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I am putting together a road bike trying to use what I already have regarding parts and I am struggling to get a basic double road compact chainset without spending too much even second hand as a lot of the other bits have took me over budget for this build to be honest.
I am now thinking could I use a STX-RC chainset (22/32/42) on the road bike, I have a 73mm square taper Shimano Bottom bracket also which is for a triple chainset to use as the frame (a mid 90s Cannondale is also 73mm shell width)
The other issue is that my left shifter is for a double chainset (Ultegra 6500) would i be able to set it up using just the middle and big ring? And I have a Tiagra 4503 triple fron derallieur which if i`m right should give enough range for the shifting?
I am going to be running this bike as a 9 Speed as I know the chain width varies.
Has anyone tried a similar type set up with this and is it going to be reliable regarding shifting.
It's really going to be one of those try it and see jobs - particularly if the front mech can swing out enough to work with the wider chainline.
Don't see why it wouldn't. I ran a mtb triple chainset on a cross bike. But I used a mtb front mech.
Should be fine, but you may want a shorter BB spindle (assuming the current one is the one the cranks were intended to be used with, because the chainline for middle/outer on a triple is further out than for a double, and chainline at the rear is further in on a road hub than an MTB. You may want to go as much as 10mm shorter, but you might have to keep an eye on chainstay clearance and possibly even the crank hitting the cup of the BB. Give what you’ve got a go and then see if it needs changing, and if so check how much clearance you have (remembering that a change in spindle length affects each side by half as much).
My road bike has a Truvativ MTB crankset on it, but I’m only running the the middle and big ring as it had a double front mech. I had to use a few spacers on the BB but it’s been working fine for the last 6 years.
@jwildcard ... I have a Tiagra compact chainset that I would probably be willing to part with if interested, and an Ultegra BB. Email me on Kevin (dot) Harley (dash) Roberts (at) Virginmedia (dot) com if interested.
(Just for the record, a road Chainset doesn't fit a MTB frame ... Well, not in my case! 🙄)
Agree with dovebiker, ie it’s probably a ‘suck it and see’ thing.
It was common for early 90s road-touring bikes to have MTB triples. Mine has a Shimano Biopace. Works like a dream.
*edit Ignore the pedals. I have peculiar requirements 🚵🏼♂️.
Square taper is ideal for this sort of thing because axle lengths and hence chainline/Q factors can be tweaked with a (relatively cheap) BB swap.
I suppose you could also just remove the Granny if you wanted to run it as a double also. If you could source an appropriate 48t in the future a 48/32 double would probably be quite a good combo...
My galaxy touring bike has 3x9 xt matched up to tiagra shifters and it's always worked like a dream. Almost annoyingly so in fact as it probably is more consistent than the much never 105 I have on another bike.
I've just built up a 3x9 HT2 XT Trecking chainset with 3x9 Sora shifters and front derailleur and an XT 9 speed rear derailleur. Front indexing is the tricky bit but if you match the shifter and front derailleur and fiddle with the BB length (obv not an option with HT2), you should get something that works. Trial assemble it first with the BB you have to see if you need another BB. You might get lucky.
Thanks for the responses regarding running this triple.
Ive just measured the BB Shell and is infact a 68mm width. I still need to check the bottom bracket spec I have but I will go ahead and try it as suggested then I can see how it is sitting chainline wise and if it is going to fit. I could infact remove the inner chain ring couldn`t I? The front mech I have should be ok to work with this chainset as it was for a triple anyway, but the shifter is a double (9Speed ultegra).
The 73mm BB may work ok if there is enough thread on the NDS cup.
I wonder how well a road mech will work with smaller rings but some above says it's ok.
You should be able to get it to work OK, but a 42t big ring is very small for a road bike. Years ago I used a 26/36/46 on a road bike and was spinning out too easily.
I used a 26/36/46 on a road bike and was spinning out too easily.
46X11 @100 RPM = 33.6mph
46X12 @100 RPM = 30.8mph
Unless you are racing (and no one putting a triple on a road bike is racing) I can think of no reason I'd bother pedalling above that pace.
I'd admit though - 42 is small for a road bike. You sure it is 42 though - I'm sure my old STX rc was 44/32/22.
If the frame is an old MTB 135mm spaced job then IIRC most Square taper triples were meant to use a 113mm axle, of course if you're ditching a ring and trying to get the big ring to play nicely across more of the cassette you might* benefit from trying a 110mm axle
*Then again you might not...
If you're after a cheap BB you could do worse that a STRONGLIGHT JP400 comes in lots of sizes...
46X11 @100 RPM = 33.6mph
46X12 @100 RPM = 30.8mphUnless you are racing (and no one putting a triple on a road bike is racing) I can think of no reason I’d bother pedalling above that pace.
And at 80rpm which is what my legs are comfortable with, that's less than 25mph. Or pretty much every time I'm going even slightly downhill. With a 42:12 you are doing less than 22mph at 80rpm.
And at 80rpm which is what my legs are comfortable with, that’s less than 25mph. Or pretty much every time I’m going even slightly downhill.
Fair enough. 80 is very low to spin out (as opposed to your average) though. Garmin tells me the last weeks 12 hours of riding have averaged 87rpm with a max cadence of 109. I've switched to shorted 170mm cranks so I guess I have to spin a little more than most but I don't think I'm particularly supple/ fast spinning.