How Much Do Hills Affect Average Speed...
10-27-10, 05:02 PM
#51
Full Member
However, in the hills when you average 22 MPH on a course of 88 ft / mi, your average speed is limited by your climbing speed (which I'm estimating is probably 14-16 MPH range on this course?) rather than by wind resistance.
10-27-10, 05:06 PM
#52
It's ALL base...
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Ah.
I always forget when these ft per mile numbers are given that it is total ascent not net ascent. My favorite climb has a section 13 miles climbing 5.5 K ft. is like 7.9 % average grade. I am lucky to get a 10 mph average for the out and back. The problem too with switchbacks with oncoming and same direction traffic , you are lucky if you can average downhill speeds of 30 mph.
I think rollers can give you the same if not faster times than flats.
That is why the adage is "Average speed does not matter"
I always forget when these ft per mile numbers are given that it is total ascent not net ascent. My favorite climb has a section 13 miles climbing 5.5 K ft. is like 7.9 % average grade. I am lucky to get a 10 mph average for the out and back. The problem too with switchbacks with oncoming and same direction traffic , you are lucky if you can average downhill speeds of 30 mph.
I think rollers can give you the same if not faster times than flats.
That is why the adage is "Average speed does not matter"
This is unpossible.
10-27-10, 05:45 PM
#53
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Fine, serious answer:
Uphill: 10 miles at 10 mph takes 1 hour.
Downhill: 10 miles at 20 mph takes 30 minutes.
What's your average? It certainly isn't (10 mph+20 mph)/2=15 mph. Rather, 20 miles/1.5 hours=13.3 mph.
Middle school math.
Uphill: 10 miles at 10 mph takes 1 hour.
Downhill: 10 miles at 20 mph takes 30 minutes.
What's your average? It certainly isn't (10 mph+20 mph)/2=15 mph. Rather, 20 miles/1.5 hours=13.3 mph.
Middle school math.
* I haven't found a way to put as much power into a downhill stretch as I do uphill (if I did, I would reach a truly neckbreaking speed)
* as mentioned previously in this thread, wind resistance increases more than linearly with velocity - so you're better off riding your steady speed on the flat than the slow - fast up and down the hill.
Both of these effects are more pronounced the steeper the hill is (especially the downhill). So on a two-mile stretch, your average speed should be better if it includes two 50-ft hills than with one 100-ft hill; and it will be better on a ride with 100ft ascent over half a mile followed by 100ft descent over 1.5 miles then on a ride with 100ft ascent on first mile, followed by 100ft descent on second mile.
So there are perfectly good reasons why average speed should be slower on hills, but the middle-school math has very little to do with it.
Last edited by plantrob; 10-27-10 at 05:54 PM.
10-27-10, 06:05 PM
#56
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A fine comment, showing much insight into the topic. My analysis is correct, though, which makes your reply a bit shy of useful.
You illustrated a point by making the wrong assumption that (downhill speed - flat speed) = (flat speed - uphill speed). Given equal power output, the downhill speed will exceed the flat speed by much more than the flat speed exceeds the uphill speed. So your condescending answer was short enough, but unfortunately missed the mark.
No ***** Sherlock. I'm trying to illustrate a point, which I did. The detail is moot.
10-27-10, 06:19 PM
#57
Senior Member
Except that it's wrong. Or at least overly simplistic. If your power output on a flat is 200W, and you maintain that power output on the uphill as well as on the downhill, your time (and therefore your average velocity) should be identical for the flat and the hill ride (if wind resistance is the same for both rides).
Flat road - 67.98 m/s
4% up hill - 6.18 m/s
4% down hill - 1014 m/s (hey, let's call it infinite)
Time on flat road 2*D/67.98; Time on hill D/6.18.
D/33.94<D/6.18
10-27-10, 06:28 PM
#58
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Except that it's wrong. Or at least overly simplistic. If your power output on a flat is 200W, and you maintain that power output on the uphill as well as on the downhill, your time (and therefore your average velocity) should be identical for the flat and the hill ride (if wind resistance is the same for both rides). Two problems:
* I haven't found a way to put as much power into a downhill stretch as I do uphill (if I did, I would reach a truly neckbreaking speed)
* as mentioned previously in this thread, wind resistance increases more than linearly with velocity - so you're better off riding your steady speed on the flat than the slow - fast up and down the hill.
Both of these effects are more pronounced the steeper the hill is (especially the downhill). So on a two-mile stretch, your average speed should be better if it includes two 50-ft hills than with one 100-ft hill; and it will be better on a ride with 100ft ascent over half a mile followed by 100ft descent over 1.5 miles then on a ride with 100ft ascent on first mile, followed by 100ft descent on second mile.
So there are perfectly good reasons why average speed should be slower on hills, but the middle-school math has very little to do with it.
* I haven't found a way to put as much power into a downhill stretch as I do uphill (if I did, I would reach a truly neckbreaking speed)
* as mentioned previously in this thread, wind resistance increases more than linearly with velocity - so you're better off riding your steady speed on the flat than the slow - fast up and down the hill.
Both of these effects are more pronounced the steeper the hill is (especially the downhill). So on a two-mile stretch, your average speed should be better if it includes two 50-ft hills than with one 100-ft hill; and it will be better on a ride with 100ft ascent over half a mile followed by 100ft descent over 1.5 miles then on a ride with 100ft ascent on first mile, followed by 100ft descent on second mile.
So there are perfectly good reasons why average speed should be slower on hills, but the middle-school math has very little to do with it.
