General Discussion Triathlon Talk » How much does bike weight matter? Rss Feed  
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2006-08-16 11:54 AM

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Master
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Subject: How much does bike weight matter?
I have a relatively cheap road bike. It weighs 22-23 pounds. I keep hearing people say anything over 20lbs is a heavy road bike. I just don't see how shedding 5 lbs at the expense of an extra $1000-$2000 is going to help me that much. How much does each pound of bike translate into performance? Plus, I just figure that I have 30 more pounds to lose before I start counting grams on my bike.


2006-08-16 12:01 PM
in reply to: #513446

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Veteran
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Subject: RE: How much does bike weight matter?

You seem to have the same mindset that I do.  At this point, the 4 or 5lbs I would save on my road bike aren't any thing compared to the 20lbs the engine still needs to lose, not to mention the miles the engine needs to put in just to get more power from it.

I'll worry about a really nice bike when I feel it's the bike that is limiting me and not just me limiting me.

2006-08-16 12:07 PM
in reply to: #513446

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Expert
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Subject: RE: How much does bike weight matter?
Bike weight is really important for elite riders. However, I think your attitude about loosing weight before being concerned about your bikes weight is the proper way to look at it. You will gain way more peformance benefits from your own weight loss, not to mention health and general well-being benefits, then from dropping a few pounds (not to mention a lot of $$$) on a lighter bike.
2006-08-16 12:17 PM
in reply to: #513446

Master
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Subject: RE: How much does bike weight matter?
It is not going to matter a lot, but it will matter.

Right now you are 230 + 23 lbs Bike = 253 lbs

You get a 18 lb bike +230 you = 248 lbs

So you have 2% less weight with the new bike, which theoretically would make you 2% faster. (There are some people that talk about how shaving rotational weight i.e. wheels makes more than just a standard weight difference)

When you get down 200 lbs and get a new 18 lb bike, you would ~14% less weight which is a lot.


5 lbs lost on bike is 5 lbs that will be lost for good. 5 lbs on a person, can be 5 lbs that can be gained again.


More important than weight will be fit. If you are not properly fitted on your road bike, the savings in energy or more efficient use of it gained by a proper fitting will far outweigh the weight savings.
2006-08-16 12:17 PM
in reply to: #513446

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Master
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Subject: RE: How much does bike weight matter?

So lets say you have two tour de france riders.  One has a 22 lb Sora level bike, the other a 15lb dura ace.  How far ahead is the other guy at the end of 40 miles?  Are we talking seconds or minutes?

 

 

2006-08-16 12:21 PM
in reply to: #513481

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Master
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Subject: RE: How much does bike weight matter?

mnewton - 2006-08-16 11:17 AM

When you get down 200 lbs and get a new 18 lb bike, you would ~14% less weight which is a lot.

But again, at 200lbs it will still only be a 2-3% difference between the bikes.  218 total vs 223, so your same logic applies. 



2006-08-16 12:21 PM
in reply to: #513483

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Subject: RE: How much does bike weight matter?
Like in drag racing, it doesn't matter if you win by 1 second or 10 minutes .... you still win .....

As a firm believer in lighter is better and personally more than willing to shell out the extra couple of grand for it, I say if you have the money, go for it. But not until you feel that you have exhausted the body weight loss if you are over your "ideal range."
2006-08-16 12:22 PM
in reply to: #513483

Master
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Subject: RE: How much does bike weight matter?
tkbslc - 2006-08-16 12:17 PM

So lets say you have two tour de france riders. One has a 22 lb Sora level bike, the other a 15lb dura ace. How far ahead is the other guy at the end of 40 miles? Are we talking seconds or minutes?



150 lb rider + 22 lb bike = 172
150 lb rider + 15 lb bike = 165

7/172 = 4.1% lighter weight total which would make a big difference on the mountain stages. So for the same amount of work, the DA bike is 2.4 minutes ahead after one hour

You have to consider that they are near the same level of riders.


Lance Armstrong on a Sora bike vs Me on DA bike - LA beats my by miles, because he has a bigger engine
2006-08-16 12:25 PM
in reply to: #513483

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Not a Coach
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Subject: RE: How much does bike weight matter?
tkbslc - 2006-08-16 12:17 PM

So lets say you have two tour de france riders.  One has a 22 lb Sora level bike, the other a 15lb dura ace.  How far ahead is the other guy at the end of 40 miles?  Are we talking seconds or minutes?

Who are the riders?  How much do they weigh?  Riding what kind of course?  Lots of variables besides bike weight.

Again, it will make a difference and you will be faster now.  But, as you already noted, if you could lose 7lbs on your own that would be just as good (actually better because you only have to carry yourself on the run--not your bike ).  Of course the "7lb-lighter you" would be faster still on a bike that weighed 7lbs less.

Only you can decide if it's "worth" it to you.

2006-08-16 12:30 PM
in reply to: #513493

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Subject: RE: How much does bike weight matter?
tkbslc - 2006-08-16 12:21 PM

mnewton - 2006-08-16 11:17 AM

When you get down 200 lbs and get a new 18 lb bike, you would ~14% less weight which is a lot.

