Originally Posted by
Hrothgar42
It depends! The acceleration of a wheel itself depends on the moment of inertia of the wheel.
You can compare weight (or mass) if it's at the same place in the wheel.
So, using 400g tires instead of 100g tires would just be silly. And it's intuitive.
But the moment of inertia depends on the mass and the distance away from the axel. The further away, the more acceleration is affected. Heavy rims matter more than heavy hubs.
And since a disc (a proper disc, not a spokes wheel with a cover) doesn't need the extra structural support on the rim for spoke nipples, the mass at the edge of the wheel can be reduced.
TLDR: mass alone doesn't determine acceleration.
^^ This and the fact that once you get over 40kph, aero trumps weight every single time.
You might look at a match sprint and see the acceleration part, but facts are that modern sprinting with bigger gears and endurance leaning riders going long mean that there is very very rarely a 100-150m sprint to the line any more. I'd even go out on a limb and say that rarely even happens at club level any more.
Then take into account that rotational mass argument. That 700g rear wheel may sound light. But in actual fact it probably has a super light hub and lower spokes. What does that mean? That means the rim is heavy and all that mass is out at the rim, just where it isn't wanted. That makes it slower to accelerate. On a disc wheel, that 870g is spread right through to the hub, not localised around the rim. In essence I very much doubt that you will notice a big difference physically (note mentally is different). When you got up to speed, especially up around 60kph I bet you do notice a big difference in the wheels.
Finally look at events like TT. How long is the acceleration phase up to 40kph? For me, I can get over that fairly easily within 100m. For a kilo, that's less than 10% of the event where acceleration matters vs 90+% where aero matters.
If that acceleration phase is killing you so much that you consider an aero spoke wheel to be better, then there's no doubt that fitness is your issue, not wheel selection. Never underestimate just how fit you actually need to be to be a sprinter