Spinning

jpwkeeper said:

Which brings up a fascinating question, in my mind.

Why wouldn't a rider gear their bike so that their lowest gear was specifically for the worst part of their worst climb? Everyone talks about climbs being really tough, but if your gear ratio compensates for the climb, so you can spin at the same RPMs, wouldn't the climb require the same level of exertion over time (not distance) as riding on the flats? So a 1 mile climb ridden at 1/2 the speed but twice the gear ratio (I'm probably not saying that right, but you understand) would tire you out exactly the same amount as 2 miles of flat ridden in the same time?

Seriously, if you've got 9 gears, couldn't you reserve one of them for the bad part of the climb?

I'm just wondering about the psychological element of climbing. It's kind of depressing to be pedaling the same cadence and going so much slower. I'm just thinking that, by pedaling a slower cadence, it balances it out in your mind.

Of course, the math for this is definitely tricky. What climb percentage equals 2x effort, but then subtract wind resistance, which will vary depending on the two speeds, etc.

when riding uphill the velocity will be slower, such that on many bike you may not be able to get a low enough gear or specifically a cassette that has "normal" ratios on except for a very low bottom gear.

even if you could spin at the same cadence (i.e., you had a very low bottom gear) the power requirement will generally be higher than on the flat, unless the gearing is very low (and thus your velocity can be very slow, e.g., less than walking pace)

ric

KakenBetaal said:

Why would doing this make any useful difference at all?

If you imagine the cogs or teeth of the sprocket as mini cranks which extend
form axle to effective contact point with chain, by increasing the size of the
sprocket you are extending the length of the imaginary crank and just as
with the normal pedal crank, by increasing its length you make it easier to
apply the same force.

Thought I'd add my two cents: I'm a small guy and have trouble keeping up with the huge muscle rollers, but I've geared my bike with a compact crank in the front and a 12-27 in the back. On the harder hills I can blow past nearly everyone while spinning at 110 RPM plus. I've intentionally tried to increase aerobic power in order to compensate for my lack of big-gun power compared to other riders in my area. Works on the climbs, but I have to work pretty hard to hang on when it's flat.

Also, I've found for me that the 50/12 max gear combo is adequate for nearly any sprint situation - again I've developed a very high cadence and it works for me.

Thanks!

The whole gear issue it tricky. Have you ever rode and paid attention to how gears can be used to take strain off the knee? Skilled use of gears can protect from injury. My own mistakes tend to be gauging an incorrect gear on a hill and getting stuck in too big a gear.

sdorrity said:

There has to be an optimum RPM otherwise we would all be pushing massive gears any ideas what it is? If I push less than about 85 RPM my knees suffer and my legs feel heavy and I tire faster. My own optimum seems to be around 95 RPM any faster and I bounce and can't keep a good rhythm (sp?)

and mechanical efficency doesn't always carry over to bio systems otherwise tandems would have the pedals set at 90 deg to smooth out the power transfer a'la 4 stroke engines.

Regards

Steve D