Road Cycling - deep dish wheels and rotational mass

seems to me that the deeper the dish on the wheel the greater the rotational mass, which makes for more work . does the aero advantage make up for this??

You may work harder to get them going but they should have more momentum to keep them going. The mathmatics are beyond me just a year or two of physics I never use, Newton Laws and all.

I have a pair of Velocity's that are a deep dish aero wheel but weigh less than a set of cheap Shimano paired spoke non-aero wheels (think it was the 540's?). Aero wheels aren't necessarily heavier than a non-aero wheel... it depends on a lot on which wheelsets you're talking about.

That said they cruise nicely at speed, and suck in a crosswind.

The "doctrine" in "forum world" is that 40mm is the minimum for an aero advantage, therefore they should then be carbon, or else a 40mm aluminium rim would be too heavy.

well its not about total wieght its about were the weight is isnt it? like a wheel could be heavier but have less rotational mass than a lighter deep dish wheel. but you answered my question i guess as long as the aero advantage more then makes up for it they are worth it.

i guess as long as the aero advantage more then makes up for it they are worth it. Until you start going up hills, then it all goes out the window :)

G'day,

My cosmics are 300gm heavier than my Ksyriums.......On the flat, the cosmics are significantly quicker. Dunno about hills, cos the whole of OZ is only 5m above sea level.;)....either that or i avoid anything higher!

cheers,

Hitchy

Do you think the average person blowing a couple of grand on a set of aero wheels is ever going to notice a speed improvement that's even remotely worth it? If you're doing professional time trials, sure, go for it, but for the rest of us, where can you get a 400g 40mm rim? Zipp? They're 500 dollars each where I'm from, and they're not that light - and as you correctly point out, the weight is in the worst part of the wheel, at the perimeter.

If you ride where it's relatively flat and you're only interested in time trials, sure, go aero. If you're a real world rider like 95% of us, just get the lightest wheels you can afford.

Rotational mass is pure b.s, this was already discussed before. Weight is weight.

Rotational mass is pure b.s, this was already discussed before. Weight is weight.

Hmm, that's a new one to me :rolleyes:

So you’re telling me that when your bike is on a workstand, it takes NO effort to get the wheel spinning at 30 mph?

-murray

Rotational mass is pure b.s, this was already discussed before. Weight is weight.

Well, technically it's not "pure" b.s. There is an effect, but it is roughly 3rd order, so yes, it is pretty insignificant.

The more weight there is at the outside of a rotating mass, the more torque it takes to get that mass rotating. The farther the mass is located from the rotation point, the more the force needed. Ok so I just said almost the same thing twice. :) It has to do with inertia, I think. Ah memories of physics class.

Rotating weight makes a significant difference in acceleration, so commuters should get the lightest wheels and tires possible to give best performance for traffic/intersections. It wont make much difference for time trialers who go at pretty constant speed after the initial acceleration, unless the time trial is up alpe d'huez.

There is an effect, but it is roughly 3rd order, so yes, it is pretty insignificant.

Please explain.

-murray

It's fun to fantasize about minutae like rotating weight and aero advantage of a certain wheel, but remember it's the rider and not the bike that makes the most signfiicant difference. At times the advantage gained by light aero wheels is mere seconds, significant to Lance but not you.

Rotating weight makes a significant difference in acceleration, so commuters should get the lightest wheels and tires possible to give best performance for traffic/intersections. It wont make much difference for time trialers who go at pretty constant speed after the initial acceleration, unless the time trial is up alpe d'huez.

Perpetuating more myths.

you can all argue while i leave ya in the dust... :p

I must agree, for all practical purposes, "rotating weight" on bike wheels is marketing BS.
You know it is BS when you see an ad for hubs that claims lighter hubs with less rotating weight.. a hub???? in the middle of the wheel? rotating weight?? gimme a brake (errr... a break :) )!!