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spamalope 09-03-11 06:20 AM

how many speeds do i have?
looking to buy a new chain but am confused about the number of speeds i have.

i have a trek 7100 -

Shifters SRAM 3.0 Comp, 7-speed twist
Front derailleur Shimano M191
Rear derailleur SRAM X.3
Crank Shimano M131, 48/38/28 w/chainguard
Cassette Shimano 14-34, 7 speed

do i count the 3 front and the 7 back gears and need a 10 speed chain? do i only count the back ones and need a 7 speed chain or what?

new to this! thanks in advance :thumb:

HillRider 09-03-11 06:28 AM

The "speeds" a chain is concerned with is based only on the number of rear casette cogs so you need a 7-speed chain and usually you will find them labeled as 7/8-speed or 8-speed which are the same width. A 9-speed chain (9 casette cogs) is narrower and a 10-speed (10 cogs) is narrower still.

BTW, you have a "21-speed" bike. The number of total gears is calculated by multiplying the number of chainrings by the number of cogs, not by adding them.

Mondoman 09-03-11 05:48 PM

Yep, you need a 7/8 or 8 speed chain, and it'll be significantly cheaper than a 9 speed chain or 10 speed chain. However, the 9 or 10 speed chain would work on your 7-speed cassette, it would just be more expensive and probably weaker than the 8 speed chain.

I'd suggest getting a chain that includes a reusable master link to make installation and removal of the chain easy. The SRAM PC-8x0 series all include a master link, as do some other brands. Shimano uses a non-reusable special pin to join their chains.

spamalope 09-04-11 06:58 AM

makes sense, thanks much for the info. think i'll buy an SRAM chain.

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