The New Soft Brake Pedal Thread.

[Abo Bob]

You can file two flats opposing sides onto it and get an open ended spanner onto it.

[RAZOR32]

I have got R34 GTR Brembos on the front of my R32 Gtst, I fully rebuilt the Brembos when I first got them.

I have Ferado DS2500 pads and DBA 5000 rotors on the front of my R32 gts-t, and Cusco Brake master cylinder stopper and braided brake lines and RBF 600 brake fluid

and the pedal is a bit to soft-mushy at the top for my liking so changing to GTR master cylinder and GTR Brembo rear brakes will fix this problem?

Out on the track it tends to lock the rears up first as well some times?

I never had any of these problems before I upgraded all this stuff!

Any help or I dears would be great, Cheers

[Duncan]

hanyou you really need to replace that bleeder, regular bleeding is critical for braking performance

[Roy]

Update.

I installed some Ferrodo DS2500 pads all round and the pedal feels much firmer now. I would say I have to push harder on the pedal than I used to but I think that is master cylinder related.

Cool. Interesting feedback

[hanyou]

You can file two flats opposing sides onto it and get an open ended spanner onto it.

dammit why dont i ever think of smart ways like that lol.. i love you guys

hanyou you really need to replace that bleeder, regular bleeding is critical for braking performance

now that i can will do it this weekend

[Jdfnq]

What pads?

Dunno

I haven't changed them or taken them apart yet to look....

[jmac]

R34 GT-T.

Bought Feb 05. Stock everything.

Pedal mushy. Brake performance pretty average.

March 05: upgrade to Endless EuroX front, NA-R rear pads, Endless RBF650 fluid.

Pedal still mushy initially, but great bite once brakes warm. No fade at several track days.

July 06: Endless pads rooted, last-minute change to Bendix Heavy Duty pads.

Pedal and performance worse, pads dusty, brakes fading after 2 laps of QR.

August 06: Custom master cylinder stopper brace.

Pedal still initially mushy but better brake performance during a hard stop. No noticeable difference during "normal" driving.

September 06: Upgrade to DBA 4000 slotted rotors front, RDA slotteds rear, QFM A1RM kevlar pads, braided lines, Motul Factory Line fluid.

Pedal initial feel/bite much improved (VERY noticeably) but not as "solid" as some other cars (not Skylines). Brake performance fantastic. Can't comment on racetrack fade yet.

My guess is that the braided lines + fluid bleed were responsible for fixing the pedal feel.

[MANWHORE]

Jmac, you are the man. that is exactly what i am trying to solve - that initial nothingness in the pedal.

you know what i mean. like the master cylinder brace only does somethign when you press it hard.

Same as clutch lines - only when you're putting big pressure into it.

But it's that intial bit that annoys me.

The actual braking perofmance is pretty good, i can lock up the tyres easy.

[Abo Bob]

I think some cars have power assistance as well as the hydraulics that we all have. Maybe that's where the really bitey life is.

Mine still aren't bitey, just firmer.

[siksII]

Abo, as i said in the other thread (not sure if u saw it) i put down mushiness and lack of feel in most non-gtr nissans to the ABS. have u driven a non abs equivalent of your car?

[Abo Bob]

I haven't. I assume, but haven't checked, that all R34's have ABS.

[GTRgeoff]

OK some reasons you will get a soft pedal feel, either initial or overall:

Brake lines - these need to be replaced occasionally if using the rubber, especially if you race as the rubber breaks down faster under the heat stress. They also won't give the same resistance to expansion as a quality braided teflon line.

Bleeding - self explanatory, but if some air gets in they need bleeding, also brake fluid is easily contaminated with water with age and rubber lines.

Seals - either the master or calipers will eventually have a seal failure due to pitting in the bore or breakdown of the seal due to wear or particulate tearing.

Firewall flex - I've had a firewall in a Falcon crack severely around the master mount so rivetted a 3mm piece of stainless in (thought of that Duncan ) to support it. A stopper works well also. This can also happen to a clutch master if you go for a stupidly hard clutch.

Pad knockoff - as the wheel turns any misalignment of the disc mounting surfaces wil cause runout or wobbling off the plane of the disc. These mating surfaces should always be kept immaculately clean so there is minimal knockoff, which is the fluttering knocking the pad away and forcing the fluid back into the lines so the first application of the pedal is initially soft which may leave you without enough pedal for a big stop when racing. This is why race drivers use the left foot to check for pedal while still flat on the throttle and coming up to a tun at the end of a long straight.

