Henrik Y Posted January 7, 2008 Report Share Posted January 7, 2008 I'm making a list of parts that I need to build a 24" trial bike with an Inspired frame and I was thinking about the sprocket sizes.On my 26" I have 22t/19t, would 18t/14t be the same on a 24" or should I even go with a 13t?And crank length, 160mm or 170mm?Anyone that have some experience and thoughts on this that could give me some help are welcome. Quote Link to comment Share on other sites More sharing options...
eskimo Posted January 7, 2008 Report Share Posted January 7, 2008 Save you waiting for a reply theres some help here. Quote Link to comment Share on other sites More sharing options...
Tom_ Posted January 7, 2008 Report Share Posted January 7, 2008 Im going 170mm 22-16 Quote Link to comment Share on other sites More sharing options...
Skoze Posted January 7, 2008 Report Share Posted January 7, 2008 I run 175's and 18:15, it's pretty damn nice IMO Quote Link to comment Share on other sites More sharing options...
Christophe' Posted January 7, 2008 Report Share Posted January 7, 2008 Ive got 170mm and 20/16. Quote Link to comment Share on other sites More sharing options...
Felix Posted January 7, 2008 Report Share Posted January 7, 2008 22:16 is perfect. Quote Link to comment Share on other sites More sharing options...
rich4130 Posted January 7, 2008 Report Share Posted January 7, 2008 Haha i run 20/18! 20/16 is nice for normal people. Quote Link to comment Share on other sites More sharing options...
psycholist Posted January 7, 2008 Report Share Posted January 7, 2008 (edited) Here's a quick calculation to match the ratio on a 26" wheel to a 24" wheel. If you're running a 22:19 on the 26" bike that's a 1.16 ratio, that is 1.16 turns of the wheel for every turn of the pedals (22/19=1.158). To get the same ratio on a 24" bike with an 18T freewheel, first convert the ratio you have on your current bike to that required for a 24" wheel by multiplying by the ratio of the tyre diameters (If you have both sized wheels handy, a more accurate ratio can be found by using the ratio of the tyre circumferences, which are more easily measured - measure the rolling circumference while on the bike rather than trying to run a measuring tape around the tyre though). This ratio is 1.25 (1.158 x 26/24 = 1.254). To get this ratio from an 18T freewheel, divide the number of teeth on the freewheel by the ratio required (18/1.254 = 14.3). Rounding this to the nearest whole number gives 14 teeth as the closest ratio you can get (Though slightly higher). With a 20T chainring this would be 16T, or with a 22T chainring it would be 17 or 18T (This lands at 17.53 teeth, so you'd have to decide whether you like a noticeably higher or lower gear). Edited January 7, 2008 by psycholist Quote Link to comment Share on other sites More sharing options...
Henrik Y Posted January 7, 2008 Author Report Share Posted January 7, 2008 Here's a quick calculation to match the ratio on a 26" wheel to a 24" wheel. If you're running a 22:19 on the 26" bike that's a 1.16 ratio, that is 1.16 turns of the wheel for every turn of the pedals (22/19=1.158). To get the same ratio on a 24" bike with an 18T freewheel, first convert the ratio you have on your current bike to that required for a 24" wheel by multiplying by the ratio of the tyre diameters (If you have both sized wheels handy, a more accurate ratio can be found by using the ratio of the tyre circumferences, which are more easily measured - measure the rolling circumference while on the bike rather than trying to run a measuring tape around the tyre though). This ratio is 1.25 (1.158 x 26/24 = 1.254). To get this ratio from an 18T freewheel, divide the number of teeth on the freewheel by the ratio required (18/1.254 = 14.3). Rounding this to the nearest whole number gives 14 teeth as the closest ratio you can get (Though slightly higher). With a 20T chainring this would be 16T, or with a 22T chainring it would be 17 or 18T (This lands at 17.53 teeth, so you'd have to decide whether you like a noticeably higher or lower gear).Ok, thanks. I was thinking about 13t to get a little more speed. And this confirms that I will not get to far away from what I was thinking. Quote Link to comment Share on other sites More sharing options...
John Shrewsbury Posted January 7, 2008 Report Share Posted January 7, 2008 (edited) 22 -19 Edited January 7, 2008 by John Shrewsbury Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted January 7, 2008 Report Share Posted January 7, 2008 22 -19That seems really light John! What length cranks do you use? I'm currently running 18-13 with 165 cranks which is a little stiff but I'm sure I'll get used to it.Dave Quote Link to comment Share on other sites More sharing options...
Christophe' Posted January 7, 2008 Report Share Posted January 7, 2008 http://sheldonbrown.com/gears/ Quote Link to comment Share on other sites More sharing options...
John Shrewsbury Posted January 7, 2008 Report Share Posted January 7, 2008 That seems really light John! What length cranks do you use? I'm currently running 18-13 with 165 cranks which is a little stiff but I'm sure I'll get used to it.DaveRaceface northshore cranks 175, im using 22-19 on my 26 bike.I havent built my inspired yet, so may change the gearing. Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted January 7, 2008 Report Share Posted January 7, 2008 Raceface northshore cranks 175, im using 22-19 on my 26 bike.I havent built my inspired yet, so may change the gearing.Ah, that makes sense. I guess you may find you need to go to a 17T or so to make the gearing similar on the Inspired. Looking forward to the pics of the build Quote Link to comment Share on other sites More sharing options...
Ross McArthur Posted January 8, 2008 Report Share Posted January 8, 2008 22-16 is good but i suppose thats for street n stuff so if your riding tech natural you might want something a bit lighter. Quote Link to comment Share on other sites More sharing options...
011001000110010101110010 Posted January 9, 2008 Report Share Posted January 9, 2008 165mm cranks 16:13 Quote Link to comment Share on other sites More sharing options...
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