Does weight really matter

[hd reynolds]

Now before someone says......"train harder".....which is a no brainer....I am wondering if the weight of a bike really matters when it comes to hill climbing? Does the weight to money ratio make that big if a difference?

Example I can reduce the weight of my bike by 0.79lbs for $390....(changing the bar and fork) to a total weight 16.9 lbs.

So does less weight make you a better climber (which is the real question I am asking)? And is any weight change less then a pound worth the money?

Yes... reducing weight w/ your power being constant.

 

[Strid]

Now before someone says......"train harder".....which is a no brainer....I am wondering if the weight of a bike really matters when it comes to hill climbing? Does the weight to money ratio make that big if a difference?

Example I can reduce the weight of my bike by 0.79lbs for $390....(changing the bar and fork) to a total weight 16.9 lbs.

So does less weight make you a better climber (which is the real question I am asking)? And is any weight change less then a pound worth the money?

I ran some number quickly. This is a calculated example. You do 400 watts and and by doing that, you will go at 36 km/h on flats. This is the weight of you + your bikeand you're climbing a hill:

Hill, 5% @ 400 watts
85 kg ~ 24.14 km/h
84.5 kg ~ 24.20 km/h
82 kg ~ 24.50 km/h

Hill, 10% @ 400 watts
85 kg - velocity = 15.86 km/h
84.5 kg - velocity = 15.93 km/h
82 kg - velocity = 16.30 km/h

Now you race all you can up that hill. You double the power for a a couple of polka dot jersey points and a 5 km climb up that hill


5 km hill, 5% @ 800 watts
85 kg ~ 35.62 km/h ~ 8:25
84.5 kg ~ 35.68 km/h ~ 8:24
82 kg ~ 35.95 km/h ~ 8:20

5 km hill, 10% @ 800 watts
85 kg - velocity = 27.20 km/h ~ 11:02
84.5 kg - velocity = 27.29 km/h ~ 10:59
82 kg - velocity = 27.73 km/h ~ 10:49


This is what you gain from doing so. a 3 kg reduction in weight would be about equal to go from a regular bike to a 6.8 kg bike which is the minimum for a bike to be UCI road legal (and probably hella expensive). On a mountain stage, it would definitely be worth it to shave off those 3 kgs, if you're pro, but I don't know really in the real world for us mortals. I depends on your enthusiasm and your wallet.

Also, its clear that you could gain alot, just by improving things like comfort, and stiffness and things that will make the ride easier for you over just shaving off grams.

EDIT: In the calculations, wind drag is also taken into account. Should be correct. Feel free to bong my head if its not!

 

[ScienceIsCool]

Way back when I was first starting to race I did a weekly uphill time trial. It was hard and I had trouble with it. Then someone kindly taught me about correct position, rhythm and one other thing that's even more important. Breathing. It's not as automatic and efficient as you'd think. Even tense shoulders can reduce your lung volume by a noticeable amount. The effect? The following week I tried all these tips and pulled off a top ten. I had a local team's coach follow me for a while in a car and afterwards he complimented me on how well I was climbing...

What's my point? Weight is important, but it's clearly not everything. Tuning the engine and making sure it gets lots of fuel can have a huge impact. Huge.

John Swanson
www.bikephysics.com

 

[Bigbananabike]

Having read all these pages - I now feel better about my 'heavy'(by comparison with the Cannondale 6/13s etc I was picking up in a quality bike shop tonight) racing bike & better about my bank account - and leaving it in that condition

 

[mikesbytes]

Way back when I was first starting to race I did a weekly uphill time trial. It was hard and I had trouble with it. Then someone kindly taught me about correct position, rhythm and one other thing that's even more important. Breathing. It's not as automatic and efficient as you'd think. Even tense shoulders can reduce your lung volume by a noticeable amount. The effect? The following week I tried all these tips and pulled off a top ten. I had a local team's coach follow me for a while in a car and afterwards he complimented me on how well I was climbing...

