Thinking about going back to 19 inch wheels.. 20’s suck

[\dave]

I've been looking aft upgrading my 2019 ecoboost brakes and wheels. What I really am after is more rubber for spirited driving on curvy country roads than the 235/50-18 P Zero Neros provide. My initial goal was to achieve 255/40-19 like the eco PP using a 19x9 wheel. But I have changed my mind for numerous reasons, one of which is that pesky physics stuff.

The equation for angular acceleration is: Angular Acceleration = (2 x Torque) / (Mass x R2). R2 is meant to represent "Radius Squared". So, you can see that adding mass or increasing radius decreases angular acceleration.

Using the above equation, I roughly guestimated that if I switched from my stock 18x8 wheels to the 19x9 I would like, the 19x9 tire+wheel set up would need to be about 2.5 pounds less than my 18's.

As a side bar, I saw the following video where the guy shows a 5% lossoa

My 18-8 wheels weigh 24.5 pounds, which I think is a fair sweet spot for spirited driving with pot holes.

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[\dave]

I hate touch screens. I inadvertently posted before being finished - here's the rest of my post:

As a side bar, I saw the following video where the guy shows a 5% loss on a dyno due to wheels. What isn't accounted for is that the front wheels suck up energy too, so the loss is really about 10%:


My 18-8 wheels weigh 24.5 pounds, which I think is a fair sweet spot for spirited driving with pot holes. But, I want to add some traction/handling with the tires.

I'm pretty set on replacing the Nero's with Pilot Sport A/S +3. The Pilot Sports have better traction ratings, etc., etc. What do you guys think of going from the 235/50 to 245/45 or 255/40? Here are some of my tire considerations:
- The 245/45 adds 0.2" of tread width and reduces sidewall height about 8mm, both of which are positives (downsides might be a smallish looking set-up and about a 2% affect on the speedo).
- I would prefer the 255/40 which adds 0.7" of tread width and reduces sidewall height about 3mm. My big concern with the 255/40 is the cross section width would increase from 9.3" to 10". I'm concerned this might cause some roll in the sidewall (squirm) when turning or on curves. A Tire Rack guy confirmed with me that the added cross section does result in this effect. But how much?

Have any of you guys put a 255/40 on an 18x8 or done a similar thing with another size rim?

Thanks

 

[Fly2High]

I think we all agree that a 3.53 rear end is slower than the same car on a 3.73 rear.

That being true, increasing tire diameter is just like reducing the final drive ratio (3.73 -> 3.53). One benefit is that you can attain a particular speed at a lower rpm but at the cost of acceleration. You also increase top end speed with larger diameter, if you can turn them fast enough.

Putting larger wheels on a car, even if you keep the same diameter, will increase the moment of inertia making it harder to rotate the wheels. That holds both for acceleration or deceleration. You are redistributing the mass farther from the center. Think how a spinning figure skater can speed up rotation by moving their arms inward and slow by moving their arms outward.

Finally, adding more mass will also increase the moment of inertia doing the same. Harder to turn a heavier object.

 

[10SpeedDemon]

I hate touch screens. I inadvertently posted before being finished - here's the rest of my post:

As a side bar, I saw the following video where the guy shows a 5% loss on a dyno due to wheels. What isn't accounted for is that the front wheels suck up energy too, so the loss is really about 10%:


My 18-8 wheels weigh 24.5 pounds, which I think is a fair sweet spot for spirited driving with pot holes. But, I want to add some traction/handling with the tires.

I'm pretty set on replacing the Nero's with Pilot Sport A/S +3. The Pilot Sports have better traction ratings, etc., etc. What do you guys think of going from the 235/50 to 245/45 or 255/40? Here are some of my tire considerations:
- The 245/45 adds 0.2" of tread width and reduces sidewall height about 8mm, both of which are positives (downsides might be a smallish looking set-up and about a 2% affect on the speedo).
- I would prefer the 255/40 which adds 0.7" of tread width and reduces sidewall height about 3mm. My big concern with the 255/40 is the cross section width would increase from 9.3" to 10". I'm concerned this might cause some roll in the sidewall (squirm) when turning or on curves. A Tire Rack guy confirmed with me that the added cross section does result in this effect. But how much?

Have any of you guys put a 255/40 on an 18x8 or done a similar thing with another size rim?

Thanks

wow this explains why I only made 478whp and my friend with the same mods made 490whp.. yeaaa I think im just going to go back to 19's

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