super sticky race rubber yet, I’ll probably change my mind after I do in a month. So I’m looking for a way to drop some weight off the system. Two piece rotors would be a great solution. The problem is, no one seems to make a 2 piece rotor for the stock z32 caliper, they are all for a big brake package. That defeats the purpose for me because a huge 2 piece will weigh about as much as a stock z32 rotor and is major overkill for my needs. And I need something that will fit under my 16”wheels (stock s14 SE alloys and R32 GTR). I’ve checked with every rotor manufacturer I can think of but can’t find anything just right, most of them don’t list any info on their rotors specifically. Here’s the best I can come up with.

AP racing has discs that will fit but I can’t find any info on the hats. Arizona z car would make custom hats but only in a minimum of 100. Not to mention that each rotor is $180.http://www.apracing.com/car/br...160/1

Wildwood has discs that are the right diameter but 20mm thick. I could separate the z32 calipers and machine out 6mm and put them back together. It would theoretically work but I’m still not sure they have any hats that would work. http://www.wilwood.com/Product...x.asp

I’ve thought about using r32 gtr calipers (296x32mm rotors) or 3000gt upgrade kits for those rotors (317x30mm I think) just to find a disc and hat combination that would work, but I haven’t found anything right there either. I’m really trying to avoid adapter plates or any custom parts to keep it simple and to keep the cost down.

Any tips on where to look or ideas to make this work would be greatly appreciated. Sorry about posting in two forums, i wanted as much exposure possible.

[Bronze MFP]

Unfortunatly a heavy rotor helps with heat absorbtion and dissapation. Yes the z32 rotors weigh a bit more than the stock 240 rotors, but I've flogged my z32 brakes down a mountain and not had any appreciable brake fade, where my stock brakes were crying for mommy. In most situations the stock brakes with good pads and fluid work great, the z32 upgrade can be overkill, but will hold up better to repeated heavy braking.If you're autocrossing and weight really matters, i'd stay stock, if you are doing extended runs where brake fade is really killing you, then think about the z32 upgrade.

[cdlong]

Unfortunatly a heavy rotor helps with heat absorbtion and dissapation.

i know that, but good two piece rotors will cool better than stock and should make up for it somewhat. with good fluid and pads, it should be able to handle anything i can throw at it.

[Nismo_Freak]

Did someone delete me and SmithSR's posts?

Or did you post this twice?

[Q45tech]

A 2 piece rotor still needs the rotor to weight a lot.......the isolated hat is just to keep the wheel hub/bearings cooler and confine stress to reduce diffential location warping.

OEM designs use one piece to transfer heat to wheel for additional heat sinking.

Rust is a killer as it impedes the heat transfer to hub then wheel.

The temperature rise vs weight is linear! 10% heavier rotor will drop rotor temp gain by 10%............the gain that is - say at 100F ambient a stop increases rotor temp by 500F a 10% heavier rotor will only gain 450F.

On single stops the time is so short that rotational vane cooling is almost nonexistent............anyway the temp continues to rise after the stop as it equalizes throughout the system.

The rotational effect of weight on a 11-13" rotor is ~~1/4 of that on a 26" tire and ~~1/2 that of a 16" wheel.

A 20 pound rotor is insignificant compared to a 40 pound wheel and tire.

Very easy to calculate the rotor rise vs vehicle weight.

http://www.sae.org/events/bce/tutorial-ihm.pdf

Look at page 3 of the followinghttp://www.tristate.edu/facult...n.pdf

[SmithSR]

That is a masterful post. Thankyou!

[cdlong]

sorry, posted it twice. i got more response in both threads than expected.

Q45, i guess my thought was that i don't really need as much capacity as the stock rotors offer.

Sports Car Revolution's project acura lost 12whp from a big brake upgrade, it has to make some difference. it may not be huge, but it's worth a look.

i used to work with the guy that wrote that SAE paper. well, i didn't work with him, just in the same office.

[ArticDragon192]

You also gotta remember that the BBK on an FF will affect power more than an FR car since power goes to the wheels with the bigger brakes in an FF car. In an FR car, the power goes to the rear wheels, which also have the smaller brakes and rotors. So power should be minimal.

[cdlong]

it only shows up on a dyno on a FF car, but on the street you still have to turn all four wheels. it doesn't matter if the wheels are powered or not, rotational inertial is always a factor.

[hannibal]

I think your best bet is the aluminum calipers. The 30mm aluminum calipers + 30mm rotors weigh 24 lbs per side vs 22lbs for the stock setup. The iron calipers and rotors weigh 27.5 lbs per side.

It would be great to find some 2 piece rotors, but the price doesnt sound like its worth it.

[onosqv]

If you REALLY want to save weight

Keep stock setup, upgrade to better pads & rotors, then install rear aluminum spindle -> you save 7lbs or so & also do s14 rear control arm if you have an s13.

Usually, ppl don't upgrade those unless they are doing the rear zbrake conversion, but hey, if you want to save weight that badly, there's one way to go.

[eddiec]

if you use the alum upright, don't you have to change out the lower shock mount to match? the z32 and s13 use different rear lower shock mounts.

[onosqv]

if you use the alum upright, don't you have to change out the lower shock mount to match? the z32 and s13 use different rear lower shock mounts.

Yes, that's why ppl don't usually go thru the trouble.

I believe some guys have drilled through their rear shocks to get it to mount right - ballsy.

