Q on wheel weights for dragracing...

[Pinoyspd17]

sup guys..

just wondering if you really want lightweight wheels on your car when dragracing...

to me, it would seem that youd want heavier wheels in front for "more downforce" onto the wheels..and maybe lighter wheels in the rear.....is that right guys?..

thanx in advance...

[oldster]

You want the least unsprung weight that you can get which would include the wheels. If the suspension works it uses the weight of the body to plant the tires and give you traction.

[Karim]

Originally posted by oldster
You want the least unsprung weight that you can get which would include the wheels. If the suspension works it uses the weight of the body to plant the tires and give you traction.

WERD

[autxr]

An extra 5 or 10 pounds on the wheels might make a difference of 0.01 seconds on the launch, but I doubt it. Once you are hooked up that gain is lost due to the INCREASE in friction. So figure a wash with heavier wheels from the "downforce" perspective (A Formula 1 car makes over 2000 pounds of downforce on certain tracks, that is enough to change grip, but 5 or 10 pounds isn't).

On the other hand, 5 or 10 pounds of rotating mass (per wheel) can rob you of several horsepower (over the entire power band), so I don't think it is a stretch to say that lighter wheels could shave 0.1 or 0.2 seconds off the 1/4 mile.

Scott

[Oo DaRk StAr oO]

Originally posted by autxr
I don't think it is a stretch to say that lighter wheels could shave 0.1 or 0.2 seconds off the 1/4 mile.

Scott

Difference between winning and losing!!!

[onigami]

lighter rims = less rotational intertia

less rotational inertia = less torque is required to turn the thing.

rotational inertia (I) is calculated in the general from K*mass*radius^2, where K is a constant. the constant depends on the type of solid.

[autxr]

Ahh, physics. I know I forgot that stuff for a reason.

Notice there is a radius SQUARED in there.

That is why light weight is only part of the equation.

WHERE the weight is matters even more (radius squared). Take a 16" wheel that weighs 10 pounds. Imagine 5 pounds is where the tire goes, and another 5 pounds is the spokes and hub.

Now, take a 15" wheel with identical weight, again, 5 pounds is the outer rim part, and 5 pounds is spokes and hub.

The 15" wheel has less rotational inertia than the 16", so even at the same weight the 15" is faster (lets pretend that the 15" tire isn't heavier - compare same brands of 205/50-15 and 205/50-16).

Scott