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Road bike setup at the moment is: Shimano Tiagra (9 Speed) Shifters / Front Derailleur / 52-39T Chainset / Short Cage Rear Derailleur / Casette 27-11T.

Will I be able to do a straight swap and install an Ultegra 6300 52-39-30T Triple Chainset designed for 10 speed? If not any other ideas? Many thanks Steve

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An important question: does your front shifter lever have three positions? If not, do you plan to exchange it? – heltonbiker Feb 22 '12 at 12:50
You will probably need to replace the crank axle -- don't know whether you were figuring on that. And the front derailer and shifter may need exchanging (and certainly some adjustment). – Daniel R Hicks Feb 22 '12 at 12:58
@DanielRHicks: Is that what the q-factor refers to? – OMG Ponies Feb 22 '12 at 15:01
I believe my shifter has 3 positions. I was hoping to install the Triple Chainset straight off but might consider a whole groupset if necessary. – steve Feb 22 '12 at 16:30
@OMGPonies -- Sorta. The "Q-factor" (strange term) is apparently the spread between the two pedals, measured at the pedal thread. But significant to triple cranks is that the right side axle sometimes needs to be a few silly millimeters longer than the left ("offset") to provide clearance for the granny. This produces a slightly off-center pedal arrangement, but not enough to notice while pedaling. – Daniel R Hicks Feb 22 '12 at 17:28

If, by "a straight swap" you mean "Can I change only the crank set, and no other parts, then the answer is in short, no, it will not be a straight swap.

If I read the question correctly, you are currently using a 52/39 double designed for 9 speed, and you want to install a 10 speed triple.

A triple shifter has 5 positions, not 3, because it requires additional "trim" positions which move the derailleur without actually shifting gears. This prevents the chain from rubbing as you get closer to extreme chain line angles. (Shifting into very large or very small cogs on both the front and rear gears at the same time.)

To do this job with 10 speed, you will need to change your shifters, front dérailleur , rear dérailleur, cassette, chain, crankset, and possibly bottom bracket bearings.

If you use 9 speed, you will save the cassette, rear dérailleur, and possibly rear shifter.

I assume your purpose is to get easier climbing type gears? If so, consider using a compact double (50/34), possibly combined with a different cassette on the rear of the bike.

It should get you quite a lot better gearing, and will only require changing the crank itself, and readjusting the gears on your front derailleur.

I hope that helps.

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