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!
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.
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...
Shimano MTB and Road shifters have the same pull ratio until you get to the Shimano MTB 10 speed. Therefore, you can use a Shimano Road 10 speed shifter with a 9 speed MTB Front or Rear derailleur, but not with a 10 Speed front or rear MTB Derailleur. This is because Shimano 10 changed the pull ratio for the MTB 10 speed drivetrain but did not change the road 10 pull ratio. Basically all 9 speed and below Shimano MTB derailleurs will work on all Shimano Road shifters. There is an exception for some of the older 7900 Dura Ace shifters which had a different pull ratio and also one of the Shimano levers with hydraulic brake lines. Heck if you can afford a hydraulic setup you can afford a new derailleur. However, some have pointed out to differences in design such as top pull and bottom pull. In most cases you'll want to get a bottom pull MTB front derailleur for use on a road bike.
It is possible to use a Shimano 10-speed mountain derailleur with Shimano road shifters. However, if the cable is attached to the derailleur in the standard position, the derailleur will move too far with each shift. The only way to make the rear derailleur function properly is to position the cable outward from securing screw. You may need to grind a back-up plate to place beneath the cable hold-down bracket so that the cable can be placed either at or slightly beyond the outer edge of the aluminum casting of the rear derailleur so that the amount of pull is slightly reduced for each cog change. You will have to experiment to get it just right. I have a pair of 2 x 10 road bikes that I built with Shimano XT 10-speed mountain derailleurs and encountered this problem, but rear derailleur shifting is now accurate on both bikes.
Actually, it's too broad to say "Shimano 10 speed road and mountain drive train components are not compatible". The MTB cassettes and chains are compatible with Shimano 'road' drive trains. Same for 11-speed.
I've a mix of decent used parts from a bike recycling project on a Kinesis cyclocross frame.
36t 10sp cassette 105 road shifters 10sp (triple front) Shimano SLX 9 speed rear derailleur Campagnolo Mirage front derailleur Dura-Ace double 9sp double chainset 7700 50/39
The 9 speed MTB SLX shadow rear derailleur works the same as a 10 speed road (like all 9 speed MTB rear mechs) same cable pull ratio so indexing is fine. A 105 10 speed mech would struggle to work with a 36t cassette and I need the 36t for lower gears with the non-compact chainset up front. Plus the slim 'shadow' profile might be useful considering off road use of bike. The triple brifter works perfectly with the campag mech and double chainring.
