21" OEM vs. 19" OEM -Why?

[GeeVee7T]

Hey Team. OK so here's the sitch: 2024 GV70 comes with 21" non-waffle rims, apparently 44lb each (off the web, I didn't weigh them). As we know, 19" rims were previously standard. I put 34lb x 19" aftermarket rims on for winter.

I've tried to understand "rotational mass" / moment of inertia / centrifugal force in Newtons and lbft... and I'll be honest, I still don't really get it. I'm seeing numbers like 17% more centrifugal force to 1:4lb or even 1:10lb for sprung vs. Unsprung weight independent of the diameter of the tire (which affects centrifugal force)... blablblaaaablabla...

OK, so enough nerd-speak - what I get from all that is:

• Lighter is better (unsprung weight)
• Smaller is better (rotational forces)
• "Better" affects: Performance (less force required to rotate/accelerate or slow down), Handling (less force required to turn off-axis and stop, i.e. less steering and brake input required -think "gyroscope"), Traction (less unsprung weight is less effort for suspension to keep wheel on the road), Comfort (less spinning force causing wheel to lift or bounce), Mileage (less unsprung weight and force to rotate - although *once spinning* heavier is better, coincidentally, think: long distance highway runs).
• Price & Availability - 19" rims (235x55-19x8.5) AND rubber can be DRAMATICALLY less expensive and far more prolific in options and availability than 21" (255x40-21x9)

However, in favour of 21" rims we have:

• May look cooler... lol.

Which brings me to my conundrum and question and reason for posting:
Do I keep my heavy, unused 21" OEM 2024 GV70 non-waffle wheels or try to sell them to subsidize a 19" aftermarket option in the Spring?

More simply put, other than "looks cool," why are so many of us routinely chasing larger diameter rims? I get it - they can look "way gooder..." but is it worth it?

 

[EdP]

OK, so enough nerd-speak - what I get from all that is:

• Lighter is better (unsprung weight)
• Smaller is better (rotational forces)

However, in favour of 21" rims we have:

• May look cooler... lol.

More simply put, other than "looks cool," why are so many of us routinely chasing larger diameter rims? I get it - they can look "way gooder..." but is it worth it?

If smaller is better, I should have kept the 13" wheels from my Corvair.

I've seen arguments for both, but IMO, larger is mostly style. Same with low profile tires that are more likely to allow wheel damage from a pothole.
Worth it? Only you can decide. Take a good look after you've driven both for some comparison under your conditions. .

 

[joegr]

...

• Smaller is better (rotational forces...

But, is it smaller? Isn't the actual diameter of the wheel (rim + tire) the same for the 19" as the 21"? (The tire for the 19" having 1" more of sidewall.)

 

[dhuhtala]

Yes, same diameter.

 

[GeeVee7T]

But, is it smaller? Isn't the actual diameter of the wheel (rim + tire) the same for the 19" as the 21"? (The tire for the 19" having 1" more of sidewall.)

True. I meant smaller rim due to weight and rotational forces, not counting the tire, which I should.

Basically if you had two rims+tires of identical weight but different diameter, the larger diameter wheel would create and require larger rotational force - I.e. more horsepower.

It's just all so baffling- bigger rims look nice but physics says they're worse in almost every way.

 

[luck11]

Hey Team. OK so here's the sitch: 2024 GV70 comes with 21" non-waffle rims, apparently 44lb each (off the web, I didn't weigh them). As we know, 19" rims were previously standard. I put 34lb x 19" aftermarket rims on for winter.

I've tried to understand "rotational mass" / moment of inertia / centrifugal force in Newtons and lbft... and I'll be honest, I still don't really get it. I'm seeing numbers like 17% more centrifugal force to 1:4lb or even 1:10lb for sprung vs. Unsprung weight independent of the diameter of the tire (which affects centrifugal force)... blablblaaaablabla...

OK, so enough nerd-speak - what I get from all that is:

• Lighter is better (unsprung weight)
• Smaller is better (rotational forces)
• "Better" affects: Performance (less force required to rotate/accelerate or slow down), Handling (less force required to turn off-axis and stop, i.e. less steering and brake input required -think "gyroscope"), Traction (less unsprung weight is less effort for suspension to keep wheel on the road), Comfort (less spinning force causing wheel to lift or bounce), Mileage (less unsprung weight and force to rotate - although *once spinning* heavier is better, coincidentally, think: long distance highway runs).
• Price & Availability - 19" rims (235x55-19x8.5) AND rubber can be DRAMATICALLY less expensive and far more prolific in options and availability than 21" (255x40-21x9)

However, in favour of 21" rims we have:

• May look cooler... lol.

Which brings me to my conundrum and question and reason for posting:
Do I keep my heavy, unused 21" OEM 2024 GV70 non-waffle wheels or try to sell them to subsidize a 19" aftermarket option in the Spring?

More simply put, other than "looks cool," why are so many of us routinely chasing larger diameter rims? I get it - they can look "way gooder..." but is it worth it?

Yep, looks better to many. Many purchase a vehicle not only for what it does, but for how it looks. Why would it be different for wheels, which make up a significant component of overall aesthetics of a vehicle? Ultimately, its all personal preference.

I have my own preferences of proportion of wheel to rubber. The 19", IMHO, are too small....too much tire sidewall. In my opinion, kinda dorky. The 21" has a more aggressive appearance while having a good proportion of wheel to rubber. I am quite finicky when it comes to this. Many have gone 22 or even bigger, and yeah, that is simply too much of an elastic band of a tire for my taste. Also, found the 19" too floaty whereas with my 21", my GV feels more planted.

