Triathlon - dura ace cassette - how many tooth works best with 53/39 crank?

hello everyone,

im new to the forum and looking for some advise on a new cassette. i recently purchase a new set of wheelsets (reynold attack clinchers) and im looking for a new cassette to go with it. im currently using a 53/39 crank with a 10 speed 12-25 cassette. i dont have a cadence meter so im not sure which setup is idea for me. i usually ride with the larger crank up front and 21,22,23 in the rear.

i've research a lot on tri bikes; felt, cervelo, kuota, etc and they all pair a 53/39 with either a 12-25 or a 12-23. any pros or cons of the two? or maybe a totally different setup all together? a 12-27? 11-xx? is there an ideal setup for tri specific vs road racing?

would i reguire a new chain if i use a setup different from my current 12-25? any advice would be appreciated.

If you're usually in the large chainring and 21,22, or 23 in back, you're probably in the wrong gear most of the time - - and in 53/23 you'll probably be wearing the chain.

If you're finding that when using the 53/12, you need to go further down, then you could get an 11-25.

If you're having trouble on hills even when in the 39/25, you could get a 27-12.

If you never ever ever use the 39/25 (viz. if you never ride on notable hills), and would fancy being able to fine-tune things to get just the right gear a little bit better, you could get a 23-12.

thanks for the insight treefox. why would a 53/23 hurt the chain? im usually 52/19-23, mostly 21, i just strive for 18+ mph on average during my races.

i hardly drop into the 39 chainring even during climbs, i just push through. probably cause i dont climb too much. i do use the 39, but its with the harder lower gears, never up in the 25.

however, the ironman 70.3 i will participate in will have 1,200 ft in elevation rise, so i want to be prepared for it. so basically, cant go wrong with a 12-25? im leaning towards a 12-23, just hope i wont regret it.

If you're usually in the large chainring and 21,22, or 23 in back, you're probably in the wrong gear most of the time - - and in 53/23 you'll probably be wearing the chain.

If you're finding that when using the 53/12, you need to go further down, then you could get an 11-25.

If you're having trouble on hills even when in the 39/25, you could get a 27-12.

If you never ever ever use the 39/25 (viz. if you never ride on notable hills), and would fancy being able to fine-tune things to get just the right gear a little bit better, you could get a 23-12.

I used an 11-23 at Honu & Vineman 70.3's and I'm not a good climber by any stretch of the imagination. I suspect you will be fine with what you have...but don't be afraid of the small ring.

thanks for the insight treefox. why would a 53/23 hurt the chain? im usually 52/19-23, mostly 21, i just strive for 18+ mph on average during my races.

What treefox is referring to is cross chaining. The greater the diagonal created with the chain ie Big front chainring and rear cog closer to the spokes puts more stress on the components and greater wear.

Check out a gear calculator such as http://www.sheldonbrown.com/gears/ and input the cassette ratio and front chainring sizes.

The resulting table will show you the gear inches. 53x23 is only a fraction taller than 39x17 which will have the chain running in a straighter line which means less transmission wear and due to the less friction within the components less wattage required for the same speed.

thanks for the info you guys. im amazed how there is so much to learn. i really want a much better bike time. anything else i can do to increase efficiency?

people keep saying cadence and im starting to realize the importance. is it necessary to get a meter that reads cadence? i have no idea what are idea gearing combos. like whats a good gear to practice on and to really develop those muscles.

What treefox is referring to is cross chaining. The greater the diagonal created with the chain ie Big front chainring and rear cog closer to the spokes puts more stress on the components and greater wear.

Check out a gear calculator such as http://www.sheldonbrown.com/gears/ and input the cassette ratio and front chainring sizes.

The resulting table will show you the gear inches. 53x23 is only a fraction taller than 39x17 which will have the chain running in a straighter line which means less transmission wear and due to the less friction within the components less wattage required for the same speed.

Well try to never use 53x23 or 25 - or 38x12 or 13. Really, you're lucky if you're not getting an annoying clicking noise from the chain against the front derailleur when you're doing this - in most setups you would.

I'm kinda at a loss as to how to explain what a good cadence would be in easy terms... um... faster is better, up to a point??