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I live near a lot of hills and am fairly new to biking. In my lowest gear I still can't keep up at an efficient pedal rate on the hills. I found out they sell "compact cranksets" which in addition to having a different bolt pattern have fewer teeth (50/34 vs 53/39).

Can I simply replace my old crank set (Shimano 105 5600, 53/39) with a new 56xx or 57xx compact crank? I'd expect to have to take a few links out of my chain too, but other than than can I keep my shifter and derailleur?

  • CS-5500 comes in a 12-27T so you may be able to pick up something there. – paparazzo Oct 20 '14 at 15:44
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You are right to say that the compact crankset will give you smaller gears to help you get over hills.

You can do a straight swap of the crankset, everything else will be compatible, although will need readjustment.

If you currently have a 5600 crankset, then you are absolutely safe to swap for another 5600 (compact) crankset. Now, the compatibility between different Shimano ranges is governed by the number of sprockets on the cassette, and the good news for you is that both 5600 and 5700 are 10-speed. So, basically, 5600 or 5700 cranksets will fit you perfectly (as would any other Shimano 10-speed road crankset).

5800 is an 11-speed system, you could probably get away with using this crankset (since the differences are small), but it will not fit as perfectly as 5600/5700.

So, looking at Shimanio's site, the part you need is either the FC-5750, or the FC-5650. The "50" appears to denote compact.

Lastly, do you know what length your cranks are? It might be worth measuring this just so that you get the same length with the new crankset. (You'll see on the Shimano site that things are available in four different lengths, the differences between each are small but they will affect your fit.) Here's an example of what you're measuring:

enter image description here

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    If you go for the SRAM crankset, you may need to change the BB. If you stay with Shimano you shouldn't need to. – Holloway Oct 20 '14 at 9:56
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    Yeah. At first, it would look like a SRAM crankset would fit, but theres a size difference on the non-drive side. But any Hollowtech crankset should work there. – Batman Oct 20 '14 at 11:01
  • thanks chaps, I hadn't realised that, I will edit my answer. – PeteH Oct 20 '14 at 11:58
  • Hollowtech II, rather than Hollowtech. – Batman Oct 20 '14 at 12:03
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You can drop in a compact crankset which has Hollowtech II compatibility. Otherwise, you can remove the existing bottom bracket and install a new one compatible with the crankset you buy. This site gives you a guide to all the bottom bracket types you can install in your frame (look under conventional threaded), in case you find you want to switch to another make of crankset.

There are some other options though (which may be cheaper):

1) If you can live with a 50-39, you can find a 50t outer ring with the 130 BCD. This may be a bit cheaper, but you still need to adjust the FD.

2) You can put on a bigger rear cassette. If you have a short cage or medium cage rear derailleur, this may require a long cage rear derailleur (e.g. a 9 speed deore).

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You'll need the FC-5650 chainring and crankarms. Reusing the BB should be OK. Yep shifter and derailleur is compatible but you will probably need to adjust the front derailleur down the seat tube to accommodate for the smaller front chainring.

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  • I want to remove larger standard and add the compact in its place. The compact is smaller right? – user1816847 Oct 20 '14 at 8:22
  • Yes. Compact is smaller. The front mech would still need adjusting though. – Holloway Oct 20 '14 at 8:40
  • The chain will probably need shortening by a couple of links. You'll have to check this. – Carel Oct 20 '14 at 13:12
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    I would have upvoted this answer and not bothered writing an answer myself, but I'm pretty sure the part you say the Op needs describes the standard crankset, not the compact. The part the Op needs is not the FC-5600, but the FC-5650 (or FC-5750) – PeteH Oct 20 '14 at 14:43

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