18's?
 

I need to increase my tire size. I have 18's in rear, what is widest I can put on car?

Depends on the width of the tire and the offset. On a 10'' tire, you can safely put 295 on there if it fits. Any more and the bead might come off. If you want more grip, which u look like u may need, u can always get a better grippier tire or get 0 camber.

I have 18x8 and 18x10 does that help?

Do you want balance or just forward grip?
Whats the offset on those wheels and are u using a spacer? Are you dropped?

I'm dropped, no spacer and not to sound to stupid but I don't know what my offsets are.

Can't really help you much without the offset. A picture of the front and rear fenders can help to tell you how much room you have. If you have a lot of room, u can fit a bit more meat in the rear.
What tires do u use right now? If they're cheap ones, u can switch to Potenza S03s. They grip real nice.. They're the tires im getting next. Michelin PS2 are nice too

All my info is underneath in my signature

Most of the time, the offset is either engraved or is on a sticker on the inside rim of the wheel. The front and rear offsets may be different. If your wheels are flush with the fender, u cant really fit bigger tires.

I'd also like to add that you can stretch the fender in the rear and give urself more room if u are near the fender. Offset determines if the tire will stick out too much though.

have you tried the search. i know i read somewhere on here where they give you all kinds of wheel combos.:twocents: i know i read it but i don't understand anything about offsets and stuff. can anyone explain or maybe give me a link to read up on it. thanks

Per his sig, this is what he has now: Toyo Proxi TS1 F245/35 R275/35

Can't he judge by what he has on now and how much room he has how much bigger he can go?