Installed a new set of Pilot Sport 4S on GT350R - completely lost that "sharp" feeling. Car does not feel stable anymore

[shogun32]

I hate to be a broken record. Supercar3

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[Mikepol2]

I hate to be a broken record. Supercar3

OK. You win. SC3 will be my next set!

 

[matthewr87]

I hate to be a broken record. Supercar3

What sizes do you use with the SC3s?

 

[shogun32]

What sizes do you use with the SC3s?

305/30. 25-30% off when you buy thru USAA. The only downside of sc3 is they don't have huge size selection and it's better in 20" than in 18 or 19. But they cover the most important sizes.

 

[IainD90]

Lots of great points above.
What I'd add to help answer OPs original question, is tire characteristics like ultimate dry grip, wet grip, breakaway, treadwear, etc., are always looked at, but often forgotten about sidewall stiffness.

In addition to what's been talked about here, a large part of what OP is describing as loss of "sharp" feeling, is due to the relative soft sidewalls of tires like PSS and PS4S, compared to SC2. The SC2, obviously it doesn't have to be said what it surrenders for greater ultimate dry performance-related characteristics at limit handling; sidewall stiffness (in conjunction with tread block design and compound type(s) of course) has a lot to do with initial turn-in response and how it translates to the feel in the steering wheel when adding steering angle.

I don't take mine to the track as often as I like, but even though I do more street driving, I've opted to keep the SC2s, because I also like razor-sharp steering response and have no qualms about some of the downsides of SC2s on the street. Having had tires in the class of PS4S/PSS and Conti ECS - really great all rounder street tires, great grip, and add a level of comfort back, but initial turn-in feel/response is too soft for my preferences, due to the relatively soft sidewalls - again, compared to something like the SC2. OPs reaction to the switch to PS4S is the same sort of reaction I had years ago, when experimenting with different tires, and resulted in me having certain non-negotiables and how I rate my tire characteristics preferences.

Hope that helps.

I believe this best answers my question - and I think you're right, the sidewall flex is what I'm feeling the most. The 305 and 315 with PS4S have much bulkier, rounder sidewalls than the SC2s or even PSS. The SC2s almost had a stretched look to them when they were on the wheels; the PS4S is quite the opposite, they appear to be almost too big for the wheel. "Razor sharp" steering response is the best way to describe what I'm missing.

It's just very strange to me that with the PSS on my old GT350, I felt the car had that razor sharp feel. My dad used to have an E92 M3 with PSS - still razor sharp. My VW has PS4S - still razor sharp. This is why I'm so confused that my 350R has lost that feeling when I have plenty experience with the Michelin street tire.

 

[IainD90]

OP has an R. So I seriously doubt changes to swaybars or any suspension components need or should happen.

OP,
I swapped out my Cup2 R tires for PS4's on my 18 R. 99% of my driving was local and street driving. I found the MP4S's to be very street compliant with soaking up bumps and pavement cracks and very little of the notorious tramline that is present from 15-18 GT350R's. That is what I personally wanted. A more daily friendly R to drive around in. If I were to push the R on a track the PS4's wouldn't be my tire of choice. Yes they don't grip and corner like the Cup2's. They are street friendly tire for sure.

So I have a 2019 R and let me tell you - the tramlining is still there with the SC2 - but basically completely gone with the PS4S. Is it worse on 2015 to 2018s?

 

[cmxPPL219]

I believe this best answers my question - and I think you're right, the sidewall flex is what I'm feeling the most. The 305 and 315 with PS4S have much bulkier, rounder sidewalls than the SC2s or even PSS. The SC2s almost had a stretched look to them when they were on the wheels; the PS4S is quite the opposite, they appear to be almost too big for the wheel. "Razor sharp" steering response is the best way to describe what I'm missing.

It's just very strange to me that with the PSS on my old GT350, I felt the car had that razor sharp feel. My dad used to have an E92 M3 with PSS - still razor sharp. My VW has PS4S - still razor sharp. This is why I'm so confused that my 350R has lost that feeling when I have plenty experience with the Michelin street tire.

It's also interesting, as you've laid out, that in a given size (say the oem GT350R front 305/30/19), tires from different brands, or even within the same brand of tire but different performance category, will look wider or less wide on the same rim.

The SC2 305/30/19 you'll notice there is some static stretch mounted on the rim, compared to the PS4S in the same size. This also helps steering sharpness, because you can think of it like "pre-loading" the sidewalls, as opposed to a no load nominal "position." As you add steering angle, any sidewall will flex, and will flex up to its maximum amount, per steering angle, cornering G, vehicle speed, etc. - by having some amount of static stretch, this reduces the amount of "time" that the sidewall needs to cover to complete this flex amount. When tuning suspension and handling, including at the OEM level, more sophisticated teams will use the tire size aspect ratio (sidewall height) and stretch/no stretch/minimal stretch, coupled with a specific rim width, as part of the tuning for the handling characteristics. (For example, on PP2, it was a deliberate decision to mount 305/30/19 SC2s all around, and stretch it over 10.5" front, and stretch it further on 11" rear width rim - same with the decision to stagger SC2 over 11" front and 11.5" rear widths on GT350R - to manage handling characteristics like understeer, oversteer, etc. for given power output, etc.)

