Changing from 50T to 48T

IanTrcp

Some help please...

I'm looking at swapping my 50T for a 48T with the aim of reducing the gap to the 34T inner ring.

Some questions:

1. Is it likely that I'll need to do more than adjust the front mech in it's present position?
2. Will I need to shorten my chain?
3. I have a long cage rear mech, fitted when I went to a 12-27 cassette. Will going to 48T on the front make it possible to revert to the short cage version?

Thanks in advance.

Smokin Joe

You won't need to shorten the chain, that would only be nescessary if you reduced the size of the inner ring by a sufficient amount. Just lower the front mech.

A short cage will easily cope with 48/34 and a 12/27 cassette, although will probably need to shorten the chain if you fit that. I can sympathise with your desire to change the outer ring. I run two compacts, 48/34 and 50/36. The industry standard of 50/34 is crap, I hated the jump between the chainrings.

IanTrcp

Smokin Joe wrote:

You won't need to shorten the chain, that would only be nescessary if you reduced the size of the inner ring by a sufficient amount.

Ah yes, that's fairly obvious isn't it! Thanks for being kind and not pointing out my stupidity!

maddog 2

1. no
2. no
3. short cage will be fine

over-the-hill

Smokin Joe wrote:

You won't need to shorten the chain, that would only be nescessary if you reduced the size of the inner ring by a sufficient amount. Just lower the front mech.

A short cage will easily cope with 48/34 and a 12/27 cassette, although will probably need to shorten the chain if you fit that. I can sympathise with your desire to change the outer ring. I run two compacts, 48/34 and 50/36. The industry standard of 50/34 is crap, I hated the jump between the chainrings.

I'm new back into this game
I've got 50 /34, 12/26. If I were to change to 36 and 27 would my lowest gear be roughly the same? I couldn't manage anything higher where I live.
What are the disadvantages of 50/34? I know I have to do a lot of jumping around. Isn't 48 a bit small on the downhills? I've got short centaur rear mech.

Smokin Joe

36*27 will only be fractionally higher than 34*26, so little you don't need to worry about it. Whether 50/34 is a pain or not is a personal thing. It gives a very big jump when you change, needing a shift of two or three sprockets at the back to find a suitable ratio. Personally, I don't like it.

As for using a 48 big ring, combined with a twelve tooth sprocket you get the same top gear that professionals used up until recent years when they were on 52*13 as a standard top, and not many of us would have the nerve to follow them down a descent.

grazer

i'll second that a 16T jump is too big a jump. also i reckon 34 on the front isnt really required unless u live somewhere really hilly

i reckon 50/36 is the way forward (i'm currently on 50/34, but will change when i get round to it)

Ken Night

Smokin Joe wrote:

36*27 will only be fractionally higher than 34*26, so little you don't need to worry about it. Whether 50/34 is a pain or not is a personal thing. It gives a very big jump when you change, needing a shift of two or three sprockets at the back to find a suitable ratio. Personally, I don't like it..

Me too, I like to use 50/36 with 13/26 (a run of 7 sprockets with 1T gaps) or 13/29 in the Alps

Smokin Joe wrote:

As for using a 48 big ring, combined with a twelve tooth sprocket you get the same top gear that professionals used up until recent years when they were on 52*13 as a standard top, and not many of us would have the nerve to follow them down a descent.

46T is also a possibility-about the same with 12T as 50/13-I spin out at around 37mph

stumpy paul

Change the inner ring to 36 then you don't have to change a thing.

I run 50/36 and 12/25 which is pretty much perfect - some good cruising gears and good climbing gears.

I then swap to a 34 for the odd very hilly sportive and again don't dhange the chain or anything.

50/36 is the way forward................

robbarker

50/36 would be a better combination as has been pointed out, although 48/34 will be fine if you value low gears rather than high. Either are much nicer in use than 50/34.

It's the compact chainset that leads you to require at least a medium (gs) cage rear mech, according to the official Shimano line at any rate. In practice, plenty of people run compacts with short cage rear mechs with no apparent ill effects.

You may not need to alter the chain - once it's all fitted, put the chain on the biggest ring at the front and smallest cog at the back - the mech cage should be oriented vertically downward.

maddog 2

anything above 40mph is more to do with the hill, your position on the bike, and the wind conditions, rather than gearing

I usually run 34/48 on a 12-25 and have hit 60mph off Kirkstone pass on a number of occasions. That fast enough for you?