# Thread: Theoretical question regarding water bottle weight and time

1. ## Theoretical question regarding water bottle weight and time

I will be riding in a couple of races this year that vary in length between 20 and 60 miles. All are well supported and I could ride with either one or two bottles of water on my bike. I ride mid-pack expert.
My question is this: If I rode with one 22 oz bottle (approx 1 1/2 pounds) instead of two bottles, how much of an impact would this have on my time?

2. Not enough to worry about it!

3. If you drop it you are toaster. 2 small bottles gives you a little more security if you are a clutz like me. And it give you more ammo to throw like a green shell in MarioKart.

4. Two bottles, use for nutrition on longer races.

5. “Every extra pound you carry above your ideal weight makes you 15-20 seconds slower for each mile of a climb” — May 12′ Issue of Bicycling Magazine

If well supported, I would go with multiple 'partially filled bottles' as per below.

I know it may be kind of 'extreme' but it doesn't make sense to me to carve ounces/grams off of a bike and then carry around extra fluid. I believe 12 oz of water weighs .78 lbs or 355 grams

On another note:
Even on a relatively short race, I approximate how much I will drink (heat, etc). And then split the difference between two small bottles.

IOW - For a 1.5 hr CX race I will split one large bottle into two small ones, in case I drop one (never have though) - less fluid in bottle makes it easier to handle, etc. (yes, I know I am carrying an extra water bottle on bike along with an extra cage)

6. Great responses; thanks all. That answers it for me.

7. Just train with both bottles. Its not that big of a deal, your over thinking it.

8. Originally Posted by scottz123
“Every extra pound you carry above your ideal weight makes you 15-20 seconds slower for each mile of a climb” — May 12′ Issue of Bicycling Magazine
Every mile of vertical? If so, thats not too much. Ill continue to not sweat it.

9. One pound at a VAM of 1200 requires about an extra 1.5 watts.

10. Originally Posted by LMN
One pound at a VAM of 1200 requires about an extra 1.5 watts.
That is beyond my pea-sized brain. What does this mean to a layperson?

11. Originally Posted by insighter
That is beyond my pea-sized brain. What does this mean to a layperson?
Sorry, I was rather brief wasn't I.

VAM is vertical ascent rate per hour. For reference Armstrong at his peak did long climbs at 1700ish. Nowadays grand tour riders climb at 1500ish. A good Cat 1 mountain biker might be able to climb at a VAM of 1200 in a race.

To figure out the extra power required to climb at a particular VAM with a weight gain use the formula:

Power = (VAM * mass in KG * 9.8)/3600.

Interestingly using this formula you can see that faster you climb the more important weight is.

12. Originally Posted by LMN
Sorry, I was rather brief wasn't I.

VAM is vertical ascent rate per hour. For reference Armstrong at his peak did long climbs at 1700ish. Nowadays grand tour riders climb at 1500ish. A good Cat 1 mountain biker might be able to climb at a VAM of 1200 in a race.

To figure out the extra power required to climb at a particular VAM with a weight gain use the formula:

Power = (VAM * mass in KG * 9.8)/3600.

Interestingly using this formula you can see that faster you climb the more important weight is.
This is very interesting! So if I am riding in a race and produce 275 watts and weigh 86 kg all kitted up, this would result in a VAM of 1174. If I weigh 87, the VAM goes down to 1160. Do I have this right?

13. Originally Posted by insighter
This is very interesting! So if I am riding in a race and produce 275 watts and weigh 86 kg all kitted up, this would result in a VAM of 1174. If I weigh 87, the VAM goes down to 1160. Do I have this right?
Yes you have it right. At least theoretically right.

The problem with the equation I gave is when you riding gravity isn't the only force you are working against. You have wind resistance, and rolling resistance too. You also have to consider thatk, particularly on a MTB bike, you are alway accelerating and decelerating.

Wind resistance and rolling resistance can be modeled (and analyticcycling.com does). However, I don't think anybody has a clear grasp on frequency and magnitude of the accelerations in mountain biking. This makes it really hard to accurately predict the effect of a weight increase.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•