So the diagnosis usually relies on when the softness occurs. If just sitting for a while and you press the pedal and have softness then on the next press it is hard then you need to see to seals. If the car is approaching 6-7 years old it may be time for all seals to be done if pedal feel is important. If after a long straight on the track it feels soft initially but through areas of multiple corners it stays hard then look at pad knockoff. If all is clean then sometimes on car machining can help.

Bleed regularly, use good fluid and inspect often. It's no good having performance without the stoppers

[Abo Bob]

Great post Geoff. I guess my caliper seals are slowly going then. I suppose I will have to go for braided lines at some stage too. What do these cost? Where do you get them?

[Beer Baron]

the ABS is definately one culprit of the intial sponge. One of my 32s has ABS, one does not. all things being equal the non ABS car has a much firmer pedal. however:

with new pads (endless carbon ceramic, CCR all round), new rotors (DBA 4000 all round), nismo brake lines, cusco master brace (big farker), motul RBF600 and a good bleed the pedal in the GTR is pretty damn good.

[RAZOR32]

I have done all those things you have said GTRgeoff and still no luck!

Any more idears??

[Roy]

If you have an R34, i would be surprised if you notice a difference with braided lines. If you do i would hazard a guess that it is more to do with the pads you may have changed at the time. Or the fact that they got a good proper bleed. My car was 8 yrs old when i changed to braided lines and there was no difference

Secondly, the rubber seals in your calipers. Well dont stress too much. Keep an eye on them, keep them clean, but i have had 3 sets through mine. Track work kills them. Thats why the good road calipers like AP/Brembo have internals seals.

Something no one has mentioned is the brake booster. We all run assisted brakes. My original one was faulty, and was replaced around the same time as my master cylinder...my brakes felt great for years after that.

Its har dto remember but i have noticed a drop off in pedal feel the past 18 months. It all went bad after a sprint at Calder. Teh drive there they were great, the drive home they have not been as good despite everything i have done with regards to maintenance.

[Abo Bob]

Hmm.. thinking out loud here. The way I see it, if you need braided lines it's because you have a spongy pedal because the lines you have are expanding. There wont be any expansion of the lines unless you have some pressure on them though so the sponginess due to brake lines can only be the part after you have full pressure on the pedal.

In other words, that initial mushiness is not brake lines because I get it before there is any real pressure on the fluid.

So back to the caliper seals.

Is this replacing of caliper seals what you might call rebuilding the calipers? Did you do it yourself Troy? Any tips or tricks? Cost?

I have recently replaced my booster. No change from that.

[nuffsaid]

My R34 GTT also doesnt have the nice pedal feel that many other cars have.

There seems to be like 2cm of play in the pedal before it starts biting.

Had the brakes checked out, its not pad knock off but perhaps some more air that needs bleeding. How can you tell if the caliper seals are rooted?

Also, I sometimes get the first pump is crap, second pump of the pedal is firm feeling.

[J_Red33]

BRace only helps with softness when you press the pedal down. The intial softness is not related to the brace, because the firewall hasn't flexed yet.

Also forgot to add, that I have changed the rubber lines. It didn't do anything which means that the old lines were fine.

That's interesting about the rotor and pad thickness. My pads are brand new, but the rotors are still the stock ones.

How thick are they meant to be new?

If the brace doesn't cure your initial mushyness you've probably got other problems or it's not pressing firm enough against the cylinder.

I put a cusco brace on my R33 S2 (NO ABS) & when I first put it on I still had that mush at the top. All I did was tighten the brace up a bit more so it pushed a bit harder against the cylinder & the mush was as good as gone.

I've done no other mods & the fluid hasn't been changed since I bought the car when it was complied, so it's due. My pads I think are also a fairly hard compound as after 18 months of driving I've still got roughly 10mm on the front (also a bit squealy when there's even mild surface rust on the disk). No doubt it will improve even more with some basic servicing.

Edited October 16, 2006 by JazzaR33

[Roy]

Is this replacing of caliper seals what you might call rebuilding the calipers? Did you do it yourself Troy? Any tips or tricks? Cost?

I have recently replaced my booster. No change from that.

Next time you change your pads just check out the condition of the seals. If they look too gone then throw some new seals through them.I have done them once myself, and twice by Race Brakes (Once in Sydney, once in Melb) Race Brakes in Melb put a seal kit thru them cheaper then i could buy the seals so....

Its pretty easy, I used RBR grease to assemble them...I find keeping them clean and all the dead pad away from them helps them last that little bit longer