Car rear is "floating" after putting new tyres

[cowboyjon]

Welp, my car is on ps5's and the rears will need changing in a few months - I was planning on putting a pair of sportcontact 7's on but this has gave me the fear

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[Malcolm Feth]

I got annoyed yesterday after trying anything. Ordered pilot super sports and will fit them on Saturday. Hopefully the problem will be gone

 

[FLtrackdays]

I got annoyed yesterday after trying anything. Ordered pilot super sports and will fit them on Saturday. Hopefully the problem will be gone

Drop the pressure on the crappy ones and do some burnouts.

 

[SoDakMk5]

Too much psi. Drop them to 32. When I replaced my stock rears I had that issue and dropped the psi down and issue went away

 

[10ICTXN]

I tried to cheap out and replaced only the rears at 20k miles, went with Continental "Extreme Contacts". As soon as they went on, I experienced the traction control pulsing the brakes for the rear on sweeping turns, not even that fast, stuff I could do in the mini van, seriously. I lowered the pressure to about 28-psi and it went away but it didn't feel as good as the OEM PSS. Last week I had a flat on the rear, after pumping in the fix-a-flat goo that they give you I went to the tire store. They said the fronts were down to cords on the inside (27K miles), I know now to examine the full tread. I went to Michelin PS4S all the way around, it feels much better, fun to drive again. I'm sticking with Michelin's from now on.

 

[FuzzyRev]

I tried to cheap out and replaced only the rears at 20k miles, went with Continental "Extreme Contacts". As soon as they went on, I experienced the traction control pulsing the brakes for the rear on sweeping turns, not even that fast, stuff I could do in the mini van, seriously. I lowered the pressure to about 28-psi and it went away but it didn't feel as good as the OEM PSS. Last week I had a flat on the rear, after pumping in the fix-a-flat goo that they give you I went to the tire store. They said the fronts were down to cords on the inside (27K miles), I know now to examine the full tread. I went to Michelin PS4S all the way around, it feels much better, fun to drive again. I'm sticking with Michelin's from now on.

As a current employee, and lifelong student of OEM systems, down to the smallest components (my specialty), and not just the what, but the why, let me share a section of an article Automotive Engineer Anthony Magagnoli wrote five years ago, in regards to why Joe Customer might be disappointed when he deviates from the OE tire...

"With the tires selected, the OEMs can proceed with development and tuning of the rest of the vehicle around them. While the vehicle dynamics areas of ride, steering, and handling might be most obviously impacted, there are many other functional areas that are tuned around the tires. Braking performance, fuel economy calculations, and powertrain tuning are all impacted. The “active chassis” group will be developing the stability control, ABS, and traction control around the tires, as will the ADAS (advanced driver-assistance systems) group. The NVH (noise, vibration, and harshness) and durability groups will also be conducting their work around the tires.

As a former vehicle dynamics performance engineer for FIAT Chrysler Automobiles, I want to give you a glimpse into how specific vehicles are tuned around the tires. One of the platforms that I had responsibility for was the Pacifica, which had eight unique tires across 17, 18, and 20-inch wheels. Between gas, plug-in hybrid, Waymo, and the new Voyager, there were nine unique damper (shock) tunings to accommodate the ride characteristics of each car riding on each tire for their intended audience. Consider for a moment that, from a ride perspective, a tire is essentially an undamped spring. You can then see how varying that component would affect things such as impact harshness and shake and how that would need to be accounted for in the damper tuning.

In regard to steering, almost every tire had a unique electronic power steering calibration for its application in each model variant. I count 13 by memory and that is without variable steering modes. Each tire possesses unique traits as to how they respond to an input and build force to move the car. In general, it was desired to make all the packages feel roughly the same in terms of steering. However, certain packages varied slightly due to purpose or market.

Based on how the tires differed, changes to EPS tuning were usually required in a few areas of the calibration. The “on-center” feel, or how “positively” the car would steer straight-ahead, was critical to driving comfort, especially over long distances. The response characteristics of the tire would alter the linearity of the effort build in the wheel as the driver steered into a corner. In other terms, as you steer, you want the wheel to communicate with a continuous build in effort as you turn harder. Not having the effort build well-matched to the tire and vehicle response could result in a car feeling anywhere from nervous and hyper-active to sluggish and unwilling to turn."

Pretty eye-opening stuff if you didn't know..

 

[10ICTXN]

Thanks, interesting, I learned something. I appreciate that. Makes you wonder about all the different set up that are being run out there in the wild.

 

[noogie]

The OEM setup is a compromise just like anything else you change in the car. If you want what the engineers intended, then stick to OE tires.

The OE tires are a bit dated and there are better options out there. Remember development of the car started back in 2014ish.

personally I would choose the 4s or extreme contact 02 over the OE tires.

