Bicycle Mechanics - Will my new drivetrain work?

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diarmuid
11-09-08, 06:55 AM
I'm about to get the credit card out and begin assembling this drivetrain for my Surly LHT which will be used for fully loaded touring. I'm not 100% sure if all the bits will get on with each other and would appreciate any thoughts. In particular, i'm not sure if the mechs will like the 8 speed chain and i'm thinking i may need a front road mech if im using bar end shifters...

Thanks for reading.

Chainrings: 20 - 34 - 46
8 speed cassette: 13 - 32
Chain: Sram 870 8 speed
Rear mech: Shimano XT M581
Front mech: Shimano LX M581
Shifters: Shimano Ultrega bar end 8 speed with Paul's thumbies

HillRider
11-09-08, 07:15 AM
It seems everything will work with one possible exception.

You didn't say what make and model crank you will be using. If it's a newer 9-speed design, the 8-speed chain may be a bit wide for it and may rub on some of the near cross chain combinations. BTW, a 9-speed chain will work fine with an 8-speed cassette if needed.

Otherwise, the 8-speed chain will work fine with the 8-speed cassette and SRAM makes good chains.

You can use the MTB front derailleur with the Ultegra barend shifters. All barends are friction front shifting and they are indifferent to what derailleur you have. The mis-match between MTB and road front derailleurs only occurs with index front shifting like STI.

Your rear derailleur will work with the Ultegra indexed barends but you must have the shifters match the cog number to use them in indexed mode. I.e. if you are going to use a 8-speed cassette, you must get 8-speed Ultegra bar ends.
diarmuid
11-09-08, 08:00 AM
Thanks Hillrider, very helpful.

Plan is to use Middleburn RS7 crank arms with an XC 5 bolt spider(http://www.middleburn.co.uk/cranks_rs7.php) and TA compact chainrings.

I have just checked the chainrings specs and they actually specify 9 speed! Doh..I didn't know chainrings cared what speed chain you put on them

operator
11-09-08, 08:15 AM
Doh..I didn't know chainrings cared what speed chain you put on them

They don't.

It's the chainring spacing, which is affected by the crank spider. Which is affected by the "speed" of the crank.
diarmuid
11-10-08, 01:23 PM
Understood, thanks.