MOT advisory fluctuation on rear brake, so passed MOT. Only discernable on rollers, not when riding. Disc appeared to be very slightly warped so replaced. Mounting surfaces cleaned up before new disc attached. New pads at same time. Pistons moving ok. Caliper pin regreased. Very few miles due to lockdowns. Still showing same fluctuation on rollers. Any help gratefully recieved please.
If it is an advisory, then you have plenty of time to play. It is possible that the new disc is warped too - if you can get the back wheel off the ground then you can rotate the wheel and use a pencil, nail or whatever to see if the disc is out of true.
I would also check to see if you have any play with rear wheel bearings [in the CARC]
Could it be the tyre - might have a flat spot?
Many thanks for your reply & suggestions. Have arranged a fixed pointer approx one mill or less from face of the disc & also from the wheel rim & very carefully & slowly rotated the wheel but cannot discern any fluctuation on either. Decided to replace the tyre recently (usual flatter area around the tyre since most of its life is vertical I guess!) & the tester did on further convo mention that he had occasionally seen fluctuation due to badly worn tyres, although this tyre was not badly worn. Apart from that on close examination I discovered a cut at the bottom of the tread pattern which when very carefully opened showed what I’m sure was the steel cords in the carcass - so the tyre had to go anyway. Will also look re your bearing suggestion. Fingers crossed it was the tyre!
Does it have ABS?
Could it be that triggering?
The rear ABS on my 2009 Stelvio, is overly sensitive, and will often trigger on even gentle down-changes (when Braking), gives a pulsing feeling.
Thank you for your suggestion. No, it’s the non ABS version - still an advisory - bearings to be checked. Hope it’s not a warped wheel!