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2003 Ford Escape AWD Tire Replacement

Hi,

I have a 2003 Ford Escape with AWD. One tire has been damaged and is not repairable. The other tires are 1 year (~10k) miles old. Without looking at the car, the tire shop told me that I must absolutely replace all four tires.

I’m looking for some actual information based on the facts of this particular AWD system, not opinion, lore, or a desire to make 4 tires’ worth of profit off of me.

From what I understand, this is an “on-demand” system. It’s basically a FWD vehicle with a center differential that allows the rear wheels to be engaged as necessary. On the dash there is a “4x4” selector switch. The setting for this switch is either “AUTO” or “ON.” Does anyone actually know how this system works?

The electronic selector switch leads me to believe that the rear wheel engagement is managed with some sort of physical actuation, not some a limited-slip coupling. If so, how does the vehicle detect front wheel slip? I would imagine it would use the front wheel speed sensors like are used for the ABS, but I’m just speculating. Since it’s an open differential right-to-left, I would think that the front right and left wheel speeds would be compared to determine if the front wheels were slipping, not comparing them to the back wheels.

The owner’s manual does not specifically address this. It just mentions something generic about making sure that all four tires are the same size. It does not address it as an issue with the AWD system. Also, “same” is not defined. Clearly there has to be some tolerance for differences tire wear, right?

Incidentally, when I asked the tire shop to explain my AWD system and why I needed to replace my tires, they told me my vehicle was “like a Subaru.” That didn’t inspire me with confidence.

Thanks for any input,

Matt

What you need is a tread depth gauge. They only cost about $2. Now measure the tread depth of all your tires. The gauge gives reading in both metric and inch, the inch being in 32nd of an inch. For example, if it reads 9, that means 9/32".

Now measure the depth of a new tire, same size, model and brand. Lets say your tires all measure 9 and a new tire measures 10. That is close enough to replace just one tire. If the old tires measure 7, then you need to replace all 4.

Most likely, the front tires will show more wear than the rears. Lets say the fronts are at 7 and the rears are at 9. If you damaged a rear tire, just replace it. If the damaged tire is a front tire, replace both of the fronts and leave the rears alone.

I’m not a big fan of regular tire rotation, but with AWD, it is necessary. Even with AWD, I would prefer to base the rotation schedule on the tire wear instead of mileage increments. Periodically, measure the tread depth and when the fronts are 1/32" shallower than the rear, its time to rotate. Another good reason for buying a tread depth gauge.

You might investigate having the new tire shaved down until its circumference matches the circumference of the old tires. I know its a tough sell to throw away good rubber but you would be throwing three fairly good tires away otherwise.

Hope this helps.

I’d shave down the new one until it’s close to the others. Probably won’t take much.

If its as you say front wheel dr and you have to press a switch then I would put the new tire on the rear and move the rear tires to the front. If it was a front tire that was damaged. If the front wheels are doing most the driving they are wearing faster than the rears anyway. Besides with only 10k on the 3 left their should not be much wear.

I think oldbodyman is correct. If you have the vehicle in FWD mode most of the time, then the two front tires need to match, but the rear tires can tolerate a bit of difference. But remember that from now on you can only rotate left/right, you can’t rotate front/rear. Shaving is also a good idea, depending on the amount to be shaved off, and assuming that you get the same model/tread pattern of tire.

If your owners manual does not specify a requirement, I would buy one new tire (matching the other 3 if possible) and not worry about it.

Your AWD system would probably not tolerate a tire or tires that differred in circumference. When the front wheels are driving, it is true that not much power is being sent to the rear differential.

For the first case, lets assume that the System Mode Selectsor is in the ‘Auto’ mode. If the front wheels are not turning at the same rate as the rear, a Rotary Blade Coupler begins to engage passing more power to the rear using a viscous coupling fluid between the plates. The rotary blades build pressure that pushes the plates closer together. If the speed differential between the front and back were continuous (as mismatched tires would cause), the viscous fluid would be heated and the rear differential oil could overheat because of the excessive load. Actually the front differential would be fighting the rear differential in a binding condition.

For the second case, lets assume that the 4WD is ‘ON’. Here, an electrical clutch is activated locking the front differential to rear differential. This would cause bind whenever the front and rear diffentials rotated at different rates. The clutch would probably slip to relieve excess torque buildup.

BTW the front and rear differentials are open side to side so if one wheel is slipping all power from that differential goes to it. I suspect that the traction control system activates the ABS braking solenoids to limit the differential spin of the slipping tire as well as folding back the engine power using the electronic throttle. This is not really germain to the subject at hand.

The best approach is to contact Ford technical service and ask how much tire circumference variance is allowed