How much is to loose

[BigArn]

Had new tires put on the RT this past Saturday, and the service guy at this bike shop told me that the rotors were shot, both front and back. And that the front rotors would need to be replaced due to the excessive amount of movement they exhibit. My question is what is normal for play in the front rotors, how much are they allowed to float? And I’m sure there is a specification on the thickness of the rotor. I can check that with my calipers. If there is material there I can have them Blanchard ground. Can ridding it in this condition elongate the holes that the bobbins are setting in?

[OoPEZoO]

never heard of that........was it a shop that works on a lot of BMW's or just a random local bike shop? I agree with the thickness maybe being an issue, but like you said, it can be checked yourself. I hope someone else with some real knowledge on the subject chimes in. I'd be interested to know

[BigArn]

never heard of that........was it a shop that works on a lot of BMW's or just a random local bike shop? I agree with the thickness maybe being an issue, but like you said, it can be checked yourself. I hope someone else with some real knowledge on the subject chimes in. I'd be interested to know

Just a local bike shop, they work mostly on sport bikes.

[Zot]

Minimum brake disc thickness is 4.5 mm or 0.177 in.for both front and back.

I would expect the bushings to wear long before the holes would become elongated.

[OoPEZoO]

I hate to be sceptical, but I spent a good 10 min last week trying to explain to a local shop that my rear brake rotor was NOT part of my rear wheel, and that I didn't remove it. He was trying to mount/balance a tire for me, and he kept saying that he couldn't do it because I removed the brake rotor from the rear wheel. He couldn't grasp the idea that my brake rotor bolts to the final drive and NOT to the wheel. I finaly just gave up, took the wheel/tire home, and ordered my own balancer from Marc Parnes.

 

I might stop back in his shop for an inspection this month, partly because I need one, but mostly because I want to show him that sometimes.......the customer is actually right.

[Zot]

Did this discussion take place in a BMW shop?

[OoPEZoO]

Did this discussion take place in a BMW shop?

 

Oh no, not at all. I guess I should have added that. It was a local independent shop that works mostly on Harley's and oddball customs.

[KER]

if the rotors are worn they need to be replaced, as far as the "bobbins" are concerned i dont believe there is a spec for movement allowed. They work just as well tight as they do loose. A few of our 1100rt's would clank down the road because the bobbins were so worn. For about $100 or less (when ordered through Chicago BMW) you can get the parts to replace the bobbins on the rotors to tighten them up, its a very easy task and takes about 30-45 minutes to do all of them. But as stated before, if the rotors are worn past their recommended thickness they should be replaced, and if i recall new rotors do not include new bobbins.

[DavidEBSmith]

The front rotors on an R1100RT can have a lot of play, to the point that they rattle. Play along the direction of the axle is OK, rotational play (grab the rotor like a steering wheel and turn) indicates you need new bobbins, not new rotors.

 

The only reason you would need new rotors is if they're worn past the thickness limit, if the holes for the bobbins have worn out so they're oversized or not round (and I don't think I've ever heard of that happening, because the bobbins are soft and the rotors are hard), or if they warp or are badly scored. And wearing out the rotors takes a lot of miles.