I have a Mazda rx7 and my and both my back tired tilt inward on the top by the wells. What your best guess?

OWWW bent axle. If it is so bad you can see a tilt like that just looking at the car

No... its not a bent axle (unless you are really unlucky) FIRST: is it lowered on springs or coilovers? that will do it, it will totally throw off your camber until you get adjustable components to counter it (adjustable rear camber arms mainly, or raise the height on your coilovers). If you are still on stock components, is it properly aligned? Simple, but its easy to overlook. If its not that...its more complicated. I'm not as familiar with the RX7 chassis so if someone knows them better, chime in please (i work 240sx/skyline mainly). What I know is on older cars there are often worn out bushings, easy to replace (I suggest energy suspension bushings) or worn out shocks or springs can do that (again, I suggest something a little better than stock like bilstein or tokico). Past that I dont know the chassis well enough to want to say more. If you really cant see anything that I mentioned, take it to a rotary specialty shop, they do all Rx7/rx8 stuff and they will be able to further inform you. Good luck

What year is the car? SA/FB models (1979 - 1985) have a solid rear axle, so if you have the tyres tilting inward you have a bent rear axle as David already posted as an option. The later models have independent rear suspension, so the possibility is that due to lowering the car the suspension geometry is thrown off or that the rear springs have started to sag badly. The rear wheels should have 0 deg 44' +/- 30' negative camber.

I disagree on the bent axle....I remember seeing this same exact thing occur on LOTS of rear wheels of mid-80's Nissan 300ZX's. No idea what caused this..I've always wondered about that though. Never had this problem on my '91 RX-7 ..go figure.

Camber alert, you have Independent rear. get a camber kit if you put an aftermarket suspension on it.

that or your suspension is shot

So much for my bent axle answer. Watch and learn, I like to do that fellas

So basically some of them had a factory posi rear end and a independent rear suspension, my 1990 conv 5 speed does it too there also toed in just a little for control on straight lines.