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Time calculations climbing vs flats

Old 04-09-24, 09:56 AM
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Time calculations climbing vs flats

Im about to ask an extremely vague question that I fully acknowledge has near limitless variables but here goes..
Giving a general scenario of two routes of equal distance one being flat, the other having a good bit of climbing (and descending) would you be faster at one of the routes? Im just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
Doing the Death Ride for the first time this summer and doing my best to overthink it.
Its 103 miles with of course time limits, I know what I can do a flat century in so hoping those numbers have at least some relation to what Im facing.
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Old 04-09-24, 09:58 AM
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You will be much faster overall on the flat route

For example I can ride flat centuries in well under 5 hours, but hilly ones can easily be 6+ hours.
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Old 04-09-24, 10:04 AM
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Originally Posted by Tomm Willians
Giving a general scenario of two routes of equal distance one being flat, the other having a good bit of climbing (and descending) would you be faster at one of the routes? I’m just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
For the same power output, the times for the flat course are going to be faster.

The basic problem is that you can't ever go fast enough downhill to make-up the time you spend going uphill. Part of the issue is that your downhill speed is limited by wind resistance.

Last edited by njkayaker; 04-09-24 at 10:09 AM.
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Old 04-09-24, 10:11 AM
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Originally Posted by njkayaker
For the same power output, the times for the flat course are going to be faster.

The basic problem is that you can't ever go fast enough downhill to make-up the time you spend going uphill. Part of the issue is that your downhill speed is limited by wind resistance.
and this whole time i thought the basic problem was that hills up are just harder than hills down.
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Old 04-09-24, 10:13 AM
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Originally Posted by Tomm Willians
Im just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
Generally, no. You're going slower uphill for longer than you're going fast downhill.
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Old 04-09-24, 10:14 AM
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Originally Posted by njkayaker
For the same power output, the times for the flat course are going to be faster.

The basic problem is that you can't ever go fast enough downhill to make-up the time you spend going uphill. Part of the issue is that your downhill speed is limited by wind resistance.
My downhill speed is often limited by my resistance to crashing and dying.
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Old 04-09-24, 10:16 AM
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Originally Posted by spelger
and this whole time i thought the basic problem was that hills up are just harder than hills down.
You could put out the same amount of power to go up hill that you do on the flats. Unless it's "too steep". It seems fairly typical that people output more power going uphill than they do on the flats.

Whatever you do, you can't ever make up the time going downhill.
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Old 04-09-24, 10:22 AM
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The flat route will be faster. You'll go slow climbing and when you get to the top to speed down, the higher speed will be averaged into the now greater cumulative total miles and thus be effectively diluted in it's effect on the average.

The only way out of this is if your hilly route has a lot more down than up.
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Old 04-09-24, 10:27 AM
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Originally Posted by base2
The only way out of this is if your hilly route has a lot more down than up.
Or, drink a lot of water at the top of every hill and pee at the bottom. (Make sure your team car carries the water to the top of the hill for you.)
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Old 04-09-24, 11:26 AM
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As the other comments said, the downhills are too short in time to make up for the long climb times. You can't even double your average mph climbing pace for a climb and descent, since that implies a zero time for the whole downhill.

(I first ran across this idea when someone posted a riddle on a BF climbing thread: A rider climbs a hill at 10 mph, then turns around and rides back down. How fast does he have to ride the downhill to average 20 mph for the up and down? Answer:"infinity" mph...)

For a fast total ride time, it does help to increase your watts on steeper portions of the climbs, and lower the watts on the descent. That cuts the most time off your ride. Especially compared to pushing hard on the flats with the increased wind resistance at those speeds. How much of a climbing watts increase? Oh, that could be complicated!

A climb+descent example:
A one mile long climb, at 8 mph: that takes 7.5 minutes. = 1/8 of 60 minutes)
Then a one mile downhill, at an extreme 60 mph: that takes 1 minute.
Total: 8.5 minutes for two miles. That's 14.1 mph average for the two miles with the 60 mph downhill pace. = (2 miles / (8.5/60)).
Or a 40 mph downhill would take 1.5 minutes, so that rider would average 13.3 mph.

I'm not fast. I would likely do about 180 watts for that 8 mph climb, approx 5.5% grade. A 250w rider would climb a grade slightly over 8% at 8 mph. (estimated from a bike-speed-power calculator.)

