How to bed in new brake discs?
Discussion
There are two sides to bedding in: discs and pads. Most of the instructions about bedding in relate to pads, the procedure depends on the type of pads but typically involving successively harder applications up to some limit. Bedding new discs into existing used pads is a separate issue and I think the usual advice is just to avoid hard applications of the brakes for the first few hundred miles while the pads impregnate the surface, and don't leave the handbrake on with the brakes hot (this will cause local impregnation which changes the grip/wear properties of the discs and lead to brake judder).
Some disc manufacturers actually recommend that when changing discs *and* pads, the discs are changed first and allowed to bed in to the old pads before fitting the new pads, because this means that the discs are ready for the heavy braking required to bed the new pads in. Personally I tend to change them together because I'm lazy!
>> Edited by GreenV8S on Saturday 11th March 14:29
Some disc manufacturers actually recommend that when changing discs *and* pads, the discs are changed first and allowed to bed in to the old pads before fitting the new pads, because this means that the discs are ready for the heavy braking required to bed the new pads in. Personally I tend to change them together because I'm lazy!
>> Edited by GreenV8S on Saturday 11th March 14:29
Ajit
Bedding in the pads is a bit of a misnomer. What you are actually doing is conditioning the surface of the disc with the brake pad material. Pagids advice is to stop you from leaving an eneven layer of pad deposit on the disc as this will lead to brake judder. I don't subscribe to the new discs/new pads theory either( because I'm too poor and too mean). If the pads have plenty of wear on them and are pretty evenly worn then stick em back on and follow the Pagid bedding in instructions with the new discs.
Steve
PS If you don't put the part worn RS29's back in then I'll have them off your hands for a reasonable sum.
>> Edited by paulburrell on Saturday 11th March 18:14
>> Edited by paulburrell on Saturday 11th March 18:14
Bedding in the pads is a bit of a misnomer. What you are actually doing is conditioning the surface of the disc with the brake pad material. Pagids advice is to stop you from leaving an eneven layer of pad deposit on the disc as this will lead to brake judder. I don't subscribe to the new discs/new pads theory either( because I'm too poor and too mean). If the pads have plenty of wear on them and are pretty evenly worn then stick em back on and follow the Pagid bedding in instructions with the new discs.
Steve
PS If you don't put the part worn RS29's back in then I'll have them off your hands for a reasonable sum.
>> Edited by paulburrell on Saturday 11th March 18:14
>> Edited by paulburrell on Saturday 11th March 18:14
Steve - sorry to be thick but I'm not sure if I understood the recommended procedure. Are we saying that bedding in pads requires successive harder applications of the brakes (eg 60 to 5mph, 80 to 5mph, 100 to 5mph)?
And bedding in discs only (with part worn pads) requires gentle braking for the first few hundred miles as per Peter's advice (GreenV8S)?
Or are we saying the procedure is the same in both cases (ie successive harder applications)?
I also have RS29s and am going through discs like no tomorrow, so am inclined to be poor and mean next time round and keep the part worn pads on.
And bedding in discs only (with part worn pads) requires gentle braking for the first few hundred miles as per Peter's advice (GreenV8S)?
Or are we saying the procedure is the same in both cases (ie successive harder applications)?
I also have RS29s and am going through discs like no tomorrow, so am inclined to be poor and mean next time round and keep the part worn pads on.
Ajit
I have RS19's on the front and they work really well and seem to be long lasting. Next time round I will try the 29's and see what difference it makes to my appalling style of driving.
Boy you were up early to get the bedding in done.
I Harris
Yes the procedure is the same whether the discs/pads are old/new or new/old if that makes sense.
As for trashing discs at a rate of knots, I can only advise that you stop buying the pre-cast OPC items and move on to some floating Alcons/Brembo's.
Regards
Steve
I have RS19's on the front and they work really well and seem to be long lasting. Next time round I will try the 29's and see what difference it makes to my appalling style of driving.
Boy you were up early to get the bedding in done.
I Harris
Yes the procedure is the same whether the discs/pads are old/new or new/old if that makes sense.
As for trashing discs at a rate of knots, I can only advise that you stop buying the pre-cast OPC items and move on to some floating Alcons/Brembo's.
Regards
Steve
Thought this might come in handy for you - Advice on bedding in pads from one of the bods at Lotus.
Nick Adams (Lotus developing engineer)
Hi Ross, Alastair and Dave recommend the following procedure for Bedding Elise Brakes in:
With new Pads and discs, or just new Pads fitted run the car around for 10/20 miles using the Brakes gently as normal to bed the two surfaces together. Once this has been done, check the surfaces of the discs and make sure here are no signs of any scoring or damage. Assuming all looks well take the car to an appropriate piece of quiet and straight, well sighted road and perform half a dozen medium pressure stops from 50 mph down to 20 mph to warm the Brakes up. Avoid more than a minute between each stop so that the temperatures do not get a chance to deteriorate too much. Once the Brakes are warm and the coast is clear, perform 2 or 3 hard stops from 70mph (where local laws allow!) to 20 mph, braking as hard as you can without locking up. Do not come to a halt between each stop, do them as fast as you can to get the Brakes really hot. On the third stop come to a halt and keeping your foot on the Brake press the Brake pedal down as hard as you can and hold it there for at least a couple of minutes, don't apply the handBrake. This hurts if you are doing it right! This will bed the pistons, shims and Pads together and will compress the pad material, giving a hard and repeatable pedal. Once the 2 minutes have passed, release the pedal and go for a short drive, using the Brakes as normal to let everything return to normal temperatures. The Brakes are now fully bedded in and ready for use in anger. Recompressing the Pads once every few thousand miles to the above procedure will help keep the pedal firm, especially if you don't normally use the Brakes hard.