My stock 19" are now my winter set. I don't care much because the vehicle is usually full of salt and crud all winter anyways. I acquired aftermarket 21" flow forged wheels (strong) that are less than 20lbs each, which I suspect is much lighter than stock. I also upsized to 265/40/21 and there are a plethora of tire options at much more reasonable prices than the stock 255 series.

 

[Husky]

Hey Team. OK so here's the sitch: 2024 GV70 comes with 21" non-waffle rims, apparently 44lb each (off the web, I didn't weigh them). As we know, 19" rims were previously standard. I put 34lb x 19" aftermarket rims on for winter.

I've tried to understand "rotational mass" / moment of inertia / centrifugal force in Newtons and lbft... and I'll be honest, I still don't really get it. I'm seeing numbers like 17% more centrifugal force to 1:4lb or even 1:10lb for sprung vs. Unsprung weight independent of the diameter of the tire (which affects centrifugal force)... blablblaaaablabla...

OK, so enough nerd-speak - what I get from all that is:

• Lighter is better (unsprung weight)
• Smaller is better (rotational forces)
• "Better" affects: Performance (less force required to rotate/accelerate or slow down), Handling (less force required to turn off-axis and stop, i.e. less steering and brake input required -think "gyroscope"), Traction (less unsprung weight is less effort for suspension to keep wheel on the road), Comfort (less spinning force causing wheel to lift or bounce), Mileage (less unsprung weight and force to rotate - although *once spinning* heavier is better, coincidentally, think: long distance highway runs).
• Price & Availability - 19" rims (235x55-19x8.5) AND rubber can be DRAMATICALLY less expensive and far more prolific in options and availability than 21" (255x40-21x9)

However, in favour of 21" rims we have:

• May look cooler... lol.

Which brings me to my conundrum and question and reason for posting:
Do I keep my heavy, unused 21" OEM 2024 GV70 non-waffle wheels or try to sell them to subsidize a 19" aftermarket option in the Spring?

More simply put, other than "looks cool," why are so many of us routinely chasing larger diameter rims? I get it - they can look "way gooder..." but is it worth it?

In a word, NO. It's purely for looks.

 

[EdP]

The 19", IMHO, are too small....too much tire sidewall. In my opinion, kinda dorky.

Nailed it ! ! !

 

[GeeVee7T]

Hahaha - "kinda dorky." Lol.

Physics Prof: "Why did you not use 19" wheels which are better, according to the laws of physics, in every way?"
Drivers: "uh... cause they're kinda dorky."

I love it.

 

[joegr]

I know a lot of people that are form over function, but I have always been firmly in the function over form camp.

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[luck11]

Lol, everything has a balance. Having 19" wheels on such an awesome vehicle, its a shame, but thats my opinion. I am a relaxed driver that puts max of 5k kms per yr. So calculating all these factors to realize nothing of significance on all those elements you mention, is a waste of time for me to even consider. My preference is a more aggressive appearance. And yes, personal preference, just like many things.

Plus, my aftermarket 21" wheels are under 20lbs if you want to get into it. Oh, and i upsized to 265/40/21...plethora of much less expensive but atill good quality tires.

If i wanted strictly "function" over form for my purposes, i would not have bought this vehicle at all.

Diff strokes for diff folks.

 

[GeeVee7T]

An anecdotal nod to the physics of larger wheels:

On (this) page reviewing the eGV70 and Lexus RZ450e:
"(range is) 220 for the RZ 450e with smaller wheels, or 196 for the RZ 450e with larger wheels"

Smaller = 18" = 56.55" circumference
Larger = 20" = 62.83" circumference
Difference = 11% more circumference
(Notwithstanding the overall dimensions may be similar - i.e. more rim, less tire)

Range = 220mi vs 196mi = ~ 11% fewer miles!

Probably coincidental, but wild that the percentage circumference increase is the same as the percentage mileage range decrease. Wild.

So... there we have it. The physics of larger wheels requiring more energy to turn. Says nothing about them looking better, I agree, and usually they do - just... also more costly.

We humans are a funny breed.

 

[Quad]

I could care less about fuel mileage, if I did then a GV70 would not be my vehicle choice. The 21s look much better and it's not even close. 19s are way too small for this vehicle and 20s should be standard.

 

[AirbusGuy]

luck11,

What aftermarket wheels did you purchase?

Thanks!!

 

[GeeVee7T]

luck11,

What aftermarket wheels did you purchase?

Thanks!!

Went with Ruffino Inception 19x8.
edit: oops you weren't asking me...

 

[steveinarizona]

Comparison:

https://www.jdpower.com/cars/shopping-guides/what-difference-does-the-wheel-size-make

"

Summary ​

Everything has pros and cons, and larger wheels are no different. To help you decide better, we will take a quick look at the pros and cons in case you have an upgrade in mind.

The cons of larger wheels on your vehicle are poor fuel economy, impact on acceleration, speedometer errors, and faster wear and tear. The more power the engine needs, the more fuel it burns and the more you’ll need to spend on gas. Larger wheels make the steering hard and the acceleration slow. There are also some issues with the speedometer when the modifications are done because the car’s system is calibrated according to the standard components of the car and making modifications to the car makes the system malfunction. The more significant impact is that the car's safety system might not respond accurately and timely.

Some advantages of larger wheels include traction, better cornering and braking, and better aesthetics. Larger wheels offer better traction, and because they have more rubber on the tire, this also means a better grip on the road. Larger tires are better for car cornering and handling than your regular tires. They also reduce the braking distance and improve braking overall, adding to safety."