Brake Rotors and Threadlock

[hampshirehog]

Even the "permanent" Loctite releases easily with some heat and none of these products are effective on exhaust temperature fasteners.

That old green Loctite was resistant to heat - it and red hermatite will be the only things left after armageddon. I think that's why they don't make it anymore. The new green stuff (there are 2 or 3 types with different numbers) is not the same as the old stuff.

[Dogma]

Well, I actually sat and thought about what I was doing yesterday and changed my mind on this. I put the antisieze, torqued it down properly, but forgot to close up the locking tabs so I still need to do that.

I'm curious though Norm as to how to check the runout like you are saying? Is it something I will see (as in a bent rotor) or something I should check with a gauge? Where should I make my measurements?

I'd say to just check the runout of the rotor assembled on the wheel, since checking the rotor off the wheel would require tools most of us don't have in the garage. Get the wheel and rotor assembly mounted on an axle so you can turn the wheel. Set up a dial indicator to read how much the rotor surface undulates as you spin the wheel and rotor assembly. Compare to tolerances that are probably published in the service manuals. Check your wheel runout while you're at it. Or, you could just make sure your mounting surfaces are clean and burr-free and not worry about it until you notice symptoms.

You could probably also reassemble the whole thing, then listen for the brake pads to drag in a pulsing fashion as you gradually apply the brake. If you never hear any pulses, it's all running true.

Or, since you own a GS and have had a high exposure to Steve, you own feeler gages (for valve clearance checking) you could use to check the gap between the rotor and a fixed reference at several points along the rotor. A good reference would be a brake caliper or caliper bracket. Something with a flat regular surface. Be careful not to flex the rotor by stuffing the gages in the gap. You'll get artificially high runout.

[7981GS]

Always clean the surfaces on the back of the rotor and the hub when installing.
Anything between them will cause a mis-alignment.

Daniel

[Normk]

Some excellent suggestions. If you lack a dial gauge, the feeler gauge suggestion may be satisfactory or you could use a crayon to indicate the run out. With care one can hold the pencil or crayon against some reference such as the caliper and position the tip until it just touches the run-out. I have found that repositioning the rotor can aleviate some run-out.

The proof, as they say, is in the pudding so if the brake feels good it is good for your purpose. The two main concerns regarding rotor alignment are: run-out and parallelism. Run-out is the side to side movement of the rotor as would be created if one were to have dropped the bike or used a hammer to hit the side of the rotor so as to bend it to one side. This can also be created by improper mounting as where some material is between the hub surface and rotor.

The second rotor issue is parallelism, or rather lack of such. This is a condition in which the rotor has a variation in thickness such that the two sides of the rotor are not parallel. This is usually a manufacturing issue or caused by improperly mounting a rotor when machining. Other issues are not relevant to the subject at hand.

It is best to mount the rotor to a hub surface which has been checked for run-out and then to check the rotor in place before setting locking tabs and such operations. As for locking tabs, some of the questions in this regards can be addressed by inspecting newer designs as it is sometimes discovered that what seems to be valid is not. An example would be the disappearance of split type lock washers which have disappeared from motor vehicle applications. http://en.wikipedia.org/wiki/Washer_...ocking_washers

left photo, right hand washer.