The BMW M programs are interesting because let's say the early F80 M3 - the OEM PSS they use is bespoke to that car, so BMW works with Michelin and may have specified unique characteristics, like a stiffer-than-aftermarket-version sidewall, although using the basic PSS as a starting point. BMW has a long history of having bespoke Michelin rubber on M cars. Other brands like Porsche, Mercedes etc., all have OEM-Tire Mfr programs, using a base tire as the starting point, and adding in certain compound and design-specific characteristics for the particular model.

Ford did the same too - for the MY2019 GT350 (non-R), most here may recall they're equipped with SC2s (as opposed to the previous PSS). Both were designed, bespoke to the GT350 per Ford Performance engineers, and differ from the off-the-shelf versions of those tires in the respective sizes equipped on GT350. FP also specified bespoke SC2s for the GT500 handling/carbon fiber track pack.

 

[IainD90]

It's also interesting, as you've laid out, that in a given size (say the oem GT350R front 305/30/19), tires from different brands, or even within the same brand of tire but different performance category, will look wider or less wide on the same rim.

The SC2 305/30/19 you'll notice there is some static stretch mounted on the rim, compared to the PS4S in the same size. This also helps steering sharpness, because you can think of it like "pre-loading" the sidewalls, as opposed to a no load nominal "position." As you add steering angle, any sidewall will flex, and will flex up to its maximum amount, per steering angle, cornering G, vehicle speed, etc. - by having some amount of static stretch, this reduces the amount of "time" that the sidewall needs to cover to complete this flex amount. When tuning suspension and handling, including at the OEM level, more sophisticated teams will use the tire size aspect ratio (sidewall height) and stretch/no stretch/minimal stretch, coupled with a specific rim width, as part of the tuning for the handling characteristics. (For example, on PP2, it was a deliberate decision to mount 305/30/19 SC2s all around, and stretch it over 10.5" front, and stretch it further on 11" rear width rim - same with the decision to stagger SC2 over 11" front and 11.5" rear widths on GT350R - to manage handling characteristics like understeer, oversteer, etc. for given power output, etc.)

The BMW M programs are interesting because let's say the early F80 M3 - the OEM PSS they use is bespoke to that car, so BMW works with Michelin and may have specified unique characteristics, like a stiffer-than-aftermarket-version sidewall, although using the basic PSS as a starting point. BMW has a long history of having bespoke Michelin rubber on M cars. Other brands like Porsche, Mercedes etc., all have OEM-Tire Mfr programs, using a base tire as the starting point, and adding in certain compound and design-specific characteristics for the particular model.

Ford did the same too - for the MY2019 GT350 (non-R), most here may recall they're equipped with SC2s (as opposed to the previous PSS). Both were designed, bespoke to the GT350 per Ford Performance engineers, and differ from the off-the-shelf versions of those tires in the respective sizes equipped on GT350. FP also specified bespoke SC2s for the GT500 handling/carbon fiber track pack.

That's all really great information thanks for taking the time to write that out. Definitely gives insight to what I'm trying to comprehend.

I definitely understand the differences between SC2s and PS4S lol.. Which I think is what some perhaps thought I was asking. But it was all about steering feel, sidewall flex, tire sizing etc.

 

[JAJ]

It's also interesting, as you've laid out, that in a given size (say the oem GT350R front 305/30/19), tires from different brands, or even within the same brand of tire but different performance category, will look wider or less wide on the same rim.

The SC2 305/30/19 you'll notice there is some static stretch mounted on the rim, compared to the PS4S in the same size. This also helps steering sharpness, because you can think of it like "pre-loading" the sidewalls, as opposed to a no load nominal "position." As you add steering angle, any sidewall will flex, and will flex up to its maximum amount, per steering angle, cornering G, vehicle speed, etc. - by having some amount of static stretch, this reduces the amount of "time" that the sidewall needs to cover to complete this flex amount. When tuning suspension and handling, including at the OEM level, more sophisticated teams will use the tire size aspect ratio (sidewall height) and stretch/no stretch/minimal stretch, coupled with a specific rim width, as part of the tuning for the handling characteristics. (For example, on PP2, it was a deliberate decision to mount 305/30/19 SC2s all around, and stretch it over 10.5" front, and stretch it further on 11" rear width rim - same with the decision to stagger SC2 over 11" front and 11.5" rear widths on GT350R - to manage handling characteristics like understeer, oversteer, etc. for given power output, etc.)

