wheel weight/hp article

[evan938]

this is for those who say "light weight wheels only help acceleration but dont free up or add any hp"

http://forums.corvetteforum.com/showthread.php?t=1328054&highlight=c6+wheel+weight

thank you.

[CTele02]

yep thats why i have 15s... to me its like putting on a lightweight pulley kit that "frees up" hp... my setup is about 7-8lbs lighter than stock steelie/mich so just ignoring the fact that this is FWD and a hyundai (not a RWD chevy) 2 wheels = 14-16lbs freed divided by 3 = 4.66-5.33 hp!!!

So evan you should also consider the weight difference in the new tiburon/sonata brakes you are putting on perhaps those will mess with your 140whp goal...

[evan938]

that is talking about rotating weight, not dead weight. the only extra rotating weight will be the rotors, and going from 10.1" to 11" will only be a couple pounds

[skeetre]

I don't think 140 should be 'too' hard to get N/A I was at 127hp with the tiburon brake kit on my front wheels.. and 17" rims. I didn't reset the ecu either, no tuning or anything.

[SWortham]

Dynojets are great tuning tools for their easy setup and creating easily repeatable results. However, they are inertia dyno's and are inherently flawed in calculating horsepower. In fact, his measured improvements would've varied on inertia dyno to inertia dyno depending on the weight of the roller.

If he had conducted the same test on a steady-state (brake) dyno, he would've seen very different results because the measured horsepower gains would be zip, zero, nadda.

That isn't to say that wheel weight doesn't make a difference because it obviously does. It's just that in my opinion you should be measuring the difference where it can be most accurately represented. That is, the wheel weight's effect on acceleration. You can determine that with some very detailed calculations, or with actual acceleration testing.

By the way, the rule of thumb is that removing 1 pound of weight from a wheel is like removing roughly 1.5 pounds of static weight from the car (in terms of how it affects acceleration). And removing 1 pound of weight from a tire is like removing roughly 2 pounds of static weight from the car.

That figure differs depending on weight distribution of each wheel you're comparing, and there's an enormous impact when it comes to plus sizing, different tire sizes, etc, etc. Once you model all of that you'll notice that the 'rule of thumb' is nearly useless when you're dealing with different tire and/or wheel sizes.

This thread goes into pretty good detail:
http://legacygt.com/forums/showthread.php?t=11206

The member 'praedet' is quite the engineering genius. He gave me an Excel spreadsheet which illustrates all of this better than anything else I've seen. I meant to make an online calculator based on his spreadsheet but I've put it off. Hopefully I'll get around to it some day. I'm sure it'll be helpful for a lot of people, because I haven't seen anything else out there quite like it.

[tharptroy]

Dynojets are great tuning tools for their easy setup and creating easily repeatable results. However, they are inertia dyno's and are inherently flawed in calculating horsepower. In fact, his measured improvements would've varied on inertia dyno to inertia dyno depending on the weight of the roller.

If he had conducted the same test on a steady-state (brake) dyno, he would've seen very different results because the measured horsepower gains would be zip, zero, nadda.

That isn't to say that wheel weight doesn't make a difference because it obviously does. It's just that in my opinion you should be measuring the difference where it can be most accurately represented. That is, the wheel weight's effect on acceleration. You can determine that with some very detailed calculations, or with actual acceleration testing.

By the way, the rule of thumb is that removing 1 pound of weight from a wheel is like removing roughly 1.5 pounds of static weight from the car (in terms of how it affects acceleration). And removing 1 pound of weight from a tire is like removing roughly 2 pounds of static weight from the car.

That figure differs depending on weight distribution of each wheel you're comparing, and there's an enormous impact when it comes to plus sizing, different tire sizes, etc, etc. Once you model all of that you'll notice that the 'rule of thumb' is nearly useless when you're dealing with different tire and/or wheel sizes.

This thread goes into pretty good detail:
http://legacygt.com/forums/showthread.php?t=11206

The member 'praedet' is quite the engineering genius. He gave me an Excel spreadsheet which illustrates all of this better than anything else I've seen. I meant to make an online calculator based on his spreadsheet but I've put it off. Hopefully I'll get around to it some day. I'm sure it'll be helpful for a lot of people, because I haven't seen anything else out there quite like it.


this is why I went with a 16" wheel and 205/45/16 tires that weigh 18 lbs each....reduced radius in addition to huge cut in tire weight (6 lbs/tire lighter than my last tires). it really improved the response of the vehicle.

and the guy saying to use calculus...thats got to be a joke....good luck developing a function to define the wheel's shape...if you were serious about it, you could take some measurements from the wheel and tire and come up with a pretty close estimate of the rotational inertia....would it be worth your time? no

[SWortham]

That's what I was thinking. But I was blown away with what that one member made in his spare time. He's an aeronautical engineer so he knows this stuff a lot better than I do. He made cross-sectional diagrams and calculations to define the moment of inertia on a few different wheel designs & sizes. And then took that data and applied it to different wheel & tire combinations. Impressive stuff.

[quickfingerz]

yep thats why i have 15s... to me its like putting on a lightweight pulley kit that "frees up" hp... my setup is about 7-8lbs lighter than stock steelie/mich so just ignoring the fact that this is FWD and a hyundai (not a RWD chevy) 2 wheels = 14-16lbs freed divided by 3 = 4.66-5.33 hp!!!

So evan you should also consider the weight difference in the new tiburon/sonata brakes you are putting on perhaps those will mess with your 140whp goal...

We have 1/3rd the (edit) horsepower compared to a C6 corvette so moving to lightweight 15's and dropping 7 lbs per corner will only free ~1.5 hp.

[CTele02]

We have 1/3rd less horsepower than a C6 corvette so moving to lightweight 15's and dropping 7 lbs per corner will only free ~1.5 hp.
watch your wording ;) 1/3 less than 100% = 2/3.... you mean to say we have about 1/3 of the power of the vette... and ill take my 2hp and carbon fiber center caps thank you very much

[Daan]

that is talking about rotating weight, not dead weight. the only extra rotating weight will be the rotors, and going from 10.1" to 11" will only be a couple pounds

When I put bigger rotors on my Miata, it made a noticeable difference even though they're not that much bigger than the stockers were. I re-used the same wheel/tire, so only the rotors were changed. Adding even a small amount of rotating mass definitely adds up, and if I paid more attention in physics class, I could tell you the formula for it... :rolleyes: The loss of steering feel was worth it because of the much improved stopping power though.