Brake boss location question
 

I need a project, wanted a touring bike, and picked up a bare metal Trek 520-no paint, decals, parts, fork etc. Factory specs and examples I have looked at indicate that this model was built for 700C wheels. The rear brake bosses on this particular frame, however, are set up for 26" wheels. I can't decide whether I should/could move the original bosses to "spec" position and get a fork to match or leave them where they are and find a 26" fork. The frame is the same size as other examples I know of with the larger wheels. When I drop a 700C wheel into the dropouts, there are adequate clearances at the bridges for fenders-it looks pretty "normal." I wonder if the finished bike will look silly with monster spaces under the fenders and around the wheels.
I started this project as an educational exercise so moving the bosses etc would fall under "tuition cost." Interesting introduction!
Thanks for your insight.

If it's a real small older 520 frame,it could have had 650 wheels on it.

I'm puzzled because that does not seem to be the case. I have a taller head tube than one in the LBS last week that had the larger wheels? And the clearances are ok for fenders at the bridges.

I'm no Trek expert but I don't think 520's were available with 26's,but the older ones were available with 650 wheels.

You are certain it's a Trek 520, not a Surly frame right? Surly will fit 26" (ISO 559) wheels to any of their LHT frames so any chance that's what you have?

I think bikes with room for 700Cs look dumb with 650s. Just my old-school opinion. Just to show you all what a retro grouch I am - I don't 'get' 650s at all, don't see any reason for them on DF bikes (they have application on recumbents however).

The cast lug at the seat tube says "TREK" and the factory id'd it as a 91 from the serial number (it was that lug, on the bare steel frame, that prompted the impulse purchase!!).It's possible I have confused myself using "26" instead of "650?" I'll give it a shot...and if it looks too goofy I can do it again.
Thanks for the input.

That's exactly what I'm concerned about! The ability of everything to fit together visuallly, in a nice way, is important.

OK get out the tape measure , how far off the axis of the hub axle CL are they?

They make sense on very small frames where they provide adequate toe clearance without having to distort the geometry.

Are you sure this is actually a 520 and not a mountain bike? http://www.vintage-trek.com/index.htm is pretty good for identifying the model from the serial number. I'd try that before assuming it's a 520.

I get about 253 mm.

Can you borrow a 700c and a 26" (559) wheel and a cantilever or V-brake caliper from someone and do a quick try-fit in the rear dropouts and brake bosses? That should remove all questions about what wheel size the brakes match.

Me too - on the nearest 26" MTB within reach. I'm no Trek expert, but I'm fairly sure you have an old mountain bike frame.

I do like HillRider's suggestion to test fit a wheel and brake though.

I have a Surly Cross Check with 700c wheels and cantilever brakes and the distance from the rear axle centerline to the brake boss centerline measures 285 mm. The difference between our relatively imprecise measurements is 32 mm and the true radial difference between 700c (622) and 26" MTB (559) wheels is 31.5 mm. I can only conclude your frame requires 26" wheels and is indeed an older MTB.

Enjoy building up your 26" hardtail MTB frame as a touring bike.
I have 2 of that sort.
.. and there are many practical benefits of rolling on 26" Wheels.
It has become the most common tire to find a spare, of some sort,
in some pretty remote places in the world .

Thank you all.

The old steel hardtails Trek used to make in Wisconsin are beautiful examples of lugged construction.

+1 :thumb: