Originally Posted by
pjw77
Hi folks--
I'm restoring a 1983 Trek 720. The bike was in disarray in the corner of someone's garage when I bought it. I've got it all stripped down to frame and components, cleaned everything up nicely, did a little paint touch up, and am now starting to think in detail about starting to build it back.
The current puzzle I've got is the drive train, and it's only a puzzle because I just don't know much about it.
Here's the "known" parts:
* I'm going to use a Suntour Cyclone GT rear derailleur
* the bike came with a Campagnolo front derailleur
* the bike came with a Sugino AT triple crankset, with a 50-tooth chainring, a 45-tooth, and a 28-tooth "granny". I plan to use all that.
* came with Suntour bar-con shifters, which I plan to use
The bike came with a 5-speed Regina freewheel. I'd like to replace this, but don't know what I can/should be looking for. Can I put a six-speed freewheel on? What about a seven?
I also don't know what I should be looking for in a bottom bracket. I guess the main thing to consider is total length?
Thanks for any help/info. (And if this is the wrong place for this post, please let me know).
So... the Trek 720. An 83 would be first year with cantilever brakes and last year with the old school Trek styling.
The Sugino AT is one of the best, and best looking triple cranksets ever made. Check out Sheldon's database-
https://www.sheldonbrown.com/bbsize.html.
I seem to remember it being 127- but there's other values in there. I've had several half step/granny crank sets but don't use them exactly in that context- but I will use the half step to find a more comfortable cruising gear- and only with 5 or 6 speed. I'm running 10 speed so my crank rings are 28-38-50. But I probably should be running a 48.
As mentioned- a 1983 Trek will not be spaced at 120- most likely 128 and you can use 126 and 130 with none of that "cold setting" nonsense- on top of it only being 2mm- it's 2mm with 47cm chainstays.
Yes you should be able to use a Cyclone GT (either first gen or MII) with 7 speed. The suntour barcons will work with that. I'd suggest getting real shift housing rather than the metal springy stuff it came with. I haven't used the old barcons with anything over 7 speed- you might have a bit of an accuracy problem at 9 and over. Again, half-step with 7 speed is dicey- someone can figure that out with a gear calculator.
Me, personally- if you're running the original DC960 brakes, I'd replace those with something cooler- XT M732, Deore MT62 or MT60 or XT MC-70- in that order.
I have a 1985 Trek 720- I've replaced most everything on it- but it's running a 10 speed triple. It's really a great great bike.
1985 Trek 720 by
Dave The Golden Boy, on Flickr
85720Yard by
Dave The Golden Boy, on Flickr
IMG_0616 by
Dave The Golden Boy, on Flickr
IMG_2402 by
Dave The Golden Boy, on Flickr
IMG_1728 by
Dave The Golden Boy, on Flickr
IMG_1715 by
Dave The Golden Boy, on Flickr