How much faster?

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Did you adjust your computer for the difference in tire sizes?

This really doesn't sound right. More details please.

So how were you decieved? you got a high end low weight wheel. Exactly as advertised.

As for the whole heavy wheel/momentum thing, there very well could be some validity to that. I know on a fixed gear bike it can help make for a more fluid pedal stroke and, because you can't stop pedaling, can help you mantain some momentum when you fatigue. I don't think it could really help you on a freewheel bike though. The lighter wheels will decelerate faster, but as long as you are turning the pedals, i'd imagine they should be faster.

I would be happy to test this out for you though, just contact me via email and i'll give you a shipping adress.

I've noticed similar unexpected performance from light wheels. It's not the ads that are deceiving, it's probably our expectations.
THe fastest wheels I ever rode were the old original Specialized Chunky-a-Monk trispokes, 10lb wheels w/ 5lb. tires.
Aero is aero, light is light, but fast is fast. Don't argue with it.
b

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"What's good for me ain't necessarily good for the weak-minded."

I calibrated the computer using the actual wheel measurements and actully used time over a closed course I do my tempo rides on. I believe that it does take less effort to accellerate on the 303's but seems to take noticably more to keep them spinning. My original race wheels were pretty good, an odd set of DA 7700 650 wheels with 16 spokes, just like the 7701's they sell now but with 34mm rims. I have a set of Pro Race tires on them and a set of Sprinter tubs on the 303s. The difference is about 2 MINUTES on a 17 mile course in similar conditions. My question is not to bad mouth the 303's, they are a fine set of wheels, I guess my expectations of them were just too high from all the reading that I had done.

That is a big difference, nearly 1 MPH. That seems like way too much of a speed difference in either direction. Your experience is your experience though, so I don't know what explanation to offer.

As one of the many engineers/physics guys on the forum, I will tell you that the difference in mass between the two wheels is not a significant portion of the amount of force it takes to accelerate your bike with you on it. And that goes for deceleration as well. Nimble lists the moment of initia (which you can think of as analogous to mass) as 117gm2 for their trispoke and a 32 spoke at 143gm2, so we are not talking big numbers here. You can consider the difference in the mass of the wheels as seperate contributing factor from the moments of inertia, but again it is small compared to the whole bike/rider combination.

What you are finding is that, the truth is, there are many factors that can make a much bigger difference in your performance than the wheelset you use. I ride a training loop with both my race wheels (nimbles) and trainers, and use a power meter. With consistent power, my average speed is much more governed by the amount of wind, heat, my weight, number of times I had to accelerate, etc, than by the wheels I am using.

Take a look at what the pro's ride. Does every pro have a rear disk/hed 3 combination? Why not, we have clearly established in this forum that that is the fastest...some claim to loose 4-5 minutes over an ironman by using a trispoke instead of a disk. How may pro's would have moved up a placing with 4 minutes improvement? And they gave that up? Something doesn't click.

If you are always slower with the 303's, I'd look at the other factors. Your mind can easily trick you into believing it is the wheels. Your legs are not nearly as sensitve as the instruments they use to measure drag in wind tunnels, and even then they cannot come up with consistent results. Heck, a water bottle is 28 ounces, thats 794 grams. More difference there than between your wheels I'll bet. Do you notice it is harder to keep your momentum when your water bottle is empty? Maybe if you are thirsty :-)

Bottom line, yup, wheels are over-hyped I think. Both your sets are cool wheels.

Dan

The Zipp 303 rim at about 40mm should be about the same as a 34mm deep rim from an aerodynamic standpoint. No way it is going to be 2 minutes slower. Maybe you were tired, maybe it was windy, maybe the hubs on the Zipp are bad, maybe the brake pad was rubbing, but there is no way the DA rims are significantly faster than the Zipps.

Go to a slight downhill, where you go at about 20miles per hour without pedaling.

switch forth and back 10 times and measure the uphill time and the downhill time (down just rolling), this will give you a very good estimate of what's happening. Don't do it twice or four times, you need at least ten.