But again, at 200lbs it will still only be a 2-3% difference between the bikes.  218 total vs 223, so your same logic applies. 

A lighter bike will help, but it's only one variable.  A bike that fits well is the most critical factor.  Then, for tris, how aero can you comfortably position yourself on that bike.  Then weight might start to become a differentiating factor.

All these things can make you a bit faster.  Do you care?  I do, but many don't.  If you don't, then save your $ and just enjoy riding.  Nothing at all wrong with that.

 

2006-08-16 12:32 PM
in reply to: #513506

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Subject: RE: How much does bike weight matter?

my theory is that I'm not worrying about a lighter bike until the engine is lighter.  partially that's a $$ issue, but also my theory is that right now, I'm building some hella strong legs pushing me and the(somewhat) heavier bike around.   When I get all buff and get a lighter bike, I'll be even faster by comparison.

 Not that I'll ever be really fast, but closer to MOP would be nice.



2006-08-16 12:34 PM
in reply to: #513519

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Giver
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Subject: RE: How much does bike weight matter?
And if you ride mostly flat courses, weight (esp. for triathletes) is negligible.
2006-08-16 12:43 PM
in reply to: #513446

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Champion
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Subject: RE: How much does bike weight matter?
Not all weight is created equal.

Going from 22 ==> 19 pounds may not be too expensive (relatively speaking)
Going from 19 ==> 16 pounds will cost you dearly.

Are you leaving one water bottle off? Skipping the repair kit/spare tube/inflator/pump? Grabbing the 192 g tube instead of the 195? You'll have to weigh all of these things in a quest for lighter bike weight.

Lighter wheels and tires will make a bigger difference when you are accelerating than other weight changes (or at other times). Some will depend on the course (you might be better off with the additional weight of a disk wheel or wheel cover on a flat course).

I think the bigger gains from higher-line components are more efficiency than weight driven, but it's hard to market quantifiable efficiency.

You're right to work on the engine first.
2006-08-16 12:51 PM
in reply to: #513446

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Runner
Subject: RE: How much does bike weight matter?
Because I'm such a geek, this thread got me wondering about how much the weight of the bike will make in terms of not just the speed of the bike leg, but also your speed coming off the bike...

follow me here: lighter bike means less energy is needed to move the bike. Less energy expended on bike means more available for run. I know that's way overly simplified, but does the basic concept make sense at all here? Or am I yet again talking out my @$$?
2006-08-16 12:55 PM
in reply to: #513559

Master
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Subject: RE: How much does bike weight matter?
Scout7 - 2006-08-16 12:51 PM

Because I'm such a geek, this thread got me wondering about how much the weight of the bike will make in terms of not just the speed of the bike leg, but also your speed coming off the bike...

follow me here: lighter bike means less energy is needed to move the bike. Less energy expended on bike means more available for run. I know that's way overly simplified, but does the basic concept make sense at all here? Or am I yet again talking out my @$$?


Yes, it makes sense. It will do one of the two following (or maybe somewhere in between):
1. You will use less energy for the same bike time and thus have move available for the run
2. You will use the same energy as before and have a faster bike time with the same amount of energy left for the run as you would have, but you are starting the run earlier because of a shorter bike time

Either way you are faster.
2006-08-16 1:02 PM
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Coach
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Subject: RE: How much does bike weight matter?
Unless you are doing a SUPER hilly course it won't matter THAT much. Yes it is important at some extent; the better engine and closer to your optimal racing weight, THEN the more it will make a difference. Some people spend lot of $$$ on light bikes and then attach 3-4 water bottles, bento box, tape GUs on the frame, attach big seat bags, air pump, etc all this for FOR RACING (it is ok for training) and end up riding a heavy bikes anyway

And yes you are better off losing the extra weight



2006-08-16 1:33 PM
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Subject: RE: How much does bike weight matter?

Scout7 - 2006-08-16 11:51 AM Because I'm such a geek, this thread got me wondering about how much the weight of the bike will make in terms of not just the speed of the bike leg, but also your speed coming off the bike... follow me here: lighter bike means less energy is needed to move the bike. Less energy expended on bike means more available for run. I know that's way overly simplified, but does the basic concept make sense at all here? Or am I yet again talking out my @$$?

I could be wrong, but I don't think you would use less energy really. The 'energy' used when ridding is your power output which is all about the rider and his 'engine'. Power output during a race will most likely be the same whether you have a 22 or 16 lb. bike.

It's like a race car: if the car is trying to go as fast as it can, the engine will only have so much horsepower whether it is on a lighter or heavier chassis. It might just move faster on the lighter chassis using the same amount of power.

But yes, at the same speeds, the lighter chassis would require less energy.

It seems to me, if you are overweight, loosing 5lbs. will not only help 'lighten your chassis' it will most like help your 'engine' be more powerful as well. So you win both ways.

2006-08-16 1:39 PM
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Subject: RE: How much does bike weight matter?
16 pounds will cost you dearly.


