SOHC.co.uk Forums > CB500/550
CB550 F2 1978 Rear Wheel Spacing
Neilw:
--- Quote from: 3scs on July 13, 2026, 08:42:58 PM ---Yes that’s an f2 swing arm with closed ends the k3 is open I think the problem is the brake plate but don’t know anything about any different ones if he takes the extra spacer out and pushes the wheel over the rear sprocket will be nearer to the centre of the chain guard and should be more in line with the front sprocket
--- End quote ---
Which might explain why both spacers were on the right-hand side when I got the bike.
Oddjob:
The 550f has the closed end type of swinging arm, the open end arms were fitted to the models with 4 exhausts as you couldn’t remove the wheel spindle to remove the rear wheel for a puncture for example. The 550f also has a slightly thinner o/s spacer than the 500 as well. It has a slightly longer boss on the brake plate to compensate. Your pictures show the wheel completely out of line, the rear sprocket should be almost directly under the chain guard and yours is way off. It wouldn’t run like that, the chain would not be inline enough for it to operate without a severe risk of it coming off. The small top hat spacer you’ve fitted doesn’t belong there. The silver coloured one goes next to the chain adjuster. So why doesn’t it fit? Seems simple if you know both models very well. It looks to me as if someone has fitted a 500 rear wheel in a 550f arm but still tried to use the 550f spacers. Measure the length of the o/s spacer and that should tell us if that’s the case, I think someone bodged it previously just to get back on the road.
Neilw:
--- Quote from: Oddjob on July 13, 2026, 08:55:28 PM ---The 550f has the closed end type of swinging arm, the open end arms were fitted to the models with 4 exhausts as you couldn’t remove the wheel spindle to remove the rear wheel for a puncture for example. The 550f also has a slightly thinner o/s spacer than the 500 as well. It has a slightly longer boss on the brake plate to compensate. Your pictures show the wheel completely out of line, the rear sprocket should be almost directly under the chain guard and yours is way off. It wouldn’t run like that, the chain would not be inline enough for it to operate without a severe risk of it coming off. The small top hat spacer you’ve fitted doesn’t belong there. The silver coloured one goes next to the chain adjuster. So why doesn’t it fit? Seems simple if you know both models very well. It looks to me as if someone has fitted a 500 rear wheel in a 550f arm but still tried to use the 550f spacers. Measure the length of the o/s spacer and that should tell us if that’s the case, I think someone bodged it previously just to get back on the road.
--- End quote ---
The os spacer is about 40mm (between 39mm -40mm).
What can i do? if it's the wrong wheel, that also means it's the wrong hub and brake plate too. What are my options? Will replacing the brake plate with a 550f one do the job, or won't it fit the hub?
Bryanj:
There are two different hub/brake plate combinations, from memory there is a difference on the outer diameter and i think you can swap one way but not the other just to confuse it.
What you need to do is sort out the sprocet side spacing to get the chain in line then work out what length you need for the other side.
If you want to keep it "standard" easy way is complete rear wheel with axle, brake plate and spacers but to use it safely all you need to do is work out what size spacers you need
Neilw:
--- Quote from: Bryanj on July 13, 2026, 09:58:52 PM ---There are two different hub/brake plate combinations, from memory there is a difference on the outer diameter and i think you can swap one way but not the other just to confuse it.
What you need to do is sort out the sprocet side spacing to get the chain in line then work out what length you need for the other side.
If you want to keep it "standard" easy way is complete rear wheel with axle, brake plate and spacers but to use it safely all you need to do is work out what size spacers you need
--- End quote ---
Removing the left spacer will sort the sprocket side out, and adding it to the right side will give the correct spacing for the wheel. If this makes it usable and safe, I'll go with that option. Longer term, I was going to rebuild the rear wheel with a new rim and spokes, now I'll look for a replacement wheel with the correct parts.
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