Warped discs ? This might help someone with similar problems.
My J hooks are causing problems after 3k miles just like the EBC discs before them and the originals before them.
Had a chat with a guy from Brembo today, I am in the motorcycle trade and have a few contacts and Brembo discs are the same principle on Bikes and cars.
I explained how I had a warped set of discs on the S3 and it was the 3rd set in 25k miles.
Anyway, the point was he said he had never seen a set of warped discs although it was possible in theory for them to warp if they were not correctly stress relieved during manufacture but as its an automated process its unlikely.
What happens apparently is a very small amount of pad material will transfer across to the disc because the disc and pad have a different drag coefficient. it will deposit evenly between the differing surfaces however once the disc has an even coating of the pad material the surfaces are no longer differing, and the material can transfer either way, so you get an uneven surface. This is not visible to the eye and is microns but its enough to alter the breaking friction on the uneven deposits on the disc. This will get worse with heat giving the impression the disc has warped however it is really just like putting a drop of oil on the disc, the pads grip better to the deposits on the disc than to the area with less deposits giving an on off on effect as the disc rotates. The only real cure for this is to get the discs skimmed back to an even surface so the friction is the same all round. This enhances the myth that the discs were warped as skimming them cures the problem.
The problem is pads that work well when cold around town will not be ideal for high performance stopping and pads that work well under great heat will not work well cold round town. The pad material is a compromise not helped by modern carbon ceramic and other high-tech compounds that work well but only under their intended driving conditions.
So you drive around and “commute” for 5k miles with no problem then one day thrash the b*&^^ck out of the thing on the motorway or even a track day and you put a deposit on the disc and your on the slippery slope.
Bottom line is my J hooks look like they are shot simply because its cheaper to fit new than mess about getting them re ground i think.
All this can be avoided i am told with proper bedding in of the pads and discs however there are so many experts out there who have completely different ideas about bedding in it still seems like a guess to me.
I was told to run them in carefully, no sudden braking or prolonged hanging on the brakes. Now i am told to bed them in with half a dozen 60mph to 5mph breaking sessions getting progressively harder and allowing the discs to cool between each session.
What i dont understand is why the brakes an my Transit have done 110k miles on original discs and pads, have to pull up twice the weight from speeds of 5mph to 90mph just like the car and yet the car is a load of hassle ....and why the factory pads and discs did the first 50k miles on the car with no problem yet the Vagbrems and the EBC are trouble ?
Just waiting now for a quote or 3 for skimming to see the next move
I am thinking that in the past i have changed discs and pads together, now i am thinking run the discs in with the already settled pads.
Breaks my heart to junk the J hooks so soon as they haven't even worn the paint off ...lol.
My J hooks are causing problems after 3k miles just like the EBC discs before them and the originals before them.
Had a chat with a guy from Brembo today, I am in the motorcycle trade and have a few contacts and Brembo discs are the same principle on Bikes and cars.
I explained how I had a warped set of discs on the S3 and it was the 3rd set in 25k miles.
Anyway, the point was he said he had never seen a set of warped discs although it was possible in theory for them to warp if they were not correctly stress relieved during manufacture but as its an automated process its unlikely.
What happens apparently is a very small amount of pad material will transfer across to the disc because the disc and pad have a different drag coefficient. it will deposit evenly between the differing surfaces however once the disc has an even coating of the pad material the surfaces are no longer differing, and the material can transfer either way, so you get an uneven surface. This is not visible to the eye and is microns but its enough to alter the breaking friction on the uneven deposits on the disc. This will get worse with heat giving the impression the disc has warped however it is really just like putting a drop of oil on the disc, the pads grip better to the deposits on the disc than to the area with less deposits giving an on off on effect as the disc rotates. The only real cure for this is to get the discs skimmed back to an even surface so the friction is the same all round. This enhances the myth that the discs were warped as skimming them cures the problem.
The problem is pads that work well when cold around town will not be ideal for high performance stopping and pads that work well under great heat will not work well cold round town. The pad material is a compromise not helped by modern carbon ceramic and other high-tech compounds that work well but only under their intended driving conditions.
So you drive around and “commute” for 5k miles with no problem then one day thrash the b*&^^ck out of the thing on the motorway or even a track day and you put a deposit on the disc and your on the slippery slope.
Bottom line is my J hooks look like they are shot simply because its cheaper to fit new than mess about getting them re ground i think.
All this can be avoided i am told with proper bedding in of the pads and discs however there are so many experts out there who have completely different ideas about bedding in it still seems like a guess to me.
I was told to run them in carefully, no sudden braking or prolonged hanging on the brakes. Now i am told to bed them in with half a dozen 60mph to 5mph breaking sessions getting progressively harder and allowing the discs to cool between each session.
What i dont understand is why the brakes an my Transit have done 110k miles on original discs and pads, have to pull up twice the weight from speeds of 5mph to 90mph just like the car and yet the car is a load of hassle ....and why the factory pads and discs did the first 50k miles on the car with no problem yet the Vagbrems and the EBC are trouble ?
Just waiting now for a quote or 3 for skimming to see the next move
I am thinking that in the past i have changed discs and pads together, now i am thinking run the discs in with the already settled pads.
Breaks my heart to junk the J hooks so soon as they haven't even worn the paint off ...lol.
