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Old 10-29-09, 10:32 AM   #1
raybo
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How does weight affect distance?

I've been wondering how a marginal amount of weight affects distance, let's call it the Marginal Length of Weight (MLW). It's units would be measured in miles per pound (kilometer per kilogram).

It seems to me that if I reduce my gear weight by 5 pounds that I should be able to do more distance within the same amount of riding time and exerting the same amount of effort (measured by fatigue at the end of the day).

I don't usually weigh my gear these days as I pretty much take the same stuff on every trip. But, I do know that when I'm not carrying camping gear (13 pounds when mailed home from Jackson, WY) that I am less tired at the end of the day.

If I had to guess, I would start at 1 to 1. That is, every pound of gear I lose is one more mile a day I can average.

I have never tried to quantify it and was wondering how the rest of you would estimate this ratio.

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Old 10-29-09, 10:46 AM   #2
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If your day is flat, it probably makes little difference. If your day is hilly, it probably makes more difference. And if the extra weight causes you to have to stop and do bike maintenance, it can make a lot of difference.
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Old 10-29-09, 11:25 AM   #3
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Old 10-29-09, 11:33 AM   #4
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Dude.... seriously
Your looking at this all wrong, the distance you cover in a day on tour is about:
1) rider ability
2) available camping / lodging / resources / food
3) calories (do you have enough energy)
4) terrain
5) wind / weather
6) traffic
7) equipment failure or the lack of
Just to name a few of the myriad of possibilities that effect mileage.

Good luck with that

Last edited by Dave Nault; 10-29-09 at 01:28 PM.
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Old 10-29-09, 11:38 AM   #5
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Don't overlook the effect of wind resistance from a big load. I'm no engineer, but I suspect that, under certain conditions, this produces more drag than the added weight does...hence the popularity of wind tunnel testing for bicycles (See: Armstrong, Lance). However, I think the effect of wind resistance may be tied into your speed...that is, it produces very little effect at low speeds and dramatically more effect at higher speeds.
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Old 10-29-09, 11:56 AM   #6
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Originally Posted by raybo View Post

If I had to guess, I would start at 1 to 1. That is, every pound of gear I lose is one more mile a day I can average.

and if the wind is from the North at 15mph and the terrain is rolling with 200' climbs with soft pavement in 90degree heat and the burrito you ate isn't digesting at all you can add the cube root of your tire pressure onto the extra hours it takes to ride East.
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Old 10-29-09, 01:16 PM   #7
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Since my gear weight is already pared to the minimum for self supported touring, all that's left to cut is this growing bulge around the middle. Hmm...Pound per mile. Might be just the motivation I need. 15 more miles/day.
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Old 10-29-09, 01:23 PM   #8
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The alleged effect of weight on cycling performance is largely a myth.

The only time weight matters is when you're working against gravity, and even then the effect is less than most people think. So unless you're comparing a super-light load to a fairly heavy load (e.g. 25 vs 75 lbs), it won't make a big difference in terms of time or effort. Especially when touring, since most tourists will stop frequently to smell the metaphorical roses along the way.

For example, let's say you are doing 10 miles that has a 5% grade. With 75 lbs of gear, that will take you approximately 2 hours, 15 minutes. Dropping 50 pounds (while expending the same amount of energy) will save you half an hour. So that's significant -- but it's also the difference between, say, a fully self-contained tour where you carry everything including the kitchen sink, and doing a credit card tour. A 13 pound difference, on the other hand, only saves you about 5 minutes on that same climb. Not a big deal. In fact, barely worth noticing for a tourer.

More importantly, as Dave basically indicated: We're not on motorcycles with a pre-determined and mechanically measured horsepower rating, it's a bicycle. The rider is the engine, and aptitude is different from rider to rider, and day to day.

