34 versus 36 compact chainring

DaveloMA · Dec 31, 2005

Hi. I'm getting a compact double on my next bicycle, and I'm trying to decide between a 34t and a 36t chainring; cogs will probably be 12-23 or 12-26 (only difference there is that the 23 has a 17 in place of the 26).

I've crunched the numbers (thank you, Sheldon Brown: http://www.sheldonbrown.com/gears/), so I know what ratios each chainring provides. What I don't know is what they're like in everyday use. The 36 seems like it would be more practical, especially in that the jump down/up from/to the big ring would be less dramatic. But, most everyone seems to offer 34t (36t is rare), so perhaps there's some meaning to that.

Any observations based on experience you can provide are welcome.

Thanks, and have a happy new year.

David

C-40 · Dec 31, 2005

equivalent gears...

DaveloMA said:
Hi. I'm getting a compact double on my next bicycle, and I'm trying to decide between a 34t and a 36t chainring; cogs will probably be 12-23 or 12-26 (only difference there is that the 23 has a 17 in place of the 26).

Several things should affect your decision. If you're getting a shimano 10 bike, there is no 12-25, you choices are a 12-23, 12-25, or 12-27. The difference is the 12-23 has an 18T for flatlanders and the others don't.

A 34T ring is about the same as having two cogs lower than you'd get with a 39 and a 36T is like one cog lower. For example, a 34/25 is about the same a 39/29 and a 36/25 is about the same as a 39/27. The big jump between a 50 and 34 creates the need to shift one more cog after shifting chainrings, while the 50/36 does not.

Unless you know you need a gear lower than a 39/27 (36/25), the compact really offers little advantage. Folks who buy Campy can just get a 13-29 cassette to use with a 53/39.

DaveloMA · Dec 31, 2005

Hi, and thanks for the quick reply. I'm looking at a Shimano 105 9-speed with SRAM cassettes, which I think does come in a 12-26.

I thought the compact might be the way to go. Hadn't much considered Campy, but now maybe I should add Veloce into the mix....

Thanks again.
David

C-40 · Dec 31, 2005

slightly different story....

With Shimano switching to 10 speed in the 105 group, you better get a great deal, otherwise I'd opt for 2006 10 speed.

The compact makes a little more sense with 9 speed. You can use a 12-23 (which has a 16T and get a low like a 39/26 with a 34/23. You still have to suffer through the extra cog-shifting. Some folks hate it and others don't seem to mind. 10 speed is more versatile. Those who need lower gears can select a 12-27 which has a 16T cog (like all 10 speed cassettes).

The problem for most folks considering entry level Campy Veloce, is the fact that the average shop either has no Campy equipped bikes or maybe 1 for every 100 shimano equipped bikes. They often don't know how to work on then either. That's why I build and wrench my own.

merobin · Dec 31, 2005

DaveloMA said:
Hi. I'm getting a compact double on my next bicycle, and I'm trying to decide between a 34t and a 36t chainring; cogs will probably be 12-23 or 12-26 (only difference there is that the 23 has a 17 in place of the 26).

I've crunched the numbers (thank you, Sheldon Brown: http://www.sheldonbrown.com/gears/), so I know what ratios each chainring provides. What I don't know is what they're like in everyday use. The 36 seems like it would be more practical, especially in that the jump down/up from/to the big ring would be less dramatic. But, most everyone seems to offer 34t (36t is rare), so perhaps there's some meaning to that.

Any observations based on experience you can provide are welcome.

Thanks, and have a happy new year.

David

David,
I have compacts on two bikes. Here in Florida, where there are few hills, I ride a 38-50. I put the 34 on when I go to the mountains. FSA sells 34, 36, 38 inner chainrings.

Mike

terry b · Dec 31, 2005

I started with a 50-34 and changed it to a 50-36. The 34 simply did not provide enough reasonable combos to use that ring for anything but climbing. I found myself riding 99.9% of the time is some big cog combo with the 50.

While you've scanned the ratios, have you compared them to what you ride now? That's the answer to what they feel like, for you. Depending on your style, you may be very happy with the 34, or you might not. Like I was. The key to understanding which one to use is to map your favorite gears across what the 34 or 36 offer and decide from there.

dogmeat · Dec 31, 2005

Go 34/50 compact first...

I just went to a 34/50 crank (FSA Energy... excellent crank, imo!) with Shimano 10 (12-27) last year. The first thing I noticed was the shifting is VERY different...

Dropping the front ring to climb, I usually shift the rear harder, TWICE. I still blow shifts, but it's getting better...

Climbing to the bigger ring after cresting a hill, I shift with both hands on the brakes- in at the same time... up to the big ring, easier by ONE... I guess because it's more of an acceleration down hill.

