As a caveat, I am not a mountain bike owner or rider. No off-road dirt trails (yet) for me. So the gearing description that follows relates to recumbent road bike riding and racing.
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I'm changing my gearing setup to accommodate the hill training.
Currently I'm running a SRAM Force 53-39 130-BCD Q-Ring setup up front with an 11-28 ten speed cassette in the back.
I'll be switching to a SRAM Force compact crank 52-36 110-BCD Q-Ring upfront and not changing the rear cassette.
Essentially, I'm giving up one tooth (from 53 to 52) on the big ring to gain three (from 39 to 36) on the small ring. The smaller the `small' ring the more likely I'll be able to climb hills with inclines in the teen percentages (i.e., 13% - 18% incline) when needed (for example, switchbacks on mountain roads, i.e., Mingus Mountain and from Sedona to Flagstaff, etc).
As well, the smaller `small' ring may be helpful when grinding up mile after mile of 7% - 11% inclines. (Yarnell Grade, Iron Springs road to Prescott from Skull Valley).
I could opt for a long-cage RD that would permit an 11-34 cassette but ... I just don't want that pizza pan size ring back there.
A comment about (what I consider to be) the relatively small big ring.
In the past, when my training and racing terrain was mostly flat with a few short 6% inclines every now and then, I would want to keep my pedaling RPM lower (85 - 95) when I had a tailwind. This RPM range suits my weight to power ratio.
My front big chain ring had 60 teeth. This allowed me to frequently exceed 30 mph for extended periods of time. (On one race [Race Across the West - 2010] I found myself averaging 40+ mph on a flat and glass smooth road with an 18 mph tailwind. This went on for more than 15 miles).
Now that my training and racing terrain is mostly hills and mountains ... I don't need a 60 tooth big chain ring. When descending even 3% declines my speed approaches 40 mph with the smaller front big chain ring. Short of the TdF these descending speeds keep me well in the competitive range.
If and when I'm racing ultra distances and have a follow vehicle and a crew it might be smart to have two bikes to accommodate both flat terrain and mountainous terrain. One bike would be geared for the flats (big front chain ring). The other bike would be geared for long and steep inclines.
Dan, People using a compact crankset around here, including myself are using 50-34 chainrings with an 11x28 cassette. 50x11 is still higher than a 53x12 so you're not giving up much on the top end and as you say gaining a lot more on the bottom end.
ReplyDeleteBTW I like to kid around that you only need two gears here in Prescott. For me that would be 34x28 and 50x11. While not really true it seems that way a times.
ReplyDeleteThat/s something to keep in mind, Mike. I've got a few 50-34 Ultegra compact cranks in `inventory.' At this point I'm trying to remain SRAM Force and Q-Ring consistent. At least on my Cruzbike Silvio. We'll see. Lot's of time; lots of options.
ReplyDeleteDan,
ReplyDelete53/36 with 11-28 is by no mean suited for long hills climbing on a bent with 700C. I run a 50/34 Qring with a 11-36 cassette and I use all gears when I climb. There is no way you'll pass grade above 13% with a chairing of 53/36 along with 11-28 casette, you will stall.