Shudder under breaking? SORTED!!

[wilsonny]

When you did the pads, did you check for corrosion of the aluminium caliper under the side plates? This causes the plates which the pad move against to lift and restricts their movement, causing numerous braking problems. If the corrosion isn't bad, it's easily a diy fix, but the bolts holding the plates can be terrible to remove. If you're familiar, Jackal has a good write up on his site on the subject of caliper refurb.

 

[les richards]

I had similar problems after new disks and pads and rectification of the lifting plates - and, yes, the bolts can be difficult to remove. Consensus on the different forums was that the bushes on the wishbones needed replacement but the mechanic who did the work felt the problem was disk distortion, even though they were new.

I spoke with Marcus Bailey of Diskskimmers and arranged for him to skim the disks. Completely cured the problem! Some decry skimming but it worked for me. If you are sure there is no play in the suspension it might be worth a phone call to Marcus 07824 903006 .

[link]http://www.discskimmers.com/[/url]

 

[Mike M]

Hi guys,

Ive a shudder under breaking around the 60 mark and when rolling to a slow stop, especially when breaking lightly. New discs and pads so not that and was there before the new discs. Feedback is through the pedal and wheel. I seem to remember a number of posts about this, linking to the refurb of alloys but I cant find anything in a search. Any ideas? The pedal feels like your pressing on a rolling egg as though something is warped.

Mike

 

[sweetcorne]

Whats about anti roll bar bushes

 

[Graham-S]

Mine were the wishbone bushes. They look OK till you get a leavereply bar to them. Perfect after and steering more responsive

Graham

 

[pse_SC]

leavereply bar?

 

[Graham-S]

Leaver bar to the front wishbones bushes at the front. There is a gap in the under try at the front

Sorry predicted text!

 

[Mike M]

This reeks of caliper plate lift .. the pads basically jam tight in the caliper unevenly, so you may well get unequal engagement of the pads side to side or laterally .. light braking accentuates this, causing vibration, heavy braking will often be quite even as all pads are forced into action. Very light precision skimming can play a part in rectification of these problems, but you must eliminate the issues of plate lift and suspension wear before going anywhere near there.

You also mention 60 mph, which is a key wheel balance resonance speed

Of course, you can get 'disk distortion' on new rotors fitted without scrupulous cleaning of the mounting faces, so don't be frightened of removing new disks to check they are not badly seated.

HTH, cheers, Maurice

Thanks Maurice and all, lots of good info. I had the wishbone bushes changed earlier this year so, definately not those. New suspension all around approx 2 years ago also. Ill have the caliper plate lift looked into.

 

[Mike M]

This reeks of caliper plate lift .. the pads basically jam tight in the caliper unevenly, so you may well get unequal engagement of the pads side to side or laterally .. light braking accentuates this, causing vibration, heavy braking will often be quite even as all pads are forced into action. Very light precision skimming can play a part in rectification of these problems, but you must eliminate the issues of plate lift and suspension wear before going anywhere near there.

You also mention 60 mph, which is a key wheel balance resonance speed

Of course, you can get 'disk distortion' on new rotors fitted without scrupulous cleaning of the mounting faces, so don't be frightened of removing new disks to check they are not badly seated.

HTH, cheers, Maurice

Maurice,

Can calliper plate lift come and go, do they settle now and again? Took the car out today and it didnt happen, however it does more often than not.

Cheers

Mike

 

[Mike M]

Ok, so Ive had the calipers checked and 3 of them were suffering for plate lift and theyve been sorted. Ive also had the discs checked for run out and everything is within the Porsche recommended levels. However, I've still got the issue of steering wheel and pedal shudder at 60mph and coming to a rolling stop with light breaking. Very little wheel shudder on the rolling stop. Everything else, steering etc has been checked and weve drawn a blank. Any further ideas worth investigating?

I have had the wheel balancing checked but Ill get it checked again at the weekend, just in case. Ive also had the wishbone bushes replaced at the beginning of the year and new anti-roll bar bushes.

 

[924Srr27l]

Ok, so Ive had the calipers checked and 3 of them were suffering for plate lift and theyve been sorted. Ive also had the discs checked for run out and everything is within the Porsche recommended levels. However, I've still got the issue of steering wheel and pedal shudder at 60mph and coming to a rolling stop with light breaking. Very little wheel shudder on the rolling stop. Everything else, steering etc has been checked and weve drawn a blank. Any further ideas worth investigating?

