Lighter wheels or a light weight driveshaft?

[Chris B.]

I have been using my stock wheels and street tires for track days. I was planning to get a set of 19-20 lb 18x9.5" wheels and 275/40-18 or 275/35-18 tires for track days. However the wheels would be about $1200 and the tires would be about $1000-$1200. I can get a set of GT500 18x9.5" wheels for about $500. That would be a savings of $700 and more then enoough for a light weight, one piece aluminum drive shaft.

It looks like the GT500 wheels weigh about 27 lbs each. So that would be another 28-32 lbs in wheel weight total on all 4 corners. The driveshaft would save me at least 20 lbs. in weight in the drivetrain.

I'm not currently racing in any sort of time trials and I do track days mainly for fun and to improve my driving skill. What would I be better off getting the lighter wheels or the heavier wheels and aluminum drive shaft?

 

[stkjock]

IMHO - which ever way would save more weight in total.

 

[Vapour Trails]

Lighter wheels

 

[Chris B.]

I looked up the wheel and tire weights and did the math. With the 19 lb 18x9.5" wheels and 275/40-18 tires, the wheels and tires would each weigh 51 lbs. With the GT500 wheels and the same tires, each wheel and tire would be 59 lbs. My stock wheels and tires weigh 57 lbs.

If I went with the GT500 wheels, the wheels and tires would each weigh 2 lb more than the stock wheels and tires. The difference is 8 lbs per corner between the 19 lb wheels and the GT500 wheels.

So basically, I'd have 32 lbs total less unsprung weight with the lighter wheels or about 20 lbs. less drivetrain weight with the light weight driveshaft.

The only advantage to the GT500 wheels I can see is that they clear the GT500 calipers. The lighter weight wheels would need spacers to clear the GT500 calipers.

 

[Jordan@JPC]

I think the total rotational inertia saved is going to be better with the lighter wheels.

Rotational inertia is:

I=m*r^2

where m is mass,

and r is the radius of the center of rotation to the center of mass. Since the radius term is squared, it affects rotational inertia more than an equal drop in weight would. Considering the r term for the wheels is going to be much larger than it would for the driveshaft, I'd get the wheels. JMHO.

 

[Random Asshole]

wheels.

 

[Infamous]

both

 

[Sleeper_08]

these are the wheels and tires I bought

http://s197forum.com/forum/showthread.php?t=30166

Weight sdavings on wheels and tires is also more important because it is unsprung weight and the lighter they are the easier it is to keep them on the ground.

 

[DusterRT]

Wheels! Gains will be small, but you'll improve acceleration, braking and overall grip via wider tires. And, of course, everyone knows how evil un-sprung weight is. Plus it's an investment you can see without having to crawl under the car.

 

[fiverivers]

Wheels and tires would be first then driveshaft. Also lighter wheels would also mean less load on the driveshaft.

 

[dkegel]

Lighter wheels

I agree.

Dave

 

[Riptide]

Wheels. +2

Not only are you shaving more rotating mass off the car that way (most likely) but your wheels are physically a larger circumference.