So I'd say, other than deciding what type of tour you want to do, or considerations for other uses (e.g. hiking), I don't see much reason to worry about a few pounds here and there.
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Old 10-29-09, 01:51 PM   #9
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The only time weight matters is when you're working against gravity, and even then the effect is less than most people think. So unless you're comparing a super-light load to a fairly heavy load (e.g. 25 vs 75 lbs), it won't make a big difference in terms of time or effort. Especially when touring, since most tourists will stop frequently to smell the metaphorical roses along the way.
Weight always matters and it matters especially when you're working near your personal limits. Think about Olympic weight-lifting, where weight differences as small as a pound can make the difference between completing a lift and failing. If you can barely managed to get a 50lb bike up and over that 10-mile long, 5% grade then adding another 13lbs to the package may increase your ride time in a very non-linear manner (e.g. because you have to stop in the middle of the climb and rest)...
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Old 10-29-09, 01:54 PM   #10
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Weight always matters and it matters especially when you're working near your personal limits. Think about Olympic weight-lifting, where weight differences as small as a pound can make the difference between completing a lift and failing. If you can barely managed to get a 50lb bike up and over that 10-mile long, 5% grade then adding another 13lbs to the package may increase your ride time in a very non-linear manner (e.g. because you have to stop in the middle of the climb and rest)...
If you kept the same power output you wouldn't need the extra rest, you would just climb slower and then descend faster.
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Old 10-29-09, 02:55 PM   #11
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dont go buying new 'light' stuff. when i was on tour, everyone i giggles at the fact that my tent was 4kg( which is a lot, but i didnt realise) they however stopped giggling when they found i out that i cover an average of 200km, its all about whats in your head
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Old 10-29-09, 03:15 PM   #12
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meh. I like lightweight. It handles better. It starts faster. It goes up hills easier. It goes faster on surfaces other than smooth tarmac.
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Old 10-29-09, 05:20 PM   #13
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Way too many variables to make any legitimate measurement. And, if you could get a real unit to measure how much it would affect you, it would be entirely subjective to you.
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Old 10-29-09, 08:08 PM   #14
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Weight always matters and it matters especially when you're working near your personal limits.
I'm afraid you are incorrect on this point.

If you're on a flat tour, weight will make no difference whatsoever. Zip, nada, zero, none. Aerodynamic penalties from your bags and riding position will slow you down more than weight. Gravity has no effect when you are moving forward without an incline; you're getting slowed down by friction, primarily aerodynamic drag and a little bit with rolling resistance.

With climbs: 5-10 pounds, unless you're doing absurd amounts of climbing, won't matter. 15, 20 pounds, then it starts to add up. The question there is, what's more important to you, and which in the long run really helps you go further -- an extra 5 miles on a given day, or the 15 pounds of supplies or creature comforts.


Quote:
Originally Posted by sstorkel
Think about Olympic weight-lifting, where weight differences as small as a pound can make the difference between completing a lift and failing.
Err... That doesn't change the fundamental physics or mechanics of the situation. Cycling, especially touring, is completely different in almost every way I can think of from weightlifting. It's not comparable.


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Originally Posted by sstorkel
If you can barely managed to get a 50lb bike up and over that 10-mile long, 5% grade then adding another 13lbs to the package may increase your ride time in a very non-linear manner (e.g. because you have to stop in the middle of the climb and rest)...
Uh huh. 15 extra pounds on a 5% climb requires (theoretically) an extra 7 watts, i.e. you're burning an extra 15 or so calories on that 10 mile climb. That's like, what, two carrots? 15 pounds is a little over what I normally consider "negligible," but on a climb like this it's a little bit worse than a dirty drive train.

Also, cyclists -- even pro racers -- are not riding in the anaerobic zone or even near max HR all day long. If you were, you'd bonk in short order. I.e. most tourists may need to rise to the occasion every now and then, but you really aren't riding at your absolute physical max every single day, all day long. Nor do I see how it makes sense to presume that cyclists are so precise that they carry exactly what they know is their "absolute limit" of weight.

Last but not least, at least some tourists (including me) just really don't care about shaving off every last second of performance when they're on a tour. Numerous other characteristics are more important, e.g. comfort and robustness. There's a reason why touring bikes tend to be 25-30 lbs and use a Brooks B17 and fenders, as compared to a 15 lb racing bike with bars 5" below an ass-hatchet 180g saddle....
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Old 10-29-09, 08:21 PM   #15
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As I've mentioned in other threads in this forum, when Francisco Moser set the 1 hour distance record in Mexico City in 1974 he ADDED weights to his wheels to help him.

