plowmanjoe

So I picked up a 90's trek 950 mtb for $40 on clist that i'm using as my winter beater/ commuter/ grocery getter. My other bikes are too nice to be locked up up outside in NYC.

I'm changing out the tires for something faster and throwing on some townie style bars. Maybe getting some fenders and a rear rack but otherwise trying not to mess with it too much.

I'm used to riding with 165mm cranks and these are 175. So I'm thinking of trying to find some shorter cranks if it can be done for cheap enough, maybe find something used.

The 7 gears in the back are working fine. I wouldn't mind going 1x7. I just don't know anything about compatibility. Would I be able to just throw a single speed/ track cranks on there? Or do I need to go with a narrow wide chainring? and would I need a new bottom bracket to keep the chainline nice? These are all new things to me.

John Valuk

Cool! If one of those turned up for that price on my local CL, I'd be all over it.

If you're interested in finding out more details about what you have, you might look at the Vintage Trek site.

They have a list of models by year and color, which might allow you to identify the year. They also have scanned copies of some of the Trek technical manuals that include fairly detailed information about original components, frame geometry, etc.

That doesn't directly answer your questions, but it might be useful to know details about the original bottom bracket, crankset, etc. when you're considering options.

plowmanjoe

Thanks. Mine is purple and green fade, so apparently it's a '95

alcjphil

Many single speed and track cranks are designed for a 1/8" chain. They won't fit the chain on a bike with a derailleur

John Valuk

Here's the page that has links to the scanned catalogs and technical manuals: Trek, Fisher, Klein, LeMond and Bontrager Bike Catalogs.

veganbikes

I would recommend against 1x7 having done it I did not care for it at all. I found some gaps that annoyed me to no end, the bike moved to a 1x9 and I am set. Same 11-32 cassette but with the gaps filled in by the two other cogs. I would recommend a narrow wide if you can. Mine is running a RaceFace NW chainring and has been flawless for years. You could go with a 130BCD crank and the correct bottom bracket for your usage but a 144bcd track crank wouldn't be as practical you can find older campy chainrings that are for multi speed set ups but honestly they are all quite large and wouldn't be good for your situation.

I am personally running an older Tiagra Hollowtech II crank with the ring in the middle position and a AC Cross Wizard chain guard on the outer and everything is fine and dandy. You might just able to remove chainrings and go from there and test it out and if you find you need something different get a different ring.

plowmanjoe

I'll keep the 7 in the back for now and adjust if I find the setup lacking. I normally ride a fixed gear, so my guess is 7 will be enough for me. But we'll find out.

plowmanjoe

If i swapped out the chainring, it should work, right? or are there other compatibility issues?

mack_turtle

a track crankset with a BB spindle that allows the arms to clear the chainstays should work. the trick will be getting the chainline correct too. a narrow chainring made for a 8+speed chain should be fine.

as for the limits of a 1x7, it's probably fine for a casual, utilitarian bike. if you're used to riding one gear all the time, it won't bother you. for roadies who are used to at least 2x11, the gaps in cadence would be annoying. if you have it loaded down with groceries, you'll appreciate having more than one gear. NYC is not known for it's elevation changes, so it will be fine.

blakcloud

If this is a beater bike, why throw that kind of money into it by purchasing new to you cranks? I would keep the 175's but if I HAD to replace them I would buy a cheap triple so that I wouldn't have to buy a new bottom bracket. Put the chain on the middle chain ring and don't shift on the front, now you have a virtual single ring outfit. The front derailleur will keep the chain from dropping off. At any rate try the 175 first before throwing money into this project, you may find you like it.

mack_turtle

I don't think you'll get much benefit from shorter cranks. I am not all that familiar with fixed gear city riding. do you like shorter cranks because you're less likely to pedal-strike the ground when turning? since the bike in question can coast, you'll adapt quickly to that like any human and it won't be a problem.

tkamd73 

The crank arm lengths on my bikes vary from 165 to 180mm. I notice the difference for the first couple of miles, then forget about it. I wouldn’t bother changing them out, not that big of deal. Tim

70sSanO

Here is your issue. Cheap, as in less than $50 with BB, 165mm triple cranks are pretty much gone right now. A couple years ago you could find a cheap Vuelta or Deore triple and run the center chainring. Could even move the outer to the middle if you wanted.

With the pandemic, supply lines are gone and it remains to be seen what products are brought back when things get re-stocked.

I’d ride it as is and figure out how the gearing fits where you ride. If things get back to normal you’ll have an idea of what works for you.

John

plowmanjoe

I've been riding it as is for a couple weeks now. I definitely don't prefer the 175, but maybe it's something I can get used to. Also not in a rush to throw money away. I want to get educated on this stuff so I know what to keep an eye out for if I do find a really good deal on something.

plowmanjoe

I'm a shorter rider, so 165 feels much more natural to me. I'm riding in a lower saddle height with this new bike and not spinning as smoothly. That being said, maybe just sticking to it is the solution.

plowmanjoe

very logical plan, thanks.

veganbikes

1X7 is a lot more than 1x1 for sure. One should have multiple bikes with various gearing options and at least one fixed gear or single speed (in my case two)

Moisture

going from 175 to 165 is a downgrade. Why would you do that?

This is not an idea frame geometry for a city commuter bike. Don't put any work in it other than maybe some new bars.

Blues

I have a purple and green '95 Trek 930 I use as a Cruiser. I added pull back bars, a rear rack and smoother tires to it. The 14-28T freewheel was worn out so I changed it to a 13-34T and I run the front chain on the middle 32T ring for my riding in my hilly local area. A derailleur hanger extender was necessary for the larger rear cog. The low gear is fine for my hills. I can spin out around 20 mph in high gear on the 32T chain ring, but I don't have this bike to go faster than that. It's a comfortable get-there Old Geezer bike. I'm essentially running it as a 1x7 and love it.

plowmanjoe

maybe I should be upgrading to 190 then. do you have any good recommendations?