3 pound weight difference?

[Somerandom18]

I remember swapping out 30 lb wheels to 19 lb wheels on my Hyundai. Now that made a difference. 3 lbs? Hahaha.

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[Yoshoobaroo]

Originally Posted by churchx

Yoshoobaroo: but then again something like Kosei K4R, while probably as easy to damage as you say, are cheap enough to buy another wheel instead of damaged one.

That's true, but if a wheel disintegrates, you're also at a much higher risk of crashing rather than if your wheel just bent a bit. I like to err on the safe side now if I can.

[gkubed]

Originally Posted by FR-Sky

Take out your spare tires, you instantly get 23lb free up.

Thanks for the reminder. I can't fit the spare over my brakes either way.

Or maybe I should carry around a big spacer...hmmm...

[dobbrz]

Take out the owners manual. That is easily 2.5lbs.

[Spuds]

So, I did some calculations about a year ago to see what kind of inertia you can remove from the drive train, and how that would translate into "wheel torque gains" (reduction in inertial losses). Interesting/difficult problem if you want a precise result, but I was just looking for estimates which makes it less complicated mathematically. But I digress....

As I recall, I found that reducing wheel weight by 4lb and tire weight by 1lb for all 4 corners would result in about a 2 ft-lb "gain" in wheel torque in a second gear pull. This was assuming starting from a completely stock 86, along with manymanymany more assumptions.

I don't think you are going to feel a 2ft-lb difference. Im still all about reducing unsprung and rotational weight (because energy losses are evil), just thought Id share my findings/predictions on the "butt dyno"matter.

[churchx]

Spuds: but .. you'll also enhance braking & cornering & suspension work (=more grip). That all is slight, but seeing how at some races it's fractions of seconds that sets apart, and given that raceteams have budget to afford expensive forged wheels, i see no reason for them to not go for that slight & expensive but nevertheless - advantage. Even more so for relatively underpowered cars like ours in NA form.

[Spuds]

Originally Posted by churchx

Spuds: but .. you'll also enhance braking & cornering & suspension work (=more grip). That all is slight, but seeing how at some races it's fractions of seconds that sets apart, and given that raceteams have budget to afford expensive forged wheels, i see no reason for them to not go for that slight & expensive but nevertheless - advantage. Even more so for relatively underpowered cars like ours in NA form.

I'm with you 100%. If it were up to me, I'd go for the lightest wheels and tires combination I could get (meeting other performance thresholds of course) for both handling and performance, no matter how small. I was avoiding the handling bit because I don't have any analysis or experience to add to what has been discussed before.

[churchx]

Braking it's just the same as with acceleration, rotational inertia. Wheel is like flywheel. The lighter it is, less energy needed to spin it up or slow it's spinning.
Cornering .. now that is least improved, just from generic overall car weight lightening, and there are other areas in car where more weight can be shed for less.
Suspension - due less unsprung weight, coilovers have to move less unsprung mass up and down, making lighter wheel quicker/easier to follow holes/bumps on road surface, improving contact & grip.
Of course, all of that is slight, very often below 'butt-dyno detecting treshold' .. but if one goes thorough with lightening everything, light forged wheels are nice thing to upgrade too, if not of their high price, often 3-4x cast wheel price , thus if one evaluates all possible gains with price, it might aswell be not best gains per buck investment area.
For myself i solved price issue in simple way. I simply bought used forged wheel set for 1/4th the cost of new, for around what new cast wheels cost . 400eur for 6.2kg 17x7.5 forged wheel set imho are worth it . 11.6kg less from wheels alone.