Question about bike gearing.
I am new to EN and also pretty new to triathlon. I am learning a lot by reading through all the forums and the info in the Wiki. I do have a question about bike gearing though. I purchased my first tri bike on ebay this winter. I got a 2006 Cervelo Dual. It came with front and rear Dura-ace. It has a standard crank and when I took it to my LBS I had them try to put a compact crank on it but they couldn't because the front derauiler bracket is welded on too high. Couldn't lower the front derauiler enough to make it work. The bike also came with an 11-23 cassette but I have purchased an 12-25 cassette so I am in compliance with the EN gearing standard. I don't want to suffer the fate of being out of compliance.
I am planning on doing Kansas 70.3 this summer and IMWI this year also. This will be my first shot at these distances. The more I read, I see people saying that you can never have enough gears. So, do I need more easy gears in my cassette? Can I put an 11-28 cassette on this bike and will it work? Will the shimano 105 11-28 cassette from my road bike work with these derauilers and chain or will I damage something? Will the 12-25 cassette be enough?
I have a powertap and have gone through the OS so I am confident I will have a good plan for the race but don't know if I will have enough gears for the hills. Maybe I am over-thinking this too much but I am impressed by how much all of you know about this stuff and would love to hear you thoughts.
By the way, I am a bigger guy 6'4", 210 pounds so I have a lot to get up and down the hills. Current FTP 216.
Comments
For you:
Here ya go: SRAM Rival or Force cassette, in >25t + 12t cogs. I plan to get a 25-12 Force. Note that the Red cassettes all come with an 11t, which you'll never see, they are $$$$$. I have a 26-11 on my road bike. Great gearing for mtn riding (26t + compact for climbing, 11t + 50t doesn't spin out until >41mph = great for fast descents. But it was $$$$$ and not worth the extra dough...though the inner cog is annodized red and looks pretty cool, which in the end is probably all that matters
@Brant - Coach R has good advice. I am also 6'4", and just a couple LBs lighter. I've done IMMoo with a standard crank and survived... It was NOT pretty. Each of those rollers takes a little too much out of you each time going up.
Get a Compact any way you can! Sell blood if that's what it takes!
With our weight and the higher speed descents, I could be macho and recommend the 11t, but in all reality, once you're going downhill fast enough to need it, even with a "small" 50t big ring, you should be coasting.
I did IM CdA last year with a compact (34/50) and 12/27 and it was good.
As for Kansas, I ass-u-me it is flat enough that you may be fine with a standard crank (39/53) and a 25t in back.
Here is a "is it good enough" tip: Find a moderate hill, 6% is a good guideline. Check your wattage at 80rpm or better. If you need FTP or more to hold that rpm, you can use lower gears.
-Joe
Yes, the 28t will probably buy you 8-10rpm (SWAG) over the 27t. However, you will see a larger cadence gaps in the gears vs a 27-12. A cadence gap is where there is a relatively big jump in the number of teeth (ie, the the cassette goes from a 23t to a 19t, for example) and results in a gap in your cadence: in one combination of gear and speed, you're pedaling at 80rpm, too low for you, and you feel a need to shift. You shift, but the cadence jumps to 97rpm...too fast and you can't get comfortable.
This is a consequence of going up in the gears. 21-11 on a 10-spd bike will have no gaps. 23-11...none. 25-11....you'll feel it. 27-12...even more so. The benefit of a compact crank is that you can run a "close ratio" cassette on a course that you'd otherwise need something more spread out. For example, if I had a standard crank for IMWI I'd probably run a 27-12, but the compact allows me to run a 25-12, a closer ratio with very little cadence gap at my expected cruising speed.
Another way to do it is to build yourself a "frankencassette:" take a couple cassettes and mix and match the cogs to get the gearing that you want. I used to do this back in the day, it worked.
That's great advice, thanks! I already have SRAM Force DR so might investigate compact cranks as well.... also what's your recommendations on crank length or is it entirely personal? I'm riding 175s because they came with the bike, but would it be worth going smaller if I was going to be purchasing a compact?