I have a commute/light touring bike, currently with a square-taper triple. I'm thinking about fitting a 48/34, 11-34 9 speed double. As far as I can tell, currently only SRAM sell a new 48-34 crankset (VIA, Apex, or S-100). These need a GXP bottom bracket. I also can't find any information on price - could anyone hazard a guess at how much all of this would cost? Also, will it fit in my existing bottom bracket?

My other option is to buy new chainrings, and source a crank. It seems that 104mm BCD 48t outer chainrings are more common, so I suppose I would have to find a MTB double crank. I currently have a square taper BB, but it would be nice to go to a hollowtech one.

I would appreciate any comments on the above - am I missing anything? Should I stick with a triple?

what are the rings on your triple? have you considered just taking the small ring off and then getting the appropriate sized individual rings? it's easy enough to limit your derailleur, so you don't have to buy all new.

the other option is to ebay a standard 50/34 compact double in 110bcd and just swap the larger ring, although 50-48 would not make much of a difference. here's one for $30 Vuelta Montagna Compact Road Crankset Square Taper 50 34 170 or 175 New | eBay

SRAM 48/34 rings are standard 110mm BCD and will work on any 110mm BCD crank, even a vintage 110/74 triple mounted on a short square taper spindle to make it like a double.

I personally would avoid 104mm BCD MTB cranks, as they tend to have very wide Q-factors, wider than road triples, and I really don't see a problem with running a triple besides Q-factor.

Don't base your decision on trying to use your old bottom bracket just find a crankset which suits you (or use your old one with new rings as suggested) and buy a BB to go with it.

I could :-) However, I don't really like the crank on there. I'm also thinking about an upgrade to Hollowtech/GXP BB.



Thanks! That's a great tip.

Thanks for the info! I don't really have much against a triple, but the marginal gains in weight, aesthetics, simplicity, set-up, and use, all add up.

You are not looking hard enough:
Cranksets - Components
https://www.compasscycle.com/shop/co...-double-crank/

My pockets aren't deep enough

But they're shiny.

I'm not a huge fan of GXP. 22mm spindle, 22.2mm bearing.

Welcome to the Personal Shopping Service Thread. Please relax while we complete your shopping for you.

Personally, I hate 50-34 for commuting (see here if you want to see the ugly discussion). I think 46-34 is OK. My main commuter currently has 39-30 (a triple with the outer ring replaced with a bashguard).


Shimano Metrea is supposed to have a 46-32 option, but like SRAM VIA it may not see a lot of after-market offering. Who knows? It was supposed to be out by now.


If you aren't worried about Q-factor and chainline there are a lot of MTB doubles available that might work for you.


I've spent a lot of time obsessing about gearing, and have gone through periods of really wanting some kind of double to work. In general, I've concluded that I really prefer triples. Component manufacturers don't seem inclined to support me in this opinion.

Ah damnit now I'm back to square one! I happen to really like the range of speed available on the 39t. I rarely leave the 39t on my commute, which has a few lumps and a lot of starting from standing. Saying that, the outer 48t on my proposed double, along with a 11-34 cassette, would only be one gear "faster" than the existing 39t and 11-32 cassette.

for nine speeds there is a 12-36 cassette, most are 11-34. so a double =34x36..this is not low enough for me for the touring part.

I prefer triple, a 24 smaller ring and a 34 rear sprocket, 24x34. 19.2 gear inches or 20 max, for those special occasions when I don't want to walk.

I use a square taper also, Phil wood bb keeps going, so hard to change.

The doubles, imho, change more than the crank rings, it means going 10sp min, the rear derailuer, chain,
, larger cog in the cassette, 42? any one. the rear derailuer,

greg
old and in the way.

why not a 38 or 39 or even 33T single up front? my commuter is a 1x7 with a 33 up front and an 11-28 8 speed in the back with the smallest cog locked out due to frame clearance. it has a really low gear, is very simple to setup, adjust, and maintain, and the highest gear will still get it to 25mph, which is more than I need when loaded or towing a trailer.