Is there anything out there that can help me decide what chainring and rear cassette combination would be best for me? It seems like something that takes into account watts/kg might be beneficial. I’m currently using a compact chainring. The extra easy gear helps going up hills but I find that I have no gears to go to when I’m going downhill. I’ve been focusing on going back to my more natural cadence in the 80-85 rpm range rather than spinning at 95+ even up hills as seemed to be conventional wisdom after Lance. It seemed harder at first but seems more natural (again) now. The added benefit seems to be more over all power and less fatigue when I do encounter hills. I feel like I’m giving up a lot of speed going down the hill though. I’m about to get my first tri specific bike and want to pick the best gearing options for me.
When I started, I just bought the stock Cervelo Dual and figured out after a year or so that I wanted more easy gears and added a different cassette and then eventually compact cranks. Don’t feel like you have to make the decision right off the bat. You can change up the gearing later without too much expense.
There can still be some nice advantages to a compact crankset if you choose for your cassette carefully. If you have 50/34 compact, you could run that with an 11-26 SRAM cassette. 34/26 will allow you to climb walls and is far easier than the 39/27 gear that would be the easiest practical gear choice with a standard crank. On the downhill side a 50/11 is a taller gear than a 53/12 which is what you’d likely be running with a standard crank.
If you are currently spinning out a 50/11 then you would spin out a 53/12 even sooner. If you really need something taller than a 50/11 (not likely in tri as you can easily pedal at 35 mphs with a 50/11 and there are basically no tri’s that benefit from being able to pedal above 35mph) then you are going to have to give up some on the climbing side. That does not seem like a smart choice. Far less is lost not being able to pedal above 35 mph than would be lost grinding up a climb at 50 rpms.
For flatter courses you could run a 11-23 cassette have have lots of very small ratio changes which is nice to be able to dial in the perfect gear on the flats.
Beyond that you might have to look at using a long cage derailleur so you can run more larger than a 27 in the rear and/or increasing the size of big ring (keeping in mind the front derailleur can only handle a max difference of 16 teeth and maintain decent shifting).
I’m a fan of 50/34 11-26 combo.
A couple of options here:
Use a SRAM 11-29 (yes they do exist) rear cassette which will give you an absurdly wide range, but somewhat wide spacing between gearsSwitch to a triple front (i think they are great, i know they have a bad rap). This will let you use a LOW range cassette like a 12-23 and still have a huge gear range and very close spacing between gears. Downsides- some people hate triple fronts, and they can be a bit hard to tune.
I don’t know of one that uses watts/kg but there are a couple of gear calculators around. Speed and cadence are the determining factors for gear selection. If you can do 300watts, you’re not magically going to be able to produce more/less than that at a different cadence.
Sheldon Brown’s site has a gearing/cadence calulator that you can configure with various cassette options. Allows you to work out speed at 90rpm and things like that.
Alternatively fixedgearfever.com has a spreadsheet pursuit calculator which does rpm/speed/distance/time for gearing. Single gear at a time though.
Regarding cadence - an average of 90rpm is supposed to be the best. Frank will pop along in a moment and tell us that slower is better/more efficient.
I reckon most people are in the 80s as there’s no way people are doing 90+, or 100+ with a 53 ring on the front unless they never use anything smaller than a 16 sprocket at 40kph. Conversely, if you are a low cadence athlete, a 53 ring will probably be ideal. You hear stories of folks using a 56 or bigger, but again they’re only useful if that gearing allows you to do the cadence you want at the speed you can do.
If you are a high cadence athlete, the traditional road gearing, i.e. a 53 ring, is too big unless you can consistently do 23-24mph on the flat.
As an aside, I ride at 95 to 100 rpm on the track. For pursuiting I use 51x15 at 97rpm (43kph). My tri bike has 53x12 on it. I’m not doing 97 rpm on that by any means. I do know of a guy in the UK who has a 77 tooth chain ring. He does about 65rpm though.
Echoing what Justin said… I ran a 50/34 11-23 combo for a long time and it gave me all the gears I needed for everything but the most insane climbs (34-23 is roughly equal to a 39-25) and had nice tight gear ratios so I could keep my cadence / wattage where I wanted them.
If it was a hilly ride the compact front and a 12-25 was very capable and I did a few hill climbs (11%+ for 5+ miles) on the 12-27.
All that said - on a tri bike, in an area with hills you can’t really beat the 50/34 and 12-25 combo.
X2 on the SRAM 11-26. I run mine on a 50/36 compact set-up on my Cervelo P2C and I have every gear I could ask for.
Dave
What about running a 52/36 on the compact cranks and using the 11/26 on the back. This still gives you a good climbing gear with the 36/26 rear but gives you a more on the top end with the 52/11.
I’ll be running the new Dura Ace and it doesn’t look like 11-26 is an option. They do have 12-25. Is that pretty much the same thing?
you’ll lose a bit at the top and low end (obv.) but make it back in having your gear ratios spaced closer together - meaning it’ll be easier to maintain a comfortable cadence.
There really isn’t any reason why you’d need an 11 tooth cog in a triathlon and there isn’t much that you couldnt get up in 34-25 that you’d use the 26 cog for.
