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Old 06-13-2020, 09:26 PM   #1
Berserker2
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Also: '18 Nissan Frontier

Default Run Flats?

Apologies in advance if I overlooked a relevant thread, but all the run flat info seems to be 10 years old. I understand the technology has come a long way since then.

Background

It's about time to replace the OE tires on my '18 STI, and I've decided to go with All Seasons on 18" rims for year-round driving.

My chosen tire is the Michelin Pilot Sport. On prior vehicles I have done the Bridgestone and Continental all seasons and want to try something different. And the Michelins have an excellent rep.

Run Flat Or No?

Tire Rack lists two versions of the Pilot Sport A/S 3+: a regular version and a "ZP" run flat version. In 245/40-18 size both versions are listed as 26 lbs on the Tire Rack site. (Which seems counter-intuitive, so I need to double-check the weights with another source.)

The main problems I have heard with run flats are sidewall stiffness and treadwear.

Treadwear seems to literally be "old news", per my research. As for stiffness, that's a good thing, amirite? Regardless, I find it hard to believe anything can feel more brutal than the OE tires on 19" dubs, LOL.

So, anyone have any experience with run flat tires and any wisdom to share?

For The Curious ...

My car is a winged CWP '18 STI Limited, bone stock. I'm leaning towards 18x8.5 Rota KB-F wheels in Hyper Black wearing 245/40-18 Pilot Sport A/S 3+ tires.

The wheels are listed at 19.45 lbs (!). The combined weight of that combo should be 45.45 lbs, for a 6.95 lb savings per corner. That's a total savings of 27.8 lbs of unsprung spinny stuff.

Thanks!

Thanks in advance for any information or advice!
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Old 06-22-2020, 08:54 AM   #2
Norm Peterson
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'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by Berserker2 View Post
The main problems I have heard with run flats are sidewall stiffness and treadwear.

.... As for stiffness, that's a good thing, amirite?
Not necessarily. Too much of it - I'm thinking of tire vertical stiffness here - makes for more harshness than performance gain, and at some point you actually start giving up mechanical grip. Road roughness would cause wider variations in instantaneous tire grip - "coefficient of friction" goes down when the load goes 'heavy' and has less tire load to work with when it goes up as the tire goes 'light', for a net loss. Separately, sidewall stiffness is going to attract more of the contact patch load toward the shoulders, and as the tire contact patch pressure becomes less uniform over the patch area, total tire grip decreases even when tire vertical load remains the same.



Quote:
Regardless, I find it hard to believe anything can feel more brutal than the OE tires on 19" dubs, LOL.
With that in mind, I don't see run-flats being a good option for you. And FWIW, "dubs" have always meant 20's, not 19's.


Just so you know, I'm running PS A/S 3+ in 245/40-18 on 18x8.5" wheels on our '19 WRX for the cooler months. It doesn't snow too much here most years, and being retired I generally don't have to go out in snow or really bad weather any more if I don't want to, so the winter/snow performance of a top-shelf all-season tire is sufficient for my winter needs here (greater Philly region). These are on a separate set of wheels, as I do keep summer performance tires on my main cars during the warmer weather. And I do drive with a fair bit of enthusiasm through the curves and corners. Year round.


Norm
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Old 06-22-2020, 02:30 PM   #3
Berserker2
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Quote:
Originally Posted by Norm Peterson View Post
I'm running PS A/S 3+ in 245/40-18 on 18x8.5" wheels on our '19 WRX for the cooler months
Appreciate the info!

I wound up ordering that exact tire in that exact size. Non-run-flat.

For wheels I went with the Enkei PF01 in 18x8.0 +40. 18.7 lbs each. Saw some pics of the CWP WRXes wearing these, and they looked really clean.


Quote:
Originally Posted by Norm Peterson View Post
And FWIW, "dubs" have always meant 20's, not 19's.
Today I learned. Thanks!
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Old 06-22-2020, 02:41 PM   #4
Norm Peterson
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

Default

Nice.


I also got Enkei wheels, but I went with the Raijins in 18x8.5, +50. Die-hard corner-carver, not willing to give up the half inch of wheel width from the OE 8.5".


Norm
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Old 06-22-2020, 02:56 PM   #5
Norm Peterson
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Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

Default

Here's a link to a newsletter article on run-flat tires that just hit my inbox. Just keep in mind that there probably is some tire mfr agenda going on in the background, so read it for the tech.

https://www.tirereview.com/science-r...464G7082134F2S


Norm
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Old 06-22-2020, 03:45 PM   #6
Ernest
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Default

Get a normal tire. Friends that had run flats always have stories that are not fun. Rarely hear these stories about good ole normal tires. They are literally made so lazy people who don't know how to change a tire don't have too, at a significant cost.
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Old 06-22-2020, 03:48 PM   #7
Norm Peterson
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Location: our wrx IS the family sedan
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

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Quote:
Originally Posted by Ernest View Post
Get a normal tire.
(he did)


Norm
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Old 06-22-2020, 10:12 PM   #8
Berserker2
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Also: '18 Nissan Frontier

Default

Quote:
Originally Posted by Norm Peterson View Post
I went with the Raijins in 18x8.5, +50.
Gorgeous wheel. I thought hard about them.


Quote:
Originally Posted by Norm Peterson View Post
Here's a link to a newsletter article on run-flat tires that just hit my inbox.
Thanks, that was interesting. Made me feel better about not going with runflats. It was not a compromise I needed to make.
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Old 06-23-2020, 07:21 AM   #9
Norm Peterson
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Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by Berserker2 View Post
Gorgeous wheel. I thought hard about them.
The split-spoke design has been my favorite since the Cosmic wheels for compact and subcompact cars came out in the early 1970's.

Two of the sets of wheel I have for my '08 Mustang are variations on the split-spoke.


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