The only thing I would change about your analysis is the 120 gram tubes. I race on latex tubes which weigh around 70 grams and in races where I carry a spare tube, I carry one of those Bonti 60 gram super small tubes and put one in special needs.
It drops about 100-125 grams from the equation, but more importantly a bunch of watts in rolling resistance and bulk from my seat pack.
I’d do it without the spares in there since its the rotational weight difference, not the overall bike weight difference which is the big difference maker when it comes to wheels. Do that and you’ve got a 625 g difference (11 ounces per wheel) in rotational weight between the two sets. Even in a relatively steady state triathlon ride, that is an energy saver.
I’d do it without the spares in there since its the rotational weight difference, not the overall bike weight difference which is the big difference maker when it comes to wheels. Do that and you’ve got a 625 g difference (11 ounces per wheel) in rotational weight between the two sets. Even in a relatively steady state triathlon ride, that is an energy saver.
No it isn’t, please see the mathematics:
http://forum.slowtwitch.com/gforum.cgi?post=2171971;search_string=wheel%20weight%20math;#2171971
Who makes the lightest tubular tire?
I stand corrected. Its just so much easier to just shoot from the hip instead of actually knowing what your talking about . . . . .
I did some poking around and found this whcih you might find interesting. I was thinking the analyis you cited might only apply to climbing but this guy lays it out for flat riding too. It appears wheel weight does not even make that much difference even in a criterium. http://www.biketechreview.com/reviews/wheels/63-wheel-performance
I still want tubulars though … . . They are so cool.
One thing that I’ve not seen analyzed regarding sprinting and rotational inertia, is that there is an energy cost to thrashing a bike back and forth…which some people do a lot when they sprint. A spinning wheel has a lot of inertia… you can demonstrate this by spinning a wheel in your hands and then turning it. The less inertia the wheel has the lower this loss would be. In all the sprinting analysis I’ve seen (including the ones I’ve done) this is ignored… only the cost of spinning the wheels up is considered.
common misconception, i had it too until I found that analysis.
there was a really cool, but horribly flawed test I read once, where they attached 5lbs of water to the frame, did a power meter controlled hill climb, then added 5lbs of water to the wheel, but injecting it into the tube
and they got a much slower time that way
well, the problem there is they totally ignore how water will affect rolling resistance!
I stand corrected. Its just so much easier to just shoot from the hip instead of actually knowing what your talking about . . . . .
I did some poking around and found this whcih you might find interesting. I was thinking the analyis you cited might only apply to climbing but this guy lays it out for flat riding too. It appears wheel weight does not even make that much difference even in a criterium. http://www.biketechreview.com/reviews/wheels/63-wheel-performance
I still want tubulars though … . . They are so cool.
I like it, you are REALLY hunting for reasons to worry about wheel weight a lot! 
One thing that I’ve not seen analyzed regarding sprinting and rotational inertia, is that there is an energy cost to thrashing a bike back and forth…which some people do a lot when they sprint. A spinning wheel has a lot of inertia… you can demonstrate this by spinning a wheel in your hands and then turning it. The less inertia the wheel has the lower this loss would be. In all the sprinting analysis I’ve seen (including the ones I’ve done) this is ignored… only the cost of spinning the wheels up is considered.
Who makes the lightest tubular tire?
Veloflex has some right around (and even below) 200g that are streetable.
Tire levers.
I like it, you are REALLY hunting for reasons to worry about wheel weight a lot!
Not at all… give it a try. Even with the wheel spinning at a slow speed, it takes a lot of force to turn or tilt it. If I wasn’t so lazy, I’d figure out the loss myself… but I’m sure it won’t be trivial for a thrasher.
Tire levers.
I figure either configuration has one tire lever, one MicroInflate, and one CO2, so it’s a push.
maybe the thrasher just ends up not needing to move the bike as far? =)
but I’m sure it won’t be trivial for a thrasher.
Because there is more resistance? Maybe. But what if it’s the same motion… how much energy is lost?
less energy is lost as they are pulling against a more solid platform =)
i dunno i got 100 internet points says it doesn’t matter based on pure useless intuition
Because there is more resistance? Maybe. But what if it’s the same motion… how much energy is lost?
Whipping the bike back and forth certainly requires energy that doesn’t contribute directly to moving it forward. The reason why people do it is to bring the downward moving pedal up a bit using the arms and also to maintain balance while applying high force out of the saddle. I don’t believe that the amount of motion will vary much depending on the bike’s resistance to this motion, but rather the rider’s style. There are much larger forces in play than the force required to tilt the bike.
So… if the tilting back and forth is going to be the same amount regardless of the bike’s weight or inertia, then higher inertia will simply result in an added loss.
I think you’re right on. I did a similar analysis myself, but looked at probably two dozen combinations of front/rear wheels, tubular vs. clincher. Some clinchers are only marginally heavier than tubulars of comparable rim depth. Others have a larger difference, as in your results. I eventually chose tubulars, but weight was not the only factor.
I figure that in most cases, tubular wheels are probably faster than comparable clinchers due to weight, marginally better aerodynamics and rolling resistance (which is a subject of much debate). Assuming that’s true, I’m willing to put up with the headache of gluing them up and the potential of having to change one in the race for the chance to go a little faster. If I flat, my PR is out the window, anyway, regardless of how fast I change the tire!
So am I to understand that you guys don’t all race with solid-core tires?
Conti 4000’s are 205g each, not 225
there was a really cool, but horribly flawed test I read once, where they attached 5lbs of water to the frame, did a power meter controlled hill climb, then added 5lbs of water to the wheel, but injecting it into the tube
and they got a much slower time that way
You’re probably referring to this one: http://www.training4cyclists.com/how-much-time-does-extra-weight-cost-on-alpe-dhuez/
There was 26s difference (interval length was around 52 minutes) but this should be adjusted because he averaged 2W higher while riding with water on the frame. When you put the data in the power to speed calculators 2W translates into 20s. So this adjusted difference is only 6s (I don’t know the configuration of the ascent, so I used 9% grade as an approximation)
If you’re considering the weight of the glue for tubulars, then add the weight on rim tape for the clinchers.