I'm going to be running kts coilovers w/ the rear shock mount, so I'm ok, hehe, too bad for cdlong - however, that would get weight down even more... drilling holes... mmmm, speed holes. HAHA.

[Bronze MFP]

If you REALLY want to save weight

Keep stock setup, upgrade to better pads & rotors, then install rear aluminum spindle -> you save 7lbs or so & also do s14 rear control arm if you have an s13.

Usually, ppl don't upgrade those unless they are doing the rear zbrake conversion, but hey, if you want to save weight that badly, there's one way to go.

If you are talking about rear camber control arms, i have a pair for sale since I installed my cusco arms. fyi

[crzycav86]

if you use the alum upright, don't you have to change out the lower shock mount to match? the z32 and s13 use different rear lower shock mounts.

Yes. You need a fork-type rear shock mount for it to work. If you have coilovers that have ride-height adjustment via shock mount, you can simply buy a new pair of shock mounts for the z32. The threads are usually the same.

If you have shocks, you can get rear shocks from a z32. They bolt up to the rear of the s13.

It's not really that much of a hassle if you haven't upgraded the rear shocks yet.

[onosqv]

If you have shocks, you can get rear shocks from a z32. They bolt up to the rear of the s13.

Has anyone verified this? Does it affect other things like overall height, etc? If it bolts up, AWESOME! Another reason for more ppl to do it who haven't done too much suspension yet, .

[crzycav86]

Well, I haven't used the shock myself, but I first heard it from a guy on zilvia. Then it was verified by a prominent member here on NICO(I think it was smith).

[skydragoness]

No one's mentioned Q45 brakes at all. Why is that? They're better than OE, but not as much overkill as Z32 brakes are. I'm sure there isn't as much of a weight gain with those vs. the Z calipers too.

[onosqv]

No one's mentioned Q45 brakes at all. Why is that? They're better than OE, but not as much overkill as Z32 brakes are. I'm sure there isn't as much of a weight gain with those vs. the Z calipers too.

Because the thread title is "Z brake upgrade"... HAHAHHAHAHA, i'm kidding. Yes, those are also a good alternative, plus there will be much better wheel clearances.

BUT, I like overkill... tee hee.

[Chingon]

No one's mentioned Q45 brakes at all. Why is that? They're better than OE, but not as much overkill as Z32 brakes are. I'm sure there isn't as much of a weight gain with those vs. the Z calipers too.

The diameter is the same as the 300zx and it's 28mm + calipers are iron. The best option I see is the 26mm aluminum caliper. I remember that in "project silvia" of scc, the weight difference was something like 2 pounds max w the 30 mm one.

You mention the gtr r32's as well. Apparently they are the lightest of all, despite being 32 mm. I looked into this venue, because as you may already know, it has 30% better cooling, due to the curve vanes inside the rotor. I also looked into the wilwood route to see if I could piece together a set of 2 piece rotors, but having no dimensions for the originial rotors this proved difficult.

[Chingon]

Well, I haven't used the shock myself, but I first heard it from a guy on zilvia. Then it was verified by a prominent member here on NICO(I think it was smith).

It fits, but spring rate and shock dampening are significantly different. Spring is swappable though. I hear one of the skylines uses same strut design, but w/240 specs.

[cdlong]

The diameter is the same as the 300zx and it's 28mm + calipers are iron. The best option I see is the 26mm aluminum caliper. I remember that in "project silvia" of scc, the weight difference was something like 2 pounds max w the 30 mm one.

You mention the gtr r32's as well. Apparently they are the lightest of all, despite being 32 mm. I looked into this venue, because as you may already know, it has 30% better cooling, due to the curve vanes inside the rotor. I also looked into the wilwood route to see if I could piece together a set of 2 piece rotors, but having no dimensions for the originial rotors this proved difficult.

good info, i didn't know about the curved rotors, but it won't matter if i swap in two piece rotors. disk brakes australia has specs on thier website but i couldn't find anything to fit them either. here's their catalogue.http://www.dba.com.au/dba_cata...4.pdfto cut to the chase, they are 296x32 and 54mm total height, the only thing i can't find is the mounting face thickness. it's probably the same as the z32 rotors. a 7mm face thickness will give it about a 15mm offset or about .7". most hats are around 2" so it's a bit challenging to find something that works.

i'm pretty sure the weight SCC refered to was for the brembo F50 setup, which has two piece rotors and light weight calipers.

[cdlong]

No one's mentioned Q45 brakes at all. Why is that? They're better than OE, but not as much overkill as Z32 brakes are. I'm sure there isn't as much of a weight gain with those vs. the Z calipers too.

to be honest i am mostly going for the pedal feel and bling factor of the fixed calipers. i could just get good pads and lines for the stock brakes but i don't want to.

with the same size rotor and pad they should actually perform the same as the z32 system (as far as heat capacity)

[cdlong]

ok, maybe i do need a little more fade resistance and power, i got my new tires on and i can't even lock them up. they faded after one really hard stop. though they are still stock.

[Onizuka]

Wilwood seems to be the best route, as you can order any hat & rotor combo. This is especially important as the rear brakes require a hat that can accept the rear drum Ebrake.

[turtl631]

Q45 brakes also cause more front bias than Z32 brakes (when using just the front calipers). There's a post on either FA or Zilvia where someone calculated the bias differences.