Changing chainring on compact crank

[jroux]

I have an ultegra compact crank(50-34), can I change the bigger chainring to a 52 or even 54? What do I need to take into consideration? Had a look through older posts, but too many results on compact, if there is an older post just send me the link.

 

Thanks

[Wheelsuck]

Dont think so, the spacing on the compact does not allow for a standard chainring...I had the same issue with my SRAM so not sure if it is the same as Shimano

[Minion]

Compact cranks have a bolt circle diameter (BCD) of 110mm. You can get aftermarket 110BCD chainrings going up to 54T. They tend to be less stiff than their smaller counterparts, though. You would also need to get a bigger small chainring since most front derailleurs are only 16T capacity e.g. with a 54T outer ring, the inner can be no smaller than 38T.

 

Edite: a link to some chainrings:

http://harriscyclery.net/product-list/parts-1400/chainrings-1405/chainrings-110-mm-bcd-1279/

Edited October 31, 2011 by Edman

[jroux]

Mmmm, thanks guys. Seems like for now I'll have to play around with the cassette then.

[Antoo]

Check out Cape cycle systems, the SRAM distributors, 'cause SRAM has a variety of chain wheel sizes available.

You can go up to 52/38 chainwheels on a Compact crank. I have made the conversion....

[Nickzta]

Hey,

 

What level are you riding at and what are you trying to achieve with this?

 

 

Reason I ask, is that I've recently added a 55T/42T to the front and popped an 11-28 cassette onto the back. I am riding short crank arms. (Cant remember the length, but it's not 17cm)

Edited October 31, 2011 by Nickzta

[jroux]

Check out Cape cycle systems, the SRAM distributors, 'cause SRAM has a variety of chain wheel sizes available.

You can go up to 52/38 chainwheels on a Compact crank. I have made the conversion....

 

 

Thanks, will have a look!

[jroux]

Hey,

 

What level are you riding at and what are you trying to achieve with this?

 

 

Reason I ask, is that I've recently added a 55T/42T to the front and popped an 11-28 cassette onto the back. I am riding short crank arms. (Cant remember the length, but it's not 17cm)

 

I'm no pro, for one. I haven't even ridden with the compact crank yet, still needs to get fitted on the bike. I was just interested what my options are if I don't like it. As far as I could gather from reading is that to achieve the same speeds as a normal 54T you'd need to up your cadence, thus if you have an 11-23 cassette you could more or less offset the effect of the smaller front chainring. I was just interested if it does not work for me, if I could just add a 54T chainring on.

 

I'm no bike expert but how does a 55T/42T front and 11/28 rear compare to a normal 54/39 front and 12/25 rear. Do you have the same effect on the extreme ends of the cassette? Does this apply more to how your riding style is in the end or is the variants more aimed at what you ride more often example hills, flats, etc?

Edited October 31, 2011 by jroux

[David Marshall]

I have a Excel spread sheet which is handy for comparing gear ratios. PM me your email address if you want it.

[Longbarn Killer]

What about chain length? A bigger chain ring may require a new chain.

[Nickzta]

I'm no pro, for one. I haven't even ridden with the compact crank yet, still needs to get fitted on the bike. I was just interested what my options are if I don't like it. As far as I could gather from reading is that to achieve the same speeds as a normal 54T you'd need to up your cadence, thus if you have an 11-23 cassette you could more or less offset the effect of the smaller front chainring. I was just interested if it does not work for me, if I could just add a 54T chainring on.

 

I'm no bike expert but how does a 55T/42T front and 11/28 rear compare to a normal 54/39 front and 12/25 rear. Do you have the same effect on the extreme ends of the cassette? Does this apply more to how your riding style is in the end or is the variants more aimed at what you ride more often example hills, flats, etc?

 

55 with 11 is super fun on a slope or downhill, you will feel that you can keep cranking out the power for much longer that on 53 with 12 (that was what I had)

 

I could never slip up a hill, my natural cadence is slower than average. I run out of breath keeping up with the pack. When I started spending a lot of time on the bike I was on a triple 53/38/27 with 12/23 8speed at the back. I found that I lived in the 53, dropping onto the 38 for big hills and really struggling to get over the top. If I used the granny gear (front 27) that just frustrated me and made crazy, frikken spinning forever getting nowhere.

Over the top and I'd pop it into 53 and 12 and fly down the hill to catch the pack. I almost always couldn't keep my feet turning fast enough downhill and was completely out of breath by the time I caught up to the pack.

 

With a 55/42 on this bike, I find I can rest easier on the flats and I have a smoother, slower motion, so I recover easier. I can pedal down big descents without feeling that the cranks are getting away from me. On a hectic hill I will drop into 42 with 28, for me that is much easier than 53 with 23. But most of my hill climbing is done in 42 with 26.

 

Dude, I really don't blame you for look for more info on this, I did that for 6 months before I started playing. But play a bit, see what works for you. Test it for yourself. Maybe buy some less expensive 2nd hand parts and go for a few rides with that see how you feel.