Sparky Bird

I weigh 150 pounds and I am six feet tall. My friend is 200 pounds and is also six feet tall. If we are looking at the same bike frame, will its stiffness be more of an issue for my friend than me? I was considering getting the Specialized Roubaix Pro but hear that the S-Works Roubaix is stiffer. I was also considering getting the Orbea Orca but hear that the Opal is stiffer. Am I too light to have any real advantage in getting the stiffer bike? Would the heavier person be the one that might be more interested in getting the stiffer frame if given the option.

brianallan

test ride, test ride, test ride!

DXchulo

I suck at physics, so this is bound to be dead wrong, but here it goes:

The stiffer the frame, the more your energy goes straight to moving the bike. Bigger guys tend to have more power, right? So one way to look at it is that a big guy can afford to lose a couple watts because he has a lot to spare. Little guys, on the other hand, need to protect their precious little watts as much as possible. 1 watt lost might mean more to you than it would mean to him, and 1 watt will move 150 lbs more than it will move 200 lbs.

However, one thing to consider is that super stiff frames can end up being less comfortable. Most of your energy is put into moving the bike, and the energy from bumps in the roads will be put into your body. In general it seems like bigger guys can take more of a beating, so this might not be as much of an issue.

Point

Actually, as has been posted here many times, there really is no correlation between frame stiffness and efficiency. With anymaterial, as long as the material is stressed under the yield strength, it will rebound to it's original form with essentially no loss in energy.

ALAN frames in the 80's were supposed to be the most flexible, but many races were won on them. Same with early CF frames in the late 80's.

Sheldon Brown, Kirk Frameworks, Scot Nicol and others have great web pages explaining this without me rehashing it all.

silversmith

I'm a big guy who rides nearly every day of the year. My favorite bike is my most flexible ride -- a 1987 lugged aluminum Sakae Ringyo. It's probably one of the most flexible bikes ever.

It is certainly the fastest bike I've ever ridden.

MichaelW

Stiffness is the ability to resist bending force. The more force you can apply, the stiffer your frame needs to be. Big, strong and heavy riders need stiffer frames than short, weak, skinny ones.

Point

Well, your first line is the only one you're right on. There is no need to a stiffer frame for efficiency, just personal preference.

MichaelW

My point was not that a stiffer frame is neccessarily better than a bendier frame for any one individual. Any individual rider can chose whether they prefer a stiffer or bendier frame, that is personal choice.
The point was that where you have 2 riders of widely differing capabilities and want to equip them with a frame with the same "feel" (ie the same frame deflection when they pedal) then the bigger, heavier, stronger one needs a stiffer frame.
It makes no sense to fit out a 4'8" old lady tourist with a frame capable of resisting the stress of a 6'6" professional sprinter.
If you look at production frames, smaller models with smaler triangles are actually stiffer than the largest ones.