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]

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.

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]

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.

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.

[mickwinf]

I think you are correct Ken, pic here of 500 hub

[mickwinf]

see how all the ribs are equal, the f2/k3 have one rib that is lower. so this 500 hub not compatable with the f2 brakeplate as this pic.

[Oddjob]

There is another difference I’ve just remembered but it is only visible when the sprocket carrier has been removed. The Cush rubbers on the 500 are different design than the later 550 ones. Other than those 2 points they are very hard to tell apart.

[Neilw]

i've been doing some measuring.

The internal diameter of the brake hub is 180mm, with a depth of the brake face measuring 33mm.

The axle has a diameter of 20mm.

AI reckons someone has replaced the bearings from 17mm to 20mm and used a 20mm axle, replacing the 17mm, possibly from a cb750.

The brake plate must have been bored out to 20mm, as none are standard at this diameter (however, AI gets confused on this when questioned) except the CB750, but that wouldn't fit the hub I have, as it is too deep and would foul.

I'm having a CB550 brake plate delivered tomorrow and will see if it fits the hub. It may well be 17mm, in which case I have to decide if
A) I want to get rid of the extra spacer, and if the plate fits, I have it bored out to 20mm, or
B) keep what I have and use the existing spacers, or
C) replace the bearings in the hub, get a 17mm axle and use the new plate I have purchased (assuming it fits). If it doesn't fit, replace the hub as well!

Cheapest is B, neatest would be A, getting back to stock C, but most expensive.

[Bryanj]

I think the one bearing is a 6304 which is a 20mm bore as standard. AI is about as usefull as a chocolate fire guard

[McCabe-Thiele (Ted)]

If you look at this item (156396720375) made by Max Haywood, he was a member here, he will make you a bespoke spacer if you know the width you need at a sensible price
 
He says in his listing he can make what you need, tell him you are a sohc member,

[3scs]

This shows the difference between 500 and 550 the fins on the 500 hub lol the same height the 550 one fin is lower, also inside the 500 hub there’s some smaller holes, couldn’t you just line the sprockets up then get a spacer made up the correct length to fill the gap left on the brake plate side

[Neilw]

If you look at this item (156396720375) made by Max Haywood, he was a member here, he will make you a bespoke spacer if you know the width you need at a sensible price
 
He says in his listing he can make what you need, tell him you are a sohc member,

Thank you

[Neilw]

This shows the difference between 500 and 550 the fins on the 500 hub lol the same height the 550 one fin is lower, also inside the 500 hub there’s some smaller holes, couldn’t you just line the sprockets up then get a spacer made up the correct length to fill the gap left on the brake plate side

Thank you for the pics, i can see what you mean re the difference. I definitely have to cb500 one. And regarding the spacer, that is my most likely route in the short term.

[Oddjob]

If the bearing markings match the bearings specified by Honda then AI is wrong. I suspect it’s wrong anyway as the hole in the swinging arm wouldn’t match the bearings either.

Nice few pics by 3scs, the extra holes on the 500 plate are the holes used by the cush rubbers, the 550 used different cush rubbers that didn’t need these holes so were omitted by Honda.

TBH the solution seems fairly easy, just get a spacer either made or try a 500 spacer and see how that goes. Or just use that weird spacer until you find the parts you need.