Gear envy

Posted by SuperClydesdale on April 12, 2010 under Commentary | Be the First to Comment

I’ve written several times on the need for different gearing for large riders than that of smaller riders.  While Clydesdales may have massive legs and big engines, we are hauling significantly more weight up the hills.   This has prompted a lot of discussions over the years, as Clydesdales have felt obliged to explain their disadvantage on the hills and defend their decision to put on a compact crankset.  I’m developing a serious complex I’ve come to call gear envy – “man, I wish I could ride up this hill in that gear!”

There is no disputing the laws of physics that result in the disparity in climbing difficulty, and my historical efforts over the years have yielded some interesting information.

There are three primary forces at work against a cyclist:

  • Road friction
  • Wind resistance
  • Gravity

The difference in road friction between a Clydesdale and a whippet is supposedly relatively small (see the end of this article for some data), and I will accept that for the purposes of this discussion.  Wind resistance should actually work in favor of the larger rider, as the amount of surface area doesn’t increase substantially with a larger rider vs. a smaller one, while maximum power output increases with larger riders.  That said, I’ve seen some big dudes whose surface area was pretty significant.   When your surface area is hitting your thighs – and your knees are hitting man boobs, it’s significant.  But, for most Clydesdales, the wind resistance is not as significant for us as it is with smaller riders.   It’s on level ground where wind resistance becomes the primary force you are trying to overcome, and that’s where us larger riders tend to have an advantage.

Gravity is the big one.   No running away from that (only coasting away from it, and then you’ll have to climb back up the damn hill later on).    Naturally, I’m known as quite the downhill specialist, so the fact that I can coast past a smaller rider who is pedaling feverishly down a steep hill is telling (and fun).   Unfortunately, going the other way on the hill turns the tables.  The steeper the hill, the greater the power required to climb it, and the power output required to haul a big boy up a 9% grade will quickly make a Clydesdales’ bigger engine a moot point.   There’s tons of research on this, as well as some simple calculators online  to allow you to amuse yourself at work (when you’re supposed to be updating that spreadsheet that your boss told you about last week).

Just some quick examples from the calculator at www.exploratorium.edu reveals some interesting results for a rider with a 17 pound bike riding up a 9 degree slope at 8 mile per hour:

  • 223 pound rider (me) on a 17 pound bike (240 total pounds), 640 watts required
  • 180 pound rider on a 17 pound bike (197 pounds total), 496 watts required

That’s a massive difference in the amount of work required.  Good news is that I can invest a few thousand dollars and get a 15-pound bike to replace my 17-pound bike, and then it will only take me 599 watts.

At least now, I know that unless my 180-pound riding partner is going at least 10.3 miles per hour, I’m kicking his ass.  He’s pulling away from me, but I’m still totally destroying him in the watts department.

The simple calculator is fun because to calculate the power requirements precisely, taking into account rolling resistance, wind resistance, etc., would be a considerable undertaking.   Just imagine how long it might take just to calculate your surface area (the area of the shape of your body and bike pushing through the air).

Because I cannot escape gravity, I’ve put a compact crank on my racing bike, and a triple on my “climbing bike.”   The climbing bike was built up for my ultra-distance rides last year, and for the significant climbing rides I was doing.   There’s no way that I was going to complete the Markleeville Death Ride without a triple.  Not going to happen.

I had a bit of a wakeup call not too long ago on a training ride.  I came upon a big dude (not tall, just  heavy. His bones were large).  He was spinning up a long grade at about 5 miles per hour.  I fell back and spoke to him for a few minutes, and discovered that he actually rides more than me.  He had 6,000 miles in the last year!   I couldn’t help but think that the guy was pedaling in such easy gears that he was able to ride 6,000 miles and still be considerably overweight (or he was eating like a beast).   I took that as a sign – time to crank up the power output on my rides.  Not that I’m a slouch, but I certainly needed to kick the “granny gear” habit up the steep hills.   Out of the saddle!

Now, I’ve decided that I want to work on increasing my power, and try to address some of my gear envy.   I want to force myself to ride in smaller chain rings (in the back, obviously), and get up out of the saddle more.  It’s easy to slip into a “spin up the hills” mentality if you’re not on guard, which means that you’re not only going slower, but you’re also not putting out a lot of power, or pushing your fitness level.   One of my goals for this season is to really build up leg strength.  I’m surprised at how fast it’s had an impact.   Not only am I going entire rides (40 mile rides with > 3,000 feet of climb) regularly, but I am using lower and lower gears.   I have not been using my small ring on the triple crankset at all, even up the dreaded Beatty Hill.

Most of these are rides that I am doing alone.  Under the pressure of a fast-paced group ride, I may trash my legs and end up on the triple, but the amount of time I spend in the “safety net” gear ratios is declining, and my leg strength is improving.

Some interesting links (if you’re a total geek like me):

http://www.exploratorium.edu/cycling/aerodynamics1.html (best simple calculator)

http://www.sportsci.org/jour/9804/dps.html

http://www.mybikeapps.com/Apps_/How_BikeEnergy_Works.html

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