How to test warped discs?
Discussion
Dave Brand said:
Mars said:
You'd need to change to a very hard compound, one which abbraded the disc surface over a period of time. Such pads just don't exist outside of the racing arena, and I'm not even sure such a hard pad exists there.
You're confusing "hard" with "abrasive". But I got my quoting right.
-DeaDLocK- said:
I have it on good authority that it takes some serious braking to actually warp a brake disc; the kind of braking that most of us will never see this side of a few consecutive laps at a track day.
What is regarded as "warping" (brake judder) is 95% of the time actually uneven build-up of brake pad material on the surface of the disc due to incorrect bedding-in of the brakes or bad braking habits.
The cure is to even out the disc again, either by undergoing a re-bedding in procedure, or more reliably, a disc skim followed imemdiately by proper bedding in to prevent reoccurence.
This is, apparently, one of the biggest car myths. Most folks, and many mechanics, think actual metal warping is commonplace.
+1What is regarded as "warping" (brake judder) is 95% of the time actually uneven build-up of brake pad material on the surface of the disc due to incorrect bedding-in of the brakes or bad braking habits.
The cure is to even out the disc again, either by undergoing a re-bedding in procedure, or more reliably, a disc skim followed imemdiately by proper bedding in to prevent reoccurence.
This is, apparently, one of the biggest car myths. Most folks, and many mechanics, think actual metal warping is commonplace.
edo said:
-DeaDLocK- said:
I have it on good authority that it takes some serious braking to actually warp a brake disc; the kind of braking that most of us will never see this side of a few consecutive laps at a track day.
What is regarded as "warping" (brake judder) is 95% of the time actually uneven build-up of brake pad material on the surface of the disc due to incorrect bedding-in of the brakes or bad braking habits.
The cure is to even out the disc again, either by undergoing a re-bedding in procedure, or more reliably, a disc skim followed imemdiately by proper bedding in to prevent reoccurence.
This is, apparently, one of the biggest car myths. Most folks, and many mechanics, think actual metal warping is commonplace.
+1What is regarded as "warping" (brake judder) is 95% of the time actually uneven build-up of brake pad material on the surface of the disc due to incorrect bedding-in of the brakes or bad braking habits.
The cure is to even out the disc again, either by undergoing a re-bedding in procedure, or more reliably, a disc skim followed imemdiately by proper bedding in to prevent reoccurence.
This is, apparently, one of the biggest car myths. Most folks, and many mechanics, think actual metal warping is commonplace.
I guess there isn't a bodgeit way of testing if the disks aren't flat then?
eltax91 said:
fatboy b said:
-DeaDLocK- said:
I have it on good authority that it takes some serious braking to actually warp a brake disc; the kind of braking that most of us will never see this side of a few consecutive laps at a track day.
You've not driven 80's & 90's Fords, have you? 
My Octavia and the Mrs' A3 get through discs every 40k ish. Even the top quality ones. I treat them as a service itemBlue Meanie said:
Oooh, the wrong brigade are out today. The guy asked to know how to test for it. I gave him a solution to see if they are. I'm certainly not convinced by the whole 'warping is a myth' brigade, and not do I think that it is a pad issue. I've changed pads before, and still had the wobble. Warping IS an issue, and no-one is arguing about how it happens.
Simply changing the pads won't remove the uneven build up of pad material from the disc though will it? Which is what is meant by the pads being to blame.I've experienced juddery brakes previously after a trackday with DS2500 pads. Cleared it up by re-bedding the pads.
Found this website very usefull:
http://www.stoptech.com/tech_info/wp_warped_braked...
zx10ben said:
-DeaDLocK- said:
I have it on good authority that it takes some serious braking to actually warp a brake disc; the kind of braking that most of us will never see this side of a few consecutive laps at a track day.
I have it on my authority that two good laps of the Nurburgring will do the job!I've 'warped' brake discs on my current cars, on both occasions at track days. First set were crap from EBC that warped within a few laps of hard use. I had no such problems with Brembo discs. The second occasion was on an 80s Ford with repeated stops from high speed.
Although there is technically a difference between warped discs and uneven pad material buildup on the discs, there is no difference to the owner as the symptoms are the same. I've also on a few occasions tried to get warped discs skimmed by a machine shop, but have often found the hassle and cost involved mean its better just to buy new discs. I've been quoted £30+VAT per disc for skimming, then have the hassle of removing them from the car, taking them to a machine shop, picking them up again and refitting them, at which point they might only have 50% life remaining at best.
Although there is technically a difference between warped discs and uneven pad material buildup on the discs, there is no difference to the owner as the symptoms are the same. I've also on a few occasions tried to get warped discs skimmed by a machine shop, but have often found the hassle and cost involved mean its better just to buy new discs. I've been quoted £30+VAT per disc for skimming, then have the hassle of removing them from the car, taking them to a machine shop, picking them up again and refitting them, at which point they might only have 50% life remaining at best.
Olivera said:
I've 'warped' brake discs on my current cars, on both occasions at track days. First set were crap from EBC that warped within a few laps of hard use. I had no such problems with Brembo discs. The second occasion was on an 80s Ford with repeated stops from high speed.
Although there is technically a difference between warped discs and uneven pad material buildup on the discs, there is no difference to the owner as the symptoms are the same. I've also on a few occasions tried to get warped discs skimmed by a machine shop, but have often found the hassle and cost involved mean its better just to buy new discs. I've been quoted £30+VAT per disc for skimming, then have the hassle of removing them from the car, taking them to a machine shop, picking them up again and refitting them, at which point they might only have 50% life remaining at best.
I disagree. At least if its uneven pad build-up it can be remedied faily easy by the owner without doing anything but a few hard stops.Although there is technically a difference between warped discs and uneven pad material buildup on the discs, there is no difference to the owner as the symptoms are the same. I've also on a few occasions tried to get warped discs skimmed by a machine shop, but have often found the hassle and cost involved mean its better just to buy new discs. I've been quoted £30+VAT per disc for skimming, then have the hassle of removing them from the car, taking them to a machine shop, picking them up again and refitting them, at which point they might only have 50% life remaining at best.
I see your point that it feels just as bad either way though.
Edited by John D. on Thursday 6th January 22:08
John D. said:
Good link for the unbelievers to investigate!"In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures."
Gassing Station | General Gassing | Top of Page | What's New | My Stuff