2005 Mazda 3i wheel alignment

We bought a used 2005 Mazda 3i five months ago. The rear tires wore almost bald on the inside, so we just replaced them–the mechanic said the wheels are way out of alignment but that it’s not possible to align the rear wheels on this car unless we buy an after market kit. Questions: If the car isn’t built to be aligned, does adding a kit mess up how the car is designed to work and possibly make something else not as efficient or safe? I don’t know much about cars. Is there something I should know about why a company would build a car that couldn’t be aligned? I like the car otherwise, but I feel sort of ripped off because the kit, the installation, and the alignment would cost about $500.

Look at the rear tires from the rear of the car. Do the tops of the tires slant in? Check this with a normal load in the car. If they do, you maybe carrying too much weight in the rear. If it looks normal and the tires were almost worn out when you bought it, the previous owner may have carried a lot of weight in the rear and you wont have the same problem.

If the tires are slanted in and you are not carrying anything heavy, then something is wrong in the rear. It could be as simple as a camber adjustment which should not require any kit.

This would not be the first make or model that required an aftermarket kit to be able to set the camber.

I don’t think the Mazda 3 has any camber adjustment on the rear and VDCdriver is correct that your car is not the only one to ever suffer from a problem like this.
It has happened with many makes and models and can affect front or rear alignment.

My Merkur also suffered from the same problem (too much negative camber which is what causes excessive wear on the inside edges) amd it had to be modified with a kit.
Unfortunately, every brand of car made suffers from glitches. You are not ripped off; you simply have to play the hand you’re dealt and move on.

There is a company who’s main product is rear camber kits,I could probably “google” it up but again rear camber kits are normal,the price you are quoted seems high. See if you can locate the part online.

Thank you. I’m learning!

I appreciate your explaining that needing a kit is not that uncommon. I never heard of it and didn’t want to be taken advantage of – though I have no reason to mistrust our mechanic.