Body roll with new tires?????

dmaxstang · Jun 29, 2007

I had a new set of Toyo Proxes 4's put on the stang yesterday and all the sudden it feels like the car has more body roll than before and i guess the only way to explain this is to say that it feels like the rear end is chasing the front end when cornering even the slightest bit. Does that make sense to anyone, also the car feels like it has more front end rise when it hit the gas, just kind of weird. Maybe because the others were way worn out and there was no rubber left to roll in the corners but the car handled like it was on rails. One single motion at a time cornering and now it feels alot different. What do you think or have you seen with a brand new set of rubber?

LV51FER · Jun 29, 2007

The stock rubber has fairly high sidewalls - 235/55s. I don't know what size tires your new ones are but tires vary as to sidewall stiffness. Sidewall stiffness and profile will also affect the immediacy of turn-in feedback from the front. Softer or harder rubber will also provide a slip/grip/wear trade-off. Personally I don't like the stock tires so moved to a 35 profile which cuts the feeling of roll you get off the stock tires.

It may just be that the tires need bedding in. It takes a few miles before the newness wears off the shiny rubber and you get a better grip as the rubber wears.

dmaxstang · Jun 29, 2007

LV51FER said:
The stock rubber has fairly high sidewalls - 235/55s. I don't know what size tires your new ones are but tires vary as to sidewall stiffness. Sidewall stiffness and profile will also affect the immediacy of turn-in feedback from the front. Softer or harder rubber will also provide a slip/grip/wear trade-off. Personally I don't like the stock tires so moved to a 35 profile which cuts the feeling of roll you get off the stock tires.

It may just be that the tires need bedding in. It takes a few miles before the newness wears off the shiny rubber and you get a better grip as the rubber wears.

They were simply replaced. They were and are Toyo Proxes 4 255/35/20 tires. I can't explain it. Wondering if something else happened because they had to do a little work on the ride because 3 of the lug struts on the right rear were stripped thanks to the morons at Firestone who also punished my rim if you know what i mean a while back. those were replaced by this shop.

Barry06GT · Jul 4, 2007

Simply replaced? I did not think 20's came from the factory. I thought 18's were the largest Ford does. Am I missing something here?

kingmeirl · Feb 16, 2008

SAME EXACT THING HAPPENED TO ME TODAY!! That's actually why I am here. I got the proxies put on ONLY the back. 245/50/16. Now, going down the highway and I turn the steering wheel just a little, it feels like the rearend is steering itself. It makes me very nervous, not to mention I am going to the autocross in the morning and dont have time to go back to kauffman and raise my voice... Anyway did you ever figure out what happened????

bigcat · Feb 16, 2008

check the tire pressure.

Frank S · Feb 16, 2008

Tires have a lubricant in the tread, so they will come out of the molds easily. "Mold release", it's called It takes a few miles to wear off. Until it's gone, tires typically seem slippery.

Also could be a matter of tall tread blocks squirming under cornering forces; they lean over, grab a bit, stand up again, grab a bit, on and on. The sensation is like slippery.

Of course, the other suggestions may contribute to the sensation.

Tires of the same nominal size don't always act the same. I had a car my brother borrowed once. He ran the front tires bald, and my Dad bought a pair with the same numbers, but another manufacturer. Wth them on the rear, everything was OK. When I moved them to the front, I could barely keep the car on the road, it jumped and tramlined to strongly. Back on the rear, they were calm again.

kingmeirl · Feb 17, 2008

Now that you mention it, I do believe it is because the tire is of a softer compound than what I had on there before, plus the tall tread blocks. They set all my tires to 32 psi, but I am going to bump it up to 40 for the autocross today, plus i think i'll drive a little harder this morning to try to work them in good. I have new proxies and had really worn fuzion zri's. I would HIGHLY recomend the fuzion ZRI's if you need a really cheap tire to use in a burnout competetion

SpartaPerformance · Feb 18, 2008

Give the tires a few miles to break in...if you still have the same problem then I guess the Proxes 4 is NOT a good choice for the s-197...remind me not to sell any to my customers!! As for running 40psi....uuuuuummmm NO. Why would you run 40psi on an autocross or any situation? 40 psi you're going to severely narrow the tread contact patch and you'll be sliding everywear.

kooldawg6 · Feb 18, 2008

tommyroc said:
As for running 40psi....uuuuuummmm NO. Why would you run 40psi on an autocross or any situation? 40 psi you're going to severely narrow the tread contact patch and you'll be sliding everywear.

+1! I don't know why you'd ever have to go above 32-34 psi.

Perhaps they're looking for better gas mileage while racing

jay07 · Feb 19, 2008

kooldawg6 said:
+1! I don't know why you'd ever have to go above 32-34 psi.

Perhaps they're looking for better gas mileage while racing

I do 40 psi on the fronts when I autocross, seems to help a lot, but I drop the rear pressure down to 28 or so. I'm still tinkering with exactly what combo works best though.

kooldawg6 · Feb 19, 2008

40 works better than 35-36? I would think that it would decrease the tread footprint and you'd loose traction(as tommyroc said)while achieveing less rolling resistance...double edge sword.

kingmeirl · Feb 19, 2008

I run 40 psi in the autocross, as I was told by fellow autoxers because you want to keep the sidewalls from rolling over. I ran them on the normal 32 and the switched to 40 and could tell a huge difference, lots of rolling over of the tires at 32 psi. Stiffer sidewalls are better then more tread touching the ground in autocross, and the opposite is true at the strip...

o0Dan0o · Feb 19, 2008

I think you should get some better tires for auto-x then... When the load (pressure) on rubber increases it's coefficient of friction decreases. While the total friction per unit area increases, the contact area decreases more quickly giving you a net loss.

Similarly, a common misconception is that a wider tire gives you a greater contact patch. Thats not true, the contact patch is determined by pressure in the tire and nothing else. The tire width determines the shape of the contact patch, which is equally important.
Dan

SlideWRX · Feb 22, 2008

Actually it's pretty common to run 40 psi at auto-x. Most people start around there, work out a good front/rear pressure balance (to get the car to over/understeer the way they want), then go up down with the set to find optimum grip.
At auto-x, tire pressure only goes up ~1psi between runs. At track days, psi can easily jump up 6-10 psi, so they start the day around 30-34 psi and adjust after they've been running. They do aim for 40ish psi, however. Even the guys with the super stiff sidewall tires run high pressure, so it's not just trying to correct for a soft sidewall/rollover.
40 psi isn't a hard & fast number; I have a note for myself to try 38f/39r for the next event. Those numbers will likely change, as I have Koni's to install. once I install those, I'll use those more to tweak over/understeer, and try to match air pressures front/rear.

wider tires give you a wider contact patch, which, all other things equal is better.

As for the original question, as someone mention mold release stuff can effect the handling, air pressure levels & balance front/rear, and tire design (stiffer/softer sidewalls).

Tom

anthony05gt · Feb 22, 2008

I had a squirrely feeling under new tires many times over the years. Give them 100 miles or so and it should probably go away.

Body roll with new tires?????

dmaxstang

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LV51FER

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dmaxstang

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Barry06GT

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kingmeirl

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bigcat

start with the upper hole, and if more traction is

Frank S

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kingmeirl

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SpartaPerformance

kooldawg6

mine works really well and can take a fair amount

jay07

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kooldawg6

mine works really well and can take a fair amount

kingmeirl

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o0Dan0o

SlideWRX

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anthony05gt

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Body roll with new tires?????

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