Changing to compacts

Hey y'all. Thinking about the possibility of changing my standard cranks to compact. I currently run shimano 105 5700l (if that means anything) and have a couple of Q's for all the technically minded peeps out there

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!

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Permalink Reply by Alasdair McLellan on June 4, 2012 at 14:53

How will that help to LOWER your gearing (which is the reason you'd fit compacts...)?

Permalink Reply by Matt Jones on June 4, 2012 at 14:57

My question was to Dstone , who was seemingly having issues with a 50-12 top gear, Not to Trent.

Permalink Reply by Alasdair McLellan on June 4, 2012 at 15:25

Sorreh. :)

Permalink Reply by Dstone on June 4, 2012 at 20:24

I dont use the 12 or even the 13 as it is!

Permalink Reply by Jim Cooper on June 8, 2012 at 22:52

+1. Not often used.

Permalink Reply by Trent on June 4, 2012 at 15:13

Thanks for all the feedback guys. i REALLY appreciate it. i think i will just have to make do for the time being as to swap them out seems like a hassle. i can get the cranks easily but then it is another cost to get them to to the LBS to swap them out and just a bit too hard at this time of year.

Thanks all once again.

Permalink Reply by Terry C on June 4, 2012 at 16:21

It's a five minute job, and an easy DIY. The correct tool is not expensive, and will be an investment if you plan on being a long term rider.

Permalink Reply by Trent on June 4, 2012 at 16:27

definitely plan on being a long term rider Terry. just have to look at the overall cost

Permalink Reply by Terry C on June 4, 2012 at 16:35

Glad to hear the "long term" bit !  Over the years, I have spent several hundred dollars on special bike tools, and they really are worth it. The job can be done at home, when you need it, and at little cost.

 I must admit, that the only time that I tried compacts, i just did not feel comfortable with them. At the age of 72, and now living in a hilly part of north west Tasmania, I still find a 39 / 27 quite adequate for those conditions.

Permalink Reply by Tim B on June 4, 2012 at 16:57

Just for reference, using good old Sheldon Brown's gear calculator http://sheldonbrown.com/gears/

a 39 x 25 combo produces a gear of 42.1 gear inches

a 39 x 27 combo produces a gear of 39.0 gear inches

a 34 x 21 combo produces a gear of 43.7 gear inches

a 34 x 23 combo produces a gear of 39.9 gear inches

a 34 x 25 combo produces a gear of 36.7 gear inches and

Looking at the numbers above (the higher the number the harder the gear), and using Sheldon's calculator, you can get an idea of what you gain and loose by going larger on the rear or changing to compacts 

Permalink Reply by Tim B on June 4, 2012 at 16:41
Trent, you can buy the required tool for around $5
http://www.bicyclestore.com.au/shimano-tl-fc16-hollowtech-ii-crank-...

It really is only a ten minute job

This is the Shimano instal instructions http://www.shimano.com.au/media/techdocs/content/cycle/SI/105/SI_1M...
Permalink Reply by Trent on June 4, 2012 at 16:42

wow thanks Tim!!! greatly appreciated!!!!! thats really awesome. thanks for posting those links.

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