weight vs performance

[allmotor_integ]

i just purchased some 17" Velox VX-8 for my Ls integ i was wanderin how much of an impact will it have on my quarter mile time. is it true that it affects your rotational speed.

[Nikolai]

Affects your rotational speed?! As in, you're doing dough-nuts and want to do them faster? The wheels rotational speed? Buddy, it's really hard to reply to a post like this without some details....

Try giving us your stock tire size and your new tire size, and then we can calculate what the difference in circumfrence is, and therefore the error that your speedometer will have after installation (as well as gas mileage, which is why I think all you idiots on here that think you're getting incredible/shitty gas mileage for absolutely no reason need to bust out your calculators).

Better quarter mile times may come from better traction, if it's a wider rim, but chances are that rotational moment of inertia will not be affected enough to make a significant improvement in weight (unless these are some bad-a magnesium rims that I've never heard of before).

Post some more info, and good luck!

Nick

[xdannyx25]

well weight has to do with it, but with low profile tires it will be harder to get traction in the quarter, and also now it will take more horsepower to reach a higher speed due to more weight, it takes more to turn them now, and diameter of them

[Nikolai]

I don't think you're right about the weight thing..........Aftermarket rims, though having a larger diameter, are generally lighter than stock rims (with the exception of the "especially light '96 GS-R rims")..........DIameter and weight are not proportional, also because you generally have lower profile tires with a larger rim. Also, the diameter has nothing to do with how much power it will take to get you through the quarter, but your gearing and speedo accuracy will definitely change if there is a significant circumfrence difference in tires.

Nick

[gsr24]

the wieght could hurt you but prob not. with the larger diameter and wider rim, you will have more surface area the the tire in contact with the cement so that will help in that area of spinning. you will accellerate slower because of the larger diameter outside of the tire. on the other hand i think you may have better high end accelleration because if you think about it, the larger rim with more wieght will have more enershia and its kindof like tying a weight to the end of a long sring compared to a short string. it doesnt take as much energy to spin it in a circle when the string is long. idn it seems like a good theory but im not sure.

[G2Integrity]

I've been wondering this for a while too. Where is the trade-off point? Larger tires = better traction, yet worse acceleration. Smaller tires = worse traction, better acceleration. Larger, lighter rims is good cause they're lighter yet are larger. So where the point where the two intersect on a graph, so to speak. What size/weight is best?

Btw, I'm rolling on stock 1990 alloy rims.

[White98LS]

Just for some information, stock GS-R wheels (G3) are 16lbs, and the '96's are 15.5lbs, not a huge difference.

Also, at least in 17", very few aftermarket wheels are lighter than 16lbs. The Rota Attacks are 15.5, the Volks, SSR Competitions, and many other expensive, mostly forged wheels are less than 16lbs, but most aftermarket wheels in 17" are 20-24lbs, a huge difference from 16lbs.

And yes, a wider tire will generally give you better traction, but a bigger diameter tire will effectively elongate your gearing, slowing your acceleration.

I am getting 15" Rota Attacks in a month or two because A) they are light, cheap and strong somehow, and B) Realtime Racing's ITR's run on 15"s, so sign me up too.

[junglistgsr]

Originally posted by Nikolai
I don't think you're right about the weight thing..........Aftermarket rims, though having a larger diameter, are generally lighter than stock rims (with the exception of the "especially light '96 GS-R rims")..........DIameter and weight are not proportional, also because you generally have lower profile tires with a larger rim. Also, the diameter has nothing to do with how much power it will take to get you through the quarter, but your gearing and speedo accuracy will definitely change if there is a significant circumfrence difference in tires.

Nick

aftermarket rims with larger diameter are generally lighter? thats biggest load of horseshit ever dude, sorry. I dont know of many 17" wheels that weigh in at about 15-16lbs which is what stock integra wheels weigh (except steelies which weigh like 19lbs). Lower profile tires usually also weigh more due to needing more material and fibers and all that to strengthen the sidewall and usually being wider than stock wheels.

