Need help from drivetrain guru'

cubedean
cubedean Posts: 670
edited August 2014 in Workshop
I'm currently restoring/rebuilding a 1985 Gios, however i plan to open the rear end to accept 130mm spacing for a modern wheelset.

While doing this I would like to keep the existing Dura Ace 7400 group-set (which is currently 7sp with down tube shifters). Is there any way to run an 8 or 9sp cassette & still use the 7 speed rear derailleur?

I believe the actual spacing of a 9sp cassette is the same as the 7sp, so in theory it wouldn't be outside of the range from the existing RD. Would it be just a case of finding a 9sp indexing down tube shifter?

If this isn't possible then i suppose i need to rethink my options.
Transition Bottlerocket

Comments

  • The Rookie
    The Rookie Posts: 27,812
    A 7 speed rear mech will work with 8 or 9 speed shifters, the only slight problem is that some 7's don't have enough lateral movement to cover an 8/9 speed cassette (same width), but most will.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • rolf_f
    rolf_f Posts: 16,015
    cubedean wrote:
    I believe the actual spacing of a 9sp cassette is the same as the 7sp, so in theory it wouldn't be outside of the range from the existing RD. Would it be just a case of finding a 9sp indexing down tube shifter?

    Don't bother with indexing. Half the joy of DT shifters is not having any indexing to worry about and it doesn't serve any useful purpose with DT shifters anyway. Your existing shifters should be fine as long as you can switch off the indexing.
    Faster than a tent.......
  • cubedean
    cubedean Posts: 670
    Rolf F wrote:
    cubedean wrote:
    I believe the actual spacing of a 9sp cassette is the same as the 7sp, so in theory it wouldn't be outside of the range from the existing RD. Would it be just a case of finding a 9sp indexing down tube shifter?

    Don't bother with indexing. Half the joy of DT shifters is not having any indexing to worry about and it doesn't serve any useful purpose with DT shifters anyway. Your existing shifters should be fine as long as you can switch off the indexing.

    Thanks, i'll look into it then.

    Current shifters are dura ace 7400.
    Transition Bottlerocket
  • cubedean
    cubedean Posts: 670
    I've checked the shifters and they do have the option for friction so I will go ahead and attempt it. I suppose I need to check the chain compatability with the existing chainrings aswell.
    Transition Bottlerocket
  • cycleclinic
    cycleclinic Posts: 6,865
    Why stop at nine speed. I friction shifted a 10 speed cassette for over a year and I always got the right gear. Also a 10 speed chain does work fine on 7/8 speed rings. Ignore all of shimano's proclimations about chainring/chain compatibility there is not enough difference between 7/8 speed rings and 10 speed ones to actually cause a problem.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • cubedean
    cubedean Posts: 670
    thecycleclinic wrote:
    Why stop at nine speed. I friction shifted a 10 speed cassette for over a year and I always got the right gear. Also a 10 speed chain does work fine on 7/8 speed rings. Ignore all of shimano's proclimations about chainring/chain compatibility there is not enough difference between 7/8 speed rings and 10 speed ones to actually cause a problem.


    Thats good to know, I'll keep my eyes peeled for a nice set of wheels now then & space the frame to suit a 130mm rear end.
    Transition Bottlerocket

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