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spinning must be good(7 posts)

spinning must be goodDougSloan
Feb 7, 2003 7:07 AM
I did have my Pista geared at 44x16 (73.2 inches -- 96 rpms @ 21 mph), until I hurt my knees doing far too many big hills in December. So, I geared it down to 48x18 (70.9 inches -- 100 rpms @ 21 mph), thinking I would go a little slower and take it easy for a while. I use this bike for my daily lunch time rides, about 15-18 miles, trying to average 19-20 mph, even with lots of stoplights.

Anyway, to my amazement, I'm finding it's easier to handle 21 mph on the flats with the lower gearing, even though it's only a couple of gear inches. Go figure. Is that too small a difference to matter, and is this all in my head, or do you think there can be sort of an rpm "threshold" that makes it easier to maintain a certain speed?

Doug
Engineers study this in car enginesKeeponTrekkin
Feb 7, 2003 11:30 AM
and I'm not too familiar with the details. Basically, moving the engine requires energy and moving the vehicle requires more energy. The phenomenon is real, not in your head (although non-scientific testing, especially at lunch hour, is always suspect).

In simple terms, the power required to move the bike per pedal stroke is less at the higer cadence. It must be that the total power required to move your legs and the bike is less at this particular combination of gearing, speed, etc. Therefore, you perceive "it's easier to handle".

It quite likely is.

Valle
it's horsepower vs. torquedesmo
Feb 7, 2003 2:03 PM
a fine line for peak performance in combustion engines, and the cyclist. it's real, and it's good to know where it is. in engines it's constant messing around matching rod length, bore, stroke, cylinder heads and cams. on a bike you find the sweet spot when you realize you can climb faster sitting on a smaller gear, or like you experiance being able to hold the same speed on flats with less effort and gear.
this has to be critical for an hour record, thenDougSloan
Feb 7, 2003 2:18 PM
I'd guess for an hour record you'd want to do a lot of experimenting, right?

Hmm. The whole point of this sort of makes a case for lots of gears, actually.

Doug
this has to be critical for an hour record, thendesmo
Feb 7, 2003 3:19 PM
yup, the smaller the powerband the more gears you need to fine tune the output. I've been riding all this week on my newly restored 70's bike with a 14-18 5 speed cluster. lots of fun but the sweet spot does not last long. it feels more like riding my fixie than a modern 10 speed drivetrain, as I'm pushing way more gear than I usually would. actually if I had not been riding so many 74 inch fixed miles the last couple of months I'd probably be a wreck on the 5 speed bike.
mmmm ... but will it still be true in a month?Humma Hah
Feb 8, 2003 12:58 PM
I've experienced the same thing, but then long-term found I lost the advantage.

The day we met, I had dropped the front chainring from 46T (stock) to 42T. I'd run TD Palm Springs stock, but the Solvang was an extra 2000 ft of climbing. Even with the drop in gearing, I twanged one knee, something I've not done before or since.

But then, thinking the lower gearing was working well, I left the bike that way all year, only gearing it back to stock in December. It quickly became obvious that riding the lighter gearing in Northern Virginia had atrophied my leg muscles. Within a couple of months of gearing back up, I'd noticed a simultaneous drop in BF and rise in weight, visible difference in my quads, and I was climbing the little bumps around here in a decidedly more sprightly fashion and averaging a better speed.

Train a little higher, race a little lower, and beware of anything that makes riding "easier". Short, of course, of your recent practice of making things so hard you wreck your knees.
good pointDougSloan
Feb 8, 2003 8:42 PM
But this is a training only bike. I guess I'll just have to go faster. Thanks.

Doug