Break judder & screeching 944S2

[Bananaman]

Last year I had new disk's & pads fitted & calipers ovehauled priour to Le-MAns trip.
I was getting a lot of screeching noises at low speed breaking B4 trip.
On the return journey after som sprited breaking I was getting a lot of judder coming through the stearing at 80pmh+ (worse the higher the speed).
The garage that fitted the breaks have told me that screeching is normal with modern pad matterials (but it sounds crap!!!!!!!!!!!!) I also got them to have a look at the disk's & they measured them at 2 thou out which they said was OK ???
They also noticed that one of the disk's had an area of pitting on it that they thought was due to water geting trapped against the disk by the pad as the car can be left for a few days-week at a time on the drive.
I was planning on
A. Taking the pads out & giving the faces a rub with some Wet & Dry paper as i think they may be slightly glazed ???
B. Getting disk's skimmed ???

Any thoughts.........

[Thom]

Some reasons for judder :
1) piston calipers exposed to excessive oxydation can lead to uneven pad wear and cause some judder
2) badly bled brake system can make the ABS trigger happy and make the car feel juddering under even light breaking (although it's not proper brake judder)
3) the pads guiding plates can go out of shape and cause uneven pad wear, then back to point 1)

[Bananaman]

Thanks for the response but as i said the breaks had just been totally overhauld & once problem occured i got them to have another look at them. he garage i use is a well respected Specialist so i doubt they would have missed the problems you mention ???
It doesn't feel like an ABS thing especially as it only occurs at high speed (100mph+ coming back through France was a bit hairy)
I think that
A. I might have glazed the pads
&
B. I might have worped the disk's slightly, would 2 thou make that much difference?

[Thom]

Mine did the ABS thing at any speed. Sounded pretty awful and loud when braking hard.
As for glazed pads, I do not think you would able to brake at all if the pads were glazed.

>> Edited by Thom on Tuesday 23 November 10:46

[Bananaman]

Thom said:

Mine did the ABS thing at any speed. Sounded pretty awful and loud when braking hard. As for glazed pads, I do not think you would able to brake at all if the pads were glazed. >> Edited by Thom on Tuesday 23 November 10:46

The beraks sound OK at speed, just screeching at low speed, garage said it was due to lack of Asbesdos in modern pads causing break dust build up?????????
Judder only appears at high speed.
I think I'll whip the pads off give them a rub down & clean up the calipers & see what happens.....

[Buster44]

Have a look at this thread, the wet & dry treatment to disc & pad worked for me. Removes uneven pad deposits.

www.pistonheads.com/gassing/topic.asp?t=138604&f=48&h=0

[Bananaman]

Buster44 said:

Buster44 13:33 -------------------------------------------------------------------------------- I was told by a technician that the deposits can be removed from the disc face with 80 grit wet & dry paper. The pad face should also be cleaned up with 400 grit wet & dry. Tried this on my cerbera when suffering with a persistent juddering pedal and it cured it no problem.

Cheers, I'll give that a go.........

[softinthehead]

probably a silly question but how are your tyres? Uneven wear? pressures ok and equal? tracking checked lately?
I once got really dreadful high speed judder which the garage said was due to uneven wear on front tyres. I thought they were taking the p**s 'cos they loked okay to me but blow me down if a new set didnt sort it out

[flash666_uk2004]

hi

high speed judder could aslo be wheel balance i had same on my 928 got all wheels balanced for £20.00 and is now perfect

gordon

>> Edited by flash666_uk2004 on Tuesday 23 November 22:44

[iguana]

softinthehead said:

I once got really dreadful high speed judder which the garage said was due to uneven wear on front tyres. I thought they were taking the p**s 'cos they loked okay to me but blow me down if a new set didnt sort it out

Yip not uncommon.

Also on a 944 odd judder under braking can be wishbone bushes, is the wheel also a bit twitchy at high speed?

The sqealing is odd, did they put new squeal shims in?

[Bananaman]

The car is otherwise stable at speed, the tyres are fine, when the breaks were done one of the front wishbones was replaces and the other checked, basically when i bought the car I had it checked over, full service and replaced any items that needed replacing (including disk's, pads & caliper ovehaul), I spent the money so that the car would fell tight (which it does) just got these little niggles with the breaks.

I'll try the Wet & Dry treatment & get back to you with the results.

[zoom_jones]

iguana said:

softinthehead said: I once got really dreadful high speed judder which the garage said was due to uneven wear on front tyres. I thought they were taking the p**s 'cos they loked okay to me but blow me down if a new set didnt sort it out Yip not uncommon. Also on a 944 odd judder under braking can be wishbone bushes, is the wheel also a bit twitchy at high speed? The sqealing is odd, did they put new squeal shims in?

Ditto for me, was getting pretty bad brake judder, specialist said all wheels balanced and disk run out were fine. Rear tyres were shot though, replacing them relieved the judder massively.