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I'm quite new to upgrading parts, and trying to put together a Cyclocross / Touring bike and getting quite confused about compatibility.

Can I use 10 speed Tiagra Sti shifters with triple Deore 10 speed chainset, 10 speed Deore Xt front mech and 10 speed rear mech?

If not what would be the best way to go?

Thanks in advance!

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Shimano's gear splits pretty much into two - road components and mtb components - see their web site for more details. As regards which way you should jump, I'd say to go road if you're going to be riding on-road, mtb if you'll be riding significant off-road. As regards mixing road and mtb components, if you're buying from scratch, why would you? I mean, you probably could in some cases, but you wouldn't need to. You'd just be complicating things. For example if you want Tiagra (i.e. road) shifters, why not use other road components for the rest of your mech? – PeteH May 2 '14 at 21:09
Mountain rear derailleurs tend to be a bit more robust and able to handle larger cassettes, which is useful for touring purposes. In cases where weight weenie-ing isn't important (e.g. touring bikes like Trek 520 or Surly Long Haul Trucker, which can use a good low gear), you often see a Deore or similar spec'd rear derailleur (and often bar-end shifters, for reliability relative to brifters). – Batman May 3 '14 at 7:07
I've been searching this and other forums to answer a similar but more specific question about my 12 year old road bike with gears and wheels for touring. I had been struggling with the FD not shifting so well on my 3 x 9 drivetrain for the last 400 miles or so and determined to replace square taper crank with Shimano Hollowtech as my old crank wobbled under load, plus the FrontDe was old enough that it was actually worn away a good bit from chain rub. New crank fits and runs solid with new middle and old big and granny rings, but I could not find an 8-9 speed Sora triple FD on the internet so – user24008 Jan 6 at 2:23

If you ride a lot of steep hills and want to spare your knees you can have road shifters in the front and use a long cage RD and use a larger mountain cassette in the back. I've done this mixed set up with both SRAM Force (double) and Shimano Ultegra triple road gearing in the front and cage RD's in the back with mountain cassettes in 10 speed. I had a Shimano 105 long cage RD on my son's last bike with a 11-32 cassette (which is 2t beyond "spec" but worked perfectly). If you want a bigger cassette then you'll have to get a mountain RD.

As far as the comment about chains, remember these 3 letters: KMC. They are the OEM for Shimano chains. They use a "magic link" which is like the SRAM "power link" but better because the KMC 10 speed links are removable once snapped in (just like the SRAM 9 speed power links which is removable). SRAM 10 speed power links can not be removed once snapped into place. Btw, you can buy just the KMC magic link which will work with Shimano, SRAM & Campy chains!

The earlier comment of sticking to one brand has merit because the spacing is different between brands. In other words you can mix road and mountain front and rear derailleurs as long as you stick to the same brand whether its SRAM or Shimano. However, there are exceptions (but they can require elaborate operations).... I once had road Campy brifters and used Shimano mountain RD and cassettes (because campy rear cassettes didn't go low enough in previous years). I had to bring instructions that I found on the web to my lbs (because they didn't think it could be done) and they successfully completed the set up. Btw, that was in the 9 speed era...

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Shimano road shifters have to be matched with road front derailleurs, and mountain shifters have to be matched with mountain front derailleurs (technically, you could use a pulley like a JTek Shiftmate, but thats a dumb solution due to price reasons). Theres no compatibility difference in the rear (update: see the comment - the following holds up to 9 speed between mountain and road), except mountain derailleurs are normally long cage and can take bigger cassettes (and thus are favorable in a touring context). Stick with one brand for shifters, front derailleur, rear derailleur (crossing brands is possible, but more complicated as there is no standard for how much cable shifters have to pull, and you may need pulleys to change the cable pull to get things to work).

Front derailleurs are normally also matched to if they are double and triple and are specified for what range of chainwheels they work most favorably with (you can find this on the data sheet for the front derailleur - this is less important with friction on the front, but brifters can be finicky). In choosing a front derailleur, you also should make sure that the front derailleur can be mounted on your frame and the cable pull is in the right direction for your frame.

The particular crankset you pick's compatibility will be determined by if you have a bottom bracket that matches it in the bike, along with if its a double/triple (matching the front derailleur) and within the appropriate tooth range and has appropriately sized tooth jumps. To quote Sheldon Brown (article linked later): "Shimano's "10-speed" triple front derailers are optimized for a 13 tooth difference, typically 52-39. Most other Shimano front triple derailers are optimized for a 10 tooth difference between middle and large ring.". The speeds on the front derailleur are marketing term - you don't really need to stick to them since the speeds are determined by whats in the back(but obviously, Shimano wants you sell you an entire groupset, and 10 speed systems use narrow chains, so you should have a 10 speed FD, 10 speed RD, 10 speed chain (you could use a lower speed FD, but it might not be as crisp) ).

I recommend reading this article for seeing what goes into selecting a front derailleur and this one as well.

In terms of price, the shifters will be the biggest expense and will determine the FD. Regarding the RD see the comments, so you don't need to worry about it. Once you pick the shifters, you can pick a relevant FD and crankset.

Also note that a 2x10 or 3x10 setup is pricey relative to many 2/3x8 or 2/3x9 systems- the chains don't come with master links by default (and are pricey), and since things are narrower, they can be more annoying. Will the extra 1 in the rear buy you anything? Probably not.

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Shimano 10 speed road and mountain drive train components are not compatible. Unfortunately this compatibility ended at 9 speed due to changes in cable pull. You can run a 9 speed mountain RD with a 10 speed road shifter however. – DWGKNZ May 1 '14 at 22:14
Good point. Put a note in the post for that. – Batman May 1 '14 at 23:06

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