SOHC.co.uk Forums > CB500/550
CB550 F2 1978 Rear Wheel Spacing
Oddjob:
Remove that odd spacer. Fit the wheel but omit the o/s spacer. Push the wheel as far as it can go and measure the gap left by the missing spacer. As I said the 500 brake plate has a smaller protruding central boss, you can tell it’s a 500 brake plate btw because the 550 has ribs on the piece hanging down where the torque arm bolts too, the 500 is smooth. If you look at the pics 3cs posted you can see the ribs. If IIRC the new gap should match the old 500 spacer, if it does just buy one of those. I’ve fitted 500 wheels into 550s and vice versa and then aligned ok. So hopefully that’s a simple solution. Could be wrong of course as it a few years now since I did this.
Oh and finding a another 550f hub may not be as easy as you think. The rear drum liners crack a lot, probably why you’ve got a 500 wheel in there. If the liner in that hub is ok fixing the spacing could well be much easier.
Neilw:
--- Quote from: Oddjob on July 13, 2026, 10:23:33 PM ---Remove that odd spacer. Fit the wheel but omit the o/s spacer. Push the wheel as far as it can go and measure the gap left by the missing spacer. As I said the 500 brake plate has a smaller protruding central boss, you can tell it’s a 500 brake plate btw because the 550 has ribs on the piece hanging down where the torque arm bolts too, the 500 is smooth. If you look at the pics 3cs posted you can see the ribs. If IIRC the new gap should match the old 500 spacer, if it does just buy one of those. I’ve fitted 500 wheels into 550s and vice versa and then aligned ok. So hopefully that’s a simple solution. Could be wrong of course as it a few years now since I did this.
Oh and finding a another 550f hub may not be as easy as you think. The rear drum liners crack a lot, probably why you’ve got a 500 wheel in there. If the liner in that hub is ok fixing the spacing could well be much easier.
--- End quote ---
The gap without the additional spacer is 15mm, so if that is the difference between the 500 and 550 brake plate i'll do as you say and get a 550 one. There is one for £35, which i can return, so looks the best way forward.
Oddjob:
There may be a problem with that idea Neil. IIRC the 550 brake plate does not fit the 500 brake drum, I seem to recall trying it and being surprised that whilst the drums look identical they were different. It seems to foul on the outside edge. Maybe someone with both hubs and plates can confirm if I’m remembering correctly.
Neilw:
--- Quote from: Oddjob on July 13, 2026, 11:32:37 PM ---There may be a problem with that idea Neil. IIRC the 550 brake plate does not fit the 500 brake drum, I seem to recall trying it and being surprised that whilst the drums look identical they were different. It seems to foul on the outside edge. Maybe someone with both hubs and plates can confirm if I’m remembering correctly.
--- End quote ---
I don't "know" that I have a 500 wheel, it's just what's been suggested on this thread. It could be that I have a 500 brake plate in a 550 wheel.
I don't know how to identify whether the wheel/hub is from a 500 or 550, as the only difference identified so far is the brake plate.
I can do the check if my offer on the plate is accepted. if it doesn't fit i can return it.
This bike just keeps giving and giving!
Oddjob:
Evidently the difference between the 500 and the 550 hub is the outside ribs in the centre. Trigger explained it one time many years ago. IIRC the difference was the 500 had them all the same size and the 550 had one smaller in size right at the edge. Not sure now if they were stamped with a model number inside the drum, if so the 500 would be 323 and the 550 is 374. Not sure if a search of the forum would shed more light on this topic but it’s definitely been discussed in the past.
Hope that helps.
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