The New Soft Brake Pedal Thread.

[nuffsaid]

So what do symptoms do poor seals have on a car?

Cheers

[Abo Bob]

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.

[nuffsaid]

Sitting a while meaning stopped at the lights?

I get the following (and only sometimes):

Coming to a set of lights, press brake pedal, lack of feel and has alot of travel, release and then press brake pedal again, much much better feel and bite, less travel to hit that biting point.

Is that the same?

[GTRgeoff]

That will be a seal problem if you are stationary, if driving for a while it could be knockoff.

Without having a look into the master as well initial soft pedal could be the bypass dimension. In order for the piston to fill with fluid as the pads wear the pressure seal has to bypass the feed tube from the reservior. If it is set to go too far past it will force fluid back into the reservior until it goes past (soft pedal) and then the pedal will firm up, but now we are getting real picky. Every mm it moves though is magnified by the pedal ratio.

This site is alway interesting and does better diagrams than I have time for. http://auto.howstuffworks.com/master-brake1.htm

[Cubes]

My breaks feel quite awesome now that I'm running decent pads.

At the very start of the pedal travel it feels light, however with decent pads its very grabby in this area on light breaking, very noticably in car parks etc. After the light pedal travel area the pedal goes hard; its almost like on and off, light then hard; at this point the car is breaking rather hard.

I used to run fairly hard crappy pads that felt dead and made the feel pedal hard with no grab that made the car feel as if it was difficult to pull up; I had to really stomp on the brakes to lock the wheels.

Now that I'm running Ferodo pads I find myself easily over braking; I just can't seem to get used to how touchy the brakes are, especially as mentioned above in car parks.

I have yet to drive a new car that has a better pedal feel than my old R32. The closest pedal feel to mine is the 100series V8 Landcruiser. Interestingly the pedal travel feel is similiar, its got a light grabby area at the top that then goes harder, the exception is with the r32 the hard area is harder but it also has a hell of a lot more grab.

So my advice; try different pads, pads make a huge difference to pedal feel. EDIT: You already have.

[nuffsaid]

What Ferodo pad are you running?

[Cubes]

Only a street pad... GP2 I believe they were.

They have slightly better grab than the Ultimates I used to run but unfortunately they throw out just as much dust. Unsure how they cope with high speed and lots of cornering as I don't really go that hard; a brisk drive through the hills they are perfectly fine with no signs of fade, thats all that matters.

[Topaz]

My brake pedal squeals, like theres air being pushed out. Broken seal somewhere probably, should get a new master cylinder me thingks.

[ali-turko]

no dont replace it coz i got the squeal aswell and replaced mine didnt make a difference

[nsm034]

finally got my car to the brake shop. Had the discs machined at the local tyre shop to fix the soft pedal feel. But after they had done them i started to get a wobble in the front end. So i went to a proper brake place only to discover that the tyre shop had only machined one side of the disc. The back side was almost new and the front was just about down to the wear limit and they had also machined a wobble in them. So now i'm up for 2 new front rotors. So I'm getting slotted ones and red stuff pads in the front aswell. They're going to give it a full look over at the same time. Hopefully this will fix the soft pedal feel. Will post the results

[nsm034]

finaly got the car to the brake shop and got 2 new front rotors and red stuff pads and a flush. made a huge difference the soft feel has completely disapeared

[Birth]

Hi guys,

What prices have you paid for new rubber and braided lines? I was thinking of taking mine off and having Pirtek put new rubber onto the stock end pieces. Don't know what this would cost either.

[johnGTS-t]

ive just put braied hoses on and ive got a softer pedal than i did before. getting new rotors and a caliper kit and see what happens. ive never had a problem with braking but the pedal has always been soft.

[Duncan]

well ultimately its a pretty simple system. There is either air in the lines or a bad master cylinder if you have just put braided lines in

[Birth]

JohnGTST what did you pay for the lines?

[T04GTR]

old car, also a car that has been driven hard will have softer seals,hoses,and just generaly abit worn in all the hydrolics. also using a "performace" brake fluid also softens the seals making the pedal soft aswell.

unfortonatly there isnt much to do about it. sometimes its air stuck in the abs unit. and sometimes its just a case of soft seals. new pads feel soft untill fully bedded too. using a bigger master cylinder is a option. but you have to swap over the proportoning valve in the origonal cylinder or you will crack rear disks and or overheat the fronts.

oh and pad knock off from wheel bearings is pretty common. especaly if you have bigger disks fitted.

[dangerbones]

my R33 GTST type M has awesome brakes most of the time no mushyness at all, until about a month ago! i put my foot on the brake pedal and got nothing but floorboards.. that was interesting, i was approching the back of a car parked at a red light rappidly, luckily it pulled up ok... i hadn't been driving it hard at all, there was no reason to assume the fluid had boiled, so i had decided it was the master cylinder, until the problem went away the following day, then reappeared the following week and dissappeared yet again until this morning when i found myself going slower and slower even as i accelerated more and more, the front brake calipers have locked on, i now have bright blue rotors and they have magically released... so i will be rebuilding the master cylinder and calipers and bleeding it would seem...

any one else had calipers lock on like that?

[battery]

ok so on the subject of rubber vs braided lines it seems the only real benefit to braided is that they last longer?

[battery]

heres a more "exotic type" of brake line, i present to you the "cable tie brake line"

im guessing its to help hold the pressure yeh?

Edited December 26, 2007 by battery

[a20089]

ok so on the subject of rubber vs braided lines it seems the only real benefit to braided is that they last longer?

Not realy, as explained earlier a rubber line will over time expand with the pressure of the braking fluid the braided lines fix this problem. But unless you do lots of mountain drives or track work, you probably won't notice much if any difference.

Saying that they are better and I have them.