Juddering Brakes

[944 LIL]

When I brake LIL judders - the faster the speed the more violent the juddering. This was mentioned when I bought the car. I've had the disks changed - no change. Any ideas / common problems / diagnosis suggestions.

 

[SteveSJS]

Talk to Jon Mitchell garages Christchurch - he can use an on-car lathe to skim the disks which will either vastly reduce or cure the problem - Did mine!! (UIL)

 

[Fen]

Oli (zcacogp) had a thread about it maybe 2 months ago that would be worth a read.

 

[Black_JPN]

Colin, take it into GT One in Chertsey, they'll skim the discs (I think on then car) and you'll be sorted I reckon.

 

[Indi9xx]

If the car judders under braking there is a chance that its not the fault of the brakes, it could be the suspension bushes. If for example the caster mounts are becomming soft with age, as you brake they will deflect, rebound and cycle between these states and cause a judder. Sometimes they can also cause the brakes to pull to one side which can seem like the brakes are out of balance. There is also a chance that the brake disks are not mounted onto a 100% true surface. a minute amount of debris between the brake disk and hub will cause judder under braking. As steveS said, we have an on the car brake disk lathe setup, which can be used to true up warped disks, but often we find that there is another cause of brake judder, which often means that lathing the disk is treating the symptom not the cause. So the lathe is often for a last resort or for other brake problems (such as rusted, pitten, groved but healthy disks).

 

[RC18B 911 turbo]

Could it be that they were not bedded in properly when they were put on to the car don't know if that would cause juddering though.

 

[zcacogp]

ORIGINAL: Fen Oli (zcacogp) had a thread about it maybe 2 months ago that would be worth a read.

Fen, thanks for remembering. Yes, I had a similar sounding problem, the thread about it is here: http://www.porscheclubgbforum.com/tm.asp?m=396508&mpage=1&key=&#396508 Mine eventually ended up being the brake disks not sitting straight on the hubs. Taking them off, throughly cleaning the backs of them (and the fronts of the hubs), re-assembling with a torque wrench to do the wheel nuts up to the correct tightness (130-wotsits) and doing them in up in a correct order (13524 for instance) solved it for me. I also found that over-tightening the counter-sunk retaining screw that holds the disks on didn't help at all - it got the disk squiff from the outset, which caused a number of problems. I found I had much better results when this screw (or screws - there are two per wheel) was only done up little more than finger-tight. BUT I bow to the infinitely greater wisdom of Jon Mitchell (indi9xx) - if he says that there are loads of other things that can cause the same symptoms then he is right ... Oli.

 

[jackregan]

It might be worth checking the run out of the discs - that might show a problem without really spending anything[]

 

[zcacogp]

Checking the run-out will tell you whether the problem is disk-related, yes. But don't assume that run-out means warped disks. (A mis-aligned disk will show run-out on both the front and back face - although measuring back face run-out is very difficult 'cos of space issues for the DTI gauge.) I bought a DTI gauge from eBay for about £20 delivered. Not the best made piece of equipment in my workshop, but it will suffice for occasional jobs. (Although I managed 33 years without needing one, so am not sure how much use it will get in the future! [] ) Oli. ETA: Actually Colin (OP), I notice you are in Camberley. If you wanted to borrow my aforementioned high-qualitym precision-engineered DTI then you'd be most welcome. I'm in Bow. Other side of town. Should you ever venture to these parts. Or drop by one Saturday for a cuppa and a few hours of tinkering. Let me know.

 

[944 LIL]

Thanks to everyone who's responded - apologies I've been away for a few days and missed the updates. Oli - I'd be delighted to come up to town for a natter - is Bow home? Are you around over Christmas / New Year or would it suit you better to wait til January? I'd hoped to service the car this weekend but my mate /mechanic has dreadful man flu and has cried off - I'd like to do the service before I go any any major (or even minor) adventures.

 

[zcacogp]

Colin, Yes, Bow is home ... Time before Christmas is in short supply, and I'd suggest afterwards. Saturday 3rd or Sunday 4th could be possibilities. In fact, a sevrice on my S2 will be due about then too, so if you wanted to do two at once that would be a possibility as well as a gander at the brakes. My reservation is the weather - I don't have a garage, and any tinkering is done on the street. It's a quiet street so that isn't a problem, but bring your thermals! Oli.

 

[944 LIL]

Oli I hope to have service done by then Would still be good to get your thoughts on brakes and other creaks and groans I get from LIL. I'm beginning to chill about them but would like a view.... Drop me an email with your details and we can hook up. colin.dougan@bt.com

 

[zcacogp]

Colin, OK ... more than happy to spend a few hours tracing a few creaks and groans! We can drink some tea and generally put the world to rights (in a 944-centric way, that is!) PM sent. (Actually, that is a complete lie. PM will be sent once I have written this!) Oli.

 

[paulf968]

Also, check for plate lift on the calipers, which then traps the pads, which can then cause judder due to uneven pad despositions on the discs. Had a severe bout of this on my racecar which was compeletly cured by refurbing the calipers AND ALSO do what Oli said on assembly ie clean all surfaces and not too tight CSK screws paul f