Bike Forums - View Single Post - ??s about front ring sizes / #teeth

01-08-11 | 09:55 AM

#20

Barrettscv

Have bike, will travel

Joined: Feb 2006

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From: Lake Geneva, WI

Bikes: Ridley Helium SLX, Canyon Endurance SL, De Rosa Professional, Eddy Merckx Corsa Extra, Schwinn Paramount (1 painted, 1 chrome), Peugeot PX10, Serotta Nova X, Simoncini Cyclocross Special, Raleigh Roker, Pedal Force CG2 and CX2

Quote:

Originally Posted by HillRider

I don't know what the OP's crank configuration is but big-big+1" is never a mistake unless you change the cassette for a larger one without adjusting it.

I agree.

I'm assuming that the OP has the 53, 42, 30t OE crankset and a 12-25 cassette as stated. Installing a 26t granny gear will require a chain wrap range of 40, the 39t chainwrap range of the Shimano GS RD has a safety factor. He is right at the upper range of the RD chain wrap capacity.

I first assumed that he had a 50t big chainring, so my first calculation is off. However he should still shorten the chain using the Big-Big +1 as you suggested. I would be suprised if he had slack on the small-small combo after resizing.

Michael

Last edited by Barrettscv; 01-08-11 at 10:45 AM.

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