upgrading from compact

[montage]

Shimano's 52 or 53 tooth's fit compatible with their compacts? I.e. replacing the 50. Want to keep the 30 for that hill spinning ability

 

[Will1985]

I thought compacts only go down to 33t?

You need to make sure that the difference between inner and outer is not too great. 52/38 works though...

 

[montage]

actually it is a 34T I have.....oops.

 

[Will1985]

What's on the back?

 

[montage]

11-25

 

[alecstilleyedye]

it's for this reason i went triple rather than compact. for toughest climbs i have 30x25, and for the descent i have 52x13. and a whole range of ratios in between…

 

[MartinC]

The rear mech should cope but you might find the front mech doesn't. It's a bigger ring and a bigger jump from the 34 ring - but it's only a 2/3 tooth difference and might work so it's worth a try. Can you get a 52/53 ring to fit the bolt centres on your compact chainset?

 

[montage]

The rear mech should cope but you might find the front mech doesn't. It's a bigger ring and a bigger jump from the 34 ring - but it's only a 2/3 tooth difference and might work so it's worth a try. Can you get a 52/53 ring to fit the bolt centres on your compact chainset?

The front mech is actually designed for a standard double....so hopefully should be ok.

I guess it is just a case of getting 52t to bolt onto the compact chainset.

 

[Young Un]

get a 52-42, you know you wan't to. This is what I have, although I do have a 30 on the inside but this is soon going to dissapear when I become more of a weight weenie

 

[montage]

get a 52-42, you know you wan't to. This is what I have, although I do have a 30 on the inside but this is soon going to dissapear when I become more of a weight weenie

Because my allready sodded up knee's will disagree.

 

[Young Un]

Because my allready sodded up knee's will disagree.

Ah yes, I know about knees being trouble, so a 42 inner probably isn't the best solution

 

[Will1985]

I don't get it. 50x11 is bigger than 53x12 anyway, so you're just doing it for the sake of an extra 7" at the top end. Isn't grinding what screws knees up?

FWIW - you can get TA compact rings from 33 all the way up to 61!

 

[Joe24]

I don't get it. 50x11 is bigger than 53x12 anyway, so you're just doing it for the sake of an extra 7" at the top end. Isn't grinding what screws knees up?

FWIW - you can get TA compact rings from 33 all the way up to 61!

Exactly.
And, if you are struggling to keep up and your in 50/11, then may i suggest that you either try harder, or get fitter?
On my Giant SCR4, that had 50/12 i think, or it might of been 50/13, and at the end of a ride i was in a chaingang and we were doing about 32mph for a good few miles.
Get fitter rather then making the gear bigger. Unless ofcourse, you just want to put a 52/53 on to boast........

 

[skwerl]

The front mech is actually designed for a standard double....so hopefully should be ok.

I guess it is just a case of getting 52t to bolt onto the compact chainset.

The mech is the same for standard and compact. The limitation is the number of teeth difference between the rings. Have a look at Shimano website. I know my SRAM has a max diff of 16t so 50t is the biggest that will go with a 34. I imagine Shimano range will be much the same. 52:34 is 18t difference. Probably too much.
You'll also have to watch for chain length if you you're running 52:34 to 11:25

 

[jimboalee]

For every two teeth you take off the chainring, the radius reduces by 4.05 mm.
A 18 tooth difference will be 36.5 mm. I can't see a problem.