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Should I do this?

Old 07-26-20, 10:54 PM
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Sjtaylor
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Should I do this?

I have an 11-32, 9 speed cassette matched to a 48-38-26 with a Deore long cage derailleur on an 1984 Trek 720 touring bike frame I recently posted about. Gear inches go from 120 to 22, a little too high and probably not quite low enough for hills, my weight and fitness level. I’m thinking about trying a 12-36 cassette which would take the gear inches from 108 to just under 20. I’d like that better.

I’m not sure if the derailleur will eat enough chain to allow shifting to all the gears. I’m guessing probably not from what the current gearing shows. If I promise to not shift into the 48 in front and 36 in back should I try the 12-36?

I’m not sure what would happen to a loaded touring bike if I tried to shift to the forbidden 48 to 36 although I promised not to. Does anyone else ride with a forbidden gear?

Thanks.
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Old 07-27-20, 01:49 AM
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Bill Kapaun
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I just when to a cheap 22-32-44 crank to solve a similar issue. <$60 for a crank & BB.
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Old 07-27-20, 04:46 AM
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Originally Posted by Sjtaylor View Post
If I promise to not shift into the 48 in front and 36 in back should I try the 12-36?.
Your chain MUST be long enough to allow this, you will eventually forget and shift into that combination and damage will result. Much better to have a long-enough chain and a slack chain in 26-12
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Old 07-27-20, 06:38 AM
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Originally Posted by Sjtaylor View Post
I’m not sure what would happen to a loaded touring bike if I tried to shift to the forbidden 48 to 36 although I promised not to.
Broken derialleur, bent derailleur hanger, broken wheel because the bent derailleur got inside the spokes, broken chain, even a crash...

Don't do it. Just don't. You will eventually make a mistake and use the "forbidden" gear. We all do.

If the derailleur can't take the range, use a long chain that is slack in the little-little combination. Maybe you won't be able to pedal in that combination, but at least it's difficult you'll break anything in the process.
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Old 07-27-20, 10:15 AM
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Sjtaylor
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I'll put on the 12-36 cassette and install a new chain sized to run in the the forbidden gear. I like the slack chain scenario better. Thanks.
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Old 07-27-20, 11:35 AM
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The difference in cogs in the back goes from 21 to 24. Add in the front difference of 22 and you go from 43 to 46. The long cage rd is supposedly maxed out at 45T difference. I suspect that the 1 tooth over spec will not matter much if you leave an extra link in the chain.

But yeah, never count on controlling that ratio and never using big/small. The times you have the big front chainring and you have to drop the gearing quickly would soon take care of that idea. Not safe.

But your may already have a new chain on that sucker. Good luck. Enjoy the ride.
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