RoadBikeReview.com's Forum Archives - Fixed Gear


Archive Home >> Fixed Gear


gear range for horizontal dropout SS(6 posts)

gear range for horizontal dropout SSmattcrout
Apr 16, 2003 11:16 AM
I'm putting together a SS and have a '83 frame with horizontal dropouts. The crank is a SR super custom (that's Super Record right? Is that a good crank?) that is a 52/40. i took off the 52 and am going to keep the 40 on there for now. does it matter if it's on the inside or outside? (trying to keep this cheap) i have a 7-speed cassete for a freehub that i'm going to fill with spacers and my cog of choice. my question is, how big of a range of cogs can i put in the back without having to change the chain. if i put a 15 on, and pulled the axle all the way to the back of the dropout, and get the chain all set up, how big of a cog can i switch that out with without making the chain bigger? (i'd just move the axle towards teh front of the dropout) hope that makes since. Does this sound like a good ratio? thanks
Generally speaking........bungalowbill
Apr 16, 2003 11:44 AM
you can usually go up to a two tooth difference using a frame with semihorizontal dropouts (I'm assuming this isn't a frame w/track type fork ends). So, you should be able to use a 17 as well. This isn't guaranteed because some dropouts are longer than others and you have to take the chainring size and chainstay length into account as well.
40/15 is a good ratio for a variety of riding- I ride a 42/16 (about the same as 40/15) and I've found it's just about the perfect gear for flat as well as rolling terrain.
re: gear range for horizontal dropout SSSteve_0
Apr 16, 2003 12:11 PM
1 tooth change = 1/8th inch change, IIRC.
Put the chainring ...Humma Hah
Apr 16, 2003 12:32 PM
... whereever you get the straightest chain alignment. Since you're building up a freewheel from an old 7-speed and spacers, you've got huge latitude as to where to place it.
Lots of leeway...SenorPedro
Apr 19, 2003 5:29 PM
Hey Matt,

Glad to hear that everything worked out with picking up the bike from my Dad. A little advice if you want it-

A rule of thumb that I heard from a crusty old track racer was that for every change of 4 teeth in the drivetrain, then you add or subtract a link accordingly to keep the rear wheel in relatively the same place in the dropouts. I.E. You might have a 42-18 setup, so technically if you went to a 44-16 you wouldn't have to change your chain length, if you went 42-14 you could take out a link, and if you went 46-18 you would add a link. This supposedly allows you to keep the same center to center distance from the BB to the rear axle.

But that may be an old man's tale - I haven't tried it, so I don't know.

Something I have found to be more reliable is this website:
http://www.peak.org/~fixin/formfmu.html

It allows you to enter some basic data, then it gives you gear combinations that will work with your chainstay length.

With the chainring, it doesn't really matter where you put it; you have plenty of adjustability by putting your cog on a cassette hub. If I was going for the really cheap method, I would get some spacers so I could use the same chainring bolts, then put the ring on the outside, with the spacers where the inner ring would go. This would be aesthetically pleasing to me, leaving the whole crank surface flush and all. But it is totally up to your own preferences.

Good luck, lets see it when you get 'er done!

-Peter
About that crank...Straightblock
Apr 24, 2003 8:51 AM
It's probably not a Super Record (Campagnolo) but a Sakae Ringyo(sp?) made in Japan. They were pretty common on a variety of bikes at that time. SR made several models, some were pretty nice, but they're not Campy.