I’m thinking of getting a set of Compact cranks for my tri bike. What do you think I should get for the rear?
Currently I have a 26/12. I live in MN, pretty flat overall, but definitley some hills.
Right now I have 55/42 with 26/12 on my tri bike, 53/39 with 23/11 on my road bike. I never used to give
gearing much consideration, so I just used whatever came on the bike. What do you think I should be running?
Thanks for the help.
11/23 with compacts will give you a better range and closer ratios than a 12/26 with 53.
So, you are running superman 55/42 cranks now on your tri bike, live in the flatlands, and want to change to compacts? Reasoning?
Don’t get me wrong, I love compact cranks (what I run). I’d suggest 50/36 up front and an 11/23 then based on what you said. I run a 12/25, but live in a much hillier area.
Thanks for the feedback. I don’t know why I have 55/42…like I said, I just didn’t pay attn to it back when I bought the bike.
My reasoning for considering Compact cranks is that I’ve read about people liking more positions within their riding range.
Maybe a better approach is to make sure that I am running 11/23??
As far as flatlands, I said that to convey that I was not in a mountianous region. We have plenty of hills.
This is dumb question, but I will ask anyway. Can’t I just buy and swap the gears to a 50/36? What makes it a compact crank?
Also, I read something about having to change the front deraileur? Is that true? Thanks much, this is a huge help to me.
This is dumb question, but I will ask anyway. Can’t I just buy and swap the gears to a 50/36? What makes it a compact crank?
Also, I read something about having to change the front deraileur? Is that true? Thanks much, this is a huge help to me.
No, the bolt circle on standard cranks won’t accomodate a 36 (or a 34). ‘compact’ refers to the bolt circle being smaller (110 instead of 130) to allow smaller chainrings.
Maybe, maybe not. On some bikes you might be able to slide the front der down far enough and adjust it to shift acceptably. I switched mine out for a compact-specific front der and I can’t say I noticed significantly better shifting. Try it with the current front der before spending more money.
The big advantage of a compact crank is the ability to get a 34 small ring for serious climbing. To get that you give up some top end (i.e. only having a 50T big ring). My recommendation is to just get new rings for your existing crank (ex. a 53/39). I trained in MN (Highland Park in St. Paul) for four years, and it doesn’t have the sustained climbing that requires a compact. I raced there with a 52/42 and a 12/23 (bikes had fewer gears back then). These days I’d go with a 53/39 and an 11/25 (or 12/25 if the climbing’s still a concern).
I now live in NorCal where we have 5mile climbs at 7% on many of the popular loops and I put a compact (50/34 and 12/25) on my road bike.
KR - you’re running a 55x42 - I gotta ask is this on a 650 bike or a 700 bike 'cause that matters in a gearing question.
Ian
it’s a 700c. But I am interested in your response both ways, 650c and 700c. I’m trying to understand the
advantages/disadvantages for my bike and my womans (she rides 650).
Thanks a lot for the help.
just checked her ride, she has 56/39 with 12/25. 650c.
She racing IMWI this Sept and I want to make sure she has some good climbing gears.
I run a 50/34 up front with a 12-25 but live in a very hilly area. At first all my buddies poked fun at the ratio, then I showed them how to climb…they don’t poke fun anymore
If you really want to dig into this subject then get friendly with the gear chart here http://www.sheldonbrown.com/gears/ . When you tweak the wheel size (650 to 700) it makes a fairly dramatic change (as in one you could arguable “feel”) in the gearing. That’s why a lot of 650 bikes come spec’d with 54x42. When you tweak even the crank length it will change the gearing too but to a far lesser extent. You can plug all your options into Sheldon’s calculator a note the gear inches for each. While gear inches is a fairly precise way to look at your gearing you can start to associate how, for example your 54x12 “feels” in relation to the gear inches to your 42x26 “feels” and those gear inches and then you can plug in what a different set of rings or a different cassette would “feel” like as you see how the granny gear might become easier to climb the ultra long/steep climbs and as the big dawg might become something that has you spinning-out at 42mph rather than spinning out at 45mph - and you can see the gaps (ie. on a flat course it’s nice to have a cogs that are just one tooth or two teeth off from each other - like an 11-21 -so you can match the perfect cadence to the perfect “flatness”. When a cassette spans a larger distance - like a 12x27 for example - then some cogs are several teeth different from one another and that can be annoying).
Okay, now for some more rubber-meets-the-road relevant thoughts: riding at a smooth, fluid cadence of somewhere around 87-103ish might be really, really nice for triathlon as you can make the bike go fast but still have some legs for the run. This differs from, say, mashing out 70rpm for 40k and then running off that type of ride. My guess is that you could get a nice cadence out of your current gearing but you might have more “spinny” options from 53x39 rings with your current 12x26 cassette. So in short, no, I don’t think you should go to compact, I think you should stay with your current cranks (assuming they are 130 bolt spacing) and get some new rings of 53x39. If your race calendar consisted of Auburn International Half, Wildflwoer Long Course and then IM Lanzarote (all kooky hilly courses) then it would be much easier to make an argument for new compact cranks (with 110 bolt spacing) so you can go down to rings of 50x34 (or 52x36 if you’re into splitting hairs as I am).