 

[trey8100]

i had this issue on my corvette before so i called the tire manufacturer and he informed me that the tires i purchased were for a much heavier car so he told me to run less tire pressure than i was and it remedied the problem

 

[lucky phil]

As a current employee, and lifelong student of OEM systems, down to the smallest components (my specialty), and not just the what, but the why, let me share a section of an article Automotive Engineer Anthony Magagnoli wrote five years ago, in regards to why Joe Customer might be disappointed when he deviates from the OE tire...

"With the tires selected, the OEMs can proceed with development and tuning of the rest of the vehicle around them. While the vehicle dynamics areas of ride, steering, and handling might be most obviously impacted, there are many other functional areas that are tuned around the tires. Braking performance, fuel economy calculations, and powertrain tuning are all impacted. The “active chassis” group will be developing the stability control, ABS, and traction control around the tires, as will the ADAS (advanced driver-assistance systems) group. The NVH (noise, vibration, and harshness) and durability groups will also be conducting their work around the tires.

As a former vehicle dynamics performance engineer for FIAT Chrysler Automobiles, I want to give you a glimpse into how specific vehicles are tuned around the tires. One of the platforms that I had responsibility for was the Pacifica, which had eight unique tires across 17, 18, and 20-inch wheels. Between gas, plug-in hybrid, Waymo, and the new Voyager, there were nine unique damper (shock) tunings to accommodate the ride characteristics of each car riding on each tire for their intended audience. Consider for a moment that, from a ride perspective, a tire is essentially an undamped spring. You can then see how varying that component would affect things such as impact harshness and shake and how that would need to be accounted for in the damper tuning.

In regard to steering, almost every tire had a unique electronic power steering calibration for its application in each model variant. I count 13 by memory and that is without variable steering modes. Each tire possesses unique traits as to how they respond to an input and build force to move the car. In general, it was desired to make all the packages feel roughly the same in terms of steering. However, certain packages varied slightly due to purpose or market.

Based on how the tires differed, changes to EPS tuning were usually required in a few areas of the calibration. The “on-center” feel, or how “positively” the car would steer straight-ahead, was critical to driving comfort, especially over long distances. The response characteristics of the tire would alter the linearity of the effort build in the wheel as the driver steered into a corner. In other terms, as you steer, you want the wheel to communicate with a continuous build in effort as you turn harder. Not having the effort build well-matched to the tire and vehicle response could result in a car feeling anywhere from nervous and hyper-active to sluggish and unwilling to turn."

Pretty eye-opening stuff if you didn't know..

My FIL spent 35 years testing and developing cars at the Holden test ground and he always advises using the tyres the car originally sold with as replacements. I agree that would be a wise decision except the reality is that the tyres evolve year by year so 10 years down the track, tyre brand XYZ in name size and rating will be a significantly different product than it was when fitted as an OEM tyre. Good advice but hard to make happen in reality.

Phil

 

[FLtrackdays]

Thanks, interesting, I learned something. I appreciate that. Makes you wonder about all the different set up that are being run out there in the wild.

I’m on a square setup 6 months out of the year and gotta say…. It’s fantastic!!!!

https://apexwheels.com/fitment-guides/toyota/supra/toyota-gr-supra-wheel-and-tire-fitment-guide

It’s the 1st size when you scroll down on the Apex guide above Maxxis Victra is my track tire of choice. But I’ll use others if I can get a good deal on them.

Currently back on my OEM wheels and tires. I went down on the recommended psi. Felt like they were going to pop from what I’m used to. I turn off lane assist. That alone will make the car feel unstable at the worst times. I don’t expect much from the OEM ones. They get me from point A to B.

I highly recommend you use your free track day. Or pay to do one in the Supra. You will get a much better feel for your car and/or meet some people that can get the car to feel the way you want it to.

https://gr.drivenasa.com

 

[razorlab]

I highly recommend you use your free track day. Or pay to do one in the Supra. You will get a much better feel for your car and/or meet some people that can get the car to feel the way you want it to.

https://gr.drivenasa.com

Do you work for NASA? You put this in 99% of your replies here, usually not even related to the actual post you are replying to.

“who wants to go to boba with me?”

You: “ you should get your car on track with NASA!”

 

[FLtrackdays]

Do you work for NASA? You put this in 99% of your replies here, usually not even related to the actual post you are replying to.

“who wants to go to boba with me?”

You: “ you should get your car on track with NASA!”

LOL true hahaha… I don’t work for NASA but… I do think he’d enjoy the car more and it’ll fix every problem I really need to cut it down to 80% of the post

 

[Malcolm Feth]

All problems gone. I put back Super Pilot Sport tyres and the car feels normal!

On previous tyres it didn't really matter whether I do 2.6 bar or 2.1, although on lower pressure it was a bit better. I was still getting quite a lot of traction control issues and car felt unstable at higher speeds. Horrible experience.

Never in my life I would say that tyres could make such a massive difference.

Thanks you guys for all the tips and suggestions

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