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Hello Chaps,

I've not been here for a few months, but have been out enjoying the bike.

Recently I noticed a wheel speed vibration while using the front brake, and have since replaced the front discs, as I suspected a warped disc. All the bobbins look good, and are a good but not rigid fit. I did not replace the pads, as there was plenty of material left, and it's been a heavy month (my second bike's front master cylinder sprung a leak). The pistons are all free in the calipers. Wheel bearings seem fine.

As I understand it, my bike has been fitted with later brakes (BMW branded Brembo calipers), with 320mm diameter discs. I was led to believe that the discs track should be 32mm, and so that is what I have ordered and fitted (I sorted this out while away from the bike...)

The discs I removed had a 38mm track, and had an unused part on the inside of part of the disc. Measuring that suggested 32mm should just be enough.

I fitted the new discs, and it appears that the pads are running so that the inside couple of mm of pad touch the "spoke" on the disc as it rotates. Certainly, I am getting a higher frequency vibration whilst braking, that could be 5 times wheel speed I guess. The wheel speed pulsing has gone however.

Does any of this make sense, and do you think that the discs/pads will bed in to smooth out the vibration? I can't see that it is much different to the wavy edge discs that some bikes use.

If anyone has any ideas, I'd be grateful. Thanks

Gordon

front wheel bearings seem to cough up symptoms like vibrating pads/discs.

A few have had this

Al

Could well be the front wheel bearings; had to get mine replaced at 77k.

Early R1100S up to about 2000ish had discs which were 4.5mm; non-ABS.

Later bikes had 5mm discs. How do I know? I recently had to replace the worn discs after only 85k miles. Motorworks supplied 5mm Brembo discs. The mechanic fitting the discs for me then had to source new bobbins to suit the thicker discs so that everything tightened up.

BMW and Brembo apparently do not now make 4.5mm discs for the R1100S; Thankfully the 5mm versions could be made to fit with different bobbins.

In agreement here, its very likely the wheel bearings. £15 AllBalls and an easy fix. Drift out one set from the inside through the other bearing, turn over and drift out the other set, place new bearings in the freezer for a few hours, drift in with a suitable tool, I use a socket on the outside of the bearing.

Was it really in October I asked about this??? Time flies with new jobs, housing projects and the like.

I'd been using my other bike for a bit, and finally got round to changing the front wheel bearing on Good Friday. I can't report back on any change, however, as like an idiot I went up the road, breathed on the brake lever with a bit of power on, locked the front wheel, and slid down the road for a bit... Arse.

It could be worse - there wasn't anybody around for the bike to hit, I'm okay, and the bike itself could be worse. I'm very glad I put all my kit on for a very short test ride! I am a bit annoyed at my own stupidity, but I guess it's a lesson learned.

If I can't find the answer somewhere on here, there will be another technical question coming up.

Seems like the wheel bearings are a common cause, my 12S was the same, changed discs etc to no avail. New bearings and all good

Changed bearings on mine made no difference except I was £50 lighter. Needed new discs