Tire/rim sizes... NEED HELP!!

[mother_russia]

Sup ladies and gents.
So about a week ago, I got my first e30.
It's currently undergoing some maintenance, and while it's in there, I got some questions.

In the future, once I save up some more money, I'd like to boost the m20.
Knowing that one day I might make a decent amount of power, I'd like to get a good rim/tire setup so that I won't be spinning through all my gears.

I want to know, what's the widest tire size that I can fit in the front and the back without causing too many problems?(Considering that I'll be low on coilovers)

Oh and one more thing. I don't understand how to read rims yet.. Yeah, I'm kind of a beginner to all this, but someone PLEASE help me haha..
I understand how to read tire sizes(i.e. 225/45/17), but I don't understand how to read rim sizes.
For example: 15X6.5 +38 MB Wheels 4X100

All I know is:
4x100 = bolt pattern
15 = rim size
6.5 = rim width? not sure.
+38 = no idea

[e30leigh]

4x100 pdc bolt pattern. yip
15" rim diameter. yup
6.5" rim width. yup again. going well so far lol
+38 is offset. thats an important one. its basicly how far in or out the wheel sits. its measured from the very centre of the rims width to the bolt face of the wheel. the part that touches the hub on the car when its bolted on. offset is an art. itll make or brake the car. in terms of where the wheel sits. the clearance it gives for turning on the front and tyre clearance. so that one is very important. it takes some thinking. best to go with tried and tested sizes here if your new to the game.

as for tyre size. i know 225 fits all goods with about a +20-15 offset. some guys have gotten 245's under but i think you need to pull the fenders out with that width and offset.

im personally doing an m20b25 (2.5l) build myself. and ill be running 225/45/r16s in the back and the front. with either 16x8s +20-15 all around or maybe a 9" in the back. and i believe with a decent quality tyre they will hold well enough. it also depends on your driving style. if your new to big horsepower or turbos id say its best to start slow. suspension and brakes are your best mates as fast as the start of building a car. then slowly had the power. there also no comparison for big sticky tyres.

there is a huge line up of offsets, widths, diameter wheel and tyre combos that fit these cars. some as extreme as 10" on the back and negative offsets. its all up to you man.

happy learning. hope some of this helped. also do some research on google and the forum. theres sssoooo much out there about these. its endless. since the mid 80's these things have been modded and all sorts by all sorts of different people the world over.

[mother_russia]

haha thank you soo much.
I've just been seeing alot of peoples' setups have super skinny tire/rim widths, and I was just wondering how they put down their power..

So putting 225's on 16x8, wouldn't that be a stretch?
As much as I LOVE stretching, it means less rubber on the ground, no?
What rim width would be good if I wanted to stretch out 245's? around 9.5?

[akorcovelos]

You have about 2 years worth if reading to do to even think about boosting and making the mods your mentioning. It sounds like your just regurgitating what you've seen done on the forums with no idea what it actually means.

A good place to start would be changing your timing belt and water pump.

[mother_russia]

You have about 2 years worth if reading to do to even think about boosting and making the mods your mentioning. It sounds like your just regurgitating what you've seen done on the forums with no idea what it actually means.

A good place to start would be changing your timing belt and water pump.

Two years, huh?
Well then, I better get started!

I've always just bought my wheels. I never actually bought the rims and tires separately to get what I needed. Not that bad with cars.
Water pump and timing belt are already changed.