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Sykes
08-21-2002, 01:06 AM
How much does the weight of the wheel affect a car's performance?

Let's say a 17x7" wheel that weighs 15lbs vs a 17x7 wheel that weighs 22.5lbs.

I know it will affect it bit, but how much?

Thanks!

OMOYYC
08-21-2002, 01:14 AM
To add to that question. How much does 18" and 17" wheels differ in performance (Launch and accel)?

[GaGe]
08-21-2002, 01:16 AM
Originally posted by Cwave
To add to that question. How much does 18" and 17" wheels differ in performance (Launch and accel)?

I don't know too much about wheel sizes, but i can make a prediction:

Bigger wheels will be faster on the straight, but smaller wheels will be better for cornering.

I'm not sure about this though.

OMOYYC
08-21-2002, 01:26 AM
Actually, it would seem to me that the opposite would be true. :dunno:

It takes more momentum to move a wheel with more weight distributed on the outer edges. But because larger wheel means less sidewall, thus giving less tireroll for the corners.



Originally posted by [GaGe]


I don't know too much about wheel sizes, but i can make a prediction:

Bigger wheels will be faster on the straight, but smaller wheels will be better for cornering.

I'm not sure about this though.

kenny
08-21-2002, 01:32 AM
Originally posted by [GaGe]


I don't know too much about wheel sizes, but i can make a prediction:

Bigger wheels will be faster on the straight, but smaller wheels will be better for cornering.

I'm not sure about this though.

Bigger wheels = better cornering, provided you are using similar tires just as cwave said, less sidewall roll.

OMOYYC
08-21-2002, 01:35 AM
But what about on the 1/4mile? I wonder how much difference it is with 17"s vs 18"s

I'm almost tempted to leave my 17"s on until after friday :)

Has anyone tested?

jonny
08-21-2002, 01:37 AM
Originally posted by [GaGe]


I don't know too much about wheel sizes, but i can make a prediction:

Bigger wheels will be faster on the straight, but smaller wheels will be better for cornering.

I'm not sure about this though.

Its more the exact opposite really...I thought you were a car whiz kid! j/k

buh_buh
08-21-2002, 01:37 AM
big difference.
First time I drive with my 18's on, I almost stalled because I wasn't giving enough gas. I was too used to driving with my 16's which are much lighter and smaller.

OMOYYC
08-21-2002, 01:40 AM
Hmm... do you have very light-weight 16"s though? What I'm trying to do is compare same weight 17"s and 18"s. :dunno:

Let me PM Importz and see if he noticed a difference.


Originally posted by buh_buh
big difference.
First time I drive with my 18's on, I almost stalled because I wasn't giving enough gas. I was too used to driving with my 16's which are much lighter and smaller.

[GaGe]
08-21-2002, 01:42 AM
Originally posted by jonny


Its more the exact opposite really...I thought you were a car whiz kid! j/k

I just typed it the other way around.

OMOYYC
08-21-2002, 01:43 AM
Another thing, tread width. Did your 18"s have a much wider tread than your 16"s? That usually makes a huge impact also.


Originally posted by buh_buh
big difference.
First time I drive with my 18's on, I almost stalled because I wasn't giving enough gas. I was too used to driving with my 16's which are much lighter and smaller.

OMOYYC
08-21-2002, 01:44 AM
What kind of car are you driving? I think the amount of difference you'll notice is proportion to the amount of torque you have in your car.


Originally posted by Sykes
How much does the weight of the wheel affect a car's performance?

Let's say a 17x7" wheel that weighs 15lbs vs a 17x7 wheel that weighs 22.5lbs.

I know it will affect it bit, but how much?

Thanks!

4wheeldrift
08-21-2002, 07:05 AM
Bigger wheels (don't have to be heavier too but this is usually the case) have a parasitic effect on torque. Because bulk of the mass of the wheel and tire package is further from the center of rotation, it requires more energy to make the wheel spin the same speed. There's no hard and fast rule that I know of for figuring out how much difference an extra pound of wheel makes in the quarter or anything like that, but it can have quite a profound effect on torque limited vehicles.

