New Dura Ace Gearing
So I'm getting ready to order a 2013 Trek Speed Concept with the 2013 9070 DA Di2. This new groupset is creating a number of new problems, not the least of which is utilizing an 11 speed cassette. Between that and the bike's BB90 bottom bracket (which I don't know is any particular problem) has made me wonder what I'm doing for power meters. I would prefer to stick with my Quarq, but if I needed to change to PT then I would have to pick my chainring gearing.
I have been a huge compact user and proponent, singing its praises to the masses. But they are introducing midrange gearing with a 52/36 option. I don't particularly know why, but this option seems to be a great option with the "best of both worlds". And for whatever it's worth, all sizes will be using a 110 BCD so I'm assuming they would be easy to swap out depending on race type, distance, etc.
My question about PM's is pending with the experts, but assuming I can't do a Quarq, tell me why, or why not, this wouldn't be the way to go. Keep in mind that despite there being 11 cogs on the cassette, the largest will still be the 28. I would obviously go with an 11/28 either way.
Comments
There was a recent post on ST about Quarq and 11 speed compatibility. I'll try to find it. I'm pretty sure there wasn't an issue. After all, your Quarq doesn't know what kind of cassette you're using. I can't see what the problem would be.
The BB90 thing isn't an issue. I assume you have a GXP Quarq. all you need is the SRAM GXP BB kit and you'll be good to go. GXP to BB90 is no problem. You can't go the other way. A BB90 axle will never fit into a GXP bracketed frame.
http://www.trekbikes.com/pdf/2011/service_manuals/Trek_2011_Speed_Concept_Service_Manual.pdf
Page 20 of the manual
FWIW, I've been riding 52/36 for most of my races for 2 years now, i find it is perfect for me as I can stay under my target watts on just about any climb with a 36 - 26 and the 52 give me a little more top end.
Great input everyone. All this technical bike equipment stuff is still so confusing to me. So it sounds like I can use the DA chainrings, sans crank arms, with a Quarq and Rotor 3D crank arms. I can then change one or both chainrings if I wanted to depending on course, conditions, whatever, sort of like changing a cassette and as long as I fix the calibration my power should be good.
As for my gearing question, I like the idea of having a 36 small ring. Combined with a 28 large cog in the back, the ratio is less than a 34/25 which I have ridden the Kona course with and raced at CDA with. So I would still have plenty of options at the low end. At the high end, I rarely pedal at > 35 mph which means a 50 is good for me. Ideally I could order 50 and 36 rings. If I had to stick with a stock combination I could get the 52/36 and buy a 50 later if I thought the 52 was too much for me with cadence and power gaps, etc.
Thanks for helping me to work this out everyone!
Not sure the "lift pins" will line up for a 50/36, make sure you check on that before you buy the rings. I think the 52/36 is probably the best gearing option around. With 11 speeds on the the back side, you should never run out of options to stay on your watts for almost any course.
Jeff, are you looking for another son? I'm available
@ Terry - here's photo of my son's setup - DI2 + rotor + quarq - on a Cervelo P5 w/Zipp 808
@ Rich - yea he has all the cool toys
- but he bought/paid for them - he is a good cyclist though @ 4.6 w/kg and a member of USMC tri team