Changing to compacts
1- I've seen a shim 105 5750 crank. Will this fit my existing set up?
2- do I need to change the bottom bracket?
Thanks for any feedback in advance!
Replies to This Discussion
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Permalink Reply by Donald Rintoule on
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Firstly, you can swap a Shimano 5760 cranks for 5700 cranks.
Shifters and front derailleur are standard for both the compact or standard cranks. Just remember to lower the derailleur to clear the top of the large chain ring by a couple of millimeters.
Secondly, both the Shimano 5700 and 5750 cranks use the same bottom bracket, namely the SM-BB5700. Therefore no need to install a new bottom bracket (although I believe the new 5750 cranks will come with a new bottom bracket) which you can keep as a spare if you do not sell the 5700 cranks,
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Permalink Reply by Jeremy Smith on -
As Donald said, with the addition of: You will have to shorten your chain as well, as fewer teeth means your chain will now be too long.
and if you have a set of cranks spare.....I'm looking for some....and I can do the conversion for you if you arent mechanically minded (or equipped) ;)
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Permalink Reply by Trent on -
Thanks for the feedback guys. I'll let you know Jeremy. Not sure whether to go down the crank path or just get a 28 cassette on the back
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Permalink Reply by Patrick O'Kane on -
From my experience Trent I'd go Compacts over the 28 (I've got both but I'm a girl) although changing the cassette is cheaper if that is an issue.
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Permalink Reply by Dahondude on -
Couldnt you just take off the old chain rings and put a set of compact chainrings on? Or do standards and compacts have different BCD's?
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Permalink Reply by Tim B on -
I havent found a set of compact rings that will fit the BCD of standard cranks (110 for compact and around 130 for standard from memory) yet.
I've actually done it the other way around, I have FSA compact cranks on my bike but got to the point where I wasnt using the 25 23 21 most of the time. You can get standard size rings with a 110 BCD thats easy to convert.
For any one interested in top end gears, a 50 x 11 combo actually has a bigger rollout than a 53 x 12
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Permalink Reply by Matt Jones on -
I think you can get smaller custom chain rings, but 38 is the smallest you can go on a 130BCD, any smaller and the chain will interfere with the bolts
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Permalink Reply by Tim B on
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Nothing like replying to your own post, after a bit of Googling, looks like you can get 50T chain ring with a 130BCD but the smallest you can go appears to be around a 38T small ring with a 130BCD.
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Permalink Reply by Dahondude on
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Sorry, 34T chainrings wont fit a standard crank. I should have consulted this first
http://www.stevehoggbikefitting.com/blog/2011/05/compact-cranks-vs-...
Makes a good read for anyone thinking about compacts.
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Permalink Reply by Trent on
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great article DD but now i am more confused! lol not really but i do like the sound of an 11-25 on the back with compacts
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Permalink Reply by Matt Jones on
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My searching when building up my bike found that Shimano Chainsets are not good value for money.
1: New ones dont come with a Bottom Bracket - So you'll need to use your old one, or buy a new one seperately.
2: FSA or SRAM Chainsets are much cheaper
There is no compatibility using SRAM / FSA chainsets with a Shimano groupset, many bikes will be built up with a FSA chainset in the middle of an Ultegra groupset.
The benefit with SRAM/FSA is that they usually come with a BB as well.
I'd search around on evil bay for a SRAM Apex or Force compact chainset.
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Permalink Reply by Jeremy Smith on
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If it aint broke, why do you need a new BB?
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