Triples to Doubles

[Paul on the Pearson]

Quick Technical question:-
Can you use triple STI's (sora) with a double chain set. Will it still work ok. The Giant came with a triple and as I dont use the little ring anymore am thinking of changing it over to a 52/39 (if poss), without the expense of upgrading the STI's.

[sylv]

I'm sure you can, and guess you'd have to play with the derailleur's limit adjustment screws like on a mountain bike, to prevent the chain from falling off the inside of middle ring.

This leads me to another question: I use Ultegras on a double chainring, and have noticed that on the big ring, you can sort of half-shift down to prevent the chain from rubbing on the inside plate of the derailleur, when you are in one of the largest cogs. This is very handy (in the same way as you can do it with mtb twist shifters), but I'm wondering if this is actually a feature of the shifters, or if it's actually working as for 3 rings, and I'm just lucky with the adjustments that it can work perfectly with two and allow for this little trick?

[Brett P]

I would check with a bike shop as the triple would have a longer axle. I know Campag's triple axle is 5mm longer than the cheaper double & 15mm longer than Chorus/Record.

[Grahame]

Paul - Sylv is right - they should work fine with a double, as the spacing between chainrings is the same. You'll just need to adjust the end stops on the derrailleur. And maybe adjust the cable tension so that you use the first two positions of the shifter, then the third position is "locked out" by the derailleur.

Brett is also "right" you may be able to use a bottom bracket with a shorter axle. This will bring the pedals closer together (Reduce the "Q factor") which, for most people, makes pedalling more comfortable and efficient. To minimise expense, this may not be necessary.

Is the weight saving of 1 small chainring worth all the hassle?

Sylv - I'm pretty sure it's a design feature of the STI system to allow the (narrower) road front derailleur to be "trimmed" to eliminate chain rub across the full range of the cassette. I have thought about modifying the pullarm/leverage on an old front derailleur (yes, I am just showing off that I can spell derailleur ) so that I could use this feature to run a triple chainring on my frankenbike

[Nick]

Sylv- I agree with Grahame it is used to trim the movement and is very handy indeed I use the STI's and use this feature when going from centre to outer chainring but not changing the rear gear's.

Nick.

[sylv]

Alright. Grahame, I think you just looked at how I'd spelt "derailleur":wink:

[Paul on the Pearson]

Thanks for the replies.
Its not to save any weight, its a bottom of the range giant so I'd need to remove a lot more than the little ring to make any worhwhile difference, its just that if it doesnt work out too expensive, (its not worth spending too much on the bike, better off putting the money in the still non existant fancy new bike for next year fund), a 52/39 seems to make more sence than a 52/42 and whatever the little one is. 42/26 can be a bit of a grind up the real steepies.

[Grahame]

If your present middle ring is a 42, then you can probably replace it with a 39, and leave the big and granny rings as they are. You could then have the gearing you want, with the option of a bailout gear for those really bad days. Total cost will probably be about £25 to £30.

[Dan B]

I switched from triple (52/42/granny) to double (52/39) on my Trek.

New bottom bracket (not as wide)
New front derailleur
Same STIs and rear gearing

Pete at GB's handled it. No worries.

D

[Brett P]

I just upgraded my girlfriends bike from 9 to 10 speed camapag.
All parts were bought off Ebay & I saved £70.
Worth looking into if you wanna save £££'s, the only problem is that you have to build it up yourself.
Ok if you know what you're doing!