Ekliptix
08-21-2002, 07:22 AM
Rotating mass is worth much more then regular mass when loosing weight on your car. Say you lose 20 pounds in the wheels themselves(all 4). That would be more equivilent to losing 60 lbs of dead weight in the car(numbers are very approximate).

Also, going to a bigger wheel/tire effectivlly changes the gear ratio to the ground. Smaller wheels/tires = short gear ratio. Big wheels/tires = tall gear ratio. So smaller wheels and tires should/would give you a better 1/4 mile time if they have the same tire compound and width.

I have a whole SCC article about this where they tested 1/4mi and lap times w/ different wheel sizes. I'll put it up later.

OMOYYC
08-21-2002, 08:08 AM
But typically when you increase wheel size, we compensate by putting lower profile tires so that the overall diameter is not affected.

Is that why the ITR comes with those 15" Wheels?


Originally posted by Ekliptix
Rotating mass is worth much more then regular mass when loosing weight on your car. Say you lose 20 pounds in the wheels themselves(all 4). That would be more equivilent to losing 60 lbs of dead weight in the car(numbers are very approximate).

Also, going to a bigger wheel/tire effectivlly changes the gear ratio to the ground. Smaller wheels/tires = short gear ratio. Big wheels/tires = tall gear ratio. So smaller wheels and tires should/would give you a better 1/4 mile time if they have the same tire compound and width.

I have a whole SCC article about this where they tested 1/4mi and lap times w/ different wheel sizes. I'll put it up later.

Voodoo Child
08-21-2002, 08:45 AM
Hey Cwave,
The ITR was specificaly given the 15" wheels not only because they handle quite well but they are also very light.
Most of the other ITR owners that I talk to wont even put anything bigger on their car than 16". Like Ekliptix said, weight is everything.
A good set of Spoon, Mugen or Volk rims will forsure help you out.

VC.

OMOYYC
08-21-2002, 08:48 AM
The weird thing though, is that AC Schnitzer wheels are quite heavy themselves (almost 30 lbs each). At the same time, they are HUGE a$$ expensive! Why would that be?

Redlyne_mr2
08-21-2002, 09:18 AM
I noticed a huge difference when I had my 17s on compared to my stock 14's..with the 14's the car launched hard but were scary at high speeds and didnt corner very well....the 17s hooked up nicely but didn't allow the car to launch like it did with the 14's. The 17s were a hell of alot better in the corners though and at top speeds

OMOYYC
08-21-2002, 09:20 AM
What car do you drive? Is it an MR2? What year? Turbo?


Originally posted by Redlyne_mr2
I noticed a huge difference when I had my 17s on compared to my stock 14's..with the 14's the car launched hard but were scary at high speeds and didnt corner very well....the 17s hooked up nicely but didn't allow the car to launch like it did with the 14's. The 17s were a hell of alot better in the corners though and at top speeds

Redlyne_mr2
08-21-2002, 09:24 AM
Originally posted by Cwave
What car do you drive? Is it an MR2? What year? Turbo?


ya 91 turbo

OMOYYC
08-21-2002, 09:27 AM
I s'pose 14" to 17" is a big difference. Did you have a big difference in Tread size?

Redlyne_mr2
08-21-2002, 09:34 AM
Originally posted by Cwave
I s'pose 14" to 17" is a big difference. Did you have a big difference in Tread size?
ya huge difference 225/40/17
compared to 195/65/14

OMOYYC
08-21-2002, 09:40 AM
I'm wondering if the tread size was more involved in the speed difference in acceleration?