Diameter of it DOES have to do with his 1/4 mile times. with a larger diameter you are putting more weight away from the center of the hub, the farther away from the hub the weight is...the more power or effort from the car it takes to spin that wheel. take a 15lb 15" wheel and a 15lb 17" wheel with the same exact circumfrence in tires and the car with the 15"s would be faster if the two cars were identical.

if wheelsize didnt matter then why would all the pro-drag guys be trying to squeeze the smallest wheels onto their cars that their brakes would allow? if it really didnt matter you'd think they'd run the biggest rims they could with their slicks so they could have bigger brakes for safer post-run braking. I dont see many road-race or auto-x people choosing to run huge wheels either.....best example is Realtime racing, they continue to stick with 15" forged wheels year in and year out, you'd think they'd run 17" wheels if traction was really better in turns and that weight of them didnt matter at all, fact is that it does. Super Street did a dyno of a very stock Civic with its stock steel wheels and tires....it put down like 94hp....then they strapped on your average 17" wheel with your average 17" tire and it laid down like 91hp.

[White98LS]

You probably posted at about the same time I did, because that's almost exactly what I said. Amen, brothah!!

[Nikolai]

Originally posted by White98LS
Just for some information, stock GS-R wheels (G3) are 16lbs, and the '96's are 15.5lbs, not a huge difference.

Also, at least in 17", very few aftermarket wheels are lighter than 16lbs. The Rota Attacks are 15.5, the Volks, SSR Competitions, and many other expensive, mostly forged wheels are less than 16lbs, but most aftermarket wheels in 17" are 20-24lbs, a huge difference from 16lbs.

Originally posted by junglistgsr
aftermarket rims with larger diameter are generally lighter? thats biggest load of horseshit ever dude, sorry.

Hey smart guy, I think someone already established that, but thanks for that keen bit of insight. I was speculating that 17"s would be lighter (oops, my intuition was wrong for a change). But it just goes to show that there are a few intelligent people on SHO that are beyond speculation, so I'll quit with that. Fair enough? Thanks White98LS for pointing out that I was wrong........Jung's post was 12 hours after yours....

It's stupid to speculate that an auto-X team (Realtime Racing) would use 15" rims on an for significantly less rotational inertia. In auto-X, the purpose behind the 15's with low profile tires is for lower center of gravity. A car on 15's compared to one on 17's, with the same tire profile, will be an inch closer to the ground, suspension aside. If you'd take the time to solve the applicable kinematics equations, you'd find that the overall effect of more rotational inertia on the car is insignificant, especially when other things are considered, such as handling, speedometer accuracy, and maintaining stock gearing.

Furthermore, drag cars use small rims to help facilitate sidewall deflection, which increases the contact patch at low speeds, and decreases it at high speeds, due to centripetal force of the rotating tire, effectually reducing drag. Bigger wheels simply to use bigger brakes for safety? Chutes do a lot more at high speeds than brakes could hope for....It's drag racing, not Auto-X!


You know what? All this is stupid anyway without some hard data. A 3hp loss on a roller dyno is well within the realm of error. I'd be very interested to see a reputable source that backs up your claims. Thanks for the response, though. You made me think a little.

Nick

[JUICEDGSR95]

For every one pound you take off of your cars rotating mass (wheels, brakes, drive shafts, flywheels, etc.) is equal to removing nine pounds of weight off your car. - Turbo Magazine

So with this said, if you go from stock GSR wheels at 16lbs, to lightweight Rota wheels, say 12lbs, that would save you an equivelent of 144lbs? sounds crazy but maybe its true.

When installing larger diameter wheels, you 'normaly' put on lower profile tires, therefore 'usually' you will have the same overall diameter.

[junglistgsr]

Originally posted by Nikolai

Hey smart guy, I think someone already established that, but thanks for that keen bit of insight. I was speculating that 17"s would be lighter (oops, my intuition was wrong for a change). But it just goes to show that there are a few intelligent people on SHO that are beyond speculation, so I'll quit with that. Fair enough? Thanks White98LS for pointing out that I was wrong........Jung's post was 12 hours after yours....

It's stupid to speculate that an auto-X team (Realtime Racing) would use 15" rims on an for significantly less rotational inertia. In auto-X, the purpose behind the 15's with low profile tires is for lower center of gravity. A car on 15's compared to one on 17's, with the same tire profile, will be an inch closer to the ground, suspension aside. If you'd take the time to solve the applicable kinematics equations, you'd find that the overall effect of more rotational inertia on the car is insignificant, especially when other things are considered, such as handling, speedometer accuracy, and maintaining stock gearing.

