replace of old drivetrain

stefano
stefano Posts: 254
edited November 2008 in MTB workshop & tech
Hi

I want to replace all the drivetrain on my basic 7 x 3 speed Shimano spec old mountain bike: chainset, bottom bracket, cassette and the chain. The cheapest way is to by 7 speed parts so I keep the same gear mechanisms.

Later I am planning to by new wheels also.

I have two questions:
1. If I buy a good pair of (possibly Mavic) wheels later would it be compatible with my 7 speed cassette?
2. Is a 7 speed setup compatible with 8 speed setup so I can mix and mach parts?

Thanks for your help!!!

Comments

  • I run a 7 speed cassette on my old commuting bike.8 and 9 speed cassettes are the same width,so all you need to do if you use a 7 speed cassette is to use a spacer.I got mine from Merlin,cost £2.50
    As regards shifters,the spacing between ratios should be the same,but I guess you will have to set it up so you lose the 8th gear postion.(I would defer to someone with experience on this one)
    Alternatively use non indexed shifters as I do and you won`t have a problem.
    2006 Giant XTC
    2010 Giant Defy Advanced
    2016 Boardman Pro 29er
    2016 Pinnacle Lithium 4
    2017 Canondale Supersix Evo
  • 7 to 8 speed won't work. The spacing between the cogs on the 8speed cassette are different widths to a 7speed one. So you can't use 7speed indexed shifters with 8speed cassettes. A friction shifter would work, but why not go for 8 or even 9speed. The parts are cheap now and will last as long as 7speed stuff.
    jedster wrote:
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  • stefano
    stefano Posts: 254
    I think I will buy new complete 9 speed drivetrain and later new wheels.
    All parts but the cassette can go on the bike.

    Any idea if I can put the 9 speed cassette to my old wheel that now has a 7 sped cassette?

    I have an old square taper bottom bracket, since I buy new chainset can I go for an octalink bottom bracket and octalink chainset?
  • supersonic
    supersonic Posts: 82,708
    You cannot put a 9 speed cassette on a 7 speed hub.

    You can put a 7 speed cassette on a 8/9 speed hub (8/9 cassette hubs are the same) with a 4.5mm spacer.

    If you get a new 8/9 speed wheel, with a OLD of 135mm, you need to check it will fit your frame. Some old frames are 130mm.
  • stefano
    stefano Posts: 254
    I have just seen that the rear dropout space is 130mm.
    I have a steel frame is it OK if I stretch it a bit to put a 135mm wheel?
  • supersonic
    supersonic Posts: 82,708
    Possibly.

    Go to Sheldon Browns webpage and look up cold setting/frame spreading.