Compact or full on chainring

[lmow20]

Hey guys,

I was just wondering, I have a sportive with a large 53/39 172.5mm front chain and crank. Is it possible to change the front chainring to a compact. I have SRAM rival kit, with a spare ultegra mid-cage rear derrailleur (which I believe is compatible...).

I use the bike to commute (flattish) and long sportive rides, however, next summer, I'm touring Bristol to Berlin, and thought I might need a compact front. I will have to drop the front mech down I imagine as well, yes?

Anyhoo, food for thought.

 

[Kestevan]

Changed my Tiagra 39/52 to a compact with no problems, no need in my case to change the rear derrailleur.

Slight adjustment to the placement of the front and that was that. It's made the hills much more enjoyable (if that's the right word).

 

[Will1985]

If you mean changing the chainset, then yes. If you meant swapping the rings, then no.

As Kestevan says, it is really only a case of adjusting the front derailleur.....some might say you should take a link out of the chain as well.

The easiest solution would be a like-for-like swap to a SRAM Rival Compact chainset so you don't need to worry about the fiddling with the GXP BB.

 

[Sieve]

+1
Done it several times now and it's easy enough. I do take a link out of the chain because I thougt that was essential but some don't bother.

 

[jimboalee]

Excuse me .

A "FULL ON" chainset is a 57/42.

A 53/39 is a 'box standard, common or garden, everyday' chainset.

A 50/34 is a 'Nancy boy's' chainset.

 

[Kestevan]

Jim likes to "remember" when bikes were made from girders, big cast iron girders. The wheels were solid granite and the riders wore clothes knitted from nettles.


Gears were for girlies, real men rode single speed bikes up Everest carrying pianos whilst smoking 20 woodbine.

 

[e-rider]

Hey guys,

I was just wondering, I have a sportive with a large 53/39 172.5mm front chain and crank. Is it possible to change the front chainring to a compact. I have SRAM rival kit, with a spare ultegra mid-cage rear derrailleur (which I believe is compatible...).

I use the bike to commute (flattish) and long sportive rides, however, next summer, I'm touring Bristol to Berlin, and thought I might need a compact front. I will have to drop the front mech down I imagine as well, yes?

Anyhoo, food for thought.

it's simple but why would you want to do that. Do you spend lots of time riding in the 39t at present? probably yes. So what will you do when you only have 34 or 50 to choose from? You'll be riding in the 50 (which will be too big most of the time), so you'll be using the largest sprockets to compensate - poor chainline for several thoausand miles isn't a good idea surely.

I'd recommend a triple (30/40/50). At least then you can cruise along in the 40t chainring most of the time.

I assume that you are going loaded with panniers etc. but if not just keep your 39/53.

 

[totallyfixed]

it's simple but why would you want to do that. Do you spend lots of time riding in the 39t at present? probably yes. So what will you do when you only have 34 or 50 to choose from? You'll be riding in the 50 (which will be too big most of the time), so you'll be using the largest sprockets to compensate - poor chainline for several thoausand miles isn't a good idea surely.

I'd recommend a triple (30/40/50). At least then you can cruise along in the 40t chainring most of the time.

I assume that you are going loaded with panniers etc. but if not just keep your 39/53.

Absolutely spot on, I am meeting more and more cyclists who are regretting the compact choice. IMO it was just another con, a bit like sportives, now I think about it didn't they come along at the same time?
When I am out on club runs I see some very dubious chain lines on compacts, usually from riders who are relatively new to cycling.

 

[amaferanga]

A compact with a 36 tooth inner works better than a 34. It all depends on the rider though obviously.....

In many respects a compact chainset is a really good choice since with a 110bcd you have a lot more choice when it comes to chainrings compared to with a standard double. So you can stick with the standard 34/50 or try 34/48, 36/50, 39/50, 39/52, etc. With a standard double the smallest you can go is 38 tooth inner I believe.

 

[jimboalee]

If a cyclist is so concerned about his/her gear ratios, they should buy a crankset with a spider that can take a whole range of rings. TA Cyclotourismo for example.
Then buy the complete range of sprockets singularly from the smallest availiable to 36 tooth. Then it is possible to make any cassette you wish.

Draw up a gearing map on Excel and see where the overlaps occur to produce a nice smooth progression of ratios.

OR, check the Shimano website and build ratio maps for various combinations of std chainsets and cassettes.

 

[jimboalee]

Here's some gear maps.

 

[e-rider]

A compact with a 36 tooth inner works better than a 34. It all depends on the rider though obviously.....

In many respects a compact chainset is a really good choice since with a 110bcd you have a lot more choice when it comes to chainrings compared to with a standard double. So you can stick with the standard 34/50 or try 34/48, 36/50, 39/50, 39/52, etc. With a standard double the smallest you can go is 38 tooth inner I believe.

haven't seen many 52t chainrings with 110bcd

if the standard is 130bcd then yes, 38 in minimum. with 135bcd (campag) then it's 39t min.

 

[TheDoctor]

Or we could concentrate on giving advice that would be helpful and realistic.
SRAM Rival will not shift a triple, so any suggestions for getting a triple are plain daft.
Get a compact chainset - shift the front mech down a few mm if it needs it.
I'd also get a wide ratio cassette for the back - 12/28 should be fine.
Job done.

And ignore Jimbo - he has a penchant for making the simplest question ridiculously complicated. Complete range of sprockets my ar5e...

 

[e-rider]

clearly if he went for a triple he'd have to change LH shifter and possibly a few other parts - surely that was obvious.

 

[TheDoctor]

Yes - like a whole new groupset, practically. The question was 'How easy is it to replace a 53/39 with a compact'.
SRAM cable pull is different, and they don't make a triple, so we're looking at replacing both levers, front and rear mech, chainset and BB - everything bar the brakes. That's why a triple is unrealistic.