7 speed cassette with 8 speed shifters

benny2891
benny2891 Posts: 68
edited December 2007 in Workshop
I'm looking to get a super cheap rear wheel / tyre combo to use on my turbo trainer.

My budget being super tight, I thought why not grab a used wheel off eBay ? I'm finding plenty with 7 speed cassettes, but I have an 8 speed Sora setup on my bike.

Can I swap between a 7 speed wheel on the trainer, and a 8 speed on the road without too many troubles?

Or, to ask it another way, can I use a 7 speed cassette on my bike without changing anything else (including derailuer adjustment) ?

Comments

  • SDP
    SDP Posts: 665
    just put an 8sp cassette on the ebay wheel... :wink:
    www.mjsracing.net
  • Yellow Cliff
    Yellow Cliff Posts: 231
    A 7 speed cassette should be OK with 8 speed shifters. However, it is just possible that the cassette won't line up the same as your current one (due to the spacing of the cassette body relative to the axle/cones and this would be the same if you put 8 speed on there). It is fairly simple to re-space the axle with a few extra washers on one side if you have this problem.

    I don't think that 8 speed cassettes fit on the original 7 speed ones and nor does Sheldon by the looks of it:
    http://sheldonbrown.com/k7.html#897
  • nicklouse
    nicklouse Posts: 50,675
    on a shimano set up the cog spacing and chain as the same width for the 7 and the 8 spd set ups so yes it will work.

    a 8speed shinamo cassette will not fit on a 7 speed shimano freebody/hub as it is too wide.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • aracer
    aracer Posts: 1,649
    nicklouse wrote:
    on a shimano set up the cog spacing and chain as the same width for the 7 and the 8 spd set ups so yes it will work.
    Wrong.
  • benny2891
    benny2891 Posts: 68
    Thanks for the replies.

    I was just looking at the sheldon link above, and it seems that the axle width old 7 speed hubs is typically 126mm, as opposed to the 130 my bike uses.

    Shouldn't be a problem?
  • Mettan
    Mettan Posts: 2,103
    To add a bit - I've got a 2007 "Shimano" based Road bike using a 7 speed rear wheel/hub with 8-speed shifters (bit strange, I know) - it's definately got a 130mm rear dropout - it seems that the "newish" 7-speed Shimano based bikes are running 130mm rear dropouts as opposed to the older 126mm dropout.

    Incidentally, just got my new 8-10 speed Shimano R550 rear wheel from Wiggle today, and an 8-speed cassette - looking forward to the upgrade over the next few days :)
  • oldwelshman
    oldwelshman Posts: 4,733
    If it does not fit, you can get it opened to 130 mm for about £10 and it is done cold.
    I am sure you will get a 8 speed wheel if patient :D
    Anyway how many gears do you need on a turbo? !!
    http://s290.photobucket.com/albums/ll245/oldwelshman/
    http://www.youtube.com/watch?v=aK5Bfqj5fxY
  • aracer
    aracer Posts: 1,649
    oldwelshman wrote:
    If it does not fit, you can get it opened to 130 mm for about £10 and it is done cold.
    But his bike is 130 already - the issue is getting a 126 spaced wheel (and I preusme you're not suggesting he cold sets the rear end every time he swaps from turbo to road?)
  • benny2891
    benny2891 Posts: 68
    ARACER,

    You got it right. The bike is 130mm.

    It sounds like from the replies that it might work, it might not.

    I think I'll just try and find the cheapest 8 speed / w 130mm width rear wheel I can get my hands on and save myself the hassle.

    oldwelshman,

    I've got a Cycleops magneto trainer which has progressive resistance. (whatever that means) I tend to use a fairly wide range of gears, as it's the only way to vary how hard I'm working on the thing.
  • redddraggon
    redddraggon Posts: 10,862
    benny2891 wrote:
    I think I'll just try and find the cheapest 8 speed / w 130mm width rear wheel I can get my hands on and save myself the hassle.

    £40 for the rear:

    http://wiggle.co.uk/ProductDetail.aspx? ... ar%20Wheel

    However I got the front and rear for £45 from ribble - BARGAIN!!!

    http://www.ribblecycles.co.uk/details.a ... IMWHFR0200
    I like bikes...

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  • nicklouse
    nicklouse Posts: 50,675
    aracer wrote:
    nicklouse wrote:
    on a shimano set up the cog spacing and chain as the same width for the 7 and the 8 spd set ups so yes it will work.
    Wrong.

    strange that it works.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • aracer
    aracer Posts: 1,649
    It might work, but you're still wrong - the cog spacing is different. It's also only because higher end stuff has all moved on to 9 or 10 speed that the chains are the same - back when 8-speed was as good as it got you needed to upgrade from 7-speed chain when you made the switch.

    Lots of people do manage to mix 7 and 8 speed - indeed I ran 8 cogs aith 7-speed shifters for a while back in the day. However it's far from optimum, being far more sensitive to the setup, and more likely to go out of tune, given you are relying on the tolerances in the systems which are designed to allow for wear to make it work.
  • benny2891
    benny2891 Posts: 68
    redddraggon wrote:
    benny2891 wrote:
    I think I'll just try and find the cheapest 8 speed / w 130mm width rear wheel I can get my hands on and save myself the hassle.

    £40 for the rear:

    http://wiggle.co.uk/ProductDetail.aspx? ... ar%20Wheel

    However I got the front and rear for £45 from ribble - BARGAIN!!!

    http://www.ribblecycles.co.uk/details.a ... IMWHFR0200

    I wonder how these compare to the alex rims on my SCR 3. Maybe the thing to do is get a set of these, and then use the Alex rear wheel on the turbo. But, that is a topic for another thread...

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