Just a thought. Can you machine the wheel mounting surface for the rotor 0.125" and have it give you clearance that way? You would have have to add a spacer to the caliper mounts possibly and have to check caliper to wheel spoke clearance. You might be able to use your ARP bolts that way also.

Dave

 

Well, you know how I feel



EDIT (for informational purposes)

Wall thickness approx .185-.190" ... approx .050" material removed for Rotor Head Clearance

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If everything lines up except the buttons tap the lower, get some slots milled. You should be able to leave the forks assembled.

 

I second on milling the sliders. Not dyna related but most shops doing fat tire conversions on baggers mill there sliders for clearance(yes 49mm is probably a bit beefier to be able to mill) but you’re not that far off that it shouldn’t ruin the the sliders integrity

 

Thanks for everyone's input!

How much clearance do people think is "safe" between the fork lowers and any parts of the rotating rotor (whether it's the rotor itself, the bobbins, the bolts...)? I realize a full-floating rotor can move in and out SLIGHTLY, but I don't mean that. If a bolt or bobbin clears, am I good to go, or is there a recognized margin of safety that should be maintained?

 

I think I'd be comfortable with .030" min.

Just as a point of reference, I have about .060" between my drive chain and the widest part of my rear tire.

I have been keeping a very close eye on it and have seen no evidence of contact in two years, I'm sure you know how much those parts move around...

 

Okay, progress... I pondered this for a few days before doing anything, putting the wheel on and off, old rotors, new rotors, measuring things... I definitely didn't want to start cutting into my sliders if I wasn't sure it was gonna work. on close examination, everything was close... The bobbins were definitely touching the fork legs, and so were the rotor bolts, slightly (the original button heads, not the taller ARPs). This morning I woke up determined not to be sidelined by this issue anymore. I was going to mock it up once more and make a final determination as to how close (or far) from fitting everything was. If it was really close, I would clearance the sliders... If it looked like too big a problem, I was gonna abandon the BrakeTech 330mm (13") rotors in favor of their 320mm (12.6") rotors. The 330s are 6mm thick, the 320s are only 5mm. I can't exchange them, but figured I could try selling them. I wrapped each slider with tape to see exactly where the interference was. The lower marks are the rotor bolts, in the middle are the rotor bobbins, and up top the small mark MAY have happened taking the wheel out, but it could have actually been the top of the rotor. It was honestly really tight all around.



On final examination, I decided I could clearance the sliders. First I mocked up one of the new Speed Merchant 13" brackets (replacing my original 11.5" radial mounts), just to be sure there wasn't another unexpected issue before cutting into things. They seemed to fit fine, and the caliper looked like it was in the right place.



In a perfect world, setting up the sliders on a milling machine would probably be the best way to proceed, but I don't have a milling machine (sometimes I really miss the days that I had access to an old Bridgeport). Using my angle grinder seemed prone to error, so I ran out and got this handheld belt sander. $38 at Harbor Freight. While I totally understand the anti-cheap-chinese sentiment, there is a place for it... And this was it!



The sander worked well... Very controllable, and I was able to keep the fork legs on the bike without any problem.



I started with an 80 grit belt, and then finished with 120 to smooth it out a little.



I basically brought the original clearance section (around the rotor bolts) all the way up to the top of the rotor on each slider. Actually a little bit deeper, as I took a touch off the factory-clearanced area for the bolts too. Success... The wheel now spins freely! On Tuesday (my day off), I may take a touch more off through the whole section, as it's still kind of tight. But I'm now confident this will work! Thank you everybody for chiming in!!!!



Provided all is good once together and being ridden, maybe I'll take the forks apart next winter to re-powder them. In the meantime, I'm glad I coated them in silver instead of black!

 

Note to anyone wishing to run BrakeTech rotors in a 39mm Narrow Glide front end: If you want to minimize any need for modification, go with the 320s instead of the 330s!

 

I've got that same sander and have used the crap out of it. So much so that I've been looking at upgrade paths. The good ones are quite costly, unfortunately.

Looks close to done. Should work fine and will be hidden so a quick spray of enamel should keep it protected until the forks need to come apart again.

 

Absolutely! Can't be beat for those things you would figure out how to do with out if they were more expensive, and probably won't use more than once or twice. (Apparently, cggorman found this not to be the case...)