All in all, I find it worth the hassle and slower front shifting to have the great range of gearing you get with 34/50. I've got to save my knees. I've spun out the 50 ring once... that was really fun- 50 mph tail wind!

One goal for myself in the next year is to get strong enough to spin on the flats in the 50 ring... I think that means cruising at about 22 mph or so... about where I peaked last season. Hey, if you are much faster than that, I doubt you'd be thinking Compact unless you have serious hills- and then you wouldn't be messing with the little ring.

My advice- 34/50. Ride it for a few months, and if you want to drop a bigger inner ring on, pick one up on Ebay for as cheap as possible. This is the easiest parts swap of all time.

I don't get to pass many people that I'm actually proud to pass, but when I do, it's on long hills. Them- grinding hard, Me- sitting and spinning. The nice thing about have a deep low end is you don't have to use it, but if you need it- it's there.

'Meat

TurboTurtle · Dec 31, 2005

dogmeat said:
I just went to a 34/50 crank (FSA Energy... excellent crank, imo!) with Shimano 10 (12-27) last year. The first thing I noticed was the shifting is VERY different...

Dropping the front ring to climb, I usually shift the rear harder, TWICE. I still blow shifts, but it's getting better...

Climbing to the bigger ring after cresting a hill, I shift with both hands on the brakes- in at the same time... up to the big ring, easier by ONE... I guess because it's more of an acceleration down hill.

For me, I really need to look down the road and anticipate what is coming. I also get lost in all those back gears... ah, it's getting better though.

Going back to a 42/52 set up... so much easier to figure, but my knees can't push that anymore. So now I've got 39/47 (weird, I know... on my Cyclocross bike (which sounds so much cooler than "commuter bike") but I practically stole the ring for a lot less than I could get a 48 (on eBay)) Same gig- very easy to figure the shifting, tight setup, gained some low end, but nothing like having 34. But the chain is tight, and I do bang this thing around offroad.

All in all, I find it worth the hassle and slower front shifting to have the great range of gearing you get with 34/50. I've got to save my knees. I've spun out the 50 ring once... that was really fun- 50 mph tail wind!

One goal for myself in the next year is to get strong enough to spin on the flats in the 50 ring... I think that means cruising at about 22 mph or so... about where I peaked last season. Hey, if you are much faster than that, I doubt you'd be thinking Compact unless you have serious hills- and then you wouldn't be messing with the little ring.

My advice- 34/50. Ride it for a few months, and if you want to drop a bigger inner ring on, pick one up on Ebay for as cheap as possible. I don't get to pass many people that I'm actually proud to pass, but when I do, it's on long hills. Them- grinding hard, me- sitting and spinning.

'Meat

You sure seem to go through a lot of trouble just to avoid a triple. - TF

dogmeat · Dec 31, 2005

I like to keep my hands clean when I ride...

TurboTurtle said:
You sure seem to go through a lot of trouble just to avoid a triple. - TF

Another way I get to catch and pass people on hills is when their triple drops their chain on to their crank, and they have to stop; better yet- they try to raise the chain while coasting up steep hill, lose momentum and slowly fall over on to the shoulder.

Compact, combined with 10 speeds and a big cog... it's dead solid reliable. Nothing sucks more than having your bike fail you when you are busted, brain dead, facing a steep pitch.

'meat
( maybe someday I'll need to put a Deore XT backend on... but a triple- no thanks, no interest in cyclocamping.)

bigbill · Jan 1, 2006

terry b said:
I started with a 50-34 and changed it to a 50-36. The 34 simply did not provide enough reasonable combos to use that ring for anything but climbing. I found myself riding 99.9% of the time is some big cog combo with the 50.

While you've scanned the ratios, have you compared them to what you ride now? That's the answer to what they feel like, for you. Depending on your style, you may be very happy with the 34, or you might not. Like I was. The key to understanding which one to use is to map your favorite gears across what the 34 or 36 offer and decide from there.

I did the same thing. I ride campy 10 and use a 12-25 when I train and race on a 11-23. I live on Oahu and have some long climbs that are not too steep and some steep ones that are short. I find that a 36 provides plenty of gear plus a nice close ratio to settle into a good cadence during a longer climb. The front derailleur works better and I haven't dropped a chain since changing over. I still use the conventional FD. Everyone's riding style and terrain vary, you can't cookie cutter what is right or wrong. If anyone here has ever ridden over Makapu'u pass near Hanama Bay, I can do it both directions and stay on my 50 without going any lower than a 19.

cthomas · Jan 2, 2006

Ditto on the options to switch

terry b said:
I started with a 50-34 and changed it to a 50-36. The 34 simply did not provide enough reasonable combos to use that ring for anything but climbing. I found myself riding 99.9% of the time is some big cog combo with the 50.

