22's and acceleration

[ULTRAZLS1]

Finding some mixed opinions on search etc.

If a given 22 inch wheel/tire is a couple pounds lighter than the stock 20 inch wheel and tire while also having the same tire height, (315/25/22 is actually a bit shorter for a tad better gearing) how could this possibly hurt acceleration?

same height )slightly shorter), less weight...not understanding I guess.

I could see a wider tire causing more friction against the road because of more surface area...but I would think the weight would make up for such a small detail/it would be barely noticeable. and this would apply to any rim and tire combo that is wider and not just on a 22.

anyone have a solid educated answer?

anyone installed lightweight 22 inch rim/tire options and have a SOTP difference or maybe even tested it out?

I am debating 22's...but will not do it if it is going to be costly in the accel department.

thanks, Troy

[Nine Ball]

Originally Posted by ULTRAZLS1

anyone have a solid educated answer?

Yes.

I'm a mechanical engineer, so I can explain this perfectly for you.

It isn't simply about total static weight. While that may be a factor, it is more about Moment Of Inertia. MOI is dependent on that static weight, but also the relative distance from the center of the wheel, to the location where most of that weight is. The further from the center that the weight is situated on a spinning object, the more effort it takes to spin or accelerate the object.

Generally, a 22" wheel will have a greater distance from center where its weight is situated, compared with a 20" wheel. Even if both wheels weigh exactly the same amount, it is likely the 22" wheel will take more effort to accelerate (and decelerate).

Think of a figure skater on ice. When they have their leg sticking out, they turn very slowly. When they bring their leg in closer, and stand straight up, they spin very fast. Even though both cases, the weigh the same amount.

The best performance will be found with lower diameter wheels, which have more of their weight centered around the hub area, not the outer lip area. The worst performance wheels will usually be the heavier cast aluminum wheels, since they have thicker hoops than a forged wheel does. Cast wheels also have thicker spokes, since their material cannot handle the stresses as well as a forged wheel does. This is the main reason that forged wheels are better for performance.

Hope that helps

Tony

[rolnslo]

Originally Posted by Nine Ball

Yes.

I'm a mechanical engineer, so I can explain this perfectly for you.

It isn't simply about total static weight. While that may be a factor, it is more about Moment Of Inertia. MOI is dependent on that static weight, but also the relative distance from the center of the wheel, to the location where most of that weight is. The further from the center that the weight is situated on a spinning object, the more effort it takes to spin or accelerate the object.

Generally, a 22" wheel will have a greater distance from center where its weight is situated, compared with a 20" wheel. Even if both wheels weigh exactly the same amount, it is likely the 22" wheel will take more effort to accelerate (and decelerate).

Think of a figure skater on ice. When they have their leg sticking out, they turn very slowly. When they bring their leg in closer, and stand straight up, they spin very fast. Even though both cases, the weigh the same amount.

The best performance will be found with lower diameter wheels, which have more of their weight centered around the hub area, not the outer lip area. The worst performance wheels will usually be the heavier cast aluminum wheels, since they have thicker hoops than a forged wheel does. Cast wheels also have thicker spokes, since their material cannot handle the stresses as well as a forged wheel does. This is the main reason that forged wheels are better for performance.

Hope that helps

Tony

Showoff!


I was digging deep into my brain to remember the correct terminology from college physics but kept coming up with "Law of conservation of angular momentum". MOI is what I was looking for.

[ULTRAZLS1]

Originally Posted by Nine Ball

Yes.

I'm a mechanical engineer, so I can explain this perfectly for you.

It isn't simply about total static weight. While that may be a factor, it is more about Moment Of Inertia. MOI is dependent on that static weight, but also the relative distance from the center of the wheel, to the location where most of that weight is. The further from the center that the weight is situated on a spinning object, the more effort it takes to spin or accelerate the object.

Generally, a 22" wheel will have a greater distance from center where its weight is situated, compared with a 20" wheel. Even if both wheels weigh exactly the same amount, it is likely the 22" wheel will take more effort to accelerate (and decelerate).

Think of a figure skater on ice. When they have their leg sticking out, they turn very slowly. When they bring their leg in closer, and stand straight up, they spin very fast. Even though both cases, the weigh the same amount.

The best performance will be found with lower diameter wheels, which have more of their weight centered around the hub area, not the outer lip area. The worst performance wheels will usually be the heavier cast aluminum wheels, since they have thicker hoops than a forged wheel does. Cast wheels also have thicker spokes, since their material cannot handle the stresses as well as a forged wheel does. This is the main reason that forged wheels are better for performance.

Hope that helps

Tony

I was thinking/came up with something similar to that in my head but did not think it would matter a whole lot because the rim is actually lighter than the tires. But now that I think about it most of the weight of the rim is at the outsdie and very far from center.

The weight of a 275/45/20 pirelli pzero is 36 lbs. The pzero nero in 315/25/22 is 33 lbs. The stock 20 inch wheel will have some extra weight away from the center (the furthest point) that the 22 inch wheel does not.

Given most of the weight of the rim is at the outside, I see what you are saying...but wouldnt the lighter tires offset this somewhat? And given the 22's are a few pounds lighter yet...how much more would this offset the moment of inertia?

Damnit I want 22's...I wish I knew for sure how much it mattered in this type of situation. If it was only a tenth or two I could probably live with it.

