Warped Discs?

LSPIII

LSPIII

LSPIII

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OK, so I'm pretty sure it will be warped discs, but thought I'd just check if some more-knowledgeable-types would agree.

Normal braking is fine. Heavy braking is fine up until about 60/70. Heavy braking from 120 feels downright dangerous. There's quite a vibration above the 60/70 mark that gets worse with speed. I assume this is going to be warped discs as opposed to pad knock-off (whatever that is) or any other pad-related issue?

It'll be infuriating seeing as they were only put on last June :(

Cheers
 
No such thing as warped discs. It's simply uneven brake pad deposits on the disc - probably from periods of heavy braking, followed by sitting with your foot on the brake.

Is your S3 (I'm assuming from your sig) a DSC one, so you'll be sitting on the brakes quite a lot at junctions etc?

Having the discs skimmed would alleviate the problem, then it's a case of prevention by not sitting with hot pads on hot discs at just one place, even if you sit a few feet back from the junction and just creep forward to rotate the discs while you're waiting (or, use handbrake instead of sitting on the foot brake)
 
possibly warped, but do your front discs look like the pads have left any material on there at all?

ill be working on an a3 tonight that has symptoms of warped discs but when i had a look its due to burnt pad material on the disc
 
I've got this currently on my Honda, I'm simply going to replace the disks as they were only cheap and nasty anyway. So I'm not buying quite so cheap-and-nasty disks in the future :D

Dunno how it happened, I never hold it on the footbrake, ever. Oh well.

Matt82 said:
ill be working on an a3 tonight that has symptoms of warped discs but when i had a look its due to burnt pad material on the disc
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That's what "warped discs" generally means, like Confused said. The disk actually being bent/warped is mostly a myth I thought.
 
the owner has said they get modulation through the pedal when they brake etc. the car hasnt been used for a while and the disc surface did look messy so once the other work is done i think it needs a good thrash to clean those discs up and all will be well with the world again
 
how ironic! my car has just been services and it turns out that i need pads and discs all round. The fronts need changing as apparently they are warped and one of the rears has a crack in the disc.

I also get modulation through the pedal when breaking.
 
Warped disc's aren't exactly a myth. Mine were warped on my 350z by quite a bit and enough to cause juddering when braking from speed. It couldn't be felt braking from anything under 40mph but over that was quite a violent judder through the car and steering wheel.

Jack the car up and turn the wheel by hand. Look at the pad near the disc. I could see the disc on mine moving in and out by what looked like 0.5 - 1mm.

It may be worth having a go at 'scrubbing' the discs with a some hard braking. If it was just pad deposits which quite often it can be this would clean the disc surfaces up.
Find a clear road, do a few stops of 4 seconds at 50% max brake pressure, starting from 30mph to gradually build up heat, and finishing with 3 to four 70mph stops. Stop on a level area and have a quick look (don't put the handbrake on) - the discs should be blue if you've done it right. Don't worry about the smoke!. Drive a few miles gently to let things cool down.

That should be enough to get rid of the surface deposits if there are any.

You should then also check the mating surface on the back of the disc but obviously this involves removal. If at some point the car had new discs the hub may have not be cleaned properly or something could stop the disc from sitting true.

If they are definately warped you can get them skimmed assuming they aren't too bad or just get them replaced. TBH when dealing with brakes I would never cut corners and recommend you get new discs.
 
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Confused said:
No such thing as warped discs. It's simply uneven brake pad deposits on the disc - probably from periods of heavy braking, followed by sitting with your foot on the brake.

Is your S3 (I'm assuming from your sig) a DSC one, so you'll be sitting on the brakes quite a lot at junctions etc?

Having the discs skimmed would alleviate the problem, then it's a case of prevention by not sitting with hot pads on hot discs at just one place, even if you sit a few feet back from the junction and just creep forward to rotate the discs while you're waiting (or, use handbrake instead of sitting on the foot brake)
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I do try and keep my feet off the brakes after a blat where possible, or indeed just find a quiet road to trundle down at 20/30 for 5 minutes as a cooling procedure.

I'm unsure as to the quality of the discs which is of moderate concern. I'm sure they are standard OE discs from a Leon Cupra R. The problem is the vibration is only getting worse with age.

Where can you get discs skimmed and how much (roughly) should I be looking at? I'll try to get a decent shot of the discs if I can.
 
G1dd3N said:
Could be wheel balance as well couldnt it? Worth getting that checked too.
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I'm having two tyres done in the next week or so where the balance will be checked but I'd imagine that would be noticeable under normal driving and not just hard braking?

The discs are certainly not pretty. Pics coming soon.

Edit: Would it be alright to have the discs skimmed with the current pads or would it be sensible to replace the pads at the same time? I'm still trying to work out how much pad I have left too!
 
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I would say 99% it is deposit buildup.

Unless you do track days or use your brakes like an old granny then disks don't tend to warp these days.

If you can you could try some heavy braking from 70-30 (giving 5 mins between each one) - this tends to rid buildup and also stops any squeeky pads. Do this on a private road though!!!! (Also good to do on new pads as well).
 
If the disc itself looks marked or a funny colour in places it could very well be brake pad deposits and a good "scrubbing session" may be all that it needs. Like i mentioned in an ealier post ^ ^


Wheel balance is felt usually at speed but your right it is usually felt under all driving and not just braking.
 
I'm leaning towards the point that it's probably deposits on the disk. Aside from the fact that the disks are quite scored, there are black perpendicular lines and patches around the disk, I'm guessing (like the noob that I am) that these are the aforementioned deposits? I'm just waiting for my colleague to get back so I can get a wheel off to get a decent look/pics.

If the disk has a slightly darker middle ring than the outer and inner parts of the disk is this also likely to be a problem or just a result of the deposits?

It doesn't look like they can cause such a big vibration but maybe they can!
 
It is certainly possible to notice deposit buildup at high speed only.

You would be wise to check your wheel alignment as well as having a balance check (all round) when you have new tyres anyway.
 
boxman2000 said:
It is certainly possible to notice deposit buildup at high speed only.

You would be wise to check your wheel alignment as well as having a balance check (all round) when you have new tyres anyway.
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I had the car laser aligned last year already. I'll be getting all 4 wheels balanced when the new rears go on though certainly.
 
boxman2000 said:
Have you mounted a kerb or hit a pothole since? ;)
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Seen the state of the roads? Of course I have! :p

That said the alignment last year was the first time it had been done since the car was built and they didn't need to make that many adjustments. In fact the adjustments were slight enough that they didn't even charge me for them :)
 
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