245 40 18 on 8.5 vs 9" ?

[G30M]

Hey guys I've decided my roads are too nasty for 19" wheels and planning to get a set of Pilot Sport 4S in 245 40 18

However due to global supply chain issues there are only decent 8.5" rims, unable to source 9" rims that I like that are light.

So after googling and researching for weeks I can't decide if 8.5" rims are much worse than 9" in terms of performance ...

Does anyone have any material on this? The Pilot Sport 4 that I have look like a donut on the 8.5, yet I had an only Audi S4 that had 245 40 Bridgestone Adrenalins on 8" rims and it looked fine

But i gather it's not how it looks, any resource on performance?

[Red Bread]

Yeah, 8.5 for a 245 is perfectly fine. My M Coupe came on 245s with a 9 wheel but I ran 255 and 265 on there with no issues. I run 255s on a 9 wheel now and they look perfect, a 245 would look slightly stretched.

[RM7]

Originally Posted by G99M5

Hey guys I've decided my roads are too nasty for 19" wheels and planning to get a set of Pilot Sport 4S in 245 40 18

However due to global supply chain issues there are only decent 8.5" rims, unable to source 9" rims that I like that are light.

So after googling and researching for weeks I can't decide if 8.5" rims are much worse than 9" in terms of performance ...

Does anyone have any material on this? The Pilot Sport 4 that I have look like a donut on the 8.5, yet I had an only Audi S4 that had 245 40 Bridgestone Adrenalins on 8" rims and it looked fine

But i gather it's not how it looks, any resource on performance?

The best for performance is fitting the skinniest tires on the widest rims, for a short stiff sidewall, within the tire sizes the manufacturer recommends for that rim size. What happens if you have less stiff sidewalls is when pushing it they may collapse, which is all kinds of bad. Now, that's pretty extreme, but that's basically the balance. Some of these heavier cars don't have enough rubber underfoot in the first place. 225s on these are criminal. 245s are marginal.

It actually swings the other way for wet conditions, having more sidewall allows the flex to grip longer in the wet.

I have 255s on 8.5s on the stinger, I built it up more for wet conditions on 18s though because my other car covers all the non-wet stuff. But also the issue of the stock tires not being wide enough for that mass of car in the first place.

[chris719]

Originally Posted by G99M5

Hey guys I've decided my roads are too nasty for 19" wheels and planning to get a set of Pilot Sport 4S in 245 40 18

However due to global supply chain issues there are only decent 8.5" rims, unable to source 9" rims that I like that are light.

So after googling and researching for weeks I can't decide if 8.5" rims are much worse than 9" in terms of performance ...

Does anyone have any material on this? The Pilot Sport 4 that I have look like a donut on the 8.5, yet I had an only Audi S4 that had 245 40 Bridgestone Adrenalins on 8" rims and it looked fine

But i gather it's not how it looks, any resource on performance?

245 is perfectly fine on an 8.5", but for front wheels I would prefer 9" for the stretch and stiffer sidewall.

[Alfisti]

Aesthetically it can also depend on the tyre, two brands at say 245 can be quite a different actual width, it's friggin weird.

[G30M]

the pilot sport 4 245 40 18 i have is about the same tread width as the 255 35 19 pirelli p zero run flats when i used a rule to measure

specs on tirerack confirms this!

[ntg44]

Here's what Michelin PS4S 245/40/18 tires look like on a 9 inch wide wheel.

I had the same question earlier this year and ended up choosing 9 inch for many reasons, including having just a tad bit of stretch. Look and performs great in my opinion.

I had the same tires on 8.5 inch wheels before these and it was definitely softer/mushier feeling in general. But far from bad. The sidewall was much flatter and protected the outer rim of the wheel better, so there are some beneficial tradeoffs. The biggest difference now is I need to place cardboard between the wheels when stacking them for storage, as opposed to the 8.5 inch wheels where the sidewalls kept the wheels safe. It's a minor thing but, you definitely notice it when you need to store them and you are short on cardboard and have no upcoming Amazon deliveries haha.

[Alfisti]

Yeah I have heard michelin's are a touch fat and Pirelli skinny. I have Pirelli PZERO's on my 997, i am due new rubber and a set of MPS4's showed up for an insane price but they were 305 rears vs the 295 rears from the factory. In reality that 10mm may well be 20mm which equates to 10mm extra tyre on the outer edge, which would look shite.

[RM7]

Originally Posted by Alfisti

Yeah I have heard michelin's are a touch fat and Pirelli skinny. I have Pirelli PZERO's on my 997, i am due new rubber and a set of MPS4's showed up for an insane price but they were 305 rears vs the 295 rears from the factory. In reality that 10mm may well be 20mm which equates to 10mm extra tyre on the outer edge, which would look shite.

I thought it was more the opposite, Michelin says you can go an extra 10mm over some other tire manufacturers on the same size rims, I take this to mean they are slightly undersized. I went to 295s in the front because there was nowhere in the country you could get 285s (my stock size).

[freakystyly]

Check out tire rack for the specific sizes and brands, under the specs tab there will be the section width and tread listed for each tire you want to compare.

It will also list the wheel width range for that tire.

I remember the Michelin PSS measured wider than the PS4 in the same size.

[G30M]

thanks all, very helpful!

[forcefed]

My other car has 245/45/18's on 8" rims, currently running 275/40/18 on 9" rims, 8.5" is perfectly fine.