Replacement tire problems


Mark06GT

GT Owner
Mark II Lifetime
In May 2022, my Ford dealer told me I needed to replace my tires in order to meet inspection. Since the original tires aren't around anymore, they suggested Eagle F1's as a replacement. These have a smaller sidewall than the original tires, but they thought they would work.

After they put on the new tires, I drove the car home. When I hit 70mph, the engine lost power and sounded awful. I was able to limp the remaining 2 miles to work at 45 mph. Once in the parking lot, I parked the car, turned it off and inspected it. I didn't see anything obvious, so I tried to restart it. When I turned the key, the power came on, but when I pushed the button, nothing happened. About an hour later, I came back out to the parking lot and restarted it without a problem. I was able to repeat this behavior - every time I hit 70, the engine goes into limp mode and won't go above 45.

My car has been at the dealership for months now. They say the problem is due to the smaller circumference tires. They say the computer is miscalculating speed and thinks the car is out of control, so it switches to a lower-power mode for safety. They have tried to reprogram the computer to recognize the new circumference, but the problem still exists. They said the new tire size is outside the original tire size parameters and they downloaded a custom set of values to tell the car the actual size of the tires. Long story short, after months of frustration, the car is still unusable.

I see that many of you have suggested Bridgestone tires as replacement for the original tires. I'm not sure why the dealer didn't go with the Bridgestones. They say they are dimensionally identical to the ones they put on my car. The dealer has basically given up on fixing the car and I'm not sure what to do next.

Any suggestions would be helpful.

Thanks.
 

twobjshelbys

GT Owner
Jul 26, 2010
6,053
Las Vegas, NV
Get the Bridgestones. Most aren't savvy about the Bridgestones on the GT because they don't cross reference in the standard tire cross reference tables. They are the best solution and do fit. Make sure to get the right version for the front. You want the one with "N1" in it...

Make absolutely sure the dealer returns your tire programming to the original "revs per mile" setting.
 
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B.M.F.

GT Owner
Mark II Lifetime
Jan 29, 2009
1,782
Minnesota
Order some bridgestones for it and make them put them on..
 
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fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,475
Belleville, IL
Just curious, but do you know what rpm you were at and what the water temp was on the gauge?
 
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Mark06GT

GT Owner
Mark II Lifetime
Just curious, but do you know what rpm you were at and what the water temp was on the gauge?
I don't know, but the engine wouldn't have been very hot. I had only driven a few gentle miles before experiencing it. The first time I tried it, I was probably in 3rd gear when I hit 70 (merging onto an on ramp). The second time I tried it, I was gently passing on a highway, probably in 5th or 6th gear at around 70.
 

GT@50

GT Owner
Mark II Lifetime
Dec 14, 2019
852
Issaquah
I don't buy it. About all I could imagine happening would be an ABS light if tire stagger front to rear was too large. There's no traction control so the engine would keep running fine. The computer doesn't know what gear you're in so a fault related to RPM vs MPH wouldn't be possible. If it's going into "failsafe", there should be a code that caused it. What is that code?
 
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GT101

*UK Support*
Supporting Vendor
Jan 20, 2010
380
Colchester, Essex, UK
The car is looking at wheel speed and if it sees a big mismatch between front wheel speed and rear wheel speed that's when it's getting unhappy.
We had this back in the early days of the Ford of Europe press car. The press car had gone to some journalists (in Denmark I think) and they'd done some track time with it and when it came time to drive it back to the UK where it was based the tyres were illegal so got someone locally to fit new tyres, obviously they didn't have the right size so they got the nearest they could and had to drive it back at around 50mph. Which must have been fun.
I don't believe it's possible to change these settings in the calibration. So you need a set of OE or Bridgestone tyres I'd say.
 

Pettyfan43

GT Owner
Mar 29, 2022
70
Patterson Ca.
Had no problems with changing to Bridgestones on my 06 adding 2000 miles of trouble free driving they are a huge difference over the Goodyears
 

centerpunch

ex-GT owner x2
Mark II Lifetime
Sep 16, 2005
952
OH/NC
In May 2022, my Ford dealer told me I needed to replace my tires in order to meet inspection. Since the original tires aren't around anymore, they suggested Eagle F1's as a replacement. These have a smaller sidewall than the original tires, but they thought they would work.

