What would be the best combo for speed?

Wldcat10 · Apr 7, 2015

How's it goin' everyone?

I converted my mtn bike to a single speed a little less than a year ago. I really like simplicity and clean look of the bike. When I converted it, I had geared it semi-low (32t front, 16t rear) to hit some trails. I don't really hit the trails as much as I would like. So now I am wanting to switch it to a higher gear for street riding only.

The kit I bought came with 16t, 18th & 20t rear sprockets. I want to keep the 32t front sprocket. What would be the best combo (if possible?) for some higher speeds on the road? Last night I switched to the 20t rear with 32t front and it felt almost the same as when I had the 32t/16t combo. I just want to catch some speed without feeling like I'm pedaling like a mad man and not going anywhere.

Any info/input is greatly appreciated!

alistair clark · Apr 7, 2015

Switch the 32t in front to a 46-48 front. Keep the 16t if you must.

32tx16 52
32tx18 46.2
32tx2o 41.6

46x16 73.1
46x18 65
46x2o 58.6

48x16 78
48x18 69.3
48x20 62.4

The 32x16 is your present gear. In order to get more "speed" you increase the size of your front chainwheel and decrese the size of your small rear freewheel. 52-78 numbers are the inches traveled per revolution per gear change. I use to spin a 52x13 giving me 106 my topend speed was getting close to 30 mph on the flats. But that was way back in 1980's Today I could spin that and only get 25 mph. My cadence has slowed down because of age and conditioning. My guess would be to go with 48x16 there is no way spinning a 32x by whatever will give you any amount of speed on the flats.

Bicycle808 · Apr 15, 2015

If you wanna keep the 32t front sprocket, you could swap out the rear for a 13t and get a 64" gear...compared to the 52" you got now. It won't be fast in terms of top-speed but it'd be cruisable, and you'd retain some decent low-end off the line.

Personally, if I were looking to ride it on-the-road as a fun bike, i'd shoot for something in the 65 to 70" range.... and 64" would probably be good enough for me. You can play around with this to see what you can get with spare parts you may have lying around:
http://sheldonbrown.com/gears/
I'd also suggest running singlespeed-specific sprockets front and rear, if you replace anything. Sure, sprockets designed for derailer systems will work, but any from the past 25years or so will have ramps, pins, and gated teeth which held shifting on a derailer bike, but can lead to dropped chains on a singlespeed....

IF you're trying to push really big gears for top-end speed, I guess do whatever you like, but be forewarned that it's gonna suck to climb or start rolling from a stopped position with gears like that. PErsonally, that's why I got a roadbike with multiple gears (@110" gear in top) and even my singlespeed road bike will have a 78" gear, rolling on 700x28c rubber.

An often-repeated singlespeed cliche is something like "you know you have the right gear ratio when it does n't feel right on ANYthing".... if you pick a gear that feels good going fast, it's gonna suck uphill, and if you pick a gear that feels right going up short-n-steeps, it's gonna spin out really early on flats, and forget about descents....

GuitarlCarl · Apr 15, 2015

I forget what I put on the Difference Engine, but it turned out to be the same as many teams use for cadence training, and I really like it. Google up cadence training gear and see what you get....

Carl.

roadwarrior · Jul 19, 2015

With the change to a bigger front sprocket a longer crank would help your quest for speed. You didn't mention your crank length and it has a lot to do with how much physical effort you put in to how fast you go.