Originally posted by Redlyne_mr2

ya huge difference 225/40/17
compared to 195/65/14

Redlyne_mr2
08-21-2002, 09:54 AM
Originally posted by Cwave
I'm wondering if the tread size was more involved in the speed difference in acceleration?


thats a very good question but shouldn't I have been getting better traction with the tires on the 17's...i know for a fact that the car is faster with the 14s on it.

dj_honda
08-21-2002, 10:20 AM
Originally posted by Cwave
But typically when you increase wheel size, we compensate by putting lower profile tires so that the overall diameter is not affected.



yes but once again, even tho diameter is the same, teh actual rotating mass is increased because there is more metal than tire in a bigger wheel, wheras in a smaller wheel there is more tire

just think of the top fuel dragsters, why are their wheels so small and their tires(slicks) so big?
simply put, smaller wheels = faster acceleration
bigger wheels= slower acceleration, better cornering

Tuner1
08-21-2002, 10:25 AM
A few points:

-There are lots of expensive wheels that aren't light (ACS,Z Zigen, Breyton, etc), but guess what.....they are strong! Try one of those Taiwanese 13lb wheels on a 3200lb car with 4 people it in going through a pot hole. Bang! I have even seen plenty of bent BIG $$$ wheels.

-The is NOT a perfect generic formula for calculating rotating weight vs. static weight on every car. I have heard everything for 1lb = 4lb to 1lb = 10lb. In reality it is probably closer to 1 =3 but it all depends on the wheel, tires, etc.

-The lighter the car, and the less torque it has the more it will be affected by heavy wheels.

-Overall diameter shouldn't change from 15"-17". If it does you have the wrong size tires!

Rob

OMOYYC
08-21-2002, 11:57 AM
However, traction is only essential for the initial wheel spin you get from acceleration. Once your tires get traction, the mass of the wheel + tire is your only barrier.

In your case, you would have better launch with your 17", but acceleration after the launch will be less than your 14".


Originally posted by Redlyne_mr2

thats a very good question but shouldn't I have been getting better traction with the tires on the 17's...i know for a fact that the car is faster with the 14s on it.

OMOYYC
08-21-2002, 12:04 PM
I agreed with you there. I was just commenting on someone's comment on the change of the gear ratio because of the overall diameter change :)


Originally posted by dj_honda


yes but once again, even tho diameter is the same, teh actual rotating mass is increased because there is more metal than tire in a bigger wheel, wheras in a smaller wheel there is more tire

just think of the top fuel dragsters, why are their wheels so small and their tires(slicks) so big?
simply put, smaller wheels = faster acceleration
bigger wheels= slower acceleration, better cornering

B18C
08-21-2002, 12:10 PM
Originally posted by 4wheeldrift
Bigger wheels (don't have to be heavier too but this is usually the case) have a parasitic effect on torque. Because bulk of the mass of the wheel and tire package is further from the center of rotation, it requires more energy to make the wheel spin the same speed. There's no hard and fast rule that I know of for figuring out how much difference an extra pound of wheel makes in the quarter or anything like that, but it can have quite a profound effect on torque limited vehicles.

Right on the head! Couldn't have said it better myself.

another thing is that if we are talking strictly about drag racing, I think the smaller diameter tire will suit you better. It will have more sidewall = more tire flex during launch, which is a good thing.

Now about tire diameter, it is a give and take thing. The wider your driving wheels are the more traction you get. But you also get more rolling resistance, which is a bad thing. It will affect your trapspeeds. so whether you want a wider tire or not depends on whether you think you need better launches or better top top-end.

4wheeldrift
08-21-2002, 12:10 PM
Originally posted by dj_honda


yes but once again, even tho diameter is the same, teh actual rotating mass is increased because there is more metal than tire in a bigger wheel, wheras in a smaller wheel there is more tire

just think of the top fuel dragsters, why are their wheels so small and their tires(slicks) so big?
simply put, smaller wheels = faster acceleration
bigger wheels= slower acceleration, better cornering

Its not that there is more metal, its where the mass is. You're moving more of the mass further from the center of the wheel, affecting inertia. it takes more energy to move something that is further from the center of rotation. Even if your wheel and tire package weighs the same as stock, you will still notice your acceleration performance is degraded by a larger wheel and tire combination.

dj_honda
08-21-2002, 01:28 PM
i agree with u

i just can't explain things properly

OMOYYC
08-21-2002, 01:42 PM
Now that we all seem to be in agreement, it would be very interesting to get some concrete numbers out of the scenario. I'd love to see the research results that come out, and I'm sure a lot of magazines would love to post an article on it as it shows that everyone has quite an interest in this topic.