I have had the wheel balancing checked but Ill get it checked again at the weekend, just in case. Ive also had the wishbone bushes replaced at the beginning of the year and new anti-roll bar bushes.

Hi Mike, These shimmy's can be so frustrating and often expensive as you elimate all the potentials one by one!

As I'm sure you aware by now it could be several things, unyet there's surely not much left it can be as you've replaced

and had many checked!

I'll not mention my business but I do specialise in Wheels and Porsche's and have seen this scenario many times when people

come to me to further check the wheels or tyres are not out of true or anything else I can assist with.

Your Symptoms of a shaking steering wheel at 60mph shout an imbalance at this common frequency & Speed 60 - 70 mph on most cars

This can be wheel or tyre out of round and / or run out both which can be checked by eye on a balancer, or Discs out of true, caliper pistons sticking or pads stuck, worn wheel bearings, worn top mounts, broken springs and worn shock absorbers etc...

But you've also mentioned the brake pedal is shuddering also at 60mph?

Does this and the steering wheel vibrations disappear at 80 or 90+mph?

Does the brake pedal judder when you brake from 80mph ? or even 50 or 60mph?

I use a Special 5x130 PCD 5 fingered Hub for wheel balancing as this holds the wheel exactly by holding the

5 bolt holes dead central, which is often more accurate than a metal tapered cone which is the common method of fixing

a wheel to a balancer.

I have had many scenerio's where this device comes up trumps, although I suspect yours is not this simple!

Have you had the Geometry checked also?

Roger

TWR

 

[964RS]

I've had the same issue on race cars. Just to rule out some things cheap and simple:

Tighten up all the lug nuts to the correct torque.

Check the balance of the rims (and remove any 'marbles').

Check that the mating faces of the rims and the disks are clean/flat.

Check the track rod ends (could be worn/loose).

Try without spacers/adapters (if fitted).

Trial with another set of rims/tyres to rule them out.

Check that the caliper bolts are torqued up.

CheeRS!

 

[924Srr27l]

I had similar problems after new disks and pads and rectification of the lifting plates - and, yes, the bolts can be difficult to remove. Consensus on the different forums was that the bushes on the wishbones needed replacement but the mechanic who did the work felt the problem was disk distortion, even though they were new.

I spoke with Marcus Bailey of Diskskimmers and arranged for him to skim the disks. Completely cured the problem! Some decry skimming but it worked for me. If you are sure there is no play in the suspension it might be worth a phone call to Marcus 07824 903006 .

http://www.discskimmers.com/

Yes this could be the solution ? I've also heard about "run out" of the whole assembly even with new components.

It has potential to cure this problem if everything else has been checked and / or replaced, that the lathe that spins the hub and then cuts both sides of the disc surfaces will be true with the spinning disc and may eradicate any pad knock back and the vibrations.

Roger

 

[924Srr27l]

I'm sniffing a thread hijack and/or commercial interest here .. []

Watch it !

cheers, Maurice

No, No Hijack or commercial interest at all...... Just a Porsche owner, enthusiast and an attempt to help all free

of charge!

Roger.

 

[924Srr27l]

Ok, so Ive had the calipers checked and 3 of them were suffering for plate lift and theyve been sorted. Ive also had the discs checked for run out and everything is within the Porsche recommended levels. However, I've still got the issue of steering wheel and pedal shudder at 60mph and coming to a rolling stop with light breaking. Very little wheel shudder on the rolling stop. Everything else, steering etc has been checked and weve drawn a blank. Any further ideas worth investigating?

I have had the wheel balancing checked but Ill get it checked again at the weekend, just in case. Ive also had the wishbone bushes replaced at the beginning of the year and new anti-roll bar bushes.

Hi,

I'm assuming the said plate lift calipers were removed the old plates taken out, the corrosion dealt with and new ones fitted?

And most importantly even if they were only taken out the corrosion cleaned off and they were put back, did you fit new pads?

Only if not, these will of worn irregular from when they were restricted from the jammed plates, so even now the plates

have been sorted? the pad surfaces will now not be flat to the disc from their previous slanted wear... ?

It's a similar scenario when some people get Geometry done because a tyre has worn on the inner or outer edge, but sometimes they do not replace the tyre! and a reset of the geometry on an irregular tyre surface is a false economy.

