Brake Disc has blue rings of Saturn. Normal or not.

[Richard Simpson Mark II]

I have no knowledge of BMWs, but quite a lot about bikes (started riding when drum brakes were still a regular rear-wheel fitment).

The disc should only be getting hot in use. If it is dragging sufficiently to heat up without being applied, then the situation just gets worse and worse (the disc expands with heat, gets gripped tighter, gets hotter, expands more, gets gripped tighter...you can see where this ends, and it's not pretty).

This problem started when the dealer started messing about with the bike. I'd suggest that you give them one more chance to get it right. If they are incapable of setting up a brake, then they have no business being bike dealers. Is it a franchised BM dealer, and is the bike still under warranty?

If so, a complaint to BMW customer service would be my next action. If not, Trading Standards and DVSA.

The actual problem may be caused by a number of factors...one thing to be aware of is that the disc itself may be warped now (park a bike (or car, or even truck) up with a very hot, draggy disc, and the part of the disc under the calliper will stay hot a lot longer than the rest of the disc. Result is differential cooling, and the disc warps.

A mate of mine used to organise car trackdays...part of the briefing he gave was, when you come back in off the track, don't apply the handbrake as soon as you stop or you may warp the discs. Chock the wheels instead.

[Kazz]

if you do have free play on the pedal I would exaggerate this to test, and check that play has not reduced when in a warm disc condition, but if that is OK, an unlikely but possible is that if you overfill the rubber boots over the sliders with grease you can create a pressure in the caliper mechanism this could induce a small amount of brake drag. Give the boots a gentle squeeze. Oopps Just read that the front also warming so this is probably not relevant.

Hi, the fronts was only during the abs and TC off riding with front only test. Otherwise its only the rear.

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[Kazz]

I have no knowledge of BMWs, but quite a lot about bikes (started riding when drum brakes were still a regular rear-wheel fitment).

The disc should only be getting hot in use. If it is dragging sufficiently to heat up without being applied, then the situation just gets worse and worse (the disc expands with heat, gets gripped tighter, gets hotter, expands more, gets gripped tighter...you can see where this ends, and it's not pretty).

This problem started when the dealer started messing about with the bike. I'd suggest that you give them one more chance to get it right. If they are incapable of setting up a brake, then they have no business being bike dealers. Is it a franchised BM dealer, and is the bike still under warranty?

If so, a complaint to BMW customer service would be my next action. If not, Trading Standards and DVSA.

The actual problem may be caused by a number of factors...one thing to be aware of is that the disc itself may be warped now (park a bike (or car, or even truck) up with a very hot, draggy disc, and the part of the disc under the calliper will stay hot a lot longer than the rest of the disc. Result is differential cooling, and the disc warps.

A mate of mine used to organise car trackdays...part of the briefing he gave was, when you come back in off the track, don't apply the handbrake as soon as you stop or you may warp the discs. Chock the wheels instead.

Bike is out of warranty and it's a main dealer.

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[Kazz]

Update, did the step on the caliper. Also I noticed that brake fluid was seeping out of the front brake fluid reservoir. No leak just fron under the cap. Used a paper towel and reduced the level. Checked the rear its below the max mark.
Rode the bike without applying any brakes front or rear. Checked after 2 miles disc was slightly warm. Did it again and again with slight braking, the disc is not heating up.
The wheel also moves a lot more freely.
So hopefully problem solved.
Thank you everyone for their advice.
Guess the disc heats up very quickly when used.

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[Asgard]

Update, did the step on the caliper.

What?

[Kazz]

Update, did the step on the caliper.

What?

Stand at the right rear of your bike facing the brake caliper. Grab and hold the rear subframe, place your foot on the outside of caliper, where it says BMW, hold the subframe and push the caliper with your foot. This should cause the caliper to slide on its two sliding pins and spread open. Operate the rear brake a few times to close up the caliper, then repeat the procedure. Do this a few times and your problem should be cured. If the caliper doesn’t spread when you push with your foot then it’s totally seized. It’s a good idea for everyone to do this at least once a month anyway, as it stops the rear caliper from seizing.
This

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[bikenav]

so your problem was an overfilled master cylinder? on the front or rear brake?

[Kazz]

so your problem was an overfilled master cylinder? on the front or rear brake?

Hi, the front one was overfilled but the back brake was the one not releasing. Linked brakes I suppose.

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