front rotor scary close to fork

[debauchery]

anyone run into this situation before? and if so how did you remedy it?
front right side outer surface few thousanths away from right fork cutout(right side) 1979 xs 11 special thanks for any insight

[crazy steve]

That's the 'design flaw' in the Special forks...

To fix that, loosen the axle pinch bolt and push/pull the fork until the rotor is centered in the cut-out, then tighten it. This throws the fork tubes out of alignment, but it can't be helped. This is the official FSM procedure by the way...

[bikerphil]

Yep, on my 79SF, the right rotor is about .015" from the fork. that is where it likes to be after properly aligning the forks. As long as it isn't scraping you should be OK.

[crazy steve]

Phil, I'm curious...

Shouldn't the rotor be centered in that slot? I would think that you need the rotor centered because of the pivot point for the caliper so the pads hit the rotor evenly. Not an issue with the standards, but with that weird Special brake I would think that not having it centered would promote uneven pad wear. Every time I look at that brake set-up, I wonder what they were thinking...

And I also wonder if a 'better' adjustment procedure might be to loosen the pinch bolt, then apply the brake, letting the caliper move the fork to where it 'wants' it....

[DGXSER]

I always center the disc in that slot then tighten the pinch bolt. And I always apply the brake tight on the disc before I torque the bolt holding the caliper to the fork. i have found through trial and error that leaving the disc uncentered does in fact cause brake pulsing, very similar to a warped rotor. But it got MUCH better after I centered that disc in the slot.

[bikerphil]

Steve, if I force the fork out to center the rotor I would have to hold it there while tightening the axle pinch bolt. With the calipers off the bike, if I bounce the front end of the bike with the pinch bolt loose, it wants to go to that spot .015" from the outboard side of the fork. If I remove the springs and compress the forks, it wants to go to that same .015 spot. On my particular front end, that's just where it wants to be so that is where it gets clamped every time. No abnormal wear of the brake pads either.

[debauchery]

sounds like a plan thanks guys i'll do it now, (i bought a set, or two sets rather of pads for her as an appolgie for putting her through the fork swap the other day ) does anyone know the min rotor thickness ? i got a lathe available and i feel like a fool just doing a padslap *
**yea i'm feeling a little stupid after loosening the clamp stud/pinchbolt and tightening it with the rotor more centered ***
sometimes it is simple

[crazy steve]

..does anyone know the min rotor thickness ? i got a lathe available and i feel like a fool just doing a padslap...

Don't go near a lathe with the rotors. These have to be ground, and if you try turning them on a lathe they'll gall and you end up with scrap...

Minimum thickness as per the FSM is .260" (and stock is only about .270"), so generally you don't want to mess with them. I don't doubt you could go thinner if need be, but these rarely need to be turned. If they need turning, they're usually toast...

If you want to clean them up, a maroon Scotchbrite disc will spiff them up nicely.

[SFSPECBIKER79]

rotor

i have the same problem when i changed to the slotted rotor on my 79. but when tightened up they are no movement of the wheel, side to side if so, i would be worried about it.

[11Rider]

I'm glad you posted this. I've been having a binding problem with my front forks (stiction and squeak). I checked my rotor and it was in the middle of the slot. I loosened the pinch bolt and worked the forks. The forks settled to a spot where the disc was close to the fork as you mentioned but still clearance. Tightened the pinch bolt and no more binding!

[bikerphil]

11 Rider, I'm glad I'm not the only one who finds the rotor doesn't have to be centered. Nice that you got your's sorted out.