Warped Disc ?...why ?

[Odie1]

All,

Thanks again!... I am tied to the house this weekend (on-call for work), so I will be going through all the steps mentioned... or at least the ones that I can.

I'll report back early next week.

Odie1

 

[Odie1]

OK - reporting back in...

Last Friday evening I got the front wheel off the ground, and pulled the front fender off so I could see better. It just happened to be a very quiet night just after dark.. no wind.... and I had no fans or any other noise making devices turned on.

When I spun the front wheel, I could hear a very faint <click> with each revolution. After improving my lighting, I discovered the <click> was from the disc making contact with the pad on the right hand "non-floating" caliper. Once it contacted it would then appear to "move away" form the pad.... barely a perceptible gap between the disc and pad, but you could see it disappear once the click happen on the next revolution.

Anyway, I went ahead and pulled the wheel, removed the disc, tried cleaning it up a bit, made sure all the "paper washers" were in place, ect, then re-installed with blue loctite, ect and as expected, a short test ride made it seem like I had not changed the situation.

So - I certainly could be missing something or overlooking it, but I still seem to think I have a warped (or bent since maybe I caused it last tire change) disc. I suppose the next step would be to source another one.

I did not get a chance to accurately measure the run out, or thickness, as the calipers I have only have long, flat blades to measure with...

Still open to ideas.

Thanks all

Odie1

 

[jfheath]

One possibility is that you have corrosion between the stainless steel disc and the alloy hub. You would be able to tell by probing all the way round with a sharp pointy thing.
It happens over time because of the different metals being in contact with each other and years of water. If that is the case, then part of the face on which the disc seats and to which it is bolted is no longer supporting the disc. I understand that it is possible to have the metal cleaned up, built up and then skimmed. Don't ask me how - it was a process described to me when my rear wheel did something similar many years ago. I found that I only got the pulsing when I had new pads. When I put in old pads, the caliper was able to move sideways when the brakes were clamped and they took up the slight oscilations in the brake disc, and I couldn't feel it any more.

Paper washers ? Do you mean the thin white heat shields that go on the back of the pads on the rear brakes ? Same shape as the back of the brake pads ?
If so - they don't need to be fitted to the front brake pads. If you do and the pads are new, that might be the problem. There isn't enough room for them.

A click when you rotate the wheel ? A brake pad catching wouldn't click. It would scrape. Unless the pad is at a slight angle to the disc and the leading edge of the pad is catching in one of the holes in the disc as it spins past. (Does the 1100 have holes in the disc ? - I can't remember).

If it isn't that that is clicking then what is it ? The rotor runs very close to the caliper bracket - there is a very narrow slot through which it passes and the clearance has to be at least 0.7mm. Check it isn't catching on that. If it is, it might be due to improper wheel installation. I also had one where I thought the disc rotor bolt was catching as it rotated. Clearly the wheel was installed incorrectly.

If it is that the pads are at a slight angle to the face of the disc - why is that ? Check the pad spring in the roof of the caliper. The 1100 doesn't have the same issue as the larger spring in the roof of the 1300 and LBS/CBS 3-pot brakes on some 1100s, but check it anyway - also the pad pin for smoothness, and the ability of the calipers to be pushed in and out easily when the pads aren't fitted.

Are your bearings OK ?

Sorry - I am just hurling suggestions at you with no idea of what the actual problem is. Just me imagineering. It's what I do when I have problems, and I have to visit each of my thoughts to make sure. Sometimes (enough times to make it a worthwhile exercise) I am right.

 

[kiltman]

Paper washers ? Do you mean the thin white heat shields that go on the back of the pads on the rear brakes

The one the OP is talking about are shim dampers. Item #12 in the parts fiche.