R34 Brakes On 32

[gts-t 32]

Ok so I have just installed R34 gtt front brakes on my 32gts-t. Now the bias is more to the rear / rears lock up before the fronts. Do I to now have to put a R34 master cylinder on?? When I installed the brakes I only bled the front brakes, would it make a difference bleeding the rears as well?? Also now the brake warning light is staying on.

[sweefu]

You should bleed the brakes in the proper order (furthest away from the master cylinder to closest) so RR RL FL FR. Whether you upgrade the master cylinder or not is a personal choice, how does the pedal feel? Are you still getting good braking response?

[GTSBoy]

You've got something wrong, but not with the sizing of the hardware. The R34 calipers are essentially the same as R33 and R32 calipers, so should work just fine with the R32 master. If the rears are working better than the fronts, then it is unlikely that you need to bleed them to fix the problem. (Having said that, yes, you should have bled the rears when you installed the fronts.) I would go back and bleed the front again. Use a power bleeder if you can, and be careful if you are pumping the pedal not to push it all the way to the floor, as you may damage the seal on the master by pushing it past where it normally runs in the cylinder and into the rough, crappy surface at the end of the stroke - which will cause you to need a new master as well. As a guide, when I put R33 brakes on the front of my R32, it clearly moved the brake bias forwards.

[gts-t 32]

Thanks for the replys. The brake pedal still feels very responsive and the fronts brakes work very well. At the point just before the fronts will lock the rears will first. I'll bleed all 4 and see if it fixes my problems. Thanks for the correct order to do this in. ill keep in mind not to push the pedal to far. I just hope the damage has not all ready been done to the master.

[THENIG]

I've had the same problem after I upgraded to R34 GTT front calipers on my 32.

Only found rear wheel lockup happened on the track though under very heavy braking, haven't experienced it on the street, thought it may be just because of the different pads front to rear or weight transfer/car diving under braking.

I have brand new QFM A1RM's on the back and some mystery pads on the front that came with the R34 calipers. I have ABS fitted to my gtst which is currently disconnected but was hoping to reconnect before my next trackday so I wouldn't get rear brake lockup under heavy braking. Also planned to change the front pads to something more aggressive and the rears to something more standard.

Another thing that I have noticed is ever since the upgrade the rear wheels get covered in dust about 5 times quicker than the fronts but I just assumed it was the pads.

Love to hear if you figure out any easy fixes for your problem.

Thanks for the replys. The brake pedal still feels very responsive and the fronts brakes work very well. At the point just before the fronts will lock the rears will first. I'll bleed all 4 and see if it fixes my problems. Thanks for the correct order to do this in. ill keep in mind not to push the pedal to far. I just hope the damage has not all ready been done to the master.

[GTSBoy]

I've had the same problem after I upgraded to R34 GTT front calipers on my 32.

Only found rear wheel lockup happened on the track though under very heavy braking, haven't experienced it on the street, thought it may be just because of the different pads front to rear or weight transfer/car diving under braking.

I have brand new QFM A1RM's on the back and some mystery pads on the front that came with the R34 calipers. I have ABS fitted to my gtst which is currently disconnected but was hoping to reconnect before my next trackday so I wouldn't get rear brake lockup under heavy braking. Also planned to change the front pads to something more aggressive and the rears to something more standard.

Another thing that I have noticed is ever since the upgrade the rear wheels get covered in dust about 5 times quicker than the fronts but I just assumed it was the pads.

Love to hear if you figure out any easy fixes for your problem.

That makes total sense. I should have assumed the OP didn't necessarily have well matched pads front to rear after the swap. I never used to have brake bias problems when I first got the car. But after putting the same pads in front and rear (Bendix Ultimates) it started wanting to lock the rears if you stamped the brakes, or at least lock the inside rear if you were braking quite hard on turn in. I couldn't understand that, until it was pointed out to me that it was more than likely that the OEM pads have different compounds front to rear - tweaked that way by Nissan to ensure the bias is good. Replace these with the same compound front and rear and you change that balance.

So, in your case THENIG, perhaps just try A1RMs on the front without going to a lesser pad on the front. Seeing as you only get bias issues on the track, you probably only need a small change to the balance.

[badhairdave]

Interesting,

I've also run r34gtt brakes on a 32 with factory master with no issue. I always ran a better front pad as its the one doing the bulk of the work, rears got whatever was on the shelf when i needed new ones.... non abs, no rear lock up issues unless i cocked up a 3-2 shift approaching a tight corner and even then it would only chirp the rears. Mostly track work with semi slicks.

[GTRPSI]

R32 has 280mm front rotors

R34 has 310mm front rotors.

Increasing your 280mm front rotors to 310mm will move the brake bias to the front, balancing your brake bias.

[GTSBoy]

That's excellent advice. But his problem is the opposite happened......

[GTRPSI]

No his rears are locking up first, check his first line in his post, larger front rotors will induce more front braking due to the leverage effect of a larger front rotor.

A silly way would be to fit smaller rear rotors.

[GTSBoy]

<br />No his rears are locking up first, check his first line in his post, larger front rotors will induce more front braking due to the leverage effect of a larger front rotor.<br /><br />A silly way would be to fit smaller rear rotors. <img src='http://www.skylinesaustralia.com/forums/public/style_emoticons/default/smile.gif' class='bbc_emoticon' alt='' /><br />

<br /><br /><br />

Um...no. He said he HAS fitted R34 front brakes. You can't fit the calipers without fitting the rotors (well, you could, but you'd be an idiot). And yet the car now has excessive rear brake bias. Despite having the bigger brakes at the front. That's why it doesn't make sense. It shouldn't be that way.....but it is.

[Legionnaire]

Maybe it has something to do with increased weight transfer?

By increasing front rotor size you're making fronts do more job than before, so weight transfer under brakes is now increased compared to 280mm factory brakes, front axle receives more weight now, leaving less load for the rears, so the same rear brake torque with now reduced load (i.e. grip) tends to lock up earlier than before.

How good is your suspension, shocks in particular?

Or, as per above poster's experience, you have higher COF pads on the rear axle? Or crappier rear tyres that wouldn't grip? Or wheel alignment, namely excessive rear camber? There are many reasons why you could've gotten undesirable effect after brake upgrade that have nothing to do with brakes themselves.

Edited February 2, 2012 by Legionnaire

[THENIG]

Maybe it has something to do with increased weight transfer?

By increasing front rotor size you're making fronts do more job than before, so weight transfer under brakes is now increased compared to 280mm factory brakes, front axle receives more weight now, leaving less load for the rears, so the same rear brake torque with now reduced load (i.e. grip) tends to lock up earlier than before.

How good is your suspension, shocks in particular?

Or, as per above poster's experience, you have higher COF pads on the rear axle? Or crappier rear tyres that wouldn't grip? Or wheel alignment, namely excessive rear camber? There are many reasons why you could've gotten undesirable effect after brake upgrade that have nothing to do with brakes themselves.

I wont rule out weight transfer until car sees the track again with new suspension to reduce dive under braking coming soon.

As for tyres or alignment, tyres were very sticky semi comp Direzza's and rear camber is stock, car has stock-ish rear ride height with plenty of contact patch on the rear tyres.

Im predicting in my case its purely brake pad selection. I'm curious now to see now if I can get the rears to lock up under heavy braking on the road when the pads are cold. Will have to give it a try soon.