Triple to compact?

niblue Posts: 1,387
edited January 2011 in Road buying advice
We picked up a cheap roadbike in the Edinburgh Bike-Coop sale for my wife to try as her first road bike. It's an older version of their own brand Revolution Continental Race an is the womans specific model. It's a nice fit and a reasonable spec (especially for the £150 paid!) including carbon forks, however I'm struggling a bit to get the front mech to shift in and out of all 3 rings correctly. The drivetrain is mainly 8-speed Sora with a fairly nasty looking Truvativ triple chainset, although it looks like it's only got something like an 11:23 cassette.

Rather than persevering with that triple I've got a couple of options in my spares bin, including an 11:28 8-speed cassette, a Tiagra mech (9-speed I think), a 9-speed Deore 26/36/48 chainset (a newish one) an also a 105 compact chainset (10-speed).

I'm thinking that the best option for consistent shifting plus giving a decent gearing range would be to use the 105 chainset and also fit the 11:28 cassette, retaining the existing Sora mechs and shifters. Is there likely to be any issue with using the 10-speed 105 chainset in an otherwise 8-speed set-up?



  • sungod
    sungod Posts: 16,535
    afaik the internal width of 8/9/10 speed chains is the same, but the external width isn't

    if you fit a 10-speed chainset you might need to fit a 10-speed chain - when i've fited a 10-speed 105 chainset on an otherwise 9-speed drivetrain the chain has rubbed a bit on the big ring, so i'd expect an 8-speed chain to rub more, but try it and see first

    you'll also need to adjust the front mech a bit (limit screws and check position), but otherwise i think you'll be ok
    my bike - faster than god's and twice as shiny
  • niblue
    niblue Posts: 1,387
    I've fitted the 105 compact chainset and it seems to work fine with the 8-speed chain and front mech. Can't see any sign of the chain rubbing on the outer chainring when it's on the inner.

    Certainly a lot easier to set it up for consistent front shifting as well, plus it's a lot lighter than the Truvativ triple that was on before.
  • FransJacques
    FransJacques Posts: 2,148
    No, no issue at all. I have 3 x Dura Ace 7800 cranksets all running 9sp chaiins, 1 Sedis/Sachs/Sram, 1 Sheitmano, 1 KNC. Works fine.

    Define what you mean by "chain rub"? All chains "rub" when they engage and dis-engage with the chainwheel teeth. That's mechanical friction.

    If they "rub" in another fashion or plane that might be a chainline issue. These things need careful diagnosis and description otherwise mis-information will spread, but hey, that's the internet for ya.
    When a cyclist has a disagreement with a car; it's not who's right, it's who's left.
  • schweiz
    schweiz Posts: 1,644
    also the rear mech doesn't care if it's connected to 8, 9 or 10 speed shifter it just gets moved the correct amount by the shifter. Also, I've switched a from a triple to a double up front on the BMC using the same STI (Ultegra 6500)