Greetings,
First, Im not a car professional, far from it, so I dont know much or have much experience, so maybe this is normal, but just looking to find out more since I never seen this before.
But I swapped out my stock 18x8 is250 wheels because I hit a bad pot hole and one rim was totaled. So I threw on a set of hyundai wheels which I was told would be ok, given some rubbing due to larger tires (18x7.5 +39 235/50/18) rather than my stock 225/40s.
well I used them for a while and one tire went flat, I took it off and noticed this wear



So Im wondering, if I should replace the tires with 225/40s or just these rims are not compatible with my car and I should look for new ones?

 

Looks like they are wearing on the fender opening, and if so the fender is ruined and if left untreated will be a rusty mess in about a year. If that is the inside of the wheel and tire then its likely wearing on a suspension component or bracket in the fender well area. Do you run some wild camber on it?

 

Got a better pic of the tire damage? Hard to make out what you've got there.

 

Its on the inside and this is the rear tire. Im on stock suspension. Is this weird? because I was told it would be okay since the width is smaller than stock, only thing bigger is the height which is 50 instead of 40. I even used the http://www.willtheyfit.com/ site and says should be okay. But idk if I should get new wheels or jsut smaller tires

 

I'm really surprised that you heard no rubbing It looks to me like the problem is the wheel offset. Also the Hyundai has a 54.1mm Hub measurment and the Lexus a 60.1mm. You would need hub centric rings. My advise - throw them away.

Lou

 

Right, OP said he is not car professional, LOL! At least he should've check tire wear first several days after replacement. Looks like the tire is done.

 

Where is the tread on that tire? it looks to be worn completely bald.

 

I certainly hear rubbing like when I hit a bump, most rubbing i heard was when I full turn my wheel in the front. But understood. Certainly will look for something new.
What about some 17x6.5 +55 64.1 center bore?

 

Man you've used 235/50/18 wheel on your IS ? don't listen to those lousy mechanics because they just wants to sell the wheel to you, if you don't know you should ask here or use anything within Toyota/Lexus Brands, if you use different size wheel this is what gonna happen.

Lexus IS/GS offset is +45 which you can use wheel size 225/45/17 and 225/40/18 wheel and tire offset can be from +35 to +45 on these sizes DEPEND on if your car is a RWD or AWD, Hub centric for Toyota/Lexus is 61 , for aftermarket wheel like 19in you can use 225/35/19 or 235/30/19 , this is for Stock suspension.