What is the truth behind bike weight? Does it really help THAT much?

swampy1970

I'd take a well built custom sized frame over a churned out by the thousand alucarbotanium bike. Now, if there was a off the peg frame than just so happened to match what I wanted I'd take a look. Fit is more important than an extra 1lb or two at the most. But it's all pretty much a moot point for me right now. I used to go up hill way faster on an old 7 speed equiped 653 than I do on my current, soon to be replaced frame carbon/alloy frame with Dura Ace. There's a slight matter of weighing 40lb more than I used too. LOL If I ever get back down to 140ish lbs then I'll still rejoice in the fact that a modern steel bike aint going to weight 22lbs like they used too!

Falcodore

George Hincapie in the 2006 Paris-Roubaix springs to mind (snapped steerer tube on his Trek).

Crankyfeet

Agreed IMHO

That may have more to do with the difficulty of designing and carrying out a test. It may be psychosomatic.. but a lot of top riders consider it important. For example Boonen claimed it was something that he wanted incorporated into his new frame designed specifically for him at Specialized. And that is not something that Specialized would have been proud to advertise if it wasn't a factor. That he felt their current frames to be a bit "mushy" for his needs (granted those are pretty demanding needs from his legs)

Weight is not irrelevant IMHO. It might be overhyped and over-priced. But I don't think its a non-factor. You know the physics/mechanics on acceleration and gravity.

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sogood

I think the point is, rider's perception of speed may not be translated to real speed. Boonen may like the feel of a super stiff frame (as many of us have all been brainwashed to think), but where's the data to prove that stiffer is always faster? Kirk Framework' comment of flex is an interesting read. So is there a diminishing return point on the stiffness-benefit curve? If so, maybe an adequately stiff frame for Boonen may be way over stiff for the far less powerful and lighter riders, and vice versa.

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Morphed Bianchi Camaleonte IV 2006, Ridley Damocles 2006, Garmin, Mac

Crankyfeet

You don't need to do an experiment. It's simple physics. Doesn't SOMEONE around here have some knowledge of physics/mechanics....

It is the same reason why a guy gets a better start in a 100 meter sprint by pushing off rigid starting blocks as opposed to the same guy pushing off foam rubber blocks. Any deformation of the frame is work absorbed that is not being transmitted via the chain to the rear wheel.

Also.. if you want to do an easy test to see the effects of stiffness.... just rig up a really flexible framed bike. One made of plastic, but strong enough to take the weight. Then go for a sprint. Then see if you notice any difference in your speed.

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ScienceIsCool

Yeah, I've worked out the numbers here in this forum a few times. The difference between a super stiff frame and a "noodly" frame (using measured frame stiffness) was less than 0.05% of Power. Or something like that. I can't be bothered to run the numbers again or look it up. So maybe 0.2 Watts at a big effort of 400 Watts.

In other words, the zipper on your jersey will probably have a bigger effect...

John Swanson
www.bikephysics.com

Crankyfeet

You've worked out the numbers in this forum? Theoretically? Or you've done experiments?

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Crankyfeet

It was interesting. I feel there is a flaw in his thinking on the physics of BB stiffness. The pedal stroke is a not a uniform application of force. The frame/BB absorbs the energy when pedal force is at the maximum of its cycle (around 2 o'clock to 4 o'clock) and then "springs back" most likely when the force is least (around the 12 o'clock and 6 o'clock positions). At the 12 and 6 position, the frame returning its "spring" will be absorbed by lifting the rider's weight back up... but will not neccessarily be going into the drivetrain. You can jump up and down on pedals as much as you like if they're in the 12 and 6 o'clock positions and not much force is going to go into the drivetrain.

Of course the physics of when the frame responds (springs back) is dependent on the properties of the frame. It will occur at some point after maximum applied force though.

Also, the tendency of a rear wheel to slip sideways when out of the saddle and sprinting is compensated for by tilting the frame from side to side IMO. Something you see sprinters do.

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gemship

Thankyou my thoughts are your thoughts. Seems realism is a stick in the mud.

gemship

By the way I'm very excited about the Cervelo. The damage ringed in at 5300 dollars. This also included a pair of Specialized S works cycle shoes that are so light and riding shorts and a Those feel great by the way, wish I had them sooner. oh yeah and a computer, my first so now I dont have to use my watch. With pedals the bike tipped the scales at 15.7 pounds.

Camilo

I'm not a physicist nor a strong cyclist, but my WAG is that it is a miniscule, immaterial issue until two strong riders are sprinting the last 100 meters of an important (to them) event, and a 1/2 meter difference is significant. That is 1/2 of 1 percent, right? And then, the psychological thing is just as important as measurable physical differences.

Myself? I'd like to think that it's worth it if it helps me keep up with my buddies on a hilly afternoon ride, but really, I don't care if they are 20 meters ahead at the top of a hill, they almost always would slow down enough to catch, or I'd be able to push 3 more strokes before coasting down the next hill, then I'd catch up.

Crankyfeet

I am just interested to get to the truth in the matter. I would like to know how this half of one percent figure was determined.

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kakman

I think he's referring to half a metre over a 100 metre sprint.

/k

kakman

I didn't see the thread but it seems there are regular claims about speed improvement with new bikes. There is, of course, the new bike placebo affect, but there's also the issue of fit and geometry.

My anecdotal evidence shows speed increases of around 2-3 kph when I ride the drops rather than the hoods. It's quite possible the person in question was seeing improvements, but they may have been more to do with a better position on the bike that anything else. The Soloist is very aero (and stiff) and may account for a small improvement but, as Alientaor said, the aero effect of the bike pales into insignificance compared with the rider, wheels, helmet etc. I think it's far more likely the benefits, if real, came from improved position.

Like most of us, I'm in no position to disprove what was said, so we need to keep an open mind about the possible reasons behind it.

Could this only be achieved on this bike? Possibly, but probably not.

Could it have been achieved with the previous bike? Probably, but possibly not.

Are they happy with the bike and its perceived performance? Guess that's all that matters.

As I said in my only other post on the matter, lightness is critically important to me only when lifting the bike onto the roof rack.

/k