Furthermore, drag cars use small rims to help facilitate sidewall deflection, which increases the contact patch at low speeds, and decreases it at high speeds, due to centripetal force of the rotating tire, effectually reducing drag. Bigger wheels simply to use bigger brakes for safety? Chutes do a lot more at high speeds than brakes could hope for....It's drag racing, not Auto-X!


You know what? All this is stupid anyway without some hard data. A 3hp loss on a roller dyno is well within the realm of error. I'd be very interested to see a reputable source that backs up your claims. Thanks for the response, though. You made me think a little.

Nick

I know that is why drag racers use smaller wheels, i was merely using an example. I also didnt read mr. white98ls' post before i posted......so if i repeated anything he said, my apologies.

when i spoke of 15" vs 17" wheels in an auto-x or road race situation i was referring to it in the sense that both wheel and tire combos would be the same circumfrence, which makes your point that they do it for lower center of gravity, dead.

Look, what I am saying is this......17 inch wheels vs 15" wheels will generally weigh more. The 17's have two things going against them...weight and the fact of their rotational mass. You want the weight of it to be closer to the hub so that it takes less energy to spin to the wheel since the weight isnt as far away. Its common knowledge. If you are trying to get into physics about it i'd be more than happy to but any physicist will tell you the same.

take two wheels...one 15" and one 17" both fitted with tires that make them equal out to be the same circumfrence, have them both be the same weight. Now, make both those wheels accelerate to a certain speed in the same amount of time. when at that speed the 17" wheel will be moving faster than the 15" wheel causing it to contain more kinetic energy. If it has more kinetic energy then it took more work to accelerate the 17" wheel to that speed than it did the 15" wheel. So, it takes more power to move the 17" wheel than it does the 15" wheel so the moment of inertia of the 17" is greater than the moment for the 15" wheel. The moment of inertia is directly proportional to its mass and it increases as the mass is moved further from the axis...in this case being the hub of the axle.

smaller and lighter wheels are better for acceleration. lighter wheels reduce unsprung weight which aid handling. for handling purposes, tire choice is what is important...not the diameter of your wheel. of course ridiculously large sidewalls will be bad...but the difference between 15" and 17" wheels isnt a big amount and finding 15" tires with very stiff sidewalls to help handling is easy, i have some...falken azenis.

[PupaScoopa]

For every one pound you take off of your cars rotating mass (wheels, brakes, drive shafts, flywheels, etc.) is equal to removing nine pounds of weight off your car. - Turbo Magazine

That depends on WHERE the mass is in the rotating part. That same mass has less impact in positive/negative acceleration inertia if it's closer to the axis than the outside.

I dont see many road-race or auto-x people choosing to run huge wheels either

I see these occasionally. I try to be a good sport, but it's tough to hold back the laugh when they're rubbin in the corners and running consistently slower (in more powerful vehicles) than I.

[Nikolai]

Originally posted by junglistgsr
when i spoke of 15" vs 17" wheels in an auto-x or road race situation i was referring to it in the sense that both wheel and tire combos would be the same circumfrence, which makes your point that they do it for lower center of gravity, dead.

Cool. Other than your "clarification" here, I think you're fundamentally right.


The Realtime Racing Integra Type R:

http://www.realtimerl.com/

uses a 17 x 7.5 inch SSR aluminum wheel, with Toyo 225/45ZR17 tires.

I guess the best combo would a be a lightweight, larger diameter rim with low-profile tires.

Nick

[White98LS]

I don't think I agree with the 1lb rotational mass = 9lbs. normal mass rule. It may apply in some instances, but it's definitely not exactly right, and can be way off in some situations. Say some guy is rollin' on 20" chrome wheels (not on an Integra hopefully) that weigh 45lbs. each, for a total of 180lbs (we're ignoring tires here for now, the 20" tires would probably weigh more anyway), and switches to 15" Volk TE-37s, which weigh 8.6 or 8.8 lbs each I think, or about 35lbs total. He's dropping 145lbs of rotating weight (nasty!!), which equates to 1305 lbs??? (9 x 145) In a 2610-lbs car, that's 50% of the weight effectively. I don't think the car is going to accelerate as if it weighed half as much as before.......