Do we have a tire weight thread?
 

Everyone knows light wheels are better than heavy... but what about light tires? Anyone know of a tire weight chart floating around the internet?

Tirerack.com gives you tire weights....

All you really need to know is Continental makes some of the lightest tires in a given size... Michelin and Dunlop are usually close behind.

Tire weight is even more important with the weight on the outside. Yep tirerack lists the weights. Also Tiresize as well. Got stock size Hankook Ventus Evos 19lbs. https://tiresize.com/tires/Hankook/V...-215-45R17.htm


Continental DW's are light


Pirelli PZ4 in 18's are 20 lbs
https://www.tirerack.com/tires/tires...Z4XL&tab=Sizes

Tire weight affects rotational inertia a lot more than wheel weight. However, it's still only on the order of 1.5x non-rotating mass (i.e, save 4 lb on tire weight and acceleration is improved as if you saved 6 lb).

But other tire qualities might be more important to you..

Continental tires are very lightweight, but they are in general also poorly rated for steering responsiveness and cornering stability.

https://www.tirerack.com/tires/tests...y.jsp?ttid=190
Conti DW:
"What We'd Improve: More precise steering response and handling"

I've only had one set of Conti tires. They were lightweight for sure. But the sidewalls were limp and fun-to-driveness went right out the window...

Didn't know Tire Rack listed weights. I just checked the Nitto website and they list their weights(Tire Rack doesn't sell Nitto). So the next guy who's curious will know.

Apparently, they resolved those issues with the recently released ExtremeContact Sport and it's supposed to be comparable to the Michelin PSS. I'll be trying them soon as my PSS are just about done.

Yes they were on my list too and just as important they are light 19lbs stock size. I went with the Hankooks because I was able to spend $400 for the set and get a combined
60+100+75= $235 in rebates purchasing through discountiredirect. So $165 for a set of tires aint bad:D

A lot of manufacturers list tire weights on their site, which is nice.

This. Sometimes even the faster things don't feel as fast or as good to drive.


Also, if anyone has any leads on a constant of rotational moment of inertia of an actual car wheel and tire and not the theoretical stuff that google keeps bringing up, I'd love that info. I had heard weight savings in the wheel/tire package is like saving 150% before and I'd also heard it is like 1000% and I got bored so I plugged through it.




Power required to get a non-rotating item to a certain linear velocity in a certain time is:


P=E/t=0.5*m*(v^2)/t


Where:
E= Linear kinetic energy of the item
m = mass of the item
v = linear velocity of the item (equal to car's velocity)
t = time spent accelerating






Rotational kinetic energy of the rotating wheel tire = 0.5*k*m*(R^2)*(w^2) = 0.5*k*m*(v^2) since v=R*w


w=rotational velocity (radians/sec)
R=radius of wheel/tire
m = mass of the item
v = linear velocity of the item (equal to car's velocity)


So,
Power to get a wheel/tire assembly to a certain linear velocity in a certain time equals:


P=linear kinetic energy/t + rotational kinetic energy/t = [0.5*m*(v^2)/t]+[0.5*k*m*(v^2)/t]


m = mass of the wheel/tire
v = linear velocity of the wheel (equal to car's velocity)
t = time spent accelerating
k = inertial constant of rotation for wheel/tire setup


Notice how the first half of that is the same formula as for the power required to move a non-rotating object, such as a passenger in the cabin, or the exact same wheel in the trunk. The latter part is the contribution due to the wheel rotating.


So,
Total power required for wheel assembly = power required if wheel was sitting in the trunk + [0.5*k*m*(v^2)/t]


We can choose a speed and estimated acceleration time for our cars, and a decent wheel/tire mass guestimate:


v= 60mph = 27 meters/second
t = 7 seconds (rough 0-60 estimate for an NA twin)
m = 55 lbs = 25 kg


P for non rotating = [0.5*35 kg*(27(m/s)^2)/7 sec] = 1822 watts = 2.44 horsepower is required to accelerate 25 kg to 60 mph in 7 seconds


P for rotating wheel/tire = 1822 watts + [0.5*k*35 kg*(27(m/s)^2)/7 sec] = 1822 watts + 1822*k watts = 2.44 horsepower + 2.44*k horsepower


Get your k for the wheel/tire setup and you've got your answer as to how much the rotational part adds.