Topic: Rear Brake Caliper bracket rubbing brake rotor

[riffman12]

Apologies for cross posting this from my build thread, but I know this section gets a bit more tech traffic.

here's my full post from my thread with pictures:
http://forums.sohc4.net/index.php/topic,152046.msg1745103.html#msg1745103

But basically my issue is that my brake caliper bracket is rubbing my brake rotor. Here is my kind of weird setup:

Rear wheel: 1979 CBX Comstar
Brake Rotor: 1979 CBX
Brake Caliper Bracket: 1977 CB750F, but the same part number as used on the CBX
Axle, spacers(collars): 1977 CB750F
Swingarm: 1977 CB750F

here is a picture of what's going on. You can see the rotor is nowhere near centered in the bracket:




I wonder if the two collars on either side of the hub are different sizes, but I'm worried messing with those could screw up chain line and overall axle spacing.

Can anyone shed some light here?

[Powderman]

Have you tried fitting it with the spacers reversed? Are the wheel bearings fully seated?

[riffman12]

Have you tried fitting it with the spacers reversed? Are the wheel bearings fully seated?

I can't reverse the spacers as they are different diameters on the drive and brake sides.

I feel like the bearings are seated all the way. They are touching the inner collar "snug" but I can still wiggle the collar a bit. Even if I tapped the bearing in a bit more, I don't think it would free up enough space to center the rotor in the bracket.

[Powderman]

Apparently something in the mismatch of parts is not compatible. You may have to shave a spacer or the flat on the caliper bracket to move it over and then provide a spacer on the other side of the bracket.

Being it is not mounted it is not an issue with the axle. The bracket as you claim is a CBX bracket. So the only oddball items are the spacers. Go to the parts fiche and see if the 750 and CBX spacers are the same numbers. If not that may be where the issue lies. The only thing 750 on this set up is the swing arm, correct. make sure you use all CBX spacers.

I checked and all the sleeves and collars are different between the CB750F and the CBX. If you are using 750 sleeves and collars that's the issue.

[riffman12]

Apparently something in the mismatch of parts is not compatible. You may have to shave a spacer or the flat on the caliper bracket to move it over and then provide a spacer on the other side of the bracket.

Being it is not mounted it is not an issue with the axle. The bracket as you claim is a CBX bracket. So the only oddball items are the spacers. Go to the parts fiche and see if the 750 and CBX spacers are the same numbers. If not that may be where the issue lies. The only thing 750 on this set up is the swing arm, correct. make sure you use all CBX spacers.

I checked and all the sleeves and collars are different between the CB750F and the CBX. If you are using 750 sleeves and collars that's the issue.

but if I switch over to the CBX spacers, couldn't that mess with the side to side wheel placement in the swingarm, which could screw with my chain line?

Thanks for your help

[Powderman]

Welcome to the world of modifying motorcycles. Either way you have an issue that needs addressing. Figure the easies way to remedy it and proceed. Spacers are easy to make or modify.

[riffman12]

OK so I've ordered an entire CBX rear axle complete with spacers. I've noticed that my rear sprocket is also offset too far to the left to line up with the front sprocket...so I'm HOPING this CBX axle kills 2 birds with one stone.

I'm also reading that a '77 F swingarm should not be a direct bolt on to my '76 F, apparently it is wider and the shocks will need adapting... but I bought my bike with the '77 rear end and as far as I know, it was ridden like that. No obvious modifications to shock mounting. Everything seems to line up ok 

Anyone knowledgeable on the '76 vs '77 Super Sport swingarm differences?

[Jerry Rxman Griffin aka MuthaF'er]

77/78 F swing arm is 10mm wider on the left side. You may need to get a different 530 front sprocket from a CB650 that only has onw shoulder on it and not 2 since it mounts to the end of the output shaft vs sliding on like the 76 and earlier. Run a straight edge along the width of the rear up to the front. A good straight yard stick might work. Verify the edge is straight first.

I gotta find a +10mm rear axle for my project.

[riffman12]

Thanks again for your help, Jerry.

would the shocks still mount up ok with the mismatched swingarm? I'm confused with how my swingarm would be too wide, yet the shocks would mount up ok

I'll take a picture of the chain line once I have the new CBX axle in next week

[Jerry Rxman Griffin aka MuthaF'er]

I felt that I would be able to mount mine cockeyed but I went ahead and used a top secret adapter since everything else was offset 10mm.