Topic: Same tire on slightly wider wheels? How does that even work?

[aadesh37]

I know this is going to sound like a super dumb question to people who really know wheel fitment, but bear with me please because I am just not grasping this.

I'm shopping around for a second wheel set for my not-yet-in-my-driveway 2020 Levorg. OEM on this car is 225/45R18, rims are 18x7.5 with an offset (they call it inset here!) of 55.

The fenders are pretty tight on the Levorg and I don't want to inch up or down, but I was thinking...maybe go just a little wider? And sure enough, on a couple of the wheel shopping sites I have checked out, they are offering 18x7.5 or 18x8 options.

But the thing I can't wrap my brain around is that the tire size for both is the same. So I was looking at some of the tire manufacturer's pages and sure enough there is a pretty serious width range for tires, like up to two inches.

So how does that actually work? I don't work with tires so I can't understand how, if you put the tire on a wider rim, it doesn't flatten it out and reduce overall diameter. But all of the calculator sites I am looking at show that the rotational stuff is all the same.

Also is there any disadvantage to putting the same size tire on a slightly wider rim like this?

Thank you smarter people.

[capriracer]

First, think of the sidewalls as legs on a table.  You can tilt the legs in a little or tilt the legs out a little, and it will still work.  The operative word here is "little".

Within the range specified, the performance differences are minimal.  Outside that range is where there be dragons!

Too wide and the tread dearches, so it rides on the tread shoulders, wearing those faster than the center and making the car unstable.

Too narrow and the tread arches and rides in the center, making the tire wear more in the center and causes the vehicle to be sensitive to crosswinds and ruts in the road.

[Angry Chicken]

First, think of the sidewalls as legs on a table.  You can tilt the legs in a little or tilt the legs out a little, and it will still work.  The operative word here is "little".

Within the range specified, the performance differences are minimal.  Outside that range is where there be dragons!

Too wide and the tread dearches, so it rides on the tread shoulders, wearing those faster than the center and making the car unstable.

Too narrow and the tread arches and rides in the center, making the tire wear more in the center and causes the vehicle to be sensitive to crosswinds and ruts in the road.

Probably the best explanation I've heard.

[HeliDriver]

^^ Yeah, but too bad about the typo - it should be stretches. (Or maybe arches?) (Okay, read it a third time! Looks like he did mean de-arches. Is that a word?    )

And pictures are worth a thousand words. Rubber sidewalls do have lots of stretch; table legs, not so much.



Can't get the same viewpoint with a narrower rim, but this is pretty good:



The range of rim widths "works" because the sidewall is free to flex in and out.

[EV Dan]

Who else in Canada has got a Levorg in the driveway? 

[redmont]

^^ Yeah, but too bad about the typo - it should be stretches. (Or maybe arches?) (Okay, read it a third time! Looks like he did mean de-arches. Is that a word?    )

And pictures are worth a thousand words. Rubber sidewalls do have lots of stretch; table legs, not so much.



Can't get the same viewpoint with a narrower rim, but this is pretty good:



The range of rim widths "works" because the sidewall is free to flex in and out.

Stretching tires can increase the risk of sidewall blow out, so it is better to get tires with the appropriate width. That is what I did when I bought aftermarket hd wheels for my car.