Last edited by rm -rf; 04-09-24 at 11:43 AM.
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Old 04-09-24, 12:02 PM
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Originally Posted by Tomm Willians
I’m about to ask an extremely vague question that I fully acknowledge has near limitless variables but here goes……..
Giving a general scenario of two routes of equal distance one being flat, the other having a good bit of climbing (and descending) would you be faster at one of the routes? I’m just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
Doing the Death Ride for the first time this summer and doing my best to overthink it.
It’s 103 miles with of course time limits, I know what I can do a flat century in so hoping those numbers have at least some relation to what I’m facing.
Here's a 2023 rwgps route. It looks very similar to the Death Ride website's profile.
rwgps death ride

How hard to push the pace on the first three climbs? around 2500, 3100, 2500 feet high! That 3100 foot climb is more than 9 miles long! That's going to be a long amount of time.

The remaining climbs are still quite big, though. Wow, that's a 16 mile downhill toward the end. I'd need to keep at least soft pedaling on such an extremely long downhill! Coasting most of it would lock up my leg muscles.

My left side Stages power meter is so useful for long climbs. I know what watt ranges I can sustain for different time periods, so I can avoid going too hard at the beginning, and it's motivation to try to keep my watts in range.

Last edited by rm -rf; 04-09-24 at 12:07 PM.
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Old 04-09-24, 12:09 PM
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Yeah, you add more minutes climbing slowly than you can possibly subtract on the downhills. Dumb example - say 40 miles, one flat, one half uphill, half downhill with the uphills so steep you can only go up them at half your flat ground speed. Say flat ground speed is 20 mph.

So: Flat ride, 40 miles/20 mph = 2 hours. Hilly ride, that 20 miles of uphill at half speed - 20 miles/10 mph = 2 hours. So how fast do you have to go to average that 20 mph over the full route? Well, (40 - 20 miles)/(2 - 2 hours) = 20/0 = infinity (or just a shade faster than the speed of light).

Or, suppose you can go 40 mph down those hills. So you spend 20 miles/40 mph going downhill = 1/2 hour. Now, to average 20 mph overall, that means+ you have to climb those 20 miles of uphill in (2 - 1/2) = 1 1/2 hours. 20 miles/1.5 = 13.3 mph. Can you actually do that?

Mt Washington - the record up is around 54 minutes for 7.6 miles. 8.4 mph. To average an ordinary 15 mph over the 15.2 miles up and down (pretending the descent was well paved and straightish), you would have to go 15.2 miles/ 15mph = 1.013 hours (= 60.8 minutes) going 7.6 miles in (60.8 - 54 minutes)/60 minutes/hour = 7.6 miles/0.113 hours = 67.1 mph. So, to average a very ordinary 15 mph, you both have to match the all-time record on that famous climb and then average 67 mph coming down.

Yes, extreme examples. But, hills always hurt average speed, unless you step up the wattage, the hills affect the wind for the better (perhaps blocking it) or there is drafting between riders on the level ground or some mix of the three.

Last edited by 79pmooney; 04-09-24 at 07:04 PM. Reason: I changed 17 mph to 15 and missed it once (Mt Washington)
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Old 04-09-24, 01:23 PM
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Originally Posted by tomato coupe
Or, drink a lot of water at the top of every hill and pee at the bottom. (Make sure your team car carries the water to the top of the hill for you.)
huh? oh, added weight. how about just put a few rocks in your pockets. you won't even have to stop to remove them.
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Old 04-09-24, 01:25 PM
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Originally Posted by spelger
huh? oh, added weight. how about just put a few rocks in your pockets. you won't even have to stop to remove them.
A real cyclist doesn't stop to pee.
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Old 04-09-24, 03:13 PM
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Originally Posted by Tomm Willians
Im about to ask an extremely vague question that I fully acknowledge has near limitless variables but here goes..
Giving a general scenario of two routes of equal distance one being flat, the other having a good bit of climbing (and descending) would you be faster at one of the routes? Im just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
Doing the Death Ride for the first time this summer and doing my best to overthink it.
Its 103 miles with of course time limits, I know what I can do a flat century in so hoping those numbers have at least some relation to what Im facing.
No vagueness required. As others have noted, the flats are ALWAYS faster than hill. The physics are relatively simple and can be calculated with pretty high accuracy.
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Old 04-09-24, 03:36 PM
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Originally Posted by tomato coupe
Or, drink a lot of water at the top of every hill and pee at the bottom. (Make sure your team car carries the water to the top of the hill for you.)
An issue of a bike magazine that I read in the late '60's or early '70's reported the rumor that some riders on some teams were known to cheat while racing in the Alps by being handed up "water" bottles at the top of a long descent that were actually filled with lead pellets. They'd then exchange bottles at the bottom.