What are the exact sizes (width and aspect ratio, molded on the side) of the tires they put on the car?
 

centerpunch

ex-GT owner x2
Mark II Lifetime
Sep 16, 2005
952
OH/NC
My car has been at the dealership for months now. They say the problem is due to the smaller circumference tires.

MONTHS?

WTF? Are they waiting for the tires they installed to magically change size?

The answer is, duh, to take off the tires that they should never have installed on the car, and install tires that are the correct size.

The oem Goodyears and the Bridgestones have diameters almost exactly the same, and have been used by hundreds of GT owners.

Put the Bridgestones on and find a new dealer who has an IQ above 50.
.
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tires.jpg
T
 
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Derry

GT Owner
Mark II Lifetime
Apr 5, 2006
339
buffalo, NY
n my second set of Bridgestone's, never had issues and much better tires than the originals.
 
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nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
OP - This is a real easy one. Your dealer screwed up. They put on the wrong size tires and they don't work. Stupid. They should know better.

Get the Bridgestones and you are done.

Find another dealer with a brain.... though admittedly not an easy task.
 

GT@50

GT Owner
Mark II Lifetime
Dec 14, 2019
852
Issaquah
If tires screwed it up, and it can't be programmed, what does the 3.90:1 gear swap do?
 
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2112

Blue/white 06'
Mark II Lifetime
Upside will be the Superior ride
If tires screwed it up, and it can't be programmed, what does the 3.90:1 gear swap do?

Is it the ABS sensor that is measuring and comparing tire revolutions?
.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
If tires screwed it up, and it can't be programmed, what does the 3.90:1 gear swap do?
It is looking at the speed (revolutions) of the rear tires versus the front tires. Changing gears or drive ratios does not change that relationship. Wrong size tires do.
 
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extrap

GT Owner
Mark II Lifetime
Jul 16, 2020
1,751
Gainesville FL
Another happy Bridgestone owner here.
 

GT@50

GT Owner
Mark II Lifetime
Dec 14, 2019
852
Issaquah
Yes, ABS looks at SS's. I doubt the engine looks at them.
I'm saying that, if the tires aren't causing an ABS code, smaller tires in the rear is equivalent to the 3.9 ratio, and the 3.90's don't cause engine problems. His engine problem is something else
 

GT@50

GT Owner
Mark II Lifetime
Dec 14, 2019
852
Issaquah
And, have you ever done a burn out? Way different front to rear tire speeds.
 

HNS

GT Owner
Mar 11, 2020
96
East Coast
In May 2022, my Ford dealer told me I needed to replace my tires in order to meet inspection. Since the original tires aren't around anymore, they suggested Eagle F1's as a replacement. These have a smaller sidewall than the original tires, but they thought they would work.

After they put on the new tires, I drove the car home. When I hit 70mph, the engine lost power and sounded awful. I was able to limp the remaining 2 miles to work at 45 mph. Once in the parking lot, I parked the car, turned it off and inspected it. I didn't see anything obvious, so I tried to restart it. When I turned the key, the power came on, but when I pushed the button, nothing happened. About an hour later, I came back out to the parking lot and restarted it without a problem. I was able to repeat this behavior - every time I hit 70, the engine goes into limp mode and won't go above 45.

My car has been at the dealership for months now. They say the problem is due to the smaller circumference tires. They say the computer is miscalculating speed and thinks the car is out of control, so it switches to a lower-power mode for safety. They have tried to reprogram the computer to recognize the new circumference, but the problem still exists. They said the new tire size is outside the original tire size parameters and they downloaded a custom set of values to tell the car the actual size of the tires. Long story short, after months of frustration, the car is still unusable.

I see that many of you have suggested Bridgestone tires as replacement for the original tires. I'm not sure why the dealer didn't go with the Bridgestones. They say they are dimensionally identical to the ones they put on my car. The dealer has basically given up on fixing the car and I'm not sure what to do next.

Any suggestions would be helpful.

Thanks.
Where is your dealer located? Sounds like they screwed the pooch.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
And, have you ever done a burn out?
Ever done one at 70mph?