Can lighter and stiffer bike make climbing significantly faster
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Can lighter and stiffer bike make climbing significantly faster
Currently I own ~ 10.5kg aluminum xc bike. I like to train on uphill roads (average 8-9% of gradients or so)
Lets say I buy a crabon frame ~8kg bike. Will this make my times significantly faster?
Lets say I buy a crabon frame ~8kg bike. Will this make my times significantly faster?
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Define significant.
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I have a hard time believing carbon would be "stiffer" then the aluminum frame. Are these paved or unpaved? I'd be playing with wheel/tire/pressure choices first.
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You're the engine, so remember that as the "first factor" regardless of what's under you. Second, weight is a bigger factor than stiffness. I'd rather climb with a 15lb aluminum bike than a 23lb carbon bike any day. Third, it's easier for me to lose 3lbs than it is to make a 23lb bike become a 20lb bike (cheaper, too). Fourth, I only hear sprinters fussing about stiffness, rarely climbers.
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Assuming you weigh 70kg, dropping that 2.5 kg of bike weight will make speed 80.5 / 78 kg = 1.032 times what it was before; or save 2.5/80.5 x 3600 = 112 seconds per hour.
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You're the engine, so remember that as the "first factor" regardless of what's under you. Second, weight is a bigger factor than stiffness. I'd rather climb with a 15lb aluminum bike than a 23lb carbon bike any day. Third, it's easier for me to lose 3lbs than it is to make a 23lb bike become a 20lb bike (cheaper, too). Fourth, I only hear sprinters fussing about stiffness, rarely climbers.
But isnt bike weight different that rider weight? For example, lighter wheels means you ride faster, dont they? Or you are saying if I ride 5kg bike and weight 70kg, I will ride as fast as if I ride 10kg bike and weight 65kg?
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Not at steady speed.
Wheel weight difference doubles accelerating as you move from axle center to road surface although it's not enough to matter unless you're contesting a sprint finish.
Accelerating an extra 500g at the road surface from 0 to 20 MPH only costs you the energy it takes covering 12 feet.
Yes.
For example, lighter wheels means you ride faster, dont they?
Accelerating an extra 500g at the road surface from 0 to 20 MPH only costs you the energy it takes covering 12 feet.
Or you are saying if I ride 5kg bike and weight 70kg, I will ride as fast as if I ride 10kg bike and weight 65kg?
Last edited by Drew Eckhardt; 03-31-21 at 02:56 PM.
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Can lighter and stiffer bike make climbing significantly faster?
Nothing you can buy will make you significantly faster.
Nothing you can buy will make you significantly faster.
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And if you ride a mellowly gravel bike vs stiff race bike, there is still no significant difference when climbing and getting in and out of saddle constantly?
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Depends on how much lighter, and what "significantly" means.
If the bike+rider system is 80kg, and you slash this by 2kg, that's a 2.5% reduction in gravitational drag. When you're moving slowly up a steep hill, this might actually give you close to a 2.5% improvement in climbing speed for the same effort.
"Stiffer" is more complex. As much as "stiffness" gets talked up, power transfer losses in rigid frames usually aren't all that significant, even with frames that by modern standards are considered very flexible. There's some evidence that differences in frame stiffness can result in tangible rider power output differences due to how their pedaling interacts with that flex, but this might not be quite as simple as stiffer=better.
If the bike+rider system is 80kg, and you slash this by 2kg, that's a 2.5% reduction in gravitational drag. When you're moving slowly up a steep hill, this might actually give you close to a 2.5% improvement in climbing speed for the same effort.
"Stiffer" is more complex. As much as "stiffness" gets talked up, power transfer losses in rigid frames usually aren't all that significant, even with frames that by modern standards are considered very flexible. There's some evidence that differences in frame stiffness can result in tangible rider power output differences due to how their pedaling interacts with that flex, but this might not be quite as simple as stiffer=better.
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Of course, we're talking watts per kilogram.
On the one hand, we have J.J. Watt. Then, there's Charlie Watts. On whom would you place your uphill bet? Discuss.
On the one hand, we have J.J. Watt. Then, there's Charlie Watts. On whom would you place your uphill bet? Discuss.
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How fast do you ride now?
Once you exceed about 15 MPH, aero drag surpasses all the other factors combined that are holding you back. If you want to become significantly faster, work on your aerodynamic form and, of course, the motor. Everything else is small potatoes.
Once you exceed about 15 MPH, aero drag surpasses all the other factors combined that are holding you back. If you want to become significantly faster, work on your aerodynamic form and, of course, the motor. Everything else is small potatoes.
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"Significant" defined how?
As for less weight .... How many minutes do you spend climbing on your favorite (or least favorite) climbs? How would you be willing to spend to save three seconds on a ten-minute climb? How many seconds on a ten-minute climb would you consider "significant"?
Pretty sure any losses due to frame flexibility are not significant except to the really anal nitpickers and the guys who still use slide rules. Biggest thing with stiffness with modern frames is when sprinters can actually warp the frame enough to have stuff rubbing ... but unless you are cranking out 1600 watts .....
And as far as carbon fiber .... CF is different, not better. A CF frame is not inherently better than any other. There are engineering reasons for using CF in certain applications ... but I ride an 17-lb CF wunderbike and a 27-pound Al working bike up the same hills at about the same speed. The engine is really all that matters.
As for less weight .... How many minutes do you spend climbing on your favorite (or least favorite) climbs? How would you be willing to spend to save three seconds on a ten-minute climb? How many seconds on a ten-minute climb would you consider "significant"?
Pretty sure any losses due to frame flexibility are not significant except to the really anal nitpickers and the guys who still use slide rules. Biggest thing with stiffness with modern frames is when sprinters can actually warp the frame enough to have stuff rubbing ... but unless you are cranking out 1600 watts .....
And as far as carbon fiber .... CF is different, not better. A CF frame is not inherently better than any other. There are engineering reasons for using CF in certain applications ... but I ride an 17-lb CF wunderbike and a 27-pound Al working bike up the same hills at about the same speed. The engine is really all that matters.
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Jan Heine in his new book The All Road Bike Revolution would disagree. Page 58 for those interested.
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If you are going to convince yourself you can buy speed, go for it. The first few times on that carbon climber, you will be faster because psychologically, you will give a bigger effort to confirm your choice. Afterwards, not so much.
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No, there's world class stiff aluminum frames. High quality aluminum racing frames are as stiff as you'd be able to use or need.
But isnt bike weight different that rider weight? For example, lighter wheels means you ride faster, dont they? Or you are saying if I ride 5kg bike and weight 70kg, I will ride as fast as if I ride 10kg bike and weight 65kg?
I have absolutely no problem with people buying whatever they can afford in quality, lightweight bike products. In my experience as an aging "enthusiast" with mediocre fitness and natural ability, I really enjoy the top tier stuff I've managed to cobble together in a way that's affordable to me. It's just fun and not a horrible way to spend money.
Last edited by Camilo; 03-31-21 at 07:54 PM.
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Drummers are all about endurance and controlled substances. Charlie Watts easy.
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A race bike in any era is a highly personal choice that at its "best" balances the requirements of fit, weight, handling, durability and cost tempered by the willingness to toss it and oneself down the pavement at considerable speed. ~Bandera
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#24
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You said you are training. So do you want to train less with a lighter bike?
Do you also buy light weight dumbbells?
I heard they make CF dumbbells now....
Do you also buy light weight dumbbells?
I heard they make CF dumbbells now....
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Like a famous local racer once told me: until you're missing the podium by less than a minute, the bike isn't going to make a difference.