Topic: 75 CB550 w 78 CB550 forks - questions on caliper and rotor - help needed

[charlie27]

hi,

I am in the midst of building a 75 CB550 cafe racer with my 12YO son.  We wnwt with a fork off a '78 750F which we rebuilt.  I cked on the axle before hand and saw they both used the same PN.  The 550 has a 6 bolt hole rotor and the 750 a 5 hole rotor.  So I had no easy way to check off set, etc.  I picked up a 750 brake caliper and hoped for the best.

Come to find out it look slike the 550 rotor must be thicker then the 750 rotor and with pads fully retracted will not work with the thick disc.

some facts I am not changing the front wheel as we polished the hub and laced on new Al rims.

I am looking ideas on what it will take to make this work.

thanks

[Bankerdanny]

So you are trying to use your 550 hub and disk with a 750 fork, right? As you are now seeing, axle size is only one thing to worry about.

The '78 F used dual disk Comstar wheels, not the single disk wire wheels. So I am not surprised that the 550 wheel, which uses a narrower rim and tire doesn't line up right.

It seems to me the answer is just to find a set of 500 or 550 forks and use them. Fork seals are cheap and all the work you did on the new wheel won't go to waste.

[charlie27]

I am not willing to give up too soon.  I will figure out how to make this work right but thought someone on the site might have some info to give me head start.

[seanbarney41]

I think '72 to 76' 750 frontend will give you what you need...or you will have to do something with the axel spacers, or maybe shim the rotor, or the caliper, or grind flange on fork leg.  The ins and outs of Honda model year changes and what works with what are very tricky.  If you want to swap parts, ya really gotta do your research, or be prepared to fabricate.

[charlie27]

ok

'75 550 disc 7mm thick.  All other discs 5mm thick.

the front wheel bolts right on, the offsets look as they should be.  I am on to something to find a disc with the same bolt pattern, 5mm thick and same offset.

stay tuned.  I am not going back to the 550 fork.   

[boogiedude]

you could always have a machinist or brake shop take the rotor down to whatever thickness you need

[bryanj]

Trouble is the 750 f2 front end is a 2 year only setup so not much else transfers without a helluvalot of fabricating

[Bankerdanny]

I have to ask, why so fixated on keeping the 750F front? You aren't using the Comstars or 75-77 twin disk Goldwing wheels (An intersting option since they have aluminum rins), so what is the benefit of using the 750 forks?

[charlie27]

I think it is a better fork, it  is a bit longer as I laced up an 18" rimi versus 19"and will help set the proper ride height, mounts the caliper behind the fork leg versus in front.