Going back to your brake pads, if you didn't change them...as you lightly applied brake pressure only a part section will be

touching and compressing to the disc first and and it could be this which is vibrating as part of the pad pivots on the high points and knocks itself on the disc? Harder applications could be fine.

I've got a similar Shimmy and have been through all of this...

R

 

[Mike M]

From all your comments, I can only assume my mechanic who is an indy, Porsche Specialist has undertaken all the checks mentioned. Ive had the wheels rebalanced last night and as expected, that has made no difference at all. He stripped the callipers, cleaned and reassembled. Again Id assume if he saw any un even pad wear hed of changed them.

Skimming pads comes up a lot, also a guaranteed source of my problems according to the guys who balanced my wheels. However, if the run out has been checked on the discs and they are in limits, how would skimming help?, the results are showing they are running true.

For clarity the steering wheel vibrates quite a lot between around 70 and 58mph, even under firm breaking pressures. They also appear to be slightly worse when theres a bit of heat in the breaks.

Note, Ive had this issue on and off for 10 years or so but it has got worse more recently, Im assuming its from upgraded suspension, new wishbone bushes etc, which may of all helped reduce its effect when they were all well worn. During this time, discs and pads have been changed but the problem has never been cured.

I may look at trying substitute wheels at some point to see if that makes any diffrence.

Ido appreciate all the comments guys!

 

[924Srr27l]

From all your comments, I can only assume my mechanic who is an indy, Porsche Specialist has undertaken all the checks mentioned. Ive had the wheels rebalanced last night and as expected, that has made no difference at all. He stripped the callipers, cleaned and reassembled. Again Id assume if he saw any un even pad wear hed of changed them.

Skimming pads comes up a lot, also a guaranteed source of my problems according to the guys who balanced my wheels. However, if the run out has been checked on the discs and they are in limits, how would skimming help?, the results are showing they are running true.

For clarity the steering wheel vibrates quite a lot between around 70 and 58mph, even under firm breaking pressures. They also appear to be slightly worse when theres a bit of heat in the breaks.

Note, Ive had this issue on and off for 10 years or so but it has got worse more recently, Im assuming its from upgraded suspension, new wishbone bushes etc, which may of all helped reduce its effect when they were all well worn. During this time, discs and pads have been changed but the problem has never been cured.

I may look at trying substitute wheels at some point to see if that makes any diffrence.

Ido appreciate all the comments guys!

It's a tricky one when some things your assuming of, with as much respect as poss for the Indie,

Blimey this issue has been evident for 10 years !!! ?

I couldn' t and don't know how you have and can live with something for so long ....

Skiming pads? do you mean discs...... The discs may be fine, but the clamping device (Caliper) and the mating surfaces (Pads)

may not be totally parallel to the disc surface.....

You say the vibrations are a lot from 70 to 88mph ? (not 58)

Yes issues often show up more prominently when you replace the suspension for new and tighter components...

What does your "Upgraded Suspension" consist of, New shocks and springs? Top mounts ? track rods ends etc..

And lastly you said " also a guaranteed source of my problems according to the guys who balanced my wheels"

does this mean the wheels are slightly out but they've added loads of weight to counter balance them ? or ?

What size wheels do you have, Genuine or copies ? and how old are the tyres and what make?

I had vibrations 5 weeks ago, and I've sorted them already I just can't be doing with them as it really spoils the driving

and that's what Porsche's are all about...

Roger

 

[Dekker]

I had a similar problem on my 964 which was the drop links, the connection between the roll bar and hub. I don't know anything about 993 but guess the front suspension is similar. If the drop links are OK what about the roll bar bushes.

As for the wishbone bushes, I replaced mine against the advice of the indy who swore they were fine and he saw as we were doing them how delaminated they'd become.

 

[Mike M]

Guys, I found I couldnt answer most of the questions raised as I had to make assumptions of what my Indy had or had not done. I took the car into a different indy Wednesday for a fresh set of eyes. Dropped of Wednesday night, By Thursday 11am he confirmed the disks were warped to hell. He fitten new discs and pads all around today and called to say shes running, breaking, cruising and rolling like a dream, no shakes shudders or anything so total result. Some time a fresh set of eyes is all that is needed!

Thanks for everyones input.

 

[924Srr27l]

Great, vibes can be so annoying..........

Glad you found the Culpit!