Cheers, Nick
Nick Adams (Lotus developing engineer)
Hi Ross, Alastair and Dave recommend the following procedure for Bedding Elise Brakes in:
With new Pads and discs, or just new Pads fitted run the car around for 10/20 miles using the Brakes gently as normal to bed the two surfaces together. Once this has been done, check the surfaces of the discs and make sure here are no signs of any scoring or damage. Assuming all looks well take the car to an appropriate piece of quiet and straight, well sighted road and perform half a dozen medium pressure stops from 50 mph down to 20 mph to warm the Brakes up. Avoid more than a minute between each stop so that the temperatures do not get a chance to deteriorate too much. Once the Brakes are warm and the coast is clear, perform 2 or 3 hard stops from 70mph (where local laws allow!) to 20 mph, braking as hard as you can without locking up. Do not come to a halt between each stop, do them as fast as you can to get the Brakes really hot. On the third stop come to a halt and keeping your foot on the Brake press the Brake pedal down as hard as you can and hold it there for at least a couple of minutes, don't apply the handBrake. This hurts if you are doing it right! This will bed the pistons, shims and Pads together and will compress the pad material, giving a hard and repeatable pedal. Once the 2 minutes have passed, release the pedal and go for a short drive, using the Brakes as normal to let everything return to normal temperatures. The Brakes are now fully bedded in and ready for use in anger. Recompressing the Pads once every few thousand miles to the above procedure will help keep the pedal firm, especially if you don't normally use the Brakes hard.
Cheers, Nick
Davey S2 said:
Thought this might come in handy for you - Advice on bedding in pads from one of the bods at Lotus.
Nick Adams (Lotus developing engineer)
Hi Ross, Alastair and Dave recommend the following procedure for Bedding Elise Brakes in:
With new Pads and discs, or just new Pads fitted run the car around for 10/20 miles using the Brakes gently as normal to bed the two surfaces together. Once this has been done, check the surfaces of the discs and make sure here are no signs of any scoring or damage. Assuming all looks well take the car to an appropriate piece of quiet and straight, well sighted road and perform half a dozen medium pressure stops from 50 mph down to 20 mph to warm the Brakes up. Avoid more than a minute between each stop so that the temperatures do not get a chance to deteriorate too much. Once the Brakes are warm and the coast is clear, perform 2 or 3 hard stops from 70mph (where local laws allow!) to 20 mph, braking as hard as you can without locking up. Do not come to a halt between each stop, do them as fast as you can to get the Brakes really hot. On the third stop come to a halt and keeping your foot on the Brake press the Brake pedal down as hard as you can and hold it there for at least a couple of minutes, don't apply the handBrake. This hurts if you are doing it right! This will bed the pistons, shims and Pads together and will compress the pad material, giving a hard and repeatable pedal. Once the 2 minutes have passed, release the pedal and go for a short drive, using the Brakes as normal to let everything return to normal temperatures. The Brakes are now fully bedded in and ready for use in anger. Recompressing the Pads once every few thousand miles to the above procedure will help keep the pedal firm, especially if you don't normally use the Brakes hard.
Cheers, Nick
I'm not an engineer, but isn't this a good technique to warp your discs since the pads will extract heat much quicker out of the disc where the pad remains in contact with the disc?
The instructions will vary depending on the pads, but some of the pads I've used have had detailed instructions very different to those ones. In particular it seems common to advise *against* coming to a complete stop with the brakes applied during the bedding-in procedure as this causes uneven deposits on the disc. Some say get the pads so hot they start to fade, some don't. Really you need to follows the instructions for your particular pads.
gfreeman said:
Exactly the opposite of wot Pagid advise
(anorak on) By the way, if you clamp the brake pads to the disc, surely, with no air to cool the disc here, it would be a hotter spot not a colder spot wouldn't it?
Nope - the pad has higher thermal conductivity than still air surrounding the disc hence the pads ability to cool the disc quicker where it makes contact.
singh911 said:
I've just got back from bedding them in - using the same procedure as new pads. Seems to be fine.
BTW has anyone tried pagid rs19s - I wonder how they compare to the rs29s?
Cheers
Ajit.
Ajit I found there to be little difference with 19's and 29's, the only difference being the 29's are much harder on discs.. just my opinion...
>> Edited by Dave 321 on Sunday 12th March 23:34
Gassing Station | Porsche General | Top of Page | What's New | My Stuff