New drivetrain for a commuter restore.

I recently purchased a 1991 Schwinn Crisscross for 7 day a week, year round commuting to school/work/etc as well as some light touring in the nearby hills. My two brothers are into mountain biking and I'm thinking I might keep two wheel sets so I can throw some mountain tires on it and do some light trail riding. I'm pretty tall (6'4") and was amazed to find a bike large enough for me and for just $20 on Craigslist. Fixing up the bike is also going to serve as a fun learning experience and hobby which I'm looking forward to as much as riding the thing. I'm really new to working on bikes and figuring out parts so I'm reaching out for help/advice.

The bike currently has the Suntour XCT derailleurs, X-press shifters, and the 3 x 7 gear set up that came with it back in '91. The drive train is super worn. Lots of chipped teeth and poor shifting on both ends. Also there's a bit of chatter in the BB so I'm thinking I need to get that replaced.

I like having the flat bars on it but am planning to get a new stem that's a bit further back and higher than what it has on it now for a bit more relaxed ride position and I've got that figured out but when it comes to the drive train and shifters I'm pretty lost. I've been doing some reading around the net and am thinking that a 46/32 crankset and a 12-25 10 speed cassette seemed like it would give me the gearing that I would want but when it comes to finding/choosing a proper BB/crankset/shifters/cassette/derailleurs I'm pretty darn lost.

I saw that SRAM sells a 2 x 10 flat bar pair of shifters so I figured I'd go that route. If I do that I have to get SRAM derailluers right? Should I go with mtn or road ones and whats the difference? Also is there different ways to mount them? What kind/size of BB do I need or how can I figure that out? I'm worried that the BB shell will limit what BB I can use which may limit my crankset options. Then I don't know if I'll need a new rear wheel in order to accommodate the 10 speed cassette. I'll need a new freewheel/freehub right?

Like I said I'm pretty lost but I'm also really looking forward to all the learning and the challenge. Been reading a lot but am to the point where I need to reach out for help. Thanks ahead of time for any help you can provide.

Here's a few pics I snapped.

 

Right. The shifters need to be compatible with the derailleurs. And the derailleurs need to be compatible with the cassette. And the cassette needs to be compatible with the rear wheel.

Before we get too deep into this, please tell us the width of your bottom bracket shell (most likely 68 mm), the spacing of your rear wheel dropouts (most likely 130 mm), the size of your wheels (26" or 700c), and whether the frame is made of aluminum or steel. Rather than try to develop a spreadsheet to cover your options for all these variables (some of which will be deal-killers), it will be easier for me to recommend and for you to read if we can narrow it down.

 

SWEET bike for only $20!!!

Well, it may be a good thing that I am a steel frame aficionado ...

• FYI. Most steel framed "touring" frames from the early 90s had 135mm rear dropouts ...
• And, most steel framed "touring" frames from the early 90s had 68mm wide English threaded Bottom Brackets ...
• Those are 700c wheels/tires, of course ... And yes, the lugs + brazed rear dropouts certainly ensure that it is a steel-and-not-aluminum frame.

BTW. Before you dismiss your Chainrings & Cogs as being chipped, you should go to an LBS (or, surf the web) and look at the profile of the teeth on new Chainrings & Cogs ...

They could indeed be damaged ...

Regardless, THAT doesn't meant that your bike won't benefit from new cables & housing ... from a distance, it looks as though the bike was not neglected.

• New cables & housing may actually resolve ALL of your shifting problems.

If you are feeling ambitious, then you could buy an unlaced Shimano Freehub & re-lace your current rim onto it ...

Of course, you can buy a 700c wheel/wheelset, but you either need to be certain that the rear hub has 135mm O.L.D. or (if you are a DIYer), you can re-space the frame DOWN to 130mm (130mm is the standard Road hub O.L.D. width ... also, older/(aka "real") CX frames have 130mm rear spacing ) ...

And then, consider choosing a Cassette whose smallest tooth is 11t instead of 12t if you are still planning on a 104BCD MTB crankset.

• Regardless, IMO, your "best bet" is to simply opt for Shimano MTB derailleurs & shifters + the Road crankset of your choice rather than anything SRAM is offering ... just because a LEFT/front shifter can handle three chainrings doesn't mean that you have to set it up with that many ... you may be able to use a set of Shimano MTB shifters with the current derailleurs
• I would try the current derailleurs before buying replacements

[*]A 7-speed SunRace Freewheel will work with 8-speed Shimano shifters (and an 8-/9-speed Shimano rear derailleur)

• again, the current rear derailleur may work with whatever Shimano MTB shifters you might buy

BTW. I think you may be hard pressed to find a stem which has BOTH a shorter reach AND is taller. Consequently, you may want to consider a BMX handlebar OR a "Stingray" handlebar.

FWIW. I re-spaced the following frame's rear dropout spacing from 135mm down to 130mm so that I could use any Road wheelset on it on an as-needed basis ...

​

​

​

Although YOUR BUDGET is probably your only limitation, I think that you may want to replace components on an as-needed basis rather than making a wholesale component swap BECAUSE you may find that where you ride may include roadways which will benefit from the bike having a Road Crankset rather than MTB Crankset.

• IF the BB needs servicing, then it may be worth the $20 +/- for a 113mm, Shimano UNiversal-xx, Square Taper Cartridge BB to extend the life of the current Crankset until you have a better idea about what type of Crankset you want to use on the bike.