In switching over to the C7 X Tracker hubs I followed Ken and Howard's footsteps. I machined the rear uprights to accept a machined Bushing/spacer. In measuring the C4 hub vs the C7 X Tracker, I required a .250" spacer. Ken had measured his C and C7 bearings requiring a .190” spacer. The difference may be that the C4 bearing when I measured was not compressed with a stub shaft bolted in. The C4 bearing might require the stub shaft to be bolted to tighten the bearings. Without the stub shaft being bolted in place the bearing is sloppy. Not so with the C7 hub. I can thin up my spacer if needed when I drill and tap the mounting holes for the brake calipers. The pics show that I measured the flange to flange distance on the C4 bearing then zero'ed my caliper. Then I measured the C7 bearing and you see the -.250" result.
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The next pic shows the mounted C4 bearing next to the mounted C7 bearing with a straight edge across both of them.
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