Larry Herman

Simon, I went nuts because it was my son's car, and after suffering through him buying several different brands of "cheaper" race pads, and bitching about it at a number of events I finally bought him the good ones and TADA....problem solved. Kids

SimonExtreme

Larry

Most of the serious guys driving Evo's in the UK used to (and some still do) spend $ooo's on AP race setups while, once I git the pads sorted, the brembo's were just as good. One of the best specialists does prefer to fit different disks so that they can use less agressive pads for road work but what's a little pad squeel between friends

DaveK

I doubt I will have time to do anything about it this weekend (we have resident guests and it might be considered rude if I go out and start taking wheels off my car) - but I will take a good look at the brakes etc. when I get the chance.

Without checking the service records, I can't actually remember when the pads / discs were last done so they might be the problem. I'm a bit dubious though because the problem was quite pronounced and I've never noticed it at all before - if it was wear related I would have expected it to build up much more slowly.

DaveK

OK - I decided to be rude anyway. Couldn't see anything obvious wrong with the brakes - I will check the service record, but the discs didn't seem excessively worn.

I did notice that the wheel weights were odd on one wheel - there are actually two sets. Both on the inside of the rim, one near the center of the wheel , one on the edge - and they were about 90 degrees apart. I don't understand why I need two sets of weights on one wheel.

Also - the other wheel had one very small weight on it - there was no obvious place where additional
weights might have been and fallen off - but there was a spiral chipped into the brake dust as if something might have fallen off while the wheel was turning.

So - the first thing I will do is get the wheels balanced, and I'll see whether that makes a difference.

I did find one other rather disappointing thing - which I'll raise in a new thread.....

DarrylH

Wheel balance problems will usually show up independent of braking. If you have the vibes only while braking, wheel balance is unlikely to be the cause.

Your problem sounds like what we always called warped disks but which is really high & low spots on the disks, either due to uneven wear of the disks, or to holding your foot on the brake with hot disks and pads while at a standstill, which creates local hot spots with excess pad material on them.

TR6

I've got exactly the same symptoms. I also found the Stoptech article in my search and have really been interested in the opinions in this thread. Its quite possible that perhaps the previous owner of my car applied the brake pedal stopped when the rotors were very hot (maybe at a DE or something). Who knows. Its not too bad right now, just annoying. And my car is used for street. I'll probably just buy new rotors and pads one day soon so I can at least start with a clean slate.

warmfuzzies

Dace, weights will be where ever they need to be, one of mine has none, others have combinations...A good wheel man will rotate the tyre if he thinks there are too many weights.....


kevin

doubleurx

The stoptech site is an awesome resource. I had the stoptech big brake kit on my old wrx and the braking abitilites of that car were incredible. Anytime the vibration issue has come about it has to do with the pads. On my STI, I had the same issue after a couple of track days, switched pads, broke them in and the vibration disappeared. In general I think the vibration is a result of how the pads were broken in from new.

Sire

Dave i had a similar problem, thought allso that it was the brakes. But they were renewed and stil the steering weel was vibrating.

The problem was the steer pole (sorry if this is spelled wrong), Porsche said it was a commen problem for the 964. They renewed the pole and no vibrations anymore.

964rh

Advice needed Simon

During and after the PCGB Donnington trackday in July I suffered from vibration. I thought it may have been from pad material transfer (car's running on Pagid blues and standard discs). Disc surface was ridged with what looked like blue burn marks.
I was advised by a few people to either look at warped discs or some more cooling for the brakes when on track but I would need to change the discs to completely get rid of the shudder.
I've always suffered from a small squeak on the nsf since Andrew took my car out for a run at the last Judgement day which has never cleared.
Anyway changed the discs a couple of weeks and the rotation squeak has finally disapeared and been replaced with a virgin pig squeal on braking to which I put down to using new discs on old pads.
Anyway, so I don't have to replace discs every trackday would a brake cooling system, like Ollie's, help in the matter? I did notice that Ollies car didn't suffer with the ridging and bluing but my car has got a weight problem compared to the RS's (mines a C4).

Thanks

Rob

IanR

Another possible cause of vibration under braking is worn front wishbone bushes - have you had the wishbones replaced at all? They seem to last about 100K miles.

SimonExtreme

Rob

I didn't realise it was you on here (different user name?? assuming you are who I think you are!). The things I have considered to date re Porsche brakes are all regarding the RS. I think you have 2 added problems, as you have identified, namely the extra weight and 4WD. Both of these have an effect. I suspect that the 4WD is having the biggest effect and although I am fairy confident that RS disks don't overheat, I would be a lot more concerned about your car. The first thing I would do is to use some heat sensitive paint (from AP and others) to see what sort of temperatures the disks are getting to. That will do 2 things. Firstly, it will give you a good idea whether extra cooling is needed and secondly, it should give you an idea as to what trackday pads to use based on anticipated operating temperatures. I suspect, from the dicription of your disks, that they are getting rather hot!

I have always just accepted the brake problems of the type of car I have and tried to sort them. I haven't, until now, considered the difference between 2wd and 4. It's an interesting problem. Having had a few lunchtime beers, I might need to clear my head to think it through but I am pretty sure that 4wd means there is extra stressn the front brakes, compared with the RS or C2.

The squeeling can usually be cured by following the AP bedding in process (sorry, I don't have the link on this laptop so you will need to search). However, the squeel could still return and then you just do the bedding in process again or put up with it!


Are you coming t Judgement Day 2? If so, and I can find some (whwre did I put it!!), I will try to bring some temperature sensitive paint.

Heirsh

Dave,

I had this very annoying problem when i bought my car. Was only a problem under light braking, particularly downhill (why are all my problems downhill related?!?!?). I've replaced pads, rotors, hats, pad backings, various prayers and curses, etc. I had that shimmy off and on until I took the rotors off (again) and recleaned the mating surfaces of it and the hub. I then reassembled everything and my shimmy int he wheel under light braking was gone.

I indicated my rotor before I did this and found it in spec (new rotor mind you) but on the outside of the runout allowed. That is why i cleaned the mating surface. I reindicated the rotors and after the work the worst was a bit better, something like 60% of allowed runout instead of 90%.

I suspect that I have worn bushings in the front suspension making this issue crop up with less runout than would normally cause it.

Just my experiences. Hope they help in some small way.

964rh

Thanks Simon

I may be coming down to JD2 to spectate/help out if I can get the time off work so I make a point of coming to see you.

Rob

DaveK

Wishbones were replaced when I had the suspension done. That was a few years ago - at a guess, probably about 30K miles ago.

I brought the car to work this morning to try it out a bit more.

It doesn't seem to do it all the time - but sometimes it is more noticeable. Seems worse to me under light braking.
I checked the tyre pressures - which I realise won't just affect braking - and the fronts were a bit low, but adding air made no difference.

I guess pads / discs are the most likely suspect - although it's surprising if that's the case. Before the weekend, the last time I used the car was to go to the Lake District - it was fine all weekend including the 300 mile drive back, and there was absolutely no heavy braking all weekend.

I don't particularly want to replace the brakes because of this, so I may have to live with it until they are worn out. Must check the service record and see how old they are......