Also read the rumor that some star rider (Anquetil, Coppi, one of those guys), at the start of a tough climb, would pull his water bottle from its cage and stick it in a back pocket of his jersey - to make the bike lighter.
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Old 04-09-24, 03:52 PM
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Originally Posted by Trakhak
An issue of a bike magazine that I read in the late '60's or early '70's reported the rumor that some riders on some teams were known to cheat while racing in the Alps by being handed up "water" bottles at the top of a long descent that were actually filled with lead pellets. They'd then exchange bottles at the bottom.
Is that actually cheating though? Is there a rule against carrying extra weight on your bike?
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Old 04-09-24, 04:51 PM
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Originally Posted by PeteHski
Is that actually cheating though? Is there a rule against carrying extra weight on your bike?
Good question. Perhaps not cheating, technically, but contrary to the spirit of good sportsmanship.

Did a search and found this article.
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Old 04-09-24, 05:51 PM
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Originally Posted by Tomm Willians
Im about to ask an extremely vague question that I fully acknowledge has near limitless variables but here goes..
Giving a general scenario of two routes of equal distance one being flat, the other having a good bit of climbing (and descending) would you be faster at one of the routes? Im just curious if the increased speed of the descending on a climb essentially gives a similar time to riding a flat?
Doing the Death Ride for the first time this summer and doing my best to overthink it.
Its 103 miles with of course time limits, I know what I can do a flat century in so hoping those numbers have at least some relation to what Im facing.
As others have said, you'll be much slower on a mountainous century. I as someone who's ridden the Death Ride before, and rides those climbs on a regular basis, the long climbs stack up the fatigue in a way that even a hilly century won't.

IIRC, the course record is just under 6 hours, and that was set by a former world tour pro(Stetina.) As far as us mere mortals, anything under 9 hours is fairly fast IMO. It's very dependent on weather too...last year it hit 105F in Markleeville and I was wasting a lot of time massaging out leg cramps towards the end of the day. I'll add that the minimum starting time really isn't enforced. As long as you have lights, its pretty common practice to start early.
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Old 04-09-24, 06:00 PM
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Originally Posted by Sierra_rider
As others have said, you'll be much slower on a mountainous century. I as someone who's ridden the Death Ride before, and rides those climbs on a regular basis, the long climbs stack up the fatigue in a way that even a hilly century won't.

IIRC, the course record is just under 6 hours, and that was set by a former world tour pro(Stetina.) As far as us mere mortals, anything under 9 hours is fairly fast IMO. It's very dependent on weather too...last year it hit 105F in Markleeville and I was wasting a lot of time massaging out leg cramps towards the end of the day. I'll add that the minimum starting time really isn't enforced. As long as you have lights, its pretty common practice to start early.
Yes I noticed that, its our (3 of us) intention to start at 330am.
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Old 04-09-24, 07:00 PM
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I agree with all, flat will be faster.

Here's my 2 cents and an engineering and physics perspective (a nerds way to look at it),. If you put out the same power for both courses, and they took the same time (they do not), you would expend the same total energy. Energy = Power x Time.

The energy you put into climbing a hill, you get back descending. But you climb much slower, and therefore you lose less energy in aerodynamic losses. Going downhill, you'll be much faster, and aerodynamic losses will be very much higher. Aerodynamic losses are very non-linear and for example, if you descend just 2X faster than you climb, you will expend 8X more power in aerodynamic losses, but since you'll descend the same hill in half the time, the net result is 4X more energy lost to aero drag descending vs climbing.

Therefore, since you will have expended more energy going up and down the hill, but used the same power, it must take more time.

Even without this issue with aerodynamic losses, if the hill is steep enough, you reach a limit where no matter how fast you descend, you can't make up the time. For example, if on the flat, the route took one hour, but the climb is so steep, it takes you 1hour and 10 minutes to climb, you could descend infinitely fast, and can't make up the time.

Finally there is simply the distance. Going up and down a hill is a longer distance to travel.

Thumbs up to the OP for asking the question and generating a discussion, I'll assure you, every technical weenie on BF has asked this question to themselves. I think to most anyone, it's sort of intuitively obvious that flatter would be faster, but if you don't actually think it through, you don't know.

I'm also betting the nerds on BF will find some technical point to argue about for the remainder of the thread. I'll even wager that Special Relativity will get brought up at some point.
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Old 04-09-24, 07:08 PM
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Originally Posted by PeteHski
Is that actually cheating though? Is there a rule against carrying extra weight on your bike?
A while back, HED announced some specialty descending wheels.
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Old 04-09-24, 07:12 PM
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Originally Posted by rm -rf
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Old 04-09-24, 08:33 PM
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I'm slow, heavy and not fit for longer rides.
My climbing to descent time ratio over a 2.5% average climb course is roughly 3:1 to 2.5:1 depending on the bike.
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Old 04-09-24, 08:49 PM
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