Triple to compact?

niblue

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?

Cheers
Steve

sungod

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

niblue

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

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.

schweiz

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)