So when the rider went around the block (say ~.4 miles if each side is about a tenth of a mile) the wheels would have gone around about 300 times. Based on the valve stem location the front wheel may have gone around 300.5 times while the rear wheel went around 300 times - totally insignificant difference.

That was just to show they are not the same. I would expect that front had rotated several times. But even if it was a quarter turn 300.5:300 anything measurable is significant number if doing a TT where winning times can decided by fractions of a second. This year my son managed to beat his opponent by .033% of the total time.

But the side to side motion - the turning of the wheel to correct for the natural jarring that occurs when cycling is the primary reason it matters.

Eddie B, in his book, talked about the rear tire needing to be lighter to aid in acceleration. He did not cite any sources for the basis of his statement. I am more inclined to believe credible sources.

(Psst...that was sarcasm

Well clearly as Sagan has proven. Why do you think he accelerates with his front wheel in the air?

Because he is doing a wheelie.

Actually as he is lifting that front mass at least a foot higher than if he didn't do a wheelie, the front mass is even more significant.

You and Eddie are at opposite ends of the debate. Not sure who is right, as neither one of you really support your positions with convincing evidence. Of course Eddie has produced Olympic, Worlds, and pro riders, which does enhance his credibility somewhat.

I got an A in the kinematics section in my college engineering physics class. But I can't prove that, so you might have to go with Eddie B.

Yeah, I heard Eddie did too.

There's an advantage in putting the lightest wheel up front. Front wheels are inherently lighter, so I'm speaking in rotational inertia and mean lightest rims and tires.

This has nothing directly to do with speed, but with handling feel. The front wheel sees more side to side motion because of steering in addition to the normal side to side rocking both wheels see. Having a lighter wheel in front therefore lowers steering input forces and gives the bike a livelier feel. It doesn't directly translate to speed or efficiency, but lighter feel makes the engine feel better and might pull out a bit more output.

"degree in physical education at the University of Warsaw." Physical has the word physic in it - so it counts. Eddie B Cycling | Biography Actually I'd like to see Eddie's quote.
Anyway someone can tell me what I'm missing as this seems to all be high school physics - that Eddie B likely learned it in Poland.

There are two parts. The acceleration which boils down to which wheel moves farther and while the front does, it does very little. The second part I think makes a very big difference because the cyclist is constantly working against it. I expect Eddie B left that one out.

Distance matters. The wheel that travels farther requires more work. It might be interesting to see how much more the front moves in the turning of the front wheel. I think it is high - but I already did my video.


The second part is the rotational inertia too. And the front wheel experiences more rotational changes than the rear.
The effort required to move a spinning gyroscope - and what you get back is more similar to the front wheel than the rear. It is the front wheel you do this with every time you counter steer to turn, or get back on course. Anyway without going through messy numbers just think of the gyro exercise balls.

If these had real light wheels in them there would be far less effort / work / power used to move them. It is too hard to measure (Welcome to Nimble are the only wheels I know that posted wheel moments) and calculate is the force required to change the rotating moment of inertia of the wheel. (Dave @ Nimble was a math prodigy and graduated college at 16) posts 32 spoke wheels as 143gm^2 and his crosswind at 117gm^2) - they have some nice charts.

If it high school physics, I am sure you can site some sources of all this information, since you got an A and all. You could be right and everyone else could be completely off base. Most of this stuff is above my pay grade, but I do know credible sources (Hint, wickepedia is not a credible source). Other than that, what your saying is just blah blah blah. Your example of Sagan was ridiculous, since whenever he goes head to head with the big time sprinters, he usually doesn't win. I don't think he won a single stage last year in The Tour. Slow circles doesn't prove that will be the same outcome at speed. When riding slow, a rider turns the handle bars in the direction they want the bike to go. Do that on a 60 mph descent and you will crash. You need to counter steer. Keith Code talks about this in both his books. That is an example, by the way of citing one's source.

If your rear wheel is lighter than your front wheel you will crash when your rear wheel asplodes. If your front wheel is lighter than your rear wheel you will gain 200 watts or approximately 2 mph. That's assuming a difference of at least 100 grams.

I'm pretty sure this does not happens while moving in a straight line. I think as one turns, the front wheel has to complete a bigger circle (distance) than the rear. So you would want a lighter front wheel if it is going to do a bigger diameter circular movement. A constant speed through a circular path is still a form of acceleration.

You should be fine as long as you remove the decals from your front wheel.

Too much energy on this thread spent on an insignificant issue. A few hundred grams of extra weight on your wheels is going to have the same performance effect as a few hundred grams in your water bottle.

Fixed it for you.

I can't believe I forgot about the decals! The aerodynamic benefit from removing them is profound too.

No, it was correct the first time. The primary effect of weight is a slightly slower climbing speed proportional to the added weight as a percentage of total weight. It doesn't matter whether the extra weight is on the rims, in your bottles or on your head, a 250g increase will slow a 70kg rider down by about .3% (11 seconds slower on a 1 hour climb).

Added rim weight may be noticeable in the parking lot accelerating from a stop but it's insignificant (relative to weight in your bottle) when it counts, i.e. in a sprint at the end of a race due to the relatively low accelerations occurring in a real sprint. You'd be far better off riding a deeper, heavier rim with better aerodynamic properties even if it had a little higher inertia.

The amount of energy stored in a wheeling spinning at 30-40kph is very low and not worth worrying about.

Correct while In a perfect constant motion on a non changing gradient. But motion is never constant, or constant gradient.

I didn't say zero, I said insignificant.

That phrase is fine because it is true. Actually, both are true. There is energy required to increase the rotational energy of the wheels. You also use the wheels as a lever to apply the force that results in that same energy. Yes, the energy needed to accelerate your butt up to speed is more than the energy to spin up the wheels.