If you really want the additional gears, though, you can use the SRAM 11-26 cassette on the DA rear der. without a problem (even though it’s one more tooth differential than it’s supposed to have)
I think for most AG triathletes, even fast ones, a 46/34 front and an 11-26 or 11-28 is the way to go.
I think for most AG triathletes, even fast ones, a 46/34 front and an 11-26 or 11-28 is the way to go.
Are you serious 46/34? I run a 53/39 with a 11-23 in the back and was fine on the Wildflower HIM course. I am strong cyclist but nor super strong I did the course in about 2:40. For this course I averaged 91 RPMs. There is no way I would ever run a 46/34. I have thought about going with a smaller little ring but if it isn’t broke don’t fix it. The only people that should be running a 46/34 are newbies or ridiculously light people, but even then I would recommend a 50/34.
I’ll be running the new Dura Ace and it doesn’t look like 11-26 is an option. They do have 12-25. Is that pretty much the same thing?
No it’s not. 11-26 is a SRAM product that will work just fine with Shimano. A 12-25 will make it harder to climb and you will spin out sooner on downhills… Minor details, and since you bothered to ask the question, I’d venture to say the 12-25 might be the least appropriate cassette you could choose. At a minimum a 12-27 would be better (for the climbing).
Forget the notion that there is one cassette that works for all races and all training. Best option is to have a couple of cassettes appropriate for different courses. I use at different times an 11-21 (9 speed), 11-23, 12-25, 12-27, and 11-26. All perfectly interchangeable on the same bike. Takes about 1 minute.
so… at wildflower you averaged 33.75km/h at 91rpms. So based on that you spent the majority of your time in the 53/18 gear.
Had you gone with a 46/34, at 91rpms, you would have spent most of your time in the 46/15-16 gear. Right smack in the middle of the cassette, plus the added bonus of power savings through greater drivetrain efficiency with the smaller chainrings.
I think for most AG triathletes, even fast ones, a 46/34 front and an 11-26 or 11-28 is the way to go.
Are you serious 46/34? I run a 53/39 with a 11-23 in the back and was fine on the Wildflower HIM course. I am strong cyclist but nor super strong I did the course in about 2:40. For this course I averaged 91 RPMs. There is no way I would ever run a 46/34. I have thought about going with a smaller little ring but if it isn’t broke don’t fix it. The only people that should be running a 46/34 are newbies or ridiculously light people, but even then I would recommend a 50/34.
well, that’s roughly the same size gear I use for stand-alone TT’s (47-11). While I understand that people often prefer lower cadences over longer distance events, I’m also going a lot faster than a triathlete (since I’m doing single, shorter events), so I figure it’s a wash. A 46/11 at 91 rpm is 30mph. That’s pretty fast.
As far as the ‘what about the downhill’ argument, I find most people naturally increase their RPM on downhills, regardless of the available gears–and once you get above 38mph or so you’ve better off coasting and tucking. I’m using a 50/11 for road racing, on big mountain descents, sucked along in a pack of fast people–and I can think of only one occasion where I wish I had a bigger gear.
I use SRAM 11-28 back and 53-39 dura ace front. Works great, spacing is not horrible.
I am a pretty strong cyclist and am of the mind set that too much or too little gear is not an option. It is the only cassette I use.
Good Luck.
Forget the notion that there is one cassette that works for all races and all training. Best option is to have a couple of cassettes appropriate for different courses. I use at different times an 11-21 (9 speed), 11-23, 12-25, 12-27, and 11-26. All perfectly interchangeable on the same bike. Takes about 1 minute.
best advice on this thread. I run a 50/34 and usually, I am good with a 11/23 in the back. But when i go to the Triple T, I always use at least a 12/25 for the really steep hills.
This page http://www.analyticcycling.com/ForcesSpeed_Page.html will get you part of the way there for uphills. Plug in the total weight of rider, bike, and gear, the slope, and the power output (probably leave all others at default unless you know them) and it will give you your speed up the hill (in meters/second). Use that with your desired cadence on climbs to determine your low gear requirement.
Example: 75kg, 0.08 slope, 200W gives a speed of 3.16m/s. If you want to keep your cadence above 80rpm, you will need a low gear of 3.16/80*60 = 2.37m (or about 30"). For a typical 700x23C tire (~2.1m circumference), this would be a gear ratio of 2.37/2.1 = 1.13. If your small ring is a 34, you would need a large cog of 34/1.13 = 30.
For going down hills, it sounds like you want a cassette that starts with an 11T. If Campy or Shimano or SRAM don’t make what you want, you could check out IRD’s wide range cassettes - http://www.interlocracing.com
How does that 11-28 work for you? Do you have it on a shimano derailer? Does it shift well. I have looked at doing that cassette for my town bike to get a bit more range.
once you get above 38mph or so you’ve better off coasting and tucking.
**
I’ll echo this sentiment but make that about 25 mph for the average triathlete. It never fails each race that I pass folks pedaling furiously while I am in my full tuck. On rolling courses I generally average about 24 mph and I just softpedal between 25-30 mph and tuck anything over that.
If a triathlete is pedaling beyond 30 mph then they are wasting energy that would be better served on the flat or uphill.
Chad