Car help – discs warped, allegedly caused by new pads on old discs?

Dear hive mind…

I have an ’06 E87 BMW 1 series. Recently there has been some vibration on braking, particularly light braking, for example slowing from 50mph for a 30mph limit.

I have taken it into a garage (that I trust) and they tell me that the discs have warped which is causing the vibration. They claim that this has been caused by fitting new disc brake pads without changing the discs. Is it true that new pads on old discs cause can cause the old discs to warp? If true, why is this the case?

Sounds rubbish to me – disks last much longer than pads and I have never had to replace disks when replacing pads.

New flat pads on old uneven discs could cause hot spots when braking, which may have caused the discs to warp. Whatever the cause, I would get new pads and discs fitted at the same time 😉

Pads take time to wear in to fit the disc, so if you put new pads on and brake hard you can cause hot spots which soften the disc, which can cause warping.

Has no end of problems with this and Brembo GT discs…

Whatever the cause, I would get new pads and discs fitted at the same time

And let them bed in before any hard braking….

johndoh – that’s what I thought, discs surely far outlast pads.

By the way in case it makes a difference the car is 90,000 miles. The pads were changed about 15,000 miles ago and have lots of life left. I am not sure whether the discs have ever been changed.

Ok. I changed the pads before the discs on my last snotter. I then replaced the discs later. Que lots of wobble/vibration/pulsating when braking to follow. I was told by loads of people that the discs were warped. I did abit of research- discs are very burly things. Unless you are ragging the life out of the car with heavy braking then sitting at lights on your brake pedal I can’t see how the discs will have warped.

What happened to me- the pads had a different layer/surface on. I reconditioned/re-bedded the pads to the discs by going to my local industrial estate- accelerate to 60 then brake hard to circa 5pm (NOT stopping)- straight off the brakes and back up again. And repeat.

It worked. It took off a top layer.

Try this http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

Look under prevention

fivespot and footflaps – thanks.

Whatever the cause, I would get new pads and discs fitted at the same time

Yes, that is what the garage recommends and what I will do. Is it worth getting BMW original parts discs and pads?

And let them bed in before any hard braking….

How do I do this?

Do a search, you can’t warp discs on the road, you picked up a car disc? They’re seriously burly things.

It’s deposition of material on the surface in a uneven manner, causes uneven braking force and ‘pulses’ through the pedals.

Go out at night and do some big long stops to even up all the surfaces. Save yourself some money.

We’ve done this on here recently too.

Look at Stratstone Hull on ebay as they do genuine discs/pads for about the same price as the decent kit from ECP.

Just rebed the buggers.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

“just approach it with a balanced view as this article is responsible for the internet myth that there is no such thing as warped discs and than pad deposits are always the cause of the problem which is complete BS”

If you’re anywhere nearby then get yourself over to these guys. Worked absolute wonders on my brake problems and never had an issue since.

Disc Skimmers[/url]

someone should tell the roads in the alps its not possible to warp disks.

dial gauge and a stand on my front disks are a trip says otherwise. non vented solid disks on the front of a little van.

but ill be very susprised if new pads on old disks warped your disks.

it most likely is deposits.

roads in the alps

So that counts as heavy use then? 😉 Thing is when you are using your brakes alot on a run you can’t sit on them at junctions etc as the heat transfer will cause a hotspot.

So, I think that step one is to go to the garage and let them “demonstrate” that the discs are warped.

If the discs are visibly warped – the choice is genuine or after market discs and pads.

If the disc aren’t visibly warped – try to burn off the deposits through breaking hard. If that doesn’t work I’ll try getting he discs skimmed.

EDIT: I recognise that several posts above claim that discs can’t warp. I’m going to reserve judgement until I see what the garage shows me.

Do a search, you can’t warp discs on the road, you picked up a car disc? They’re seriously burly things.

Yes you can, I’ve warped a couple of sets of Brembo GT discs on the road and they’re massive.

I had one set skimmed which didn’t work that long and ended up replacing them. Must have gone through 3 sets of discs and pads in maybe 6 years. I did used to drive like a tit though….

May be bad batch of disc do you no the makes of the disc.

May be bad batch of disc do you no the makes of the disc.

No sorry, no idea.

I’ve warped a couple of sets of Brembo GT discs on the road

Whats your driving style?

Automatic?

Or- Do you gear down/blip the engine towards bends/engine braking on the way to a stop? Or do you just use the brakes to scrub and stop?

Really doesn’t make sense.

Maybe the driving gods can warp discs, do you really think this is what’s happened to the op?

This thread is useless without pictures TJ

Maybe the driving gods can warp discs, do you really think this is what’s happened to the op?

I’m the op and I can assure you that I’m not a driving god. That said it is a 130i and might have been driven very hard by previous owners.

I always replace disks with pads as a unit. Modern pads are much harder and so the discs wear a lot more than they used to.
Set of discs for my cars are £50 for the AudiA2 and £110 for the XC90 approx. For that kind of cost I am happy to swap them over every few years when the pads are shot. I have had warped/uneven discs in the past. Its more a fault in the casting than the fault of how you drive.

