Singlespeed & Fixed Gear - Multiple cogs for a fixie

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dersidc
10-21-03, 12:51 PM
Hey guys

I am eagerly awaiting the arrival of my new Bianchi Pista (in less than two weeks, I'm told). It will be my first fixie. I've been reading a lot about fixie riding (much of on this forum - thank you all for that!).

Here's the question: my Pista comes with a 48x16 which is a 78.8 gear inch. I am thinking about starting out lower for more spinning on my daily commute. Was thinking about 48x18 which is about 70 gear inches.

My question is how big of a cog can I put on before I have to change the chain? Is 18 going to be OK? Also, how easy is it to flip the wheel and tension the chain?

Thanks a lot

Cris

alexs
10-21-03, 02:24 PM
i went from a 48x16 to a 48x18 without needing to mess with the chain. you should be fine as long as your axle isn't too close to the inside of the dropouts.
velo
10-21-03, 03:47 PM
Isn't a 48x16 an 81?

alexs
10-21-03, 04:44 PM
Isn't a 48x16 an 81?

only if you're on 27 inch wheels. 700c gets you 78.8.
roadfix
10-21-03, 04:55 PM
only if you're on 27 inch wheels. 700c gets you 78.8.
...that's fuzzy math.....
alexs
10-21-03, 05:04 PM
...that's fuzzy math.....

*shrug*

Far be it for me to contradict Sheldon Brown.

"...to calculate: the diameter of the drive wheel, times the size of the front sprocket divided by the size of the rear sprocket."

Diameter of the drive wheel changes your gear inches. 700c wheels have a different diameter than 27inch wheels. QED.

http://www.sheldonbrown.com/gears/
Kev
10-21-03, 05:15 PM
I have a 17x19 on my fixie and 16x18 on the other one, I think any more then 2 teeth you are pushing it. I find it works best if I set the chain as short as possible for the 18x19 then the smaller gear does not let the tire go back to far.
legalize_it
10-21-03, 06:41 PM
*shrug*

Far be it for me to contradict Sheldon Brown.

"...to calculate: the diameter of the drive wheel, times the size of the front sprocket divided by the size of the rear sprocket."

Diameter of the drive wheel changes your gear inches. 700c wheels have a different diameter than 27inch wheels. QED.

http://www.sheldonbrown.com/gears/


an even better gear inches calculation includes the crank arm length...i think sheldon browns calculator includes the crank lenghth....
alexs
10-21-03, 08:47 PM
an even better gear inches calculation includes the crank arm length...i think sheldon browns calculator includes the crank lenghth....

i think sheldon's calculator uses crank length only for gain ratios (as opposed to gear inches). but yah, calculating gears is even more accurate when it's done with the crank length in mind...

http://www.sheldonbrown.com/gain.html
naisme
10-21-03, 11:00 PM
Well, I stumbled on my favorite inches 81.9. Before this my favorite inch was an 85.4, a 16t rear and a 52t engagement, love my fixie set like that. I have been playing with my setup lately, and having to replace two Surly hubs on the fixies. I thought I'd do something different, and did a homemade SS with an old cassette. I dropped a 17t on the rear freewheel and kept the 53t engagment up front, and got out this evening for my commute, sweetness!

As for the topic, I can't really answer the question as I haven't ridden a Pista. I have horizontal drops on my fixed gears, and with a flip/flop hub a difference of 2 teeth is about all the setup can handle. What you could do is get that new hub that is adjustable, and build a wheel around it, so that you can run anything you want.