Originally Posted by
GaryPitts
So I went by the Harpeth River ride this weekend to check out the vendors and see Lance in person. As it turns out, he rode right by me in a pack of 8 or 10 finishing his 100 miler and I didn't even see him
Crap!
Looking at bikes in the vendor area I noticed all the fast road bikes had compact gears up front and I'm wondering now why they don't use these on all bikes instead of just the higher end road bikes? Seems that 2 gears up front would make better sense than 3, especially when I've yet to use the small front gear.
You don't use the small gear because triple equipped road bikes generally leave the factory with huge cogs for tourists (who need them to get 50 pounds of luggage up hills) and out of shape people. With more reasonable cogs (I built up my first triple equipped bike with a 13-14-15-16-17-18-19-21 8 speed cassette, netting me ideal gearing for flat rides plus a low like 39x27 for mountains without needing to change wheels/cogs depending on whether the day's ride was headed west up the Rocky Mountains or east on the plains) you'd use it and may appreciate the tighter spacing.
For the same overall range a triple provides tighter spacing between gears when
you're not strong enough to spin a 34x26, 34x23, or 34x21 up any hill you'll encounter (with 10 cogs in back; 9 cogs reduce those to 23/21/19 and 8 cogs 21/19/18) depending on whether you prefer a 13, 12, or 11 starting cog.
Where you are strong enough the wide crank and tight cogset combine to produce limited overlap so there's a lot more front shifting, the front shifts are more involved, you use the extreme cogs instead of ones in the middle so the bike is noisier,
I currently use 50-34x13-14-15-16-18-18-19-21-23. Disregarding the fully cross-chained combinations the only overlapping gears are 50x21 and 34x14. With the wrong terrain, wind, fatigue, and rest-day combination situations with speed dropping to 15 MPH and exceeding 20 MPH there are a lot of front shifts.
With the same cassette, cross-chaining avoidance, and cadence range a 40 middle ring on a triple is good for 12 - 24 MPH. While 20-24 MPH doesn't look like a lot on paper, it takes over 60% more power to get to 24 MPH. For many flat rides you can pretty much stay on the middle ring with no shifting.
With the compact a front shift goes with five cogs in back (ex - 34x14 to 50x19 or 50x21 to 34x15) and two right shifter wiggles with Campagnolo. On the triple it'd be 3 cogs like 40x14 to 50x17 or 50x21 to 40x17.
When cruising at a comfortable 18-19 MPH I'll ride 50x21 or 34x14 on the compact which are one cog from the end and noisy. With the triple I'd ride 40x17 (in the middle of the cassette) or 40x16 (just one off).
I guess if I get into some serious hills I might be glad to have it, but what's the disadvantage to compact gears and why don't they use them on all bikes?
Wider spacing between gears for the same over-all range than a triple, more double shifting, more chain noise at cruising speeds. Mountain bikers, larger riders, and people with payloads also can't get the same range out of a compact.