Automotive theory: tire sizes (how is this decided?)

[brianl703]

That's the modern equivalent to the Marlboro Man.

Only one thing missing; orange www.bullsballs.com on the trailer hitch.

Those things used to be known as Brodozers.

 

[y_p_w]

The cars are heavier now and have much larger brakes. You can fit 18" on the new Type R but the brakes are way larger than the ITR.

Sure, but they go 20" for the appearance.

 

[y_p_w]

Wider tyres than necessary result in worse fuel economy and larger diameter rims than necessary result in a more uncomfortable ride plus increased susceptibility to wheel/suspension damage. When the above is being applied to ordinary everyday cars rather than sports cars then it has to 95% marketing.

You can say the same about suspension settings. I've been a passenger in a car with suspension so hard it defied belief. It was so bad the driver actually had to slow down which rather defeated the point of a car with a sporty image. Have buyers asked for cars this bad or is it the designers producing cars they think we should have ?

I don't get the modded cars with massive amounts of camber where they stick out of the wheel well. Some look like the tires from the Back to the Future DeLorean as it hovers and is retracting its wheels.

 

[brianl703]

I don't get the modded cars with massive amounts of camber where they stick out of the wheel well.

I don't think I've ever seen the same one twice. They must have a really short half-life.

 

[eljefino]

Cars have to be taller in the front grille/ fender area for pedestrian safety. This looks stupid with small tires. Sadly, ironically, it's harder to see toddlers standing in front.

 

[Ken_K]

Increasing tire circumference creates more contact with the road compared to widening. Benefits are a compliant ride and enhanced straight line traction. Cornering grip can be enhanced by stiffening the sidewalls, which low-profile tires offer. For passenger vehicles, taller tires with low profile sidewalls (requiring larger wheels) is the perfect balance.

 

[mco30mco]

I pine for the days of 15" rims and bigger sidewalls.

Those days will never return due to the larger brakes. Stopping distances are much better now. Traction is better too.

 

[Blueshound]

Those days will never return due to the larger brakes. Stopping distances are much better now. Traction is better too.

True. On my truck the minimum rim size is 18" to fit over the rear brake disks. It came with 20s but I'm not sure a 10% diameter reduction would make much difference. It goes, steers, and stops just fine.

 

[JohnnyG]

I can say that larger rear tires DO NOT increase understeer...

My C5 has much wider tires on the rear...during AutoX, understeer is RARELY a problem.

Considering the fact that most everyone agrees on that wider tires will provide more grip, my statement is correct.
Understeer is the tendency for the front end to push in a curve, while if the rear end gets loose, that's called oversteer.
Your C5, if equipped with OE tire sizes, would be designed to give you the handling you are getting. And almost all people prefer oversteer on a track.
The only way you can tell the difference is if you change the rear tire size on your own, THEN you can make a comparison.

 

[y_p_w]

Increasing tire circumference creates more contact with the road compared to widening. Benefits are a compliant ride and enhanced straight line traction. Cornering grip can be enhanced by stiffening the sidewalls, which low-profile tires offer. For passenger vehicles, taller tires with low profile sidewalls (requiring larger wheels) is the perfect balance.

It increases unsprung weight and makes tire blowouts easier. Everything is a balance though. It's pretty obvious that the current penchant for massive wheels has gone well beyond any performance advantages and is more about the appearance.

 

[Triple3 in Mo.]

Maybe I’m boring but I’m the opposite LOL

Same here. I want a 17 inch rim, or under. Hate low profile tires.

 

[Triple3 in Mo.]

My Geo Metro had 12" rims from the factory lol, I had to "upgrade" to the massive 13" wheels to find any tires 😂

Lol!

 

[dumkid]

the way modern cars are i would say looks are the biggest reason for tire size. imo on a fast car, handling should be the main focus for tire sizes, and on slow cars, trucks, and SUVs suspension and noise should be the main focus. i like little rims with bigger tires. on an offroad vehicle you want sidewall so you can air down the tire and get more contact patch. low pro mud tires are the most idiotic thing I've ever seen. loud, ride rough, and no sidewall to flex around rocks and stuff. if i was going to put big rims and small tires on anything it would be a slammed el camino with baby blue paint.