You can lace a 17" rim onto the XTR hub and it won't affect the speedo at all as it is driven of the gearbox.

What you will probably have to do is fit some lowering links to the rear to compensate for the drop in height (about 35mm) up front. If you leave the standard ride height at the back you will more than likely find that the steering will be very twitchy and tuck in on tighter turns.

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