HPF compares the effect of different sized wheels on the dyno

Video:

I have always found big wheels with flush setups just plain stupid if you are looking for performance.

Originally Posted by FR305

I have always found big wheels with flush setups just plain stupid if you are looking for performance.

Well, he kind of needs them for traction.

Originally Posted by Sticky

Well, he kind of needs them for traction.

Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

for example:

Originally Posted by FR305

Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

for example:

http://ll.speedhunters.com/u/f/eagam...2/IMG_4551.JPG

Oh, you mean same width but just not a "bling" ?

They are 19's.

Originally Posted by Sticky

Oh, you mean same width but just not a "bling" ?

Exactly. Bling = Weight

Originally Posted by Sticky

They are 19's.

He should have 17's Classic CCW's

European Car put wider wheels and more rubber on their Project Z4M. They got 13whp/10 ft.lbs gain over the OE wheel and tire set-up. The 18x10 Forgelines with upsized tires were 4 lbs lighter.

Originally Posted by FR305

He should have 17's Classic CCW's

Perhaps, but he can also have more than one set of wheels. One for looks, one for the track.

This is how you do it right

CCW Classics matte black centers with gloss black lips.

Originally Posted by Sticky

Perhaps, but he can also have more than one set of wheels. One for looks, one for the track.

European Car kind of had opposite findings. Their upped tire size and wider wheels, gained HP/TQ.

They attributed the gains to the lighter weight, not rolling diameter.

Ya, I guess, I know I will be running wheels for looks on the street and wheels for performance on the track.

Originally Posted by M3_WC

European Car kind of had opposite findings. Their upped tire size and wider wheels, gained HP/TQ.

They attributed the gains to the lighter weight, not rolling diameter.

It is about the weight more than anything.

The wheels here in the vid are both 19's.

Originally Posted by Sticky

It is about the weight more than anything.

The wheels here in the vid are both 19's.

He says the ratio between the tire diameter and roller diameter change, that is what caused the difference in power readings. He is not really attributing it to weight, but rather the different rolling diameters.

Originally Posted by M3_WC

He says the ratio between the tire diameter and roller diameter change, that is what caused the difference in power readings. He is not really attributing it to weight, but rather the different rolling diameters.

That is true as well but the weight also is a factor.

Originally Posted by Sticky

That is true as well but the weight also is a factor.

Yeah I agree. I think it is the bigger factor actually.

Here is some data from Europeancar's Project Z4M. They find the less rotational mass attributes to the bulk of the gains. As HPF seems to think the tire diameter is the main factor.
http://blog.forgeline.com/tag/project-z4m/

Originally Posted by LostMarine

$#@!.. im wanna put the 17's on now more than ever!!

k1's ftw

The rolling diameter is effectively changing the gearing and in this case making it taller, so the torque multiplication factor decreases with the bigger tire/wheel combo, and the weight is also a huge factor. This is a really cool video, though....I love it when shops test different things that we always talk about and put some hard numbers on them.

I wonder if the difference is as great because the car here is making such big numbers. If it was a car making 400ish whp, the difference might have been much smaller.

Originally Posted by FR305

Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

for example:

http://www.bimmerboost.com/images/im...10/12/1585.jpg

Great point. I'm thinking about going with 16's when I go to the track this coming spring. The taller side wall helps a good bit. I wonder what the tq difference was with the tire/rim swap?

tires are pretty heavy too, i wonder what the difference would be from a 305-45-18 to a 305-30-20 would be...