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Rear Brakes Not Really Working?

SS8_Gohan
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SS8_Gohan Grand Master

SS8_Gohan

Posted
Posted

hi guys'n'gals

have an ongoing issue with my rear brakes. Discs and pads are 100% (been checked twice) but the rear pads are slightly 'glazed'. Apparently there isn't enough heat getting into them?? I think it means that for some reason they're not really clamping down on the disc or something like that (as you can tell, i know next to nothing about brakes)

just bought some Motul RBF600 today, got enough for a flush and refill, so that's the first step. But i was told it won't make a difference for my problem.

ABS seems ok, warning light hasn't ever come on, and when it was tested today, the guy got the ABS to work. And i know from a recent driver training day the ABS is definitely working. But an instructor also noticed that my rear brakes never really did anything, locked up i think he said (it was on a split surface exercise). But the ABS unit seems ok.

Took the car to arguably the most well known brake place in melbourne and their solution was to put some incredibly high performance pads on the car. Now, the pads recommended were absolute top shelf, no doubt, pricey but ultra impressive pads (endless cc-x) but i couldn't quite seem to get my point across that i didn't want to fix the problem with top quality pads, i wanted to diagnose the problem first and THEN take it from there. I don't want to just cover anything up with a great product which just hides the rear brake deficiencies so that they're almost non-existent. That seem crazy to anyone? I guess i just didn't quite explain myself properly.

Soooo wondering if i could pick up brains here. Besides a completely flush and refill with top brake fluid, what else can i check for what seems to be a dodgy rear brake bias where the rear pads aren't really getting any heat in them? Does that mean that they're just not really biting on the disc at all?

Problem is, i've started at the top in terms of brake workshops and haven't resolved the problem, and don't really know where to go from here :thumbsup: (with a track day on 15th march)

cheers,

daniel

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djr81 Grand Master

djr81

Posted
Posted (edited)

If you are glazing rear pads because of insufficient heat then the answer is simple. You are probably running the wrong pad. For a rear you need something that works from cold. So for example a DS2500 as opposed to a DS3000 which needs some temperature. Some pads will glaze when used on a light duty for any length of time. Take them out & bash them with the bench grinder. A good rear pad will never do this.

The second issue is friction coefficient. What pads do you currently have front & rear?

The third issue may be air in the system. Make sure the beeld is done properly.

You always get a big front/rear temp differential. See the photo. You can check the rotor temps with a thermocouple or with thermo paint.

post-5134-1204844381_thumb.jpg

Edited by djr81
SS8_Gohan Grand Master

SS8_Gohan

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  • Author
Posted

to answer what gear i'm running...

stock, stock, stock...aaaannnd yep... stock. Everything is OEM Nissan.

I have NO IDEA whether brake fluid was done during compliance. So that was at least the first step i'm going to do with the Motul RBF600 i just bought....

  • 6 months later...
Fastrotor Proficient

Fastrotor

Posted
Posted

I believe i have the same problem. I discovered that i could stall up more on the h-brake than the foot brake ! To me thats crazy... (auto sedan) EBC reds front and EBC Greens rear.

I just this weekend, machined rotors, resurfaced pads and bled the lines, and there still weak. Rear pistons can be slid in with your hand so there not seized in any way......

Reds were 3/4 gone, and the greens looked almost new from the track days.

My concern is i need them to bite from cold, stationary so i can stall up properly for the drags..

The only thing i have left to consider is either pad type or rear bias valve .... looks to be the large hex nut extension on the master, that the rear lines screw into,

Anyone EVER have dramas with this valve ?

Gary

SS8_Gohan Grand Master

SS8_Gohan

Posted
  • Author
Posted

one place did mention to me that the Skylines have very little rear bias anyway, which could explain it... but i have no idea about the veracity of such a claim...

the bias valve maybe a good place to start

Fastrotor Proficient

Fastrotor

Posted
Posted
one place did mention to me that the Skylines have very little rear bias anyway, which could explain it... but i have no idea about the veracity of such a claim...

the bias valve maybe a good place to start

Yeah i think thats my best bet to try to replace that valve with something adjustable to find the best bias that works..... very sparse info out there on this sbuject (re R33's )...

Gary

Gav Mentor

Gav

Posted
Posted

I played around with front and rear compounds a lot on my upgraded brake set-up (CSC 4 pots 355mm, 343mm single pot).

I ended up going a fairly high temp/high performance pad on the front (Pagid RS 14 "black") and a low temp pad with a high initial "bite" on the rear (Pagid 4-2 "blue" ).

This helped balance out the braking a lot, but as djr81 says, the front bias is considerably more than the rear from factory. As a point in case I expect to go through at least 3 sets of rotors/pads for every set on the rear.

  • 1 month later...
  • 2 weeks later...
Fastrotor Proficient

Fastrotor

Posted
Posted

Hey AboBob, can you have a look at your brake master and see if it has the large hex 'nut' (bout an inch long) that the rear lines screw into, and it screw into the master cylinder. Pretty sure this is the rear bias valve.

Wonder if the R34 has more rear bias, it might be possible to swap my R33 one for an R34 one to try out.....

Also heard one of the silvias (poss S15) uses alot more and is able to swap into R33...... so little info out there.

Gary

  • 2 weeks later...

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