Warped disc?

[Andy J]

Took my bike out the other day for a quick spin. All was well for about 10-15 miles then i noticed a pulsing through the lever when braking, the dreaded warped disc! Ive only owned the bike since January and ive only done about 100 miles on it. Its a 2010 with ABS etc and has 24k miles on it. Front pads were replaced 3k miles ago by Cannon BMW in Braintree. The bike had a full BMW history so has been well looked after.

Are these bikes prone to warping discs a bit like the old Yamaha FZR/YZF series were? What causes it? Ive wasnt riding any different to how i normally do.

Am i best to replace the front discs with genuine or are there better discs out there? And most importantly, how much is this all going to cost me? Im going to pop into Cannon tomorrow as im in the area and have a chat with them anyway but i would like to get some opinions from you guys too.

 

[alex]

Could be carbon build up. Might be worth emery clothing the disc.

Most discs warp if you put a lot of energy into them and then you stop...leaving 1 section under the calipers. This causes uneven cooling of the metal which can warp.

 

[Andy J]

Im wondering if possibly the disc buttons could be dirty or corroded? I did wash the bike before putting it in the shed the last time i used it. Perhaps there was moisture where the disc rotor attaches to the buttons and a few weeks of cold weather and a little bit of damp had caused some mild corrosion? Im going to see if the buttons moves freely first and if they dont give them a clean then give it a test ride. I have seen this on other bikes where the floating rotor buttons gum up with crud.

 

[alex]

Im wondering if possibly the disc buttons could be dirty or corroded? I did wash the bike before putting it in the shed the last time i used it. Perhaps there was moisture where the disc rotor attaches to the buttons and a few weeks of cold weather and a little bit of damp had caused some mild corrosion? Im going to see if the buttons moves freely first and if they dont give them a clean then give it a test ride. I have seen this on other bikes where the floating rotor buttons gum up with crud.

Sounds like a plan

 

[powders]

Did you buy it from a dealer if so you may be covered ?

 

[andyhalk]

Had the same problem. If its not dirt behind the buttons, Carpimoto in Italy are cheap for Brembo dics. I had good service from them.

 

[alex]

Yeah Carpimoto are very good and cheap.

 

[soofsayer]

Would vibration through the bars on braking hard also be warped discs? I had this last year and changed the pads which seemed to help reduce it a lot but noticed it again a couple of weeks ago....

 

[alex]

Yes it can cause vibration. But I think material build up on the face of the disc or stuck floating pins is still more likely.

 

[bananaman]

My 2010 was on track for the last 3 years I had it, never had a problem with the oe discs?
More likey to be the 'floaters'

 

[soofsayer]

Should there be any free play/movement in the front discs (on the hp4)?

 

[Stephen]

Im wondering if possibly the disc buttons could be dirty or corroded? I did wash the bike before putting it in the shed the last time i used it. Perhaps there was moisture where the disc rotor attaches to the buttons and a few weeks of cold weather and a little bit of damp had caused some mild corrosion? Im going to see if the buttons moves freely first and if they dont give them a clean then give it a test ride. I have seen this on other bikes where the floating rotor buttons gum up with crud.

The bobbins (buttons) may not move freely on the S like they would on 2 piece floating disks but thats not an issue.

I've had some success on bmw's in the past by removing the disks completely and cleaning the surfaces of corrosion to remove 'very light warped feel'.

Should there be any free play/movement in the front discs (on the hp4)?

A little bit of forward and back play is acceptable

 

[soofsayer]

So should the discs feel rigid, no movement, that's how mine are.

 

[Stephen]

Yea, new disks feel completely rigid (they aren't, just a nice tight tolerance between the bobbin and the disk) but its not uncommon for them to develop movement, how many miles has it done? as long as the brakes feel straight when riding i wouldn't give it much thought.

 

[soofsayer]

I'm going to give the discs a really good clean with brake cleaner tomorrow evening and call it a day on that. Thanks for the input. On my KR the floating discs had a few mm of movement which was normal, was hoping that wasn't the case with the hp4.

 

[soofsayer]

Just as an update to this thread that I hijacked last month. The front vibration I was getting when braking from high speed continued to exist after cleaning up the discs. For reference it felt like all the front end of the bike was vibrating badly until I got to below 70ish and then it stopped.

The dealer (AJ) have rung me today to confirm that one of the front discs was indeed warped and both are being replaced to resolve the issue.

 

[Andy J]

How much is that going to cost? Ive been looking at the cost of discs and HPS do a pair of Brembo for ?230, genuine BMW discs which are Brembo anyway are that much each!
Ive still not managed to properly look at mine but im going to borrow a dial gauge and check for runout.

 

[Andy J]

Well i took mine out today and initially the problem was still there but after about 20 miles it went away! So def not a warped disc thankfully.

 

[soofsayer]

That's good to hear, sounds more like something got stuck in your pads or discs that has since dislodged.

Regarding the replacement discs, the quote incl fitting was ?700.

 

[alex]

That's good to hear, sounds more like something got stuck in your pads or discs that has since dislodged. Regarding the replacement discs, the quote incl fitting was ?700.

Holy hell. ???'s!
Are they Brembo HPK discs on the HP4?