1998 Lincoln Town Car trac active

If the problem started with the new tires, it's easy to diagnose that the one new tire has a different outer circumference than the old ones. That will make it rotate at a different speed which makes the anti-lock brake controller think a wheel is slipping. You need to buy four new, matching tires when the car has traction control or anti-lock brakes. You can try numerous single tires, but they have to be installed on a wheel to take the measurement to match it to the rest of the tires.

Springs and ride height modifications are things lawyers and insurance investigators love to find when they're trying to shift the blame for crash from their client to you but that will not affect the anti-lock brake system operation. The ABS / traction control needs to see all four wheels turning at exactly the same revolutions per minute. If the car only has anti-lock brakes, the computer only acts on the different wheel speeds when you press the brake pedal. The common complaint with mismatched tires is "false" or unneeded system activation when you're stopping.

Traction control is an add-on feature to the anti-lock brake system. That will engage a brake when you're NOT pressing the brake pedal when it thinks one tire is spinning faster than the others. That's what you are experiencing.

You can get away with mismatched tire sizes and tread patterns, (although that makes alignment technicians shudder), as long as the outer circumference is the same on all four. Here again, even though those mismatched tires might appear to work okay, we have to consider the legal ramifications of selling them to you. If the other guy runs a red light and causes a crash, a good lawyer or insurance investigator will convince a jury that you were partly at fault because you were less able to avoid the crash, and they will be right. There reasoning, in this case, is it is well-known that a skidding tire has little traction, therefore, little stopping power. (Avoiding that is actually the purpose of anti-lock brakes). When you have different tire tread designs, one will always have better traction, meaning stopping power. If one of the other tires starts to skid, you'll hear that, and to restore the traction you need to let off the brake pedal a little. That increases the stopping power for that tire, but the other three were not yet stopping to their highest potential, yet you let off the brakes. That means they're stopping with even less power. Stopping distance increases and you are less-able to avoid a crash.

That is the way our legal system works. You have the luxury, and the argument, that the car has anti-lock brakes, so the computer controls each wheel to prevent lock-up while maintaining the highest stopping power to each one, but with mismatched tire sizes, the computer will be confused by their different rotational speeds. You don't want to give the lawyers anything they can use against you to lessen the other guy's responsibility.

I put that legal stuff in there because car owners rarely think about it. Mechanics and shop owners have lawyers and courtrooms in the back of their mind with everything they do to your car and every service or repair they recommend. To avoid these problems they should not be selling you just one tire. If they do, and it results in the ABS system not working properly, they should be very willing to keep trying different tires until they find a set with the same measurements.