The only problem is that we need several vehicles, and each vehicle has different size wheels and tires. Our controls are as follows:

1) Wheel diameter (variable)
2) Wheel weight (should be fixed if possible)
3) Tire diameter (should be fixed)
4) Tread width (variable)

Tuner1
08-21-2002, 02:31 PM
4wheeldrift wrote:


Originally posted by 4wheeldrift
Even if your wheel and tire package weighs the same as stock, you will still notice your acceleration performance is degraded by a larger wheel and tire combination.


Sorry but I can agree with you here. I won't argue that in theory *most* larger wheel tire packages would slow the acceleration, HOWEVER, there is no way that on an E46 M3, going from the stock 18's to 19's of the same diameter you will EVER "notice" a difference in "acceleration performance". No doubt on a 90hp Civic, going from 13's to 17's of the same weight, some might notice a bit of a difference but it is not nearly as pronounced as some would like to think. Let's not forget this isn't Drag Racers R Us....many of us change our wheels and tires to a larger size for an improvement in lateral grip!

Rob

T5_X
08-21-2002, 04:48 PM
Originally posted by 4wheeldrift

it takes more energy to move something that is further from the center of rotation.

Wouldn't bigger wheels also have an affect on stopping as well because of this fact. If it's harder to get moving, then once it is moving, it'll be carrying more momentum because the point of most mass is further away from the center, therefore, it'll be harder to brake because of this extra momentum. So while bigger wheels will be more stable around corners, you'd have to lay on the brakes earlier into the turn, so maybe the fact that youre slowing down earlier might negate the advantage of being more stable around the corners. :dunno:

OMOYYC
08-21-2002, 04:56 PM
That's why many people that increase their wheel sizes also upgrade their brakes.

4wheeldrift
08-21-2002, 05:16 PM
In terms of road racing, you're generally trading acceleration for better cornering ability, either due to stiffer sidewalls, or a larger contact patch from a wider tire, or both. You won't notice the missing power as much if you are exiting corners faster anyways :D

4wheeldrift
08-21-2002, 05:21 PM
Originally posted by E36S50B32
4wheeldrift wrote:




Sorry but I can agree with you here. I won't argue that in theory *most* larger wheel tire packages would slow the acceleration, HOWEVER, there is no way that on an E46 M3, going from the stock 18's to 19's of the same diameter you will EVER "notice" a difference in "acceleration performance". No doubt on a 90hp Civic, going from 13's to 17's of the same weight, some might notice a bit of a difference but it is not nearly as pronounced as some would like to think. Let's not forget this isn't Drag Racers R Us....many of us change our wheels and tires to a larger size for an improvement in lateral grip!

Rob

You're preachin' to the choir man :) It really does depend on wheel weight though. If you are going from the stock 18s to a 19 that is relatively close in weight you on a high power car you won't notice that much of a difference. If you go from a 15lb stock wheel to a 25lb wheel, you're gonna notice that (even if you only notice a little difference, it is there) unless you're putting out some simply stupid amounts of horsepower (I don't consider 330hp stupid amounts, merely...adequate :D)

For the rest of you;

In terms of road racing, you're generally trading acceleration for better cornering ability, either due to stiffer sidewalls, or a larger contact patch from a wider tire, or both. You won't notice the missing power as much if you are exiting corners faster anyways :D

Tuner1
08-21-2002, 07:24 PM
Hey 4wheeldrift,
my entire reply (see above) was in reference to your original quote:

"Even if your wheel and tire package weighs the same as stock, you will still notice your acceleration performance is degraded by a larger wheel and tire combination."

