18" wheels: 8" vs 8.5" width

[rs4dreams]

What are some pros and cons?

[yObOyGeo]

[dparm]

Narrower is better for wet/snow.

[handruin]

Pros
Marginally/negligibly more concavity depending on the wheel.
Ability to put a 255 width tire without it looking puffy or improper load balance.

Cons
Possibly more weight
Possibly more cost

[handruin]

Narrower is better for wet/snow.

Wouldn't the tire be the only thing that matters for the wet/snow? You can run a 8.5" wheel with the same size tire that was on an 8" wheel. The road patch width and diameter shouldn't change in a steel belted radial...just the appearance of puffy vs stretched.

[oc cc]

Pros: They both suck

Cons: 19x9.5 is a better fitment

[yObOyGeo]

Pros: They both suck

Cons: 19x9.5 is a better fitment

This guy know whats up

[dparm]

Wouldn't the tire be the only thing that matters for the wet/snow? You can run a 8.5" wheel with the same size tire that was on an 8" wheel. The road patch width and diameter shouldn't change in a steal belted radial...just the appearance of puffy vs stretched.

No. With a narrower wheel you exert more force per square inch -- that helps bite through the snow and helps evacuate water/prevent hydroplaning.

[Toecutter]

No. With a narrower wheel you exert more force per square inch -- that helps bite through the snow and helps evacuate water/prevent hydroplaning.

Okay...help explain this to me please.

[dparm]

Okay...help explain this to me please.

What is there to explain? You have X weight now being applied over a smaller area, meaning it is applying more force -- that helps it chew through the snow. Tire Rack, Discount Tire, etc. all agree and tell you that if you can go slightly narrower on a snow tire, you should do it. Same thing applies to a street tire; super-wide ones are more prone to hydroplaning.

[Toecutter]

That happens with a narrower tire contact patch. I don't think that using a 0.5" narrower wheel will shrink the contact patch of the same sized tire though. It may bring in the sidewalls a bit but the tread width isn't going to change much, if at all.

[Okan509]

That happens with a narrower tire contact patch. I don't think that using a 0.5" narrower wheel will shrink the contact patch of the same sized tire though. It may bring in the sidewalls a bit but the tread width isn't going to change much, if at all.

this guy

just because tire and wheel were transposed doesn't mean you aren't both talking about the same thing

[Toecutter]

this guy

just because tire and wheel were transposed doesn't mean you aren't both talking about the same thing

I don't think anyone transposed the terms. If you refer back to post #5 by handruin, he talked about using the same sized tire on either an 8" or an 8.5" wheel. dparm then disagreed, stating that a narrower wheel (not tire) exerts more force on the snow.

I'm seeing this the same as handruin. I can't picture a change of 0.5" in rim width making any appreciable change in the tire width. That's pulling in each sidewall 1/4" and a 1/4" is pretty minor change.

I think a 245/80R18 tire will have functionally the same contact patch whether you use an 8" rim or an 8.5" rim. When tire merchants say to go narrower in the snow, they're talking about using a 225 tire instead of a 255 tire. They're not talking about using an 8" rim with a 255 tire rather than using an 8.5" rim with a 255 tire.

[handruin]

What is there to explain? You have X weight now being applied over a smaller area, meaning it is applying more force -- that helps it chew through the snow. Tire Rack, Discount Tire, etc. all agree and tell you that if you can go slightly narrower on a snow tire, you should do it. Same thing applies to a street tire; super-wide ones are more prone to hydroplaning.

I agree for a skinnier tire. My example was the same-width tire with a different width rim (which many have done on these forums). The amount of tire surface area contacting with the ground won't change in this scenario.

I don't think anyone transposed the terms. If you refer back to post #5 by handruin, he talked about using the same sized tire on either an 8" or an 8.5" wheel. dparm then disagreed, stating that a narrower wheel (not tire) exerts more force on the snow.

I'm seeing this the same as handruin. I can't picture a change of 0.5" in rim width making any appreciable change in the tire width. That's pulling in each sidewall 1/4" and a 1/4" is pretty minor change.

I think a 245/80R18 tire will have functionally the same contact patch whether you use an 8" rim or an 8.5" rim. When tire merchants say to go narrower in the snow, they're talking about using a 225 tire instead of a 255 tire. They're not talking about using an 8" rim with a 255 tire rather than using an 8.5" rim with a 255 tire.

I'm glad we're on the same page because I wasn't sure how to even ask why the force load on the road changes when the rim size changes but not the tire. The contact patch and weight distribution should stay the same unless I'm missing something?

[well_armed]

What is there to explain? You have X weight now being applied over a smaller area, meaning it is applying more force -- that helps it chew through the snow. Tire Rack, Discount Tire, etc. all agree and tell you that if you can go slightly narrower on a snow tire, you should do it. Same thing applies to a street tire; super-wide ones are more prone to hydroplaning.

I think what he was trying to say is that with the 8" tire you can get away with a 245? tire, versus a 255 on a 8.5" tire

[Toecutter]

I'm glad we're on the same page because I wasn't sure how to even ask why the force load on the road changes when the rim size changes but not the tire. The contact patch and weight distribution should stay the same unless I'm missing something?

One factor that could change the tire contact patch in this scenario would be a change in tire pressure. Increase the tire pressure enough and some of the rubber lifts off the road. Decrease the tire pressure enough and more rubber contacts the road.

[Toecutter]

I think what he was trying to say is that with the 8" tire you can get away with a 245? tire, versus a 255 on a 8.5" tire

Okay guys, it would be helpful for this conversation if everyone carefully picked his words. Wheel = metal round thing. Tire = rubber round thing.

[handruin]

One factor that could change the tire contact patch in this scenario would be a change in tire pressure. Increase the tire pressure enough and some of the rubber lifts off the road. Decrease the tire pressure enough and more rubber contacts the road.

I'm aware of that situation. I've read threads here where people describe tire pressures when racing vs not racing for similar reasons. I've also seen the air pumps near sand pits so trucks can adjust their tires for more traction in the sand, etc. Anyway, I was mainly generalizing that adjusting the rim size wouldn't appreciably change the width of the tire that contacts the road.

[Toecutter]

I'm aware of that situation. I've read threads here where people describe tire pressures when racing vs not racing for similar reasons. I've also seen the air pumps near sand pits so trucks can adjust their tires for more traction in the sand, etc. Anyway, I was mainly generalizing that adjusting the rim size wouldn't appreciably change the width of the tire that contacts the road.

I agree.