Front Brake Through (maybe)

[TimeMachine]

Hi , So while doing some winter maintenence I've accidentally modified my 78 standard front brake. Possibly. See while digging in a parts box at a local salvage biz, I believed I found a great rotor and caliper components ! Upon installing my new fine rotor I discovered it was thinner than my stock rotor. 7mm stock and now a 5mm thick rotor. Hmm, I was bummed. So I compared the height or offset and It is the same. So I noticed the 10mm wide gap on the caliper hanger. Next I grabbed my "new" hanger I pulled out of that box and yes, that gap was only 7mm..Hmm, I mounted that up to my fork and put the wheel on . Amazing ! My accidental purchase is all looking fine ! Its a lighter disc and an apparently accomodating hanger. New thick pads. I realize piston position has changed a little but I think its a winner ! My guess is I've installed components from a XJ series wheel ? I like it so far but the bike is stripped for winter so a test won't happen soon . visually identical. lighter disc. Do we have a new option and source for ideas now ? Who knows of this ? I hope others benefit from this as I apparently have ? Cheers

 

[gggGary]

Later Xs1100 XJ1100 specials 850 maybe 750 etc had those parts, some have nice slotted rotors to boot. Good find.

 

[Royboy]

SR 500 rotors are also 5mm. Good performance, less weight.

roy

 

[5twins]

Yes, I have an SR500 disc on one of my front wheels. It mates right up to the stock caliper fine without any changes. An idea I've been kicking around is trying to adapt the old style disc for use with the new style caliper. I think the old discs look nicer with that aluminum center piece and that also makes them nearly a half pound lighter. The difference in offset between the early and later discs is 5mm, the early ones being more. But if you look at the area where the bolts are that mount the disc to the carrier, you'll notice it is inset ....

If you simply flip the disc over, you will gain back about 3mm of that offset. Then, add a washer to the axle on the disc side, between wheel and fork, and I think it would line up properly. If it works, this could be a simple, no machining required mod, a way to put those nice looking older style discs to good use.

 

[TimeMachine]

Funny, Ive kept an old 75 rotor around just because of the nice aluminum center. I look at it but thats all so far. I did have two old front wheels (sold em) and seeing things like a custom XS which mimicked a 1915 flat tank board racer, Ive thought someone may want to machine that rotor center to mount a drive sprocket on ? 19's, skinny front & rear ? Just fun stuff. Now I want 5mm discs on my double disc "trailer queen" standard !