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  1. #1
    S'Cruzer pierce's Avatar
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    triple chainwheel spacing on 9 vs 7/8 speed

    is there a difference in the chainwheel spacing on triples meant for 9 speed systems vs the traditional ones used with 7/8 speed ?

    I have a bike with a nasty tourney riveted steel crankset, that I'd like to replace with something nicer like a deore 'trekking' crankset (48-36-26), but I know 9 speed chains are thinner (although not as thin as 10 speed), so I don't know if the chainring spacing is the same, so my SiS shifter will work.

  2. #2
    cs1
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    On Campagnolo the spacing is the same for 7 - 9. But Campy shifters all have basically a friction front shifter. So spacing isn't as important as Shimano which is indexed. Can you measure the spacing and compare to the crank you are looking to buy?
    1999 Waterford RSE-11, 1995 Waterford 1200, 1989 Specialized Rockhopper Comp
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  3. #3
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    Shimano spaces the two larger chainrings slightly closer together for their 9-speed cranks than their 7/8-speed ones so the narrower chain can't "skate" between the rings. When 9-speed cassettes and chains first came out, Shimano said they would work with 8-speed cranks but recommended not front shifting under load.

  4. #4
    S'Cruzer pierce's Avatar
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    I suppose I can always use chainring spacers. in fact, I did exactly that with a 50-34 FSA compact crank on my old hybrid, that I was using friction shifters with. When on the 34, the chain rubbed on the iinside of the big ring in almost any gear but the lowest rears, so I added about 2mm of spacing. I basically left that bike on the 50 and treated it as a 7 speed until it was hill climbing time, then I'd drop to the 34, and could use about the lowest 4 gears, which worked out nicely for what it was. I also used a slightly too short BB (these were square post cranks), so the big ring was almost centered on the cassette.

    But, my new hybrid has trigger shifting, and I'm liking it. I can see /eventually/ switching to a 9 speed rear but thats new shifters + RD + chain on top of the front stuff.

    FWIW, I'm looking at this crankset,
    http://www.ebay.com/itm/SHIMANO-DEOR...365#vi-content

    to replace one of these cheap tourney cranks..
    http://www.amazon.com/Shimano-M191-1.../dp/B001GSOHO0

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