What's my point? Weight is important, but it's clearly not everything. Tuning the engine and making sure it gets lots of fuel can have a huge impact. Huge.

John Swanson
www.bikephysics.com

Well said, at 78kg I am a quicker rider than I was at 74kg.

Also I had heard that the difference between a AU$10,000 bike and my AU$1,500 Giant OCR2 was 3kmh, but having read the calculations on this thread, the weight difference is only 0.5kmh (uphill). I doubt that the other attributes of the expensive bike would make it anywhere near 3kmh faster.

 

[hd reynolds]

Having read all these pages - I now feel better about my 'heavy'(by comparison with the Cannondale 6/13s etc I was picking up in a quality bike shop tonight) racing bike & better about my bank account - and leaving it in that condition

If you already have the engined tuned, there's nothing that beats a lightweight ride. It's a potent combo. A lightweight bike doesn’t mean you have to spend megabucks, just careful selection of components and/or combing ebay.

 

[sogood]

Also I had heard that the difference between a AU$10,000 bike and my AU$1,500 Giant OCR2 was 3kmh, but having read the calculations on this thread, the weight difference is only 0.5kmh (uphill). I doubt that the other attributes of the expensive bike would make it anywhere near 3kmh faster.

I agree. Hardware can only help the rider so far, then it's all up to the heart/lung/muscle... Yet again, it's all such a toy, adult toy!

 

[hd reynolds]

Lets all ride steel huffys equiped with shimano altus. Its cheap. No need for Dura Ace, Record carbon fiber and all that exotic stuff that cost more.

 

[sogood]

If you already have the engined tuned, there's nothing that beats a lightweight ride. It's a potent combo. A lightweight bike doesn’t mean you have to spend megabucks, just careful selection of components and/or combing ebay.

That's true. There's a sweet spot on the cost-weight curve and eBay helps.

The question here is, what do people consider to be "lightweight" as far as a road bike is concerned? 9.5kg? 8.5kg? 7.5kg? 6.5kg?

 

[hd reynolds]

That's true. There's sweet spot on the cost-weight curve and eBay helps.

The question here is, what do people consider to be "lightweight" as far as a road bike is concerned? 9.5kg? 8.5kg? 7.5kg? 6.5kg?

When you've tuned the engine to its limits one would start looking elsewhere to improve performance. Having taken that route, I've not spent a dime on my ride when I hit the sweet spot - in my case 7.45kgs.

poll anyone?!

 

[sogood]

When you've tuned the engine to its limits one would start looking elsewhere to improve performance. Having taken that route, I've not spent a dime on my ride when I hit the sweet spot - in my case 7.45kgs.

poll anyone?!

A poll would be interesting. At the same time, it would be interesting to differentiate what's "lightweight" for a bike assembled around steel/aluminium/CF frames.

 

[Rhubarb]

Light to me is sub 7.5kgs. However expensive bikes aren't just about weight to me. Sure light is good but as discussed it makes marginal difference to performance. High end / more expensive bikes should also be about how they ride and handle. It should be a pleasure to turn over the pedals on those puppies and feel the transfer of power to the road. They should feel sharp and easily become an extension of the body.

So while it maybe unwise to blow your hard earnt cash on small weight savings, blowing it on a beautiful machine is a totally different matter imho.

 

[sogood]

Light to me is sub 7.5kgs. However expensive bikes aren't just about weight to me. Sure light is good but as discussed it makes marginal difference to performance. High end / more expensive bikes should also be about how they ride and handle. It should be a pleasure to turn over the pedals on those puppies and feel the transfer of power to the road. They should feel sharp and easily become an extension of the body.

So while it maybe unwise to blow your hard earnt cash on small weight savings, blowing it on a beautiful machine is a totally different matter imho.

So how do you quantify that difference? How much stiffer? How much better in handling? How do you justify the extra $1500 for an upper end CF frame over that of an upper end alloy frame? Is the stiffness/handling difference b/n present day CF and alloy frames that different?