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# Chain length with new cassette.

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# Chain length with new cassette.

01-24-17, 04:10 PM
#1
Wileyrat
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Chain length with new cassette.

I'm changing out my drivetrain on my mtn bike, and I'm wondering how many more chain links I should be looking at going from a 32 to a 36 tooth cassette.

derailleur cage is the same length, so I should be good there. Chain rings are the same size, so ditto. The only difference is 11-32x8 to 11-36x10 cassette.

01-24-17, 04:46 PM
#2
Seafris
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Maths

So if you're adding a new cassette, I would first make sure that the Rear Mech can handle the big chainring and big cog combo.

(Big ring - Small ring) + (big cog - small cog) = Chain wrap capacity.

You'd have to look up the specs on the mech to see if this falls within tolerance.

Then to size the chain I usually take the chain and wrap it through the FRONT mech around the big chainring, and around the big cog (NOT the rear mech) and see at which links you can join the chain (with no slack in the chain). Then count over 2 links longer (one inch) and connect the chain at that point.

OR

Taken from Park Tools website

Simple Equation: L = 2 (C) + (F/4 + R/4 + 1)

L = Chain length in inches. Round the final result to closest whole inch figure.
C = Chain stay length in inches, measure to closest 1/8". Use chart above to find decimal measurement.
F= Number of teeth on largest front chainring.
R= Number of teeth on largest rear cog.

Example: A bike has a 42-32-22 front chainring set up. Use only the 42 for the equation. The rear cog set has 32 teeth on the largest cog. The bike measures 16-3/8" from the center of the rear axle to the center of the crank bolt. The decimal equivalent for 16-3/8" is 16.375 inches.

but that requires maths.

Hope this helps!

01-24-17, 04:47 PM
#3
HillRider
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The theoretical difference is two "half-links" or one full link (1") which assumes your chain is the correct length now, i.e. it will allow you to safely shift into big-big.

01-24-17, 05:15 PM
#4
Bill Kapaun
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Why not buy a new chin with your new cassette and then size it properly.
I like BIG:BIG +1" also.
It's quick, simple and results in a "safe" installation.

Make sure your RDER will handle a 36T cog.

01-24-17, 05:19 PM
#5
Wileyrat
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Thanks for the quick response.

This is a Deore groupset kit from Ribble (crankset, fd and rd, chain, cassette, shifters) so far that's been my only delemma.

Last edited by Wileyrat; 01-24-17 at 05:22 PM.

01-24-17, 06:44 PM
#6
dsbrantjr
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After you size and install the new chain make sure to check the length by slowly turning the cranks by hand and checking that you can shift into the big chainring/big cog combination without straining anything. STOP if things get tight. There should be some travel left in the rear derailleur cage.

01-24-17, 06:50 PM
#7
Marcus_Ti
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Big/Big+1 full link gets you the shortest possible chain.

I prefer small/small-which yields the longest possible chain your RD cage will take up. Which if you snap a chain on the road--you have sacrificial links to work with.

01-24-17, 08:08 PM
#8
trailangel
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01-24-17, 09:49 PM
#9
rm -rf
don't try this at home.

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Another vote for Big-Big + 1 inch. It's easy to do.

Here's the Park Tool Repair Guide with step-by-step instructions.
Chain Length Sizing

Last edited by rm -rf; 01-24-17 at 09:52 PM.

01-24-17, 10:51 PM
#10
nfmisso
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Shimano's published procedure for most (all ?) of their equipment says big to big plus 1"

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