PS Does anyone know exactly how much weight he added?
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Old 10-29-09, 09:05 PM   #16
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Weight doesn't affect distance, ever. Never, ever, ever, ever. 40 miles is 40 miles no matter what. If it's time to cover that distance that you're worried about, maybe you should take a minute to smell the roses, check out that coffee shop, take a dip in that stream, or talk to that cute hippie chick chilling out at the gas station.
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Old 10-29-09, 09:08 PM   #17
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Less weight = less energy used to maintain speed. Extra energy equals longer distances and better health throughout the tour.
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Old 10-29-09, 09:19 PM   #18
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There was an article in the Rivendell reader about weight and climbing. Take 3 lbs. off of the bike on a 4.5 mile climb that averages 7% and you save 34 seconds if you can go up it at 10mph.
It's best to take what you will need. When you add up the total weight which includes the engine a few pounds doesn't make a big difference.
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Old 10-29-09, 10:30 PM   #19
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Adding 25 pounds to a 200 lb bike+rider system is a 12.5% increase. For acceleration and steep hill climbing you will need to drop down about one gear (9spd) given the same power output and your speed will drop accordingly (by 12.5%).

On the flats, the added weight will make no difference but increased aerodynamic drag will. Downhill, your terminal velocity might be faster or not due to the new it changed balance between the increased mass pulling you downward and greater drag holding you back.
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Old 10-29-09, 11:24 PM   #20
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Since my gear weight is already pared to the minimum for self supported touring, all that's left to cut is this growing bulge around the middle of my body. Hmm...Pound per mile. Might be just the motivation I need. 15 more miles/day.
Now, there may be something to be said for body fat giving you more distance if you go slow. At lower levels of effort the body burns fat pretty well. Figure it like you are saving on food.
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Old 10-30-09, 05:27 AM   #21
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Now, there may be something to be said for body fat giving you more distance if you go slow. At lower levels of effort the body burns fat pretty well. Figure it like you are saving on food.
The amount of calories in a few lbs of body fat is all that you need to go slow. About 4000calories in a lb of fat. You still need water to metabolize it. Pretty sure if you're metabolizing body fat you're into bonking territory and LOW level output.
I knew a small lean guy who raced who said he would bonk if he didn't have some fat in his diet. All things being equal a lean person eating fat will be better off than a fat person trying to burn the fat on their body. When I was young and lean I did a long fast ride of 170miles in ten hours, after five hours of riding everything I ate became energy, it was a trip to notice the difference between a piece of fruit and a bag of nuts, a bottle of orange juice and a snickers bar.
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Old 10-30-09, 05:50 AM   #22
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If you had 57 feet of mosquito netting to throw over a rhinoceros, how long would it take an ant with a wooden leg to kick a hole in a beer can? True or False? ;-)
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Old 10-30-09, 08:06 AM   #23
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If you're on a flat tour, weight will make no difference whatsoever. Zip, nada, zero, none. Aerodynamic penalties from your bags and riding position will slow you down more than weight. Gravity has no effect when you are moving forward without an incline; you're getting slowed down by friction, primarily aerodynamic drag and a little bit with rolling resistance.
Does not weight affect friction? Both the friction in the bearings and the friction caused by tire flex? And is not "rolling resistance" due to "friction"? While I agree that the effect of weight on the flats may not be great, I really doubt that it is "Zip, nada, zero, none."
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Old 10-30-09, 08:52 AM   #24
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If you had 57 feet of mosquito netting to throw over a rhinoceros, how long would it take an ant with a wooden leg to kick a hole in a beer can? True or False? ;-)
That could better be answered in the road bike forum not touring bike.
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Old 10-30-09, 09:17 AM   #25
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There was an article in the Rivendell reader about weight and climbing. Take 3 lbs. off of the bike on a 4.5 mile climb that averages 7% and you save 34 seconds if you can go up it at 10mph.
Question: how many people ride a fully-loaded touring bike up a 7% grade for 4.5 miles at an average of 10mph?

Sounds like someone has been playing around with equations, rather than thinking about the real-world implications of weight. On my 16lb road bike, I'd find climbing at that speed to be challenging. Put me on a 50lb touring rig, geared the same as the road bike, and I'd be pushing to the top at 2mph... which would add a lot more than 34 seconds to the time.
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