Larger Rims affect acceleration?
10-23-11, 05:34 PM
#31
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Most factory wheels aren't forged and can weigh anywhere from 25 lbs up (Yes even 17's). If you get into the forged category, you can find wheels weighing as low as 19 lbs. A light forged wheel along with the correct tire size matched to the factory OD, could save you a bunch of unsprung weight on each corner. That along with a wider wheel would give you more footprint on the ground!
Good luck on your search for the perfect set of wheels, it's not easy!
10-23-11, 07:58 PM
#32
10-23-11, 08:01 PM
#33
That's a complicated question Calvin, and quite frankly, probably beyond my scope of knowledge, But, I'll give it a shot with my 1 year of mechanical engineering education. 
A larger rolling diameter should actually slow your car down because you get less torque. Think of it like starting your car in 2nd gear. You would, however, have a higher theoretical top speed. This is also why you try to match the rolling diameters as close as possible, so you don't mess up your speedometer.
If you had a 17" vs. 18" setup with identical rolling diameters, identical tire widths etc, there could still be a difference due to the moment of inertia implications. Think of a bicycle wheel that just happened to have all of its mass near the outside diameter and compare it to another wheel with the exact same outside diameter, but with all the mass concentrated toward the center. The latter one would respond better to torque, and thus result in fast acceleration.
So you have overall weight, moment of inertia factors, wheel widths, tire properties, etc. Lots of variables at play.
A larger rolling diameter should actually slow your car down because you get less torque. Think of it like starting your car in 2nd gear. You would, however, have a higher theoretical top speed. This is also why you try to match the rolling diameters as close as possible, so you don't mess up your speedometer.
If you had a 17" vs. 18" setup with identical rolling diameters, identical tire widths etc, there could still be a difference due to the moment of inertia implications. Think of a bicycle wheel that just happened to have all of its mass near the outside diameter and compare it to another wheel with the exact same outside diameter, but with all the mass concentrated toward the center. The latter one would respond better to torque, and thus result in fast acceleration.
So you have overall weight, moment of inertia factors, wheel widths, tire properties, etc. Lots of variables at play.
10-23-11, 09:07 PM
#36
I think we should consider one factor at a time;
1. Longer OVERALL tire circumference will impede the acceleration because the final gear ratio will be taller overall. It's just like you start rolling with second gear instead of first (no, its not that bad but I exaggerate so you get an idea). But you will get higher top speed if you have excess horsepowers to compensate with higher air drag induced by higher vehicle speed (in theory, yes because you now have taller final ratio)
2. Heavier wheel+tire will impede the acceleration, braking and cornering. Easy explanation, because it has more mass, more inertia and more unsprung weight.
3. Wider contact patch will impede the acceleration but improve the lateral G and braking. Wider contact patch, mean higher rolling resistance and higher lateral adhesion.
Now when you change the wheel diameter, you will most likely, unavoidably affect more than one factor.
For example, step up from 225-40-18 to 225-35-19 will affect both weight and overall circumference.
1. Longer OVERALL tire circumference will impede the acceleration because the final gear ratio will be taller overall. It's just like you start rolling with second gear instead of first (no, its not that bad but I exaggerate so you get an idea). But you will get higher top speed if you have excess horsepowers to compensate with higher air drag induced by higher vehicle speed (in theory, yes because you now have taller final ratio)
2. Heavier wheel+tire will impede the acceleration, braking and cornering. Easy explanation, because it has more mass, more inertia and more unsprung weight.
3. Wider contact patch will impede the acceleration but improve the lateral G and braking. Wider contact patch, mean higher rolling resistance and higher lateral adhesion.
Now when you change the wheel diameter, you will most likely, unavoidably affect more than one factor.
For example, step up from 225-40-18 to 225-35-19 will affect both weight and overall circumference.
10-24-11, 05:55 AM
#39
But for my IS250, the engine has the hard time breaking 245-45-17 loose
Putting on wider tire will worsen the acceleration.The point is that wider tires create more drag and hence more loss in power. If you drag race from a rolling start, your acceleration might suffer with wider tire.
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