[Fohn_Jargo]

The other day I got a flat tire on one of the old Fortera's on the rear. I put the spare tire on, also a Fortera, and went on my way knowing I would have to replace the rears to match the fronts, Firestone Destination AT's.

As I would enter the highway from a cross road the EPS light would come on, power would reduce, and it left me feeling very vulnerable like I was going to get stuck in the middle of the intersection.

I got around that by turning the EPS off. That, however, left me without antilock brakes. I would rather not drive around like that especially when I have my daughter in the car.

I went to Firestone this morning and had the Destination's put on. No more problem with the EPS.

So, what caused this?

Is it that, even though the two rear tires were of the same make, tread pattern, and size, they were of enough of a different hight to confuse the ESP?

 

[runit3]

Is the spare tire the same size as the other tires? My best guess is that the computer got confused from a different rim size/tire pressure and got angry from full time 4 wheel drive, having one tire not matching.

 

[Fohn_Jargo]

The front two tires matched each other (Firestone Destination AT, OEM size) and the rear tires matched each other (Goodyear Fortera, OEM size).

It was a rear tire that was flat so the spare matched it. I'm thinking that the differance between having one Fortera with 48,000+ miles on it and one Fortera with zero miles on it is what angered the computer.

Can this be confirmed by someone in the know?

I think this can also show how important it is to get the spare tire into the rotation.

 

[runit3]

The front two tires matched each other (Firestone Destination AT, OEM size) and the rear tires matched each other (Goodyear Fortera, OEM size).

It was a rear tire that was flat so the spare matched it. I'm thinking that the differance between having one Fortera with 48,000+ miles on it and one Fortera with zero miles on it is what angered the computer.

Can this be confirmed by someone in the know?

I think this can also show how important it is to get the spare tire into the rotation.

I would assume that's the problem. My old impreza had the same exact thing happen and the computer freaked on it. When I got to Les Schwab they said I had to replace all four tires or it would keep erroring. I opted to call a buddy who had an extra tire within 10% tread of my other tires. Worked out nicely.

 

[adamag25]

when driving down the road the wheel sensor are designed to pick up even the slightest difference in wheel speed. The difference of even 1/4" in tire size would most likely cause it to come on especially during extreme accel or braking.