I have an 89 crx si with the stock 14" rims. I've heard they weigh about 17 lbs each, whereas 15" konig heliums weight about 11lbs each.

Would I notice significantly better acceleration on the street with the lighter 15s, or would a 6 lbs improvement really only be worth it for the track? I'd also be going up a size which might slow down the acceleration. Anyone have any ideas?

 

Unsprung weight part 1

Unsprung weight part 2

Part two deals more with wheels.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by that other website &raquo;</TD></TR><TR><TD CLASS="quote">A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight</TD></TR></TABLE>

This is not true in every gear, probably only for first gear. As the gear ratio changes, the effect of the rotating inertia changes. The higher the gear, the less effect it has.

Overall, a good article though.

 

I went from steelies to heliums, but i also upgraded my tires. I did notice that brakeing was dramatically improved and that I could corner better, more due to the tires than the wheels though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by that other website &raquo;</TD></TR><TR><TD CLASS="quote">... Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight...

A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight</TD></TR></TABLE>Wow, that's NOT EVEN CLOSE! Other than that, it's not a bad explanation.

Each pound you lose in the wheel/tire is worth between 1 & 2 pounds, depending on where within the wheel. Lose the weight at the hub & it's only worth 1 pound. Lose the weight at the tread & it's worth 2 pounds. In between it varies linearly. That's only for acceleration. For unsprung weight, it's worth exactly the 1 pound.

Lose 5 lb x 4, that's 20 pounds. Figure it's positioned somewhere in the middle, so it's worth maybe 30 pounds for acceleration. Equivalent to lightening the car body by about 30 pounds.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drdisco69 &raquo;</TD></TR><TR><TD CLASS="quote">This is not true in every gear, probably only for first gear. As the gear ratio changes, the effect of the rotating inertia changes. The higher the gear, the less effect it has.</TD></TR></TABLE>Nope (sorry). That's the story for reduced-weight flywheels or underdrive pulleys; but for wheels it doesn't matter what gear you're in. The wheels are 'downstream' of the gears.