Wide Case (late) Rear Wheel same as Mototrans ?

[Ventodue]

I understand the difference

Something kinda told me you would ... .

It was more the underlined bit about them not being required for wheels. I've never heard of them being used to compensate for misalignment. I'd have thought the greater internal clearance would be too small to make any difference, seeing as it's only really there to deal with heat expansion.

But then along comes Colin with his tale ...

Now me, I don't think I've ever bothered with C3s in wheels and haven't had one fail. But others with more experience may say otherwise ..

[Ventodue]

FWIW, here is my experience: bevel twin wheel bearings are C3 <snip>

Interesting ... Got a reference for that, Colin, please?

[Ventodue]

And make of this what you will. The first bit picks up on Colin's contention. The second bit sounds kinda exaggerated to me. Can the differential thermal expansion of steel over a range of 5-10° make that much difference? And is there that temperature difference In a wheel bearing, anyway? Dunno ...

Source: NTN Bearings catalog
"When either of the races of a bearing is a tight fit to its mating component (i.e. shaft or housing), the resultant deformation of the ring can cause a reduction in the amount of clearance in the bearing.

A rotating bearing also produces heat due to ... <snip>. A bearing housing is usually stationary and is therefore better able to conduct heat away from the outer race of the bearing. As a result, the temperature of the inner race and the rolling elements is usually 5 to 10º C higher than that of the outer ring. This results in greater thermal expansion of the inner ring and thus reduces the clearance in the bearing."

[Duccout]

Hi Craig,

The wheel bearings fitted to my 900S2 when it was new were C3, but maybe Ducati just had those laying around (or would FPS have fitted the bearings?) and the spoked hubs that I fitted later were not exactly well machined ( I bought about thirty of them and the bearing housings varied from tight to loose) so it is possible that my bearings failed because they were too tight in the housings, but both my 620 Multi and GT1000 were fitted with C3 bearings from the factory, so I've just assumed that C3 was the norm.

There are other anomalies - my 750 Sport did not come from the factory with C3 bearings fitted to the camshaft housings, but my 900S2 did, make of that what you will....

My guess, and it is an uneducated guess, is that a C3 bearing is a 'get out of jail free card', it allows machining to be a little less precise without causing the bearings to lose too much clearance.

[LaceyDucati]

I've only ever fitted and supplied standard fit wheel bearings in singles.

Colin, I do recall something about my old bevel twin, having very tight housings. I can't be certain, but I'm fairly sure I did fit C3 bearings in those hubs. Those front hubs on the twin spoke wheels are problematic in that the separate bearing carriers are not accurately spigoted to the central hub. I recall having to release the carrier/disc bolts with the wheel assembled in the bike to centre the whole assembly. I don't have a vast experience with the Twin cycle parts (only my own) as my involvement with twins was nearly all engine related.

Regards Nigel