My 52CM, Trek 1000 was 16 pounds (probably more now with water/cages/etc. on it)... and cost me $600 new.

2006-08-16 1:41 PM
in reply to: #513629

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Runner
Subject: RE: How much does bike weight matter?
yojimbo - 2006-08-16 2:33 PM

Scout7 - 2006-08-16 11:51 AM Because I'm such a geek, this thread got me wondering about how much the weight of the bike will make in terms of not just the speed of the bike leg, but also your speed coming off the bike... follow me here: lighter bike means less energy is needed to move the bike. Less energy expended on bike means more available for run. I know that's way overly simplified, but does the basic concept make sense at all here? Or am I yet again talking out my @$$?

I could be wrong, but I don't think you would use less energy really. The 'energy' used when ridding is your power output which is all about the rider and his 'engine'. Power output during a race will most likely be the same whether you have a 22 or 16 lb. bike.

It's like a race car: if the car is trying to go as fast as it can, the engine will only have so much horsepower whether it is on a lighter or heavier chassis. It might just move faster on the lighter chassis using the same amount of power.

But yes, at the same speeds, the lighter chassis would require less energy.

It seems to me, if you are overweight, loosing 5lbs. will not only help 'lighten your chassis' it will most like help your 'engine' be more powerful as well. So you win both ways.



True, I was thinking in terms of same speed for both bikes. And you are right in that you're going to see all-around improvement by losing body weight vs. bike weight, but like I said, I'm really geeky about things, and the idea made some sense. Hmmm......losing body weight may, in some ways, affect your swim though. There's an interesting thought: Since fat is more bouyant than muscle, I wonder how losing large amounts of body fat are going to affect someone's swim....Obviously, I know times will improve, that's a given, but I wonder if the loss of fat has any effect in terms of open water swimming.

Don't mind me.....I'm having one of those kinds of days, you know?
2006-08-16 2:08 PM
in reply to: #513644

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Subject: RE: How much does bike weight matter?

Hmmm......losing body weight may, in some ways, affect your swim though. There's an interesting thought: Since fat is more bouyant than muscle, I wonder how losing large amounts of body fat are going to affect someone's swim....

I remember an article on BT with bit of a humorous slant mentioning that very thing. Something to do with 'loosing weight isn't all it's cracked up to be.'

Lower body fat does mean less buoyancy . . . at least that is my excuse in the water!

Still I don't think there are too many top triathletes trying to keep on body fat for the sake of the swim.



Edited by yojimbo 2006-08-16 2:37 PM
2006-08-16 2:14 PM
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Expert
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Subject: RE: How much does bike weight matter?
I am in the camp of those who say that weight doesn't matter that much for tri. It is very important for straight climbers and crit racers that need super fast acceleration....for tri what matters is aero.....


2006-08-16 2:35 PM
in reply to: #513446


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Subject: RE: How much does bike weight matter?
For the most part it will make almost no difference for the MOP rider, especially on a flat course. . . Unless of course the fact that you have a really really ridiculously good looking bike makes you ride more. Then it will make you a lot faster.
2006-08-16 3:07 PM
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Subject: RE: How much does bike weight matter?
yojimbo - 2006-08-16 2:33 PM

I could be wrong, but I don't think you would use less energy really.

 

You would use less energy on a lighter bike, just not in the way you're thinking.

If you average 200 watts on both a light bike and a heavy bike, you're expending energy at the same rate. But since that 200 watts would get you an extra mph (for example) on the lighter bike, you'd be expending that energy for less time.

20mph over a 40k course would have you on the bike for 1:14:34.

19mph over a 40k course would have you on the bike for 1:18:30.

So by riding the heavier bike, you'd be slower by 3:56 (hypothetically). If you're burning calories at the rate of 700kCal/hr at that 200 watts (again, hypothetically speaking), riding the heavier bike would take an extra 46kCals.

2006-08-16 3:16 PM
in reply to: #513786

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Runner
Subject: RE: How much does bike weight matter?
Thank you for completing my physics equation, Jim. I knew I had something going on in the back of my head, but it wouldn't come into the light.
2006-08-16 3:33 PM
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Subject: RE: How much does bike weight matter?
run4yrlif - 2006-08-16 2:07 PM

You would use less energy on a lighter bike, just not in the way you're thinking.

If you average 200 watts on both a light bike and a heavy bike, you're expending energy at the same rate. But since that 200 watts would get you an extra mph (for example) on the lighter bike, you'd be expending that energy for less time.

20mph over a 40k course would have you on the bike for 1:14:34.

19mph over a 40k course would have you on the bike for 1:18:30.

So by riding the heavier bike, you'd be slower by 3:56 (hypothetically). If you're burning calories at the rate of 700kCal/hr at that 200 watts (again, hypothetically speaking), riding the heavier bike would take an extra 46kCals.

Brilliant!

Scout, glad to be of service. ha ha. (nice race Sunday btw)



Edited by yojimbo 2006-08-16 3:48 PM
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