While you've scanned the ratios, have you compared them to what you ride now? That's the answer to what they feel like, for you. Depending on your style, you may be very happy with the 34, or you might not. Like I was. The key to understanding which one to use is to map your favorite gears across what the 34 or 36 offer and decide from there.

I started with the 34, but found it just a little too low for anything but climbing. FSA sells all their rings as spares, so I bought a 36 and like it much better for the terrain I ride on. I put the 34 on for any big climbing days.

I also find that I love the 50T big ring. When I used to ride a standard 53/39 I rarely rode in the 53. Just too tall. I find I now ride in the 50 almost all the time and just use the 36 (or 34) for climbing.

So, if you buy FSA you really can go either way and then swap out later.

Chris V · Jan 2, 2006

compact crank gearing

Im using a FSA 36-50 on 1 bike with a 12-25 Dura-ace 10 on the back and it works nicely it is almost the same as an 39-27 with the standard crank set up. I tried a 12-27 on the back and that really worked nice. The 36-50 I think is a smoother set up than a 34 I dont think it shifts as smooth as the standard Shimano crank but its smooth enough.I cant understand why the manufactures cant get the shifting issues fixed since the compact is such a good option and doesnt seem like a big engineering breakthrough.My other bike has a Dura-ace 9 and I have a Shimano compact on order so Im going to find out about the 34-50 combo Im hoping it will be smoother than the after market ones,I would have ordered in a 36- 50 if it had been offered

Chris V.

Fort Worth

bc165 · Jan 3, 2006

DaveloMA said:
Hi. I'm getting a compact double on my next bicycle, and I'm trying to decide between a 34t and a 36t chainring; cogs will probably be 12-23 or 12-26 (only difference there is that the 23 has a 17 in place of the 26).

I've crunched the numbers (thank you, Sheldon Brown: http://www.sheldonbrown.com/gears/), so I know what ratios each chainring provides. What I don't know is what they're like in everyday use. The 36 seems like it would be more practical, especially in that the jump down/up from/to the big ring would be less dramatic. But, most everyone seems to offer 34t (36t is rare), so perhaps there's some meaning to that.

Any observations based on experience you can provide are welcome.

Thanks, and have a happy new year.

David

My FSA compact came with a 50/34 and I didn't like it. As you mentioned, the 16 tooth jump is quite large, so for me, everytime i shifted from the 50 to the 34 i had to make 2-3 shifts on the rear cassette... did not like it. Switched out the 34 for a 36 - no problem with FSA, I believe also with Campy and Truvativ compacts - and I make one or no shifts on the cassette now.... much better. I run a 12-27 cassette and it gives me just enough low end for the short steeeeep climbs and the looooong moderate ones. I ride an '04 Specialized Roubaix, and i see that the '06 Roubaixs are all speced with a 50/36 and a 12-27. I think this combo will become very popular for a fit rider who does a lot of climbing and doesn't want a triple.

http://www.specialized.com/bc/SBCBkModel.jsp?spid=13018

tube_ee · Jan 3, 2006

One of the really nice things about the 110 mm BCD is chainring choice. There's more options here than with any other BCD. Like, 33 - 60T in one tooth increments. So don't limit yourself to the 2 or 3 choices your crank maker gave you. You can fine-tune your gearing to exactly what you want.

Granted, many of the odder combos require buying TA chainrings, which aren't cheap, but there are no better rings made.

--Shannon

TurboTurtle · Jan 3, 2006

dogmeat said:
Another way I get to catch and pass people on hills is when their triple drops their chain on to their crank, and they have to stop; better yet- they try to raise the chain while coasting up steep hill, lose momentum and slowly fall over on to the shoulder.

Compact, combined with 10 speeds and a big cog... it's dead solid reliable. Nothing sucks more than having your bike fail you when you are busted, brain dead, facing a steep pitch.

'meat
( maybe someday I'll need to put a Deore XT backend on... but a triple- no thanks, no interest in cyclocamping.)

I have a bridge to sell - sounds like you might be interrested... TF

C-40 · Jan 3, 2006

The voice of inexperience...

or perhaps only shimano experience. A triple is absolutely the best way to go for the mountains.

There is no excuse for shifting problems. I've been running Campy triples on two bikes for 3 seasons and never dropped a chain. The little to middle ring shift is the slowest shift, but not by more than a second.

Using a wide spaced MTB cassette with a compact is poor substitute for a closely spaced triple setup (like a 53/39/28 with a 12-25).

34 versus 36 compact chainring

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