10-27-10, 06:28 PM
#59
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10-27-10, 06:46 PM
#62
Senior Member
Except that it's wrong. Or at least overly simplistic. If your power output on a flat is 200W, and you maintain that power output on the uphill as well as on the downhill, your time (and therefore your average velocity) should be identical for the flat and the hill ride (if wind resistance is the same for both rides). Two problems:
* I haven't found a way to put as much power into a downhill stretch as I do uphill (if I did, I would reach a truly neckbreaking speed)
* as mentioned previously in this thread, wind resistance increases more than linearly with velocity - so you're better off riding your steady speed on the flat than the slow - fast up and down the hill.
Both of these effects are more pronounced the steeper the hill is (especially the downhill). So on a two-mile stretch, your average speed should be better if it includes two 50-ft hills than with one 100-ft hill; and it will be better on a ride with 100ft ascent over half a mile followed by 100ft descent over 1.5 miles then on a ride with 100ft ascent on first mile, followed by 100ft descent on second mile.
So there are perfectly good reasons why average speed should be slower on hills, but the middle-school math has very little to do with it.
* I haven't found a way to put as much power into a downhill stretch as I do uphill (if I did, I would reach a truly neckbreaking speed)
* as mentioned previously in this thread, wind resistance increases more than linearly with velocity - so you're better off riding your steady speed on the flat than the slow - fast up and down the hill.
Both of these effects are more pronounced the steeper the hill is (especially the downhill). So on a two-mile stretch, your average speed should be better if it includes two 50-ft hills than with one 100-ft hill; and it will be better on a ride with 100ft ascent over half a mile followed by 100ft descent over 1.5 miles then on a ride with 100ft ascent on first mile, followed by 100ft descent on second mile.
So there are perfectly good reasons why average speed should be slower on hills, but the middle-school math has very little to do with it.
10-27-10, 07:00 PM
#66
Senior Member
10-27-10, 07:18 PM
#67
VeloSIRraptor
I heard someone say that this thread was dumb... and I bet umd would say that you are an idiot.
can't say as I'd disagree
~yep
can't say as I'd disagree
~yep
10-27-10, 07:25 PM
#68
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Just to stir things up theres some psychological and physiological stuff mixed in with the gravity and the wind resistance.
Its easier to put more power down when climbing (so don't assume 200W up down and across).
I usually start conservatively on long hilly rides (short hilly ones I'm happy to smash myself from the get go, same for long flat ones).
Its easier to put more power down when climbing (so don't assume 200W up down and across).
I usually start conservatively on long hilly rides (short hilly ones I'm happy to smash myself from the get go, same for long flat ones).
10-27-10, 07:31 PM
#69
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But somehow I have a feeling that scientific analysis isn't gonna win the argument over those who prefer to say it's just all wrong (without any arguments to back it up).
10-27-10, 07:43 PM
#71
Senior Member
This thread could really use umd's inpt.
Just sayin'
Just sayin'
10-27-10, 07:46 PM
#72
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It's all science. You want the details?
Maybe easier: analyticcycling.com agrees with me - if you set the wind resistance to zero, and instead increase the rolling resistance by ten or so (which is the same as saying that wind friction is proportional to velocity), you'll see that the time for the flat ride is the same as the time for the hill ride (within 0.1%).
Maybe easier: analyticcycling.com agrees with me - if you set the wind resistance to zero, and instead increase the rolling resistance by ten or so (which is the same as saying that wind friction is proportional to velocity), you'll see that the time for the flat ride is the same as the time for the hill ride (within 0.1%).
10-27-10, 07:57 PM
#73
Making a kilometer blurry
Grumpy wasn't talking about power. If you go twice as fast down as up, you can't just average the two speeds together to get overall average speed. That's the middle school math part.
The part you're incorrectly making up as you go along can be explained by knowing that the power required to overcome air resistance at a certain speed goes with v^3 (v*v*v). Going twice as fast takes eight times (2*2*2) as much power. So, if you can hold 20mph at 200W, it will take 1600W for you to go 40mph.
Now, re-read your post #57 and post your corrections. I will give 50% credit for all corrected errors, and you might just pass.
10-27-10, 07:59 PM
#74
Peloton Shelter Dog
Hillier routes generally slow cyclists down, as evidenced by the hilly TT I did a couple of weeks ago. I averaged just shy of 18 mph, on a flat course I'm good for 22-23 mph. The fastest guy averaged about 22 mph, on a flat course that guy goes 27-29 mph. Just like on my road rides. If it's hilly, it's slower. Always. On that TT course, I'm quite confident the ascending vertical feet were offset by descending vertical feet (there were 40 mph downhill sections), but in my experience, you never make up the time you lose climbing. That's how it is in the real world where I ride and race, the Internet Sounds Good on Paper Fred World is where many of you idiots reside, so your delusions may be hard to shatter.
10-27-10, 08:08 PM
#75
VeloSIRraptor
Ah.
I always forget when these ft per mile numbers are given that it is total ascent not net ascent. My favorite climb has a section 13 miles climbing 5.5 K ft. is like 7.9 % average grade. I am lucky to get a 10 mph average for the out and back. The problem too with switchbacks with oncoming and same direction traffic , you are lucky if you can average downhill speeds of 30 mph.
I think rollers can give you the same if not faster times than flats.
That is why the adage is "Average speed does not matter"
I always forget when these ft per mile numbers are given that it is total ascent not net ascent. My favorite climb has a section 13 miles climbing 5.5 K ft. is like 7.9 % average grade. I am lucky to get a 10 mph average for the out and back. The problem too with switchbacks with oncoming and same direction traffic , you are lucky if you can average downhill speeds of 30 mph.
I think rollers can give you the same if not faster times than flats.
That is why the adage is "Average speed does not matter"
and I'm headed back to ride it again this spring ;-)