Yet, below in your latest post you are talking about adding 10lbs to each wheel. Of couse adding ~10lbs to the weight of each wheel will make a difference, but I still maintain that keeping the SAME weight wheel/tire package but going +1 or +2, it will be next to impossible to feel a difference in acceleration. Now, before all the bench racers come out of the woodwork, ask yourself....have you actually tired it? I have many times :)


Originally posted by 4wheeldrift
If you go from a 15lb stock wheel to a 25lb wheel, you're gonna notice that (even if you only notice a little difference, it is there) unless you're putting out some simply stupid amounts of horsepower (I don't consider 330hp stupid amounts, merely...adequate :D)



Happy motoring!
Rob

4wheeldrift
08-21-2002, 07:29 PM
Originally posted by E36S50B32
Hey 4wheeldrift,
my entire reply (see above) was in reference to your original quote:

"Even if your wheel and tire package weighs the same as stock, you will still notice your acceleration performance is degraded by a larger wheel and tire combination."

Yet, below in your latest post you are talking about adding 10lbs to each wheel. Of couse adding ~10lbs to the weight of each wheel will make a difference, but I still maintain that keeping the SAME weight wheel/tire package but going +1 or +2, it will be next to impossible to feel a difference in acceleration. Now, before all the bench racers come out of the woodwork, ask yourself....have you actually tired it? I have many times :)

Happy motoring!
Rob

As a matter of fact I have rob, and I notice a difference :) I notice a difference in acceleration with the same weight wheel and tire package (OZ Superleggeras and Kumho V700s, 17s vs 16s stock) between driving my car for solo 2 and road course and just driving on the street with my stock wheels. Course, on my 165hp subie its probably alot more noticeable than on a 300hp M3. All the extra lateral grip from the extra inch of sticky rubber and stiff sidewalls makes the trade off rather worth it :angel:

OMOYYC
08-21-2002, 10:37 PM
Are you using the same or different tread width? I still think that may have more of an impact on acceleration. :dunno:


Originally posted by 4wheeldrift


As a matter of fact I have rob, and I notice a difference :) I notice a difference in acceleration with the same weight wheel and tire package (OZ Superleggeras and Kumho V700s, 17s vs 16s stock) between driving my car for solo 2 and road course and just driving on the street with my stock wheels.

Hakkola
08-21-2002, 11:26 PM
Yeah, I'd expect 0-60 times to be worse with a bigger tire but 60 plus I'd expect to be better. I think this because because each rotation covers a bigger distance. Roll a tennis ball once, how far does it travel? Now roll a basketball once, it will travel further with the same rotation.

turkeysilk
08-21-2002, 11:32 PM
Originally posted by Hakkola
Yeah, I'd expect 0-60 times to be worse with a bigger tire but 60 plus I'd expect to be better. I think this because because each rotation covers a bigger distance. Roll a tennis ball once, how far does it travel? Now roll a basketball once, it will travel further with the same rotation.

I think you are sadly mistaken my good man, unless you are refering to the effect bigger wheels have on the speedometer. I suggest you read the thread over to further understand, as it has been explained more than a couple of times.

4wheeldrift
08-22-2002, 06:38 AM
Originally posted by Cwave
Are you using the same or different tread width? I still think that may have more of an impact on acceleration. :dunno:



I'm running a 225/45R17 R compound tire as opposed to the 205/55ZR16 street tires. The R compounds are my track/solo 2 only tires. They are MUCH grippier than my street tires. Tread width has more of an impact on cornering than on acceleration. There is greater rolling resistance to counter, but more of the decrease in acceleration is due to wheel mass instead of increased rolling resistance. You have to get REALLY wide compared to stock before the rolling resistance starts to make a big difference.

And hakkola, the only time that works is if the overall diameter of your wheel and tire package changes. A smaller than stock diameter results in lower overall gearing and slightly faster acceleration (assuming the same size and wieght of wheels and tire). Taller tires give you higher gearing, which gives you more top end but takes away acceleration.