Single Speed Gearing

[cbottcher]

I am converting an old MTB to a single speed and need some ideas on gear ratios. The standard seems to be a 2:1, 32 front 16 rear. Is that a reasonable gearing to start with or should I go with something lower, maybe an 18 in the rear? I am a 46 yr old middle of the pack rider at best.

Also, some of the chain rings / sprockets are designed for 3/32 chain and other for 1/8 chain. Any opinons on the prefered chain type to use?

[riderx]

I always tell people to start w/ 2:1 (assuming 26" wheels) and adjust from there if necessary. But if you've got other gears already sitting around, throw those on and see how they work.

If you use a 1/8" chain you can use either 3/32" parts or 1/8" parts. If you use a 3/32" chain you can only use 3/32" parts. I run a 1/8" chain because of parts flexibility and you can get BMX chains like KMC for cheap and they last just as long as the "highly engineered" geared chains that cost twice as much.

[hophead]

I run 32:16 for my home trails--Schaeffer, Hoyles Mill, & Black Hills. It's a good ratio for rolling singletrack with not much in the way of steep climbs. For longer and/or steeper climbs, you may be happier with an 18. I have even run a 20 for very steep long climbs. I would recommend that you get several cogs or freewheels for different terrain and experiment.

My favorite chain is a Sram 8 speed chain. The singlespeed specific chains are okay, but can rub the bash guard sometimes if you use one.

-Scott

[joep]

It depends on where you like to ride and your riding style. Some people are mashers, some are spinners. I'd start easy (32:18) and go from there. Freewheels are cheap, knees are not.

3/32 chains have worked fine for me.

Cheers!

[rmac]

I ran 32/16 for the first 5 months. When the 16t fw wore out, I went to 32/18 & was happier on the hills without too much of a drop off on twisty single track. I also switched from a narrow PC99 chain to scram's ss chain. The narrow chain was binding up at times. A 9 speed chain wasn't a good idea, but an 8 might be ok, although the inexpensive bmx/ss chains are just as durable if not more so & leave a bit of room for misalignment.

I also found & followed a good article on aligning the front ring. Once your drive train is set-up, loosen the coupling bolts on the front ring & retighten them as you very slowly rotate the cranks while checking chain tension through the pedal rotation. Tighten each a bit, working opposite bolts as you would when putting on a spare car wheel. Check that your chain tension is equal throughout the entire pedal rotation. Mine was out of wack & this really helped.

[peter6061]

I run 32:16 on my off-road 26" SS mtb. It works well at most of the rolly places around here (Wake-o-tink, Rosaryville, Schaeffer, Patapsco, Fountainhead). I'll bump down to 32:18 for 'bigger' rides (Gambril, Shed, Furnace, etc,..)

I'd start with 2:1 and see how it feels. It's easy enough to switch to an 18 in the back.

[saxman]

When you're doing an MTB conversion, sometimes the bike will dictate what gearing you can get away with. On my "Mongrel" MTB conversion, each time I've tried to switch from a 16 to 18T rear, I start having problems with the chain skipping. My chain is the perfect length for a 16T rear on a converted wheel. When I try 18T Single-Speed specific or an 18T single cog on the converted wheel, I have to lengthen the chain to the point where the chain doesn't get around the rear cog to prevent it from skipping. The hardest thing about my MTB conversion was getting the drivetrain to run smoothly. I'm stuck with 33:16, which seems to be a nice gear for the local trails around here.