Stretch and sidewall height

[Mike S]

Wow, now I'm confused.

See, in a thread I started I was told that I would have a lower profile if I was to go from my current 235/35 to a 215/35 and noticeably less rubber.

What they told you is correct. A 235/35 tire will have an 82.25 mm sidewall. A 215/35 will have a 75.25 mm sidewall.

This thread is about taking the same size tire and stretching it onto a wider wheel.

no dude
you are wrong

its MM difference, but you are wrong.
if you put a 205/40 on a 9 and a 10, the 10 will have a smaller outer diameter. i actually measured it a while back in an argument, and it was negligible, but there was a difference.

See, that's how I picture it in my head. I added a 10" wheel width to the illustration. Again, it's exaggerated, but this is what I believe is happening since the inner diameter is staying at 17".



I guess in my situation it doesn't matter. The wheels aren't wide enough for it to make a difference. I went ahead and bought 2 more tires in the 205/40 size. I'll have the 205/45's mounted on the 8" wheel and then have a 205/45 and a 205/40 mounted onto each of the 7" wheels and then compare.

[joga]

This is a 205/45/17 on an 8" wide wheel.
There is a slight stretch but nothing heavy. (Just what I wanted for my DD)

[Tuck&Poke]

no dude
you are wrong

its MM difference, but you are wrong.
if you put a 205/40 on a 9 and a 10, the 10 will have a smaller outer diameter. i actually measured it a while back in an argument, and it was negligible, but there was a difference.

i dont know how you measured that and considering the difference you measured is so small i cant agree with the validity of your claim. A tire is made of rubber, not exactly the most precise material in the world. Like i said, the circumference would have to change, and i cant imagine that changing more than a few millimeters or you'd have a warped ass tire. Even if you are indeed correct, is it anything near close for you to notice? No, so for all intensive purposes, no it doesn't change. I put a mounted 215/40 on an 8 next to my 215/40 on a 10 and i didnt register any difference. Am i gonna take a micrometer to it? No thanks.

[SeeClass]

Are you guys new here?

You need to run staggered tire sizes on staggered rims if you want the same stretch and diameter front and back.

If you want the same stretch front and back you'll need to run a 195/45/17 on the 7" rims and 215/45/17 on the 8" rims.

its MM difference, but you are wrong.
if you put a 205/40 on a 9 and a 10, the 10 will have a smaller outer diameter. i actually measured it a while back in an argument, and it was negligible, but there was a difference.

He's right, but it depends on the sidewall height and how soft the sidewall is and able to stretch. The more you stretch a tire the more it will pancake once you mount it on your car. Lets say I have a 225/40 on a 8" rim and a 225/40 on a 10" rim. The 10" rim will have a smaller diameter.

[Mike S]

Are you guys new here?

You need to run staggered tire sizes on staggered rims if you want the same stretch and diameter front and back.

If you want the same stretch front and back you'll need to run a 195/45/17 on the 7" rims and 215/45/17 on the 8" rims.

The only 195 width available in 17s in the Yokohama S drive's which run wide and a 215 on a 8" wide wheel won't show any stretch at all.

I already mounted the tires, so we're good.

[Han]

The more you stretch a tire the more it will pancake once you mount it on your car. Lets say I have a 225/40 on a 8" rim and a 225/40 on a 10" rim. The 10" rim will have a smaller diameter.

Did you even read what was directly quoted from Tire Rack? I'm sure they have no idea what they're talking about.

[aar0n.]

Did you even read what was directly quoted from Tire Rack? I'm sure they have no idea what they're talking about.

People have managed to convince themselves otherwise even though the physics behind it make it impossible for the sizes to change

[Tuck&Poke]

Are you guys new here?

You need to run staggered tire sizes on staggered rims if you want the same stretch and diameter front and back.

If you want the same stretch front and back you'll need to run a 195/45/17 on the 7" rims and 215/45/17 on the 8" rims.



He's right, but it depends on the sidewall height and how soft the sidewall is and able to stretch. The more you stretch a tire the more it will pancake once you mount it on your car. Lets say I have a 225/40 on a 8" rim and a 225/40 on a 10" rim. The 10" rim will have a smaller diameter.

is this guy fucking serious?

[Han]

People have managed to convince themselves otherwise even though the physics behind it make it impossible for the sizes to change

Okay, I understand it may LOOK taller when stretched, but the actual material is not being stretched or changed in dimensions. All a tire is doing when "stretched" is moving the mounting point of the beads from one position to another. The material is constant.

Oh, I even wrote in that link I posted that the section width (NOT DIAMETER OR HEIGHT) changes when being stretched due to how the section width is measured.

[Tuck&Poke]

the sidewall is basically unrolling