Bicycle Mechanics - Cogs
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05-25-03, 06:59 AM
I have a standard HG70 cassette 13-23 -8speed, and the maximum jump from one cog to the next is 2 teeth. LBS says I cannot have more than 2 teeth jump between cogs. I tried today replacing the 23 cog with a 25, so the jump is 21 to 25 and it works very well.
Will a 19 to 25 jump work? I have a standard SORA triple rear and FD.
I also have a triple Sora and the cassette that came with it was 11-28 (8 speed), obviously there are jumps in there of more than 2 teeth. If you want I'll checkout and post each cog. The largest cog is significantly larger that the next on over, it looks like 4 teeth.
What I can say is that a 19 to 25 jump from cog to cog probably isn't smart just from a pure cadence point of view. Even if it does work on the chain, I don't think its smart. If you want a 13-25 you could get 13-14-15-17-19-21-23-25
05-25-03, 07:25 PM
It should. My cassette has 12-14-15-16-17-19-21-25-32... which means 4 and 7 teeth near the end. No problem.
If you put a very large jump, ease the pressure while you shift. That could be a problem in racing, but not in more "casual" cycling.
Regards also from Montréal,
32 as a largest cog? what kind of bike is this road or mountain? That seems pretty huge for a road bike (I though mine was large, too large, at 28)
05-25-03, 09:16 PM
The largest "road" cog is 27t, but with the right der. you can run a 34t
05-26-03, 05:21 AM
thanks guys for the input. I have ordered a 18T cog so I will have
13,14,15,16,17,18,19,25. The 25 is for hills or 'emergency!'
05-26-03, 02:50 PM
My bikes are touring bikes. The bike I was talking about is a Trek 520 touring bike (vintage 2000). "Touring" configurations don't officially exist in Shimano catalogs, so makers of touring bikes and especially of light touring bikes mix a road crank with an MTB cassette and rear derailleur. By default, my bike came with 52-42-30 "105" crankset and an 11-30 8-speed cassette with an LX derailleur. However, I had the drivetrain swapped at time of purchase for a 44-34-22 XT drivetrain
Back when most bikes had only 10 gears, I experimented with various combinations of cogs, a few of which included fairly radical "granny jumps." I set up my wife's bike with 52-42 / 16-18-21-24-32, which met her transportation needs around hilly west Los Angeles quite well. Sheldon may still sell a (factory-standard!) 14-16-18-20-22-24-32 Shimano freewheel. I use its tighter 14-16-18-20-22-24-28 cousin on the Capo and hold the 28 in reserve in case I encounter a tough hill at the end of a long ride. I use an old SunTour V derailleur, without a spoke protector, and have never had a problem with the 24-28 shift.
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