# Weight = speed?



## multirider (Nov 5, 2007)

Are there any calculations to show how much weight savings would result in how much additional speed over a particular course?

That is, if I put out the same power on a 20 pound bike on a 5 mile course that gains 2500 feet in elevation vs putting out the same power on the same course on a 19 pound bike, how much less time would it take me?

Here's the deal . . . I'm doing a hill climb tomorrow. A weight weenie friend started suggesting ways for me to save weight. Lose the seat pack altogether -- highly unlikely I will get a flat over a short course like that. Weigh my shorts and jerseys and use the lightest. Leave my gloves in the truck. Etc. 

Of course, this gets me to thinking about my Garmin 305 -- I want the data, but that thing is kind of heavy compared to other possible weight savings!

I took a look at his suggestions and used a postal scale to see what the results might be. Well, my "Boy Scout" (be prepared for everything) seat bag is a little over a pound. Surprisingly, my lightest jersey is 50g less than the one I usually wear. My gloves are 60g. My lightest shorts save almost 100g over the comfortable shorts. 

If I save 2 pounds, will that save me a second? 5 seconds? 15 seconds? 30 seconds? Any ideas?


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## wim (Feb 28, 2005)

*Here's one program.*

http://www.analyticcycling.com/ForcesLessWeight_Page.html


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## multirider (Nov 5, 2007)

What a cool web site! Thanks!

I tried to put in the example I gave of tomorrow's race:

Save 1kg (a little more than 2 pounds)
over 10,000 meters (roughly the 5.3 miles of the race)
slope of 0.094 (0.5 mile elevation gain over 5.3 miles)
air density of .95 (9000 feet)
rolling coefficient of .008 (rough road)
with 81kg rider/bike
putting out 280 watts

and it says the 2 pound difference will save 34.55 seconds.

Can that be right? Lighten my clothes/bike by 2 pounds and I'll save 34 seconds? That could make the difference between upper-mid-pack and being on the podium. For real? 

Can anyone verify this program produces results that correlate to reality? If so, that would be great! I will be a serious weight weenie if this is true!


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## wim (Feb 28, 2005)

5.3 miles = 8,535 meter. With that change from your 10,000 meter input, I get 29.49 seconds faster. I wonder about the 0.5 mile = 2,640 feet elevation gain over 5.3 miles—you're sure?


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## multirider (Nov 5, 2007)

Oops, only 2000 feet of elevation gain. Here's the data from the race web site:

Technical Information 
Distance 5.3 miles 
Start Elevation: 9,080 feet 
Highest Point: 11,142 feet 
Total Climbing: 2,062 feet 

Here's the new result from the web site model:


Benefit From Less Weight
This Much Less Weight 1 kg 
Over This Distance 8535 meters 
On Hill of Slope 0.0714 Decimal 
Faster by 22.94 s 
Ahead by 96.39 m 
Frontal Area 0.5 m^2 
Coefficient Wind Drag 0.5 Dimensionless 
Air Density 0.9 kg/m^3 
Weight Rider & Bike 81 kg 
Rolling Coefficient 0.01 Dimensionless 
Power 280 watts 

23 seconds faster for leaving my admittedly-overweight seat pack in the truck. Wow. Glad I did that. 

So shaving 500g results in 11.5 seconds faster? 

I'm skeptical. Carbon shoes will cut 12 seconds from my time? Really? Hmmm. Still thinking about this.


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## wim (Feb 28, 2005)

On a climb, every bit of weight you can shed (doesn't matter from where) will increase your speed. The reason people are skeptical is because on the flat, shedding weight will increase steady-state speed very little or not at all.

But also consider that the program assumes a lot: no winds, no changes in rider aerodynamics (seated, standing), no accelerations or decelerations, same type of pavement, and so on. A few minutes of head wind or side wind could easily wipe out the gains you could have gotten from weight reduction. The numbers are real, but they're the _theoretical_ best—not a guarantee.

FWIW, psychology plays a part in this too. At the bottom of a climb, Jaques Anquetil used to remove the water bottle from his bike and put it into his jersey pocket. His reasoning : "it's important to have a light bike when climbing."


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## sevencycle (Apr 23, 2006)

I ride with fast Pro men/women and local racers. If I am on my 13 lb or 17 lb bikes I always end up with the same group of riders. I move up when I am in better form not lighter bike.Thats my butt dyno for what its worth. I still do like light bikes .


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## sevencycle (Apr 23, 2006)

When STI shifters first came out Lemond only used rear STI shifter because of weight but he had a big ol' Rolex (or something like it) watch on his left wrist....go figure.


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## bbgobie (Aug 13, 2007)

Is this a road race?
Your going to be in a pack all day. Only the sprint will matter...


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## iliveonnitro (Feb 19, 2006)

wim said:


> FWIW, psychology plays a part in this too. At the bottom of a climb, Jaques Anquetil used to remove the water bottle from his bike and put it into his jersey pocket. His reasoning : "it's important to have a light bike when climbing."


But if you tell him the psychology, does it still have the effect?

You got that from Tim Krabbe's (sp?) book, right?


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## wim (Feb 28, 2005)

iliveonnitro said:


> But if you tell him the psychology, does it still have the effect?
> 
> You got that from Tim Krabbe's (sp?) book, right?


LOL, probably not. I killed the magic. I read Krabbe's "The Rider" (great book), but I'm not sure if got the Anquetil anecdote from that book. I think I saw it in something written by Frank Berto long before "The Rider" came out.


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## multirider (Nov 5, 2007)

This was actually a mtb race. I borrowed a friend's 22 pound Felt Ultralight hardtail to race instead of my 30 pound Yeti 575. I wore my carbon road shoes instead of Sidi Dragons to save 170g. Wore spandex instead of baggies to save 150g.

I was in the lead pack for the first couple miles. People kept dropping. Then I was by myself for a while. When my odo said "3.6", a guy pulled up alongside and asked me what class I was in (2 minute separation between classes, we were catching people from prior races frequently) and it turns out we're both in the same class. He passes me. I pass him back. He passes me again. Pulls out a very small lead. Increases it a little. And a little more. I'm done with that and pick up the pace. Gap stabilizes. I figure with 1/2 mile to go, I'm going to give it 100% and see if I can catch/pass him. Watching my odo carefully because this is a 5.3 mile course. I'm going to hammer when I get to 4.8.

Come around a corner, big bunch of spectators and cow bells and "Go for it! Last section!" My odo reads "4.6", but there's only 100 yards left in the race. I'm up out of the saddle and giving it everything -- arms, legs, abs, back, heart, lungs, everything! 

I see his cobalt blue jersey and hammer like a wildman, just edging him out at the finish line. Wahoo!

Oops. Wrong guy. Another cobalt blue jersey about 5 guys in front of me in the finish line chute. He beat me by 6.8 seconds.

If my odo had been accurate, I'm pretty sure I would have beat him.

Coulda/woulda/shoulda. That's racing!

Though if I'd been able to drop another pound from me/clothes/bike, I would have beat him, right? But on my Yeti, I wouldn't have been nearly as close. Argh!


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## bbgobie (Aug 13, 2007)

Yes... umm... Seeing how this is road bike review...

Anyways, I'd say weight on a MTB can make a much smaller impact on a MTB. What if you could handle the terrain/twisties on your Yeti Better?
Is a 25lb FS bike that is in-efficient better than a 30lb FS bike that can both absorb bumps and pedal well?

I'm sure there's nothing wrong with your odo. Only the user.
=)


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