Hope that helps.
Ian
just checked her ride, she has 56/39 with 12/25. 650c.
Generally, your derailleurs can’t handle the jump between those chainrings. I would suggest 56x42 or 53x39 chainrings.
Since we’re on the subject - is there such as thing as 36/52? I currently run compact 34/50 with 11/28 on my tri bike - I live in the mountains and I’m not the best climber, even though I love it. I love the compact on the uphills, but I hate spinning out on the downhills. My road bike is 39/54 with 12/28 and it’s a real grind on the ups, but I love the 54 on the downhills. Thoughts?
“Generally, your derailleurs can’t handle the jump between those chainrings. I would suggest 56x42 or 53x39 chainrings”.
I’m not sure I follow you. Are you saying the front derailleur cannot handle jumping between 56/39.
I just asked her and she said it was hard for her to go up from 39 to 56. But half the time, she’s probably sitting in 12 in the back. 
No kidding.
So you are saying getting these gears closer in size to one another will make it easier? Why is this an issue with 650c bikes?
Based on the other feedback I’ve gotten, I may ditch my 42/55. What do you think about transferring this to take the place of the 39/56?
*So you are saying getting these gears closer in size to one another will make it easier? *
**
**
Correct.
Shimano front derailleurs for road double chainrings are designed to handle a maximum difference of 16 teeth between the small and large chainrings.
56 - 39 = 17
Why is this an issue with 650c bikes?
**
**
It’s an issue with all bikes.
Based on the other feedback I’ve gotten, I may ditch my 42/55. What do you think about transferring this to take the place of the 39/56?
**
**
Talk to her about which gears she uses the most on her current setup and then start doing some math to figure out which chainrings and cassettes are best for her.
Since we’re on the subject - is there such as thing as 36/52? I currently run compact 34/50 with 11/28 on my tri bike - I live in the mountains and I’m not the best climber, even though I love it. I love the compact on the uphills, but I hate spinning out on the downhills. My road bike is 39/54 with 12/28 and it’s a real grind on the ups, but I love the 54 on the downhills. Thoughts?
You can buy chainrings for a compact bolt circle aftermarket to make your gear ratio 52/36. Most compacts come in the box with 50/34 though. I’ve been looking into making the change to compacts as well.
I currently ride a road bike in Central NC, i.e. not too many hills, with a standard 53/39. A 11/23 cassette is fine for most of the stuff around here except a couple of multi-mile long climbs. I’ve been curious to switch to a 52/36 and 12/21 cassette, as most of my tri races are on flat courses. This will give a higher cadence with the closest gear ratios you can find without losing too much top end, while still having the option of changing back to a 50/34 and 12/25 or 11/26 for extended climbing in the mountains.
So far though, I’ve only been able to find 52/36 rings made by SRAM Red and FSA. Could be an issue if you’ve got a specific component preference
So far though, I’ve only been able to find 52/36 rings made by SRAM Red and FSA. Could be an issue if you’ve got a specific component preference
I put the FSA 36 tooth on my Ultegra SL crankset and it works very nicely. No different than the Shimano 34 and I think it looks better because the way the black ring has machined silver teeth on it. I didn’t like the big jump from the 50 to the 34 and didn’t need it.
I don’t think Shimano makes a 36 or 52 at all which is kinda dumb.
So far though, I’ve only been able to find 52/36 rings made by SRAM Red and FSA. Could be an issue if you’ve got a specific component preference
I put the FSA 36 tooth on my Ultegra SL crankset and it works very nicely. No different than the Shimano 34 and I think it looks better because the way the black ring has machined silver teeth on it. I didn’t like the big jump from the 50 to the 34 and didn’t need it.
I don’t think Shimano makes a 36 or 52 at all which is kinda dumb.
Shimano also doesn’t make an 11-25 cassette, which is equally dumb.
So far though, I’ve only been able to find 52/36 rings made by SRAM Red and FSA. Could be an issue if you’ve got a specific component preference
I put the FSA 36 tooth on my Ultegra SL crankset and it works very nicely. No different than the Shimano 34 and I think it looks better because the way the black ring has machined silver teeth on it. I didn’t like the big jump from the 50 to the 34 and didn’t need it.
I don’t think Shimano makes a 36 or 52 at all which is kinda dumb.
Shimano also doesn’t make an 11-25 cassette, which is equally dumb.
They do, but it’s 105. Works fine, I have one.