Anything to be aware of when switching to a compact?

[Cyclopathic]

I'm currently running a 53/42 chainring on a ten year old Shimano 105 gear set with a 9 speed block and sti's. Is life so kind that I can simply change the chainring to a 50/36 compact and off I go or will I have to replace the rear mech for one with a longer cage? Also do I have to get a specific 9 speed compatible compact? Finaly are ther any issues with the front mech or will it handle the change? Absolutely finaly is are there any other pitfalls to look out for that I have not identified?
Thanks folks.

 

[mattobrien]

If the rear mech will allow, you might find that you could gt the desired change in gearing by swapping the cassette, although you don't mention what cassette range you are running. Every chance this might be a less problematic route.

 

[smokeysmoo]

Is life so kind that I can simply change the chainring?

Sadly not, the BCD for a compact is different to that of a double, so you will have to change the whole chainset.

As regards BCD measurements, AASHTA

 

[Cyclopathic]

Sorry, my fault. I meant the chainset. I want to change the entire chainset from the 53/42 to the compact 50/36, not just the chainring. I'm just wondering what other issues there might be as listed in my op. Apologies for my schoolboy error.

 

[Andrew_P]

Sorry, my fault. I meant the chainset. I want to change the entire chainset from the 53/42 to the compact 50/36, not just the chainring. I'm just wondering what other issues there might be as listed in my op. Apologies for my schoolboy error.

I would have thought a Short Cage would be fine, you might have to run a shorter chain. Only making this observation as you are decreasing the front only?

 

[Cyclopathic]

I would have thought a Short Cage would be fine, you might have to run a shorter chain. Only making this observation as you are decreasing the front only?

Sweet. That's the kind of news I want to hear. I'll ask you again when I need to know something.

 

[boydj]

You'll have to adjust the height of your front mech. Hopefully it should cope with the bigger difference between chainrings.

 

[Cyclopathic]

You'll have to adjust the height of your front mech. Hopefully it should cope with the bigger difference between chainrings.

That's fine. I was envisaging having to change everything which would have completely defeated the object of putting this particular bike together because I've got a complete 105 group set on a bike that I want to put on a different frame with the exception of the unnecessarily (for me) large 53/42 chainset.