Changing to compact chainset

[Halfmanhalfbike]

I've got a Tiagra 52/39 and going to fit a 50/34. The compact is compatible with my 9 cog rear cassette and uses the same BB but will I need to shorten my chain for running on the 34 ring? If so, any ideas how to judge by how much. I don't want to remove too much

cheers,

 

[Theseus]

Basic rule of thumb I use is to put the chain over the big-big cogs, but not in the RD cage, pull tight, and add 1 complete link (i.e. 2 teeth worth).

 

[jpembroke]

Or, put chain on big chain ring and largest rear sprocket and run it through the rear mech. Pull it until the rear mech arm makes an angle of approx 45 degrees with chain stay. That's where you should split the chain. No doubt park tools have an article on this.

 

[e-rider]

why would you want to change to a compact - IMO they're rubbish. The small ring is useless unless you're going up a very big hill and you'll find that riding along in the large ring that you'll be using the largest sprockets all the time and will have a crap chainline, which will wear everything out quickly (unless you're going very fast and using the small sprockets)

In summary, compact chainsets are useful for:

1. going up big hills
2. going down very big hills

and are rubbish for:

1. all normal riding!

 

[montage]

You may need to lower the front deraillur

 

[peanut]

I've got a Tiagra 52/39 and going to fit a 50/34. The compact is compatible with my 9 cog rear cassette and uses the same BB but will I need to shorten my chain for running on the 34 ring? If so, any ideas how to judge by how much. I don't want to remove too much

cheers,

why not check the Shimano technical documents here. Everthing you need
http://techdocs.shimano.com/media/t...RD-4500/SI_5VX0A_En_v1_m56577569830607047.pdf

 

[jpembroke]

why would you want to change to a compact - IMO they're rubbish. The small ring is useless unless you're going up a very big hill and you'll find that riding along in the large ring that you'll be using the largest sprockets all the time and will have a crap chainline, which will wear everything out quickly (unless you're going very fast and using the small sprockets)

In summary, compact chainsets are useful for:

1. going up big hills
2. going down very big hills

and are rubbish for:

1. all normal riding!

I agree with this. A few years ago I put a compact on my winter bike and hated it. I found myself crawling up hills I used to fly up. Shifting down from the big to small ring was such a big drop that it felt like I was suddenly going backwards. Consequently I would prepare for that shift to the smaller ring by going up a few sprockets on the back. It just felt all wrong. I put the double back on and haven't looked back.

I don't understand how 50/34 ended up being the standard. I'd have thought 50/36 with an 11/25 cassette would make much more sense.

 

[peanut]

I don't understand how 50/34 ended up being the standard. I'd have thought 50/36 with an 11/25 cassette would make much more sense.

I have to agree with this. I too switched to a compact and I've found that even though I am now stronger lighter and fitter I still end up using every sprocket i've got and just going more slowly up the same hills.

As an experiment last weekend the lowest I used on my hilly loop was 34x 21t and low and behold I got round without getting out the saddle and my legs didn't drop off

34x21 is the equivalent of 38x25t so I might switch back to by double again next time I strip the bike.
I could fit a 36t to the compact but I'm really missing my 53t chainring on descents as I run out at 30mph

 

[montage]

I run a compact 50/34 with an 11-25.
Seems fine to me...but I haven't tried a standard double.

Might go to a double this winter.....but I'm sticking with compact this summer.