10 speed SLX MTB cassette with Dura Ace drivetrain.

elcani
elcani Posts: 280
edited September 2010 in Workshop
Hi - I'm going touring (Bilbao to Barcelona) on my Planet X Ti Sportive and just wanted to check that my plan to get lower gearing will work.

My intention is to use an 11-34 SLX 10 speed cassette and a long-cage Deore rear mech with my current Dura Ace 7900 (compact) drivetrain. Current biggest rear sprocket is a 27, so existing chain length should be fine if I avoid the rear two cogs when in the big ring - which I would always do anyway. That gives me a lowest gear of 26.4 inches.

Any reason why that wouldn't work? An alternative would be to cobble together a 9 speed triple system (11-32 XT cassette, Ultegra triple 52-39-30 chainset, Ultegra front mech, Tiagra shifters) from other bikes. That would give a lowest gear of 24.7 inches, but would be a lot more hassle to install (re-taping bars etc).

Cheers.

Comments

  • whyamihere
    whyamihere Posts: 7,708
    That'll work.

    I would change to a new chain though. Partly because your old one will be stretched slightly, and so will accelerate wear on the cassette, mostly for that one time when you're tired, not thinking properly, and accidentally make the shift that rips your drivetrain into tiny little pieces...
  • pastey_boy
    pastey_boy Posts: 2,083
    dont 10spd rear mechs differ slightly to 9spd ?
    Viner Salviati
    Shark Aero Pro
    Px Ti Custom
    Cougar 531
    Sab single speed
    Argon 18 E-112 TT
    One-one Ti 456 Evo
    Ridley Cheetah TT
    Orange Clockwork 2007 ltd ed
    Yeti ASR 5
    Cove Hummer XC Ti
  • whyamihere
    whyamihere Posts: 7,708
    pastey_boy wrote:
    dont 10spd rear mechs differ slightly to 9spd ?
    Yes.

    They often have a 10 written on them rather than a 9. That's the only difference though.
  • pastey_boy
    pastey_boy Posts: 2,083
    so i could use a 9spd sram x0 rear mech with 10spd doubletap shifters
    Viner Salviati
    Shark Aero Pro
    Px Ti Custom
    Cougar 531
    Sab single speed
    Argon 18 E-112 TT
    One-one Ti 456 Evo
    Ridley Cheetah TT
    Orange Clockwork 2007 ltd ed
    Yeti ASR 5
    Cove Hummer XC Ti
  • Do you really need lower than a 34 x 27? It sounds like a lot of aggro for a gear that is ver, very low. I did a short tour on my bike with 36x27 on it and only needed to get out the saddle on the 1 in 5s of Dartmoor. Speed was down to 4 mph and still pedalling!
  • whyamihere
    whyamihere Posts: 7,708
    pastey_boy wrote:
    so i could use a 9spd sram x0 rear mech with 10spd doubletap shifters
    Possibly not with that one. I seem to remember reading somewhere that Sram have different pull ratios for their road and MTB components, whereas Shimano is uniform. I could well be wrong, but it's something that should be checked before buying.
  • elcani
    elcani Posts: 280
    Thanks for the replies. I'll consider changing the chain, although the old one only has about 500 dry miles on it, so stretch shouldn't be too much of a problem. Or should it?

    I think I do need the extra gears! I'll be loaded up with four panniers plus tent, trying to take as much of the weight off my GF's bike as possible. We'll be skirting the Pyrenees, and going up some pretty big hills. Also, changing the cassette and rear mech is 15 minute job.

    Thanks.
  • John.T
    John.T Posts: 3,698
    Definately change the chain. You need quite a bit longer one for the long cage mech so you may as well make it the correct length to get all gears safely. As whyamihere says, 'you will make that wrong gear change sometime'. And regret it.
  • elcani
    elcani Posts: 280
    Very good point John - I hadn't thought about the extra cage length. New chain it is.

    Cheers.