The BMW M programs are interesting because let's say the early F80 M3 - the OEM PSS they use is bespoke to that car, so BMW works with Michelin and may have specified unique characteristics, like a stiffer-than-aftermarket-version sidewall, although using the basic PSS as a starting point. BMW has a long history of having bespoke Michelin rubber on M cars. Other brands like Porsche, Mercedes etc., all have OEM-Tire Mfr programs, using a base tire as the starting point, and adding in certain compound and design-specific characteristics for the particular model.

Ford did the same too - for the MY2019 GT350 (non-R), most here may recall they're equipped with SC2s (as opposed to the previous PSS). Both were designed, bespoke to the GT350 per Ford Performance engineers, and differ from the off-the-shelf versions of those tires in the respective sizes equipped on GT350. FP also specified bespoke SC2s for the GT500 handling/carbon fiber track pack.

Here's an article to take a look at if you haven't seen it yet. It's by @BillyJRacing who's a pro racing driver. He was engaged by Ford Performance to do the track qualification for the later GT350's and GT500.

Not All Michelin Cup 2 Tires are Created Equal - Behind the Scenes of Making Bespoke Tires | 2015+ S550 Mustang Forum (GT, EcoBoost, GT350, GT500, Bullitt, Mach 1) - Mustang6G.com

Back in 2016 when I got my GT350, the tires on the GT350 and the GT350R were unique to those cars. They didn't fit anything else at the time. While they don't have an "FP" approval on the sidewall like the later ones do, I have absolutely no doubt that they were developed and qualified for the GT350's. I've run the OEM SC2's on my 10.5/11" rims and on 11" rims on all four corners. They work great one way or the other.

 

[cmxPPL219]

Here's an article to take a look at if you haven't seen it yet. It's by @BillyJRacing who's a pro racing driver. He was engaged by Ford Performance to do the track qualification for the later GT350's and GT500.

Back in 2016 when I got my GT350, the tires on the GT350 and the GT350R were unique to those cars. They didn't fit anything else at the time. While they don't have an "FP" approval on the sidewall like the later ones do, I have absolutely no doubt that they were developed and qualified for the GT350's. I've run the OEM SC2's on my 10.5/11" rims and on 11" rims on all four corners. They work great one way or the other.

Yes I agree, I recall reading that article a while ago, a real cool read. (I think the link is missing?)

It's also interesting to see used cars listed (GT350 or otherwise) and when you look at pics of the tires, one can see if they were replaced, whether they got the OEM version or the aftermarket version, since often, the differences can be really obvious, like sidewall markings you mentioned, presence of rim protector, tread block design, etc.

 

[JAJ]

Yes I agree, I recall reading that article a while ago, a real cool read. (I think the link is missing?)

It's also interesting to see used cars listed (GT350 or otherwise) and when you look at pics of the tires, one can see if they were replaced, whether they got the OEM version or the aftermarket version, since often, the differences can be really obvious, like sidewall markings you mentioned, presence of rim protector, tread block design, etc.

Yup, fixed the link, thanks!

 

[scd603]

I need SSs for the front, once again on national backorder (I went through this on backs last year). I'm looking at options, and I put this together. May be helpful to others

You can see what I am thinking

 

[shogun32]

I need SSs for the front, once again on national backorder

https://www.tirerack.com/tires/Spec...ewall=Blackwall&partnum=23YR9F1S3XL&tab=Sizes

Goodyear.com by way of USAA.com member benefits page (for 20-30% off) may have better stock availability. Haven't checked.

 

[Thor 142]

What sizes do you use with the SC3s?

I have 325 on the rear and 295 on the front. Stock wheels. They feel great on the street. I'll tell you how they perform on the track Saturday when I get home.

 

[Chumley]

Swapped the Cup2's for PS4s' on a standard 350 on BC Forged 20x11" F 305s / 20x11.5" R 315s and absolutely LOVE them! For street driving (at least on roads around me) the Cups were miserable. Tramlining constantly even after another factory spec alignment, tried the Steeda brace b/c some people had luck with it. Really started to hate the car for casual weekend drives and often avoided certain local roads, especially if there was some roadwork in progress. If you hit some roadwork where the asphalt was abraded or rough in preparation for resurfacing, it scared the crap out of you if you weren't prepared. "Hate" might be a bit over dramatic but the drive was often just tiring around town on the cup's.

Without exaggeration there were perfectly normal looking roads where if you weren't dialing in 15-20 degrees of offset steering, you'd be in the median or other lane in seconds....right up until it began to track straight again. PS4s' COMPLETELY eliminated it, as in it tracks straighter than any other car in the house. It feels glued to the pavement - much more confidence inspiring on the street even at "spirited" speeds.

100% agree that the car feels much less light on it's feet, less "playful"? Definitely makes the car feel heavier and less quick to dart laterally. For me that's a godsend on the street. I have the Cups on the oem wheels if I can ever find the time to hit the track or even an autocross.

Finally, I'm far from a track expert but living in FL I certainly have driven Sebring, Homestead, etc, a number of times with Chin and others so I do understand a track mentality and value of tires designed for it.

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