Front Wheel Not Central After Rebuild

The wheel build cannot be affecting clearance of disc to slider.

The usual problem with Commando disc fronts is getting the rim far enough over to the disc side. The spokes have to stand almost vertical and there was a factory instruction about thumping the spokes with a rubber hammer when trueing.

I think that you must have a spacer problem that you need to sort out first.

The disc needs to be central within the caliper. Once this is correct, the rim needs to be central in the forks (but central to the stanchions, the sliders could vary in machining etc.)

You could start by measuring the depth of the disc compared with the old one. 1/4' difference would be corrected by losing 1/8" off one side. 1/8 off one side = 1/8" gained on the other =1/4". So rather than send your wheel back either fit a 1/8" spacer or remove 1/8" from the other side. The spacers for the pre Mk 3 wheel are different thicknesses than the Mk3. If you have fitted new stainless spacers you might have the wrong ones.

Had a similar problem when upgrading my Mk 1A 850 front brake with a Norvil kit - Norvil floating disc fouled right side fork leg when using same spacer arrangement as per original brake setup. A sort through my large washers and spacers tin came up with a suitable extra spacer that did the trick after a bit of filing. Excellent brake now. As you say , don't over-think the problem and just make your own spacer to give required disc clearance.

over thinking. it seems like the disc side bearing is being drawn into the hub pulling the wheel across with it. just as if there were no bearing spacer. just a thought

Steven,

Something seems odd here. If you are using a correct standard spacer between the bearings, correct width bearings and standard chrome spacer/dust covers on either side, that would create the correct total width required for parallel slider alignment. Adding an additional washer would cause the sliders to splay at the lower end and create both a side load on the fork bushes and affect slider movement. if the fork sliders are parallel after the addition of your 3/16" spacer, then one of the other components must have been undersize. It would be with checking to make sure you are have not lost the fork slider parallel alignment.

Regards,

Andy

Adding a spacer won't splay the sliders because the slider with the pinch bolt will just settle to where it wants.

Doh, doh! Yes, you are quite right, David; of course the pinch bolt slider finds its own 'comfortable' position. Apologies for giving you dodgy advice, Steven - a case of brain dump!

Andy

Previously james_fanning wrote:

Had a similar problem when upgrading my Mk 1A 850 front brake with a Norvil kit - Norvil floating disc fouled right side fork leg when using same spacer arrangement as per original brake setup. A sort through my large washers and spacers tin came up with a suitable extra spacer that did the trick after a bit of filing. Excellent brake now. As you say , don't over-think the problem and just make your own spacer to give required disc clearance.

... further memory delving reminded me it was actually my Mk 3 850 being upgraded with an RGM kit that had the disc fouling left fork legissue. I was upgrading both my 850 Commandos at the same time some four years ago- Mk 1A had a Norvil kit which fitted straight on without any problem while it was the Mk 3 with an RGM kit that needed an extra homemade spacer to give disc clearance on the fork leg. Either way extra spacer sorted it all out with disc running dead true in the AP Racing caliper.