You could probably formulate a complex equation using the different distances from center and the weight of the tires/rims and the weight distribution of the different rims and figure it out if you are bored LOL.

[Nine Ball]

Tire weight is mostly in the tread, due to the steel belting. So, they sort of wash each other out if their outer diameter and widths are the same. The sidewalls have very little weight in them compared to the tread/belted area.

Honestly, it isn't a huge amount of performance difference if we are comparing identical wheels in just different sizing. I'd estimate 1-2 tenths at the dragstrip, if you could hook on either. If the car is mostly your weekend hotrod or showcar, go with 22s. If you are the type that wants to squeeze every ounce of performance out, simply get a set of dedicated track wheels/tires for those occasional visits.

[MAYRO35]

wld spacers for stock 20's have a decrease in acceleration?

[PQ]

Originally Posted by Nine Ball

Yes.

I'm a mechanical engineer, so I can explain this perfectly for you.

It isn't simply about total static weight. While that may be a factor, it is more about Moment Of Inertia. MOI is dependent on that static weight, but also the relative distance from the center of the wheel, to the location where most of that weight is. The further from the center that the weight is situated on a spinning object, the more effort it takes to spin or accelerate the object.

Generally, a 22" wheel will have a greater distance from center where its weight is situated, compared with a 20" wheel. Even if both wheels weigh exactly the same amount, it is likely the 22" wheel will take more effort to accelerate (and decelerate).

Think of a figure skater on ice. When they have their leg sticking out, they turn very slowly. When they bring their leg in closer, and stand straight up, they spin very fast. Even though both cases, the weigh the same amount.

The best performance will be found with lower diameter wheels, which have more of their weight centered around the hub area, not the outer lip area. The worst performance wheels will usually be the heavier cast aluminum wheels, since they have thicker hoops than a forged wheel does. Cast wheels also have thicker spokes, since their material cannot handle the stresses as well as a forged wheel does. This is the main reason that forged wheels are better for performance.

Hope that helps

Tony

Originally Posted by rolnslo

Showoff!


I was digging deep into my brain to remember the correct terminology from college physics but kept coming up with "Law of conservation of angular momentum". MOI is what I was looking for.

Nerds. lol

Originally Posted by Nine Ball

Tire weight is mostly in the tread, due to the steel belting. So, they sort of wash each other out if their outer diameter and widths are the same. The sidewalls have very little weight in them compared to the tread/belted area.

Honestly, it isn't a huge amount of performance difference if we are comparing identical wheels in just different sizing. I'd estimate 1-2 tenths at the dragstrip, if you could hook on either. If the car is mostly your weekend hotrod or showcar, go with 22s. If you are the type that wants to squeeze every ounce of performance out, simply get a set of dedicated track wheels/tires for those occasional visits.

I'd say .2 is acurate. I lost over a tenth going from 21s to 22s. My 22s are wider as you know, but still.

[Darth_Emma]

I know what Nine Ball says as far as physics go is correct. But, isn't it also true that on a smaller rim, the sidewall of the tire is thicker to make a wheel diameter that is the equivalent of a larger rimmed wheel. I would think the thicker sidewall on the smaller diameter rim (say 18" rim) would give a bit more and, therefore, produce more traction, whereas a wheel with less sidewall (on say a 22" rim) would not flex as much which would not allow the tire to grab the road as well.

[Dr Jkel]

Put enough HP behind it , won't matter, LOL

[Dangeruss]

Originally Posted by Dr Jkel

Put enough HP behind it , won't matter, LOL

That was my answer!

[Dr Jkel]

Originally Posted by Dangeruss

That was my answer!

Yeah we noticed, now I'm scared. You car just sounds sick, I can only imagine how it runs.

[Hendrix-Engineering]

On my 2003 harley suppercrew I switched out my stock 20 inch harley wheels to the aftermarket 22s with the same desighn,they were a lil lighter and picked up a tenth over my best pass with the 20s and this was my first run on the 22s...I have the 22 rep wheels on my 2010 sixspeed with 490 rwhp.i never ran the car with the 20s but my first time at the track with the 22s i cut a 1.88 sixty and a 1.91 sixty and ran a 12.05 and a 12.09....

[ULTRAZLS1]

I know it seems like a small amount.

But...I have a friend with a modded ls1 4th gen that I can literally just barely edge out by a car or two every time we run. If I go 22's I bet I will lose...it is that close LOL.

It is a tough call...some of the rims I want look AMAZING in 22 inch format and I am just scared I will be disappointed if I get them in 20's....but then 20 inch forged will definitely get some extra performance.....

[600hp-lpe]

When I went from the stock 20's to a 19X10 on all 4 corners, I lost 47 lbs in weight off the tires..

My 18" set for the track lost even more weight (I forget how much more). I think it was another 20 lbs from the 19's, but the tires were MUCH wider. (315 on the front, 335 on the rear).

Both sets are a dramatic difference from stock as the diameter is smaller.

Stock diameter is 28.2"
19" diameter measured at 26.8" (11.4 wide)
18" diameter measured at 25.6" (13.2 wide)

Your first ride on a 19" from the 20's and you would not believe you are driving the same car.. it's faster, turn in is quicker, and stops better.

Tire preference is different for everyone.