Brake discs don’t actually ‘warp’ – they’re made of cast iron.

Instead ‘warping’ is just a laymans term commonly used to describe what is normally either a variation in the disc thickness caused by a poorly set up (or other problems within) the braking system, disc corrosion or pitting due to infrequent use, or by friction pad material transferred unevenly to the surface of the disc, all of which cause a juddering feel to braking.

It may be possible to remove light, uneven deposits of friction pad material by performing 3-4 emergency stops from high speed in quick succession, but if the disc thickness is compromised then only skimming and properly setting up the system (including checking disc run out) will resolve the situation. Replacing discs and pads together may only temporarily resolve the situation, especially if there’s another problem with the set up of the braking system (e.g. disc ‘run out’ where the discs are not exactly aligned with the wheel and or brake pads, quickly causing uneven disc wear).

Hope that clarifies things.

Its more a fault in the casting than the fault of how you drive

disagree, in my case as I cured it by re-bedding in.

£110 for discs for a X90 is a bargain. How much is plus VAT+fitting those ontop?

As above, your discs are unevenly worn because you have not been using them heavily enough and patches of rust have formed, either radially or circumferentially. Mrs Gti’s car has had to have two new sets of discs because she drives like a pussy cat.

As advised, try a good hard braking session somewhere away from traffic before allowing the garage to condemn the discs.

We skim loads of warped discs, usually when they are heading toward the minimum thickness. If your vehicle is on the original discs after 90K miles I would check they aren’t too thin.
Euro Car Parts will be your best bet for a quality disc at a reasonable price.

Brake discs don’t actually ‘warp’ – they’re made of cast iron.

What a load of B”$*^cks 🙄

Brake discs don’t actually ‘warp’ – they’re made of cast iron.

What a load of B”$*^cks

Care to prove otherwise Mr Troll?

OP when doing the re-bedding in- dont jab the brake, don’t sit even for a second on the brake pedal at a stop and dont slow to a stop- roll then accelerate again, keep it smooth. It’ll take a few go’s of this.

If the discs are very close to min I’d just change them though. If plenty of life- keep them. I hate it when people ditch kit that has got alot of life in it purely due to cosmetic reasons or because someone tells them that they should.

Recently on pistonheads a Merc garage changed a 3-day old tyre as it had a screw in it, rather than repair. Mad.

are you on original discs at 90k?

are you on original discs at 90k?

Don’t know but possibly. I bought the car at 75k and the front pads, but not discs, were changed then.

What a load of B”$*^cks

I’d love to know what you think they’re made of then! Cheese?

Given that they rust I’d say that they are made of cast iron. Wikipedia seems to agree.

I doubt you are on the original discs at 90k. If its got full BMW history, a main dealer worth their selling-potential would have changed his discs well before..no?

I’ve always changed discs and pads as a set due to there usually being over 50% of the disc worn away when the pads are done. After having survived a disc cracking up on a steep downhill I just don’t take the risk when it comes to a critical safety feature.

Discs do warp, especially as they wear down as the thinner material doesn’t cope with heat build-up as well as new discs. I’ve managed a 1mm run-out on a pair on an old Citroen AX, that thing used to warp discs for fun! Caused by the 3-stud wheels according to my mechanic friend.

I’d love to know what you think they’re made of then! Cheese?
Given that they rust I’d say that they are made of cast iron. Wikipedia seems to agree.

My comment was based on the fact that the troll seemed to think because the discs were made of cast iron, they wouldn’t warp 🙄

And yes cast iron does warp, even 4″ thick cast iron cylinder heads warp.

warp
w??p/Submit
verb
1.
make or become bent or twisted out of shape, typically as a result of the effects of heat or damp.
“moisture had warped the box”
synonyms: buckle, twist, bend, distort, deform, misshape, malform, curve, make/become crooked/curved, flex, bow, arch, contort, gnarl, kink, wrinkle
“timber which is too dry will warp and lose its strength”
antonyms: straighten, keep shape
make abnormal or strange; distort.
“your judgement has been warped by your obvious dislike of him”
synonyms: corrupt, twist, pervert, deprave, bend, skew
“a fanatic who warped the mind of her only child”
2.
(with reference to a ship) move or be moved along by hauling on a rope attached to a stationary object ashore.
“crew and passengers helped warp the vessels through the shallow section”
3.
(in weaving) arrange (yarn) so as to form the warp of a piece of cloth.
“cotton string will be warped on the loom in the rug-weaving process”
4.
cover (land) with a deposit of alluvial soil by natural or artificial flooding.
“the main canal may be cut so as to warp the lands on each side of it”
noun
noun: warp; plural noun: warps
1.
a twist or distortion in the shape of something.

My comment was based on the fact that the troll seemed to think because the discs were made of cast iron, they wouldn’t warp

And yes cast iron does warp, even 4″ thick cast iron cylinder heads warp.

Thanks for your comment fivespot, no offence meant to you, you tried hard, but I’d rather take the advice of someone who actually knows what they’re talking about:

Someone who actually knows what they’re talking about

if we are playing like that – try again with some peer reviewed literature.

ps did you just copy the previous link from my previous post about that link 😉