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rumatt · 08-08-2019, 12:14 AM

I figure I should update here. I got the 18" tires with Michelin 4s.

TL;DR: Overall the tires are great. Love them. And I don't stress over hitting potholes now. But they are louder and require lower pressures.

Details:

There is no issue with sidewall squirm relative to the 20's. My 18" snows have a lot more turn in squish which makes them less fun. I assumed that was mostly tread squirm or softer sidewall material, and this confirms it. The 18" 4S still feel great.

However, they are louder. There is more road noise than Tesla's 20" variant, which had some kind of foam strip embedded in them. The model 3 lets in a decent amount of road noise and it's noticeable. The current noise level is a little disappointing, but I can live with it. It's still like a Mercedes compared to the Cayman R.

Inflated to the same tire pressure (40psi) the 18" tires are actually more harsh than the 20" variant. I was always amazed at how complaint they were. However they needed even higher pressure to avoid denting the rims. The 18's allow me to safely lower them a few PSI at which point they become as comfortable as the 20's.

WTF you ask, how can an 18" be more harsh? I'm not entirely sure I understand, but I believe it's the little understood phenomenon of tire casing pressure and barlow's law. Think about bicycle tires. The larger the tire, the lower pressure you run to achieve the same ride quality and sag pct. A 1" road bike tire may be pumped to 100psi, a 2.5" mountain bike to 25psi, and a 5" fatbike tire to 8 PSI. The 18" wheel's tire has a larger rubber surface area.

This article gets into the math http://flocycling.blogspot.com/2014/...less-tire.html

08-08-2019, 12:14 AM	#32
rumatt Mugwump Join Date: Oct 2003 Carmudgeonly Ride: E46 330i, Chevy Colorado, Tesla Model 3 Location: NY Posts: 17,475	I figure I should update here. I got the 18" tires with Michelin 4s. TL;DR: Overall the tires are great. Love them. And I don't stress over hitting potholes now. But they are louder and require lower pressures. Details: There is no issue with sidewall squirm relative to the 20's. My 18" snows have a lot more turn in squish which makes them less fun. I assumed that was mostly tread squirm or softer sidewall material, and this confirms it. The 18" 4S still feel great. However, they are louder. There is more road noise than Tesla's 20" variant, which had some kind of foam strip embedded in them. The model 3 lets in a decent amount of road noise and it's noticeable. The current noise level is a little disappointing, but I can live with it. It's still like a Mercedes compared to the Cayman R. Inflated to the same tire pressure (40psi) the 18" tires are actually *more harsh* than the 20" variant. I was always amazed at how complaint they were. However they needed even higher pressure to avoid denting the rims. The 18's allow me to safely lower them a few PSI at which point they become as comfortable as the 20's. WTF you ask, how can an 18" be more harsh? I'm not entirely sure I understand, but I believe it's the little understood phenomenon of tire casing pressure and barlow's law. Think about bicycle tires. The larger the tire, the lower pressure you run to achieve the same ride quality and sag pct. A 1" road bike tire may be pumped to 100psi, a 2.5" mountain bike to 25psi, and a 5" fatbike tire to 8 PSI. The 18" wheel's tire has a larger rubber surface area. This article gets into the math http://flocycling.blogspot.com/2014/...less-tire.html Last edited by rumatt; 08-08-2019 at 12:26 AM.