Bicycle Mechanics - Changing the middle chainring on a roadbike

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DogBoy
08-18-04, 12:27 PM
I just dropped off my bike for a tune-up and the mechanic indicated that my middle chainring probably only had about 1000 miles left. That would be only 2200 miles on the ring. First off, I thought that was low, considering that I lube my chain every other ride and clean my chain every other week. But that's not the point of the post.

Since I'm going to have to replace it soon, I was wondering what I need to determine to see if I can change the ring from a 42T to a 39T. Currently I have an FSA crankset and DA 9'spd deralliers (sp). I want to switch to the 39T because I'd like to get the feel for what its like to ride a double. The small ring is a 30T and the large ring is a 52T. So, what do I need to look at to figure this out? Or, is this even an option?

sydney
08-18-04, 03:21 PM
I just dropped off my bike for a tune-up and the mechanic indicated that my middle chainring probably only had about 1000 miles left. That would be only 2200 miles on the ring. First off, I thought that was low, considering that I lube my chain every other ride and clean my chain every other week. But that's not the point of the post.

Since I'm going to have to replace it soon, I was wondering what I need to determine to see if I can change the ring from a 42T to a 39T. Currently I have an FSA crankset and DA 9'spd deralliers (sp). I want to switch to the 39T because I'd like to get the feel for what its like to ride a double. The small ring is a 30T and the large ring is a 52T. So, what do I need to look at to figure this out? Or, is this even an option? Sounds like BS to me. A middle ring should not wear out anywhere near that fast. You need a 130 BCD 39 ring and for best shifting it should be pinned and ramped like the original. Chainrings at www.peterwhitecycles.com
Don't buy that drivel of his that the difference between middle and big can be no more than 10 teeth. It's a misquote of somethng entirely differen from Shimano.
John E
08-18-04, 04:42 PM
I do not replace any chainring until the chain runs noisily or skips on it. To maximize chainring and cog longevity, replace your chain as soon as it has elongated by 0.5%, i.e., 1/16" per 24 half-links [sheldonbrown.com].

Some manufacturers specify different 52/53T chainrings for use with a 39T or a 42T inner/middle, but I really don't think it makes much difference. In fact, unless you shift under power, pinning and ramping really don't make much difference, anyway. In the good old days, cyclists did just fine without ramps, pins, or indexing, provided that they eased up on the pedal load while shifting, which is still good advice with today's equipment.