I'm in a little over my head right now, and I could really use some help please.

I'm converting a '74 Varsity to 7 speed index shifting. I've got a set of 7 speed Shimano 105 SIS Downtube clamp-on shifters which, ideally, I'd like to mount on the top tube. I figured I'd just need the Shifters, a clamp-on cable stop, and Index shifter housing.

I talked about it with the dude at my LBS and he brought up a few issues.
First the index housing is quite a bit smaller in diameter, and the plastic ferrules that you put on it are larger in diameter than a regular metal ferrule....so I guess I'll need a special Cable stop?
Second (and this is my biggest concern) he said that its not a great idea to just clamp shifters to a tube without any kind of brazed-on stop on there. That the shifters may slide around because of the tension on the cables....Personally I think that sounds like an outside chance but he's the Bike shop owner, and i'm the guy who's never put a SIS system together before.

So can you folks please help straighten me out, or at least link me to a good reference...i feel like I got in too deep

And Yes I know I'm at least a little crazy for doing this all to a varsity.



i really like the way it looks even now... I almost want to scrap my original idea and just put straight bars on it and go take it off some sweet jumps.

I've got no experience using Shimano indexed shifters on clamp-on shifter bosses. That's what I would worry about, do the clamp-ons have the correct posts.

The better bikes did have a little blivet of braze to act as a stop for the clamp band. It was nice but lots of bikes got by without it.

No personal experience with Schwinn Varsitys but a lot of old bikes have been built up with modern cables without difficulty or ill effect.

The cable housing shouldn't be a problem if you have the standard Schwinn metal ferrules. You can always wrap a bit of tape around the cable end to make it fit tight in the ferrule.

Where your shifters are mounted -- won't that interfere with the brake cable routing? Isn't there a cable stop right there for the brake cable?

If the shifter clamp goes around the top tube, it might also work around the handlebar stem. I'd be tempted to do a stem mounted setup. It would look more original and you wouldn't have to worry about them sliding around -- although I doubt that would be an issue wherever you put them.

I did a indexed conversion on a Le Tour using thumb shifters mounted on a set of MTB handlebars. Worked great and lets me shift without having to move my hands.

I had considered thumb shifters but I really wanted to keep the handlebars as sparsely populated as possible...

The shifter clamp won't fit the stem, the stem is .833" diameter...ya know, funny schwinn sizes.

You are correct that the place i have it mounted in the pic is right in front of the brake cable stop, but It won't be an issue since the housing will just go over top of the shifter clamp band.

I'll definitely need a clamp-on cable stop if they're going on the top tube though, I just don't know what to look for...

I would go stem mounted.

How are you going to run the derailer cables? Down the seat tube and down the seatstay? Housing or bare cable?

You'll need a top pull FD.

There's nothing wrong with top tube shifters. It's been done before.

The fat tires look great!

I suppose I can shim the clamp up to fit the stem. I'll still need to address the issue of a cable stop though

some looking on Harris Cyclery led me to their index shifter sales page where they say this:

That link takes you to this page https://www.sheldonbrown.com/harris/c...are-shift.html
where the only clamp-on cable stop is a standard shimano clamp-on cable stop. It looks just like the one I have in my toolkit.

All this research is just leading me to beleive that my initial idea will work and I just need to get housing and the correct ferrules.

Is all compressionless housing the same outside diameter?


Thanks Dirtdrop, I think the tires are pretty cool lookin too.
my original plan was to mount the shifters on the top tube, followed by a cable stop and have the housing run from there to the downtube cable stops, sorta like it would be run for barcons. then bare cable down the downtube to the BB and then up to the FD and back along the Drive side chainstay to the RD.

I'm, thinking it still should work...the more I read the more I'm pretty sure that clamping the shifters won't really be an issue. If someone knows otherwise please tell me.

OK I've solved the first of the issues.

Turns out that index compatible housing comes in 4mm and 5mm. my LBS only had 4mm. Now I realize I can get 5mm index housing and use standard 5mm metal ferrules just like with friction shifting.

How are you going to stop it?

Projects like this are much more interesting to me than boring restorations!

i'm enjoying it...its a real rollercoaster of emotions

I'll stop it Flintstone style... just drag my feet

no, actually Its got front and rear hub brakes I didn't want to deal with brake reach and clearance issues for these fat ass tires so I avoided the issue by building wheels with hub brakes. Plus now it will be a good winter rider when the roads are sloppy.

here's a couple pics of the hubs. They're just mounted so I can stare at it...nothing is properly adjusted yet. The front also has a built in dynamo.