Guess it's time to finally pop my proverbial "cherry" and ask some questions.

I have PM GT with 18" stock rims and want to put something a little nicer, actually a lot nicer. I was wondering if anyone here could help me out with wheel sizing. If I can I'd like to go for a staggered look, maybe 19x8.5 front and 20x9.5 rear. I'm just not sure about tire sizes and conflicts with rubbing.

I'm looking at getting these http://www.1010tires.com/wheel.asp?wheelbrand=Axis&wheelmodel=Penta]Axis Penta (Hyper Black). (http://www.1010tires.com/wheel.asp?wheelbrand=Axis&wheelmodel=Penta)

Any help would be much appreciated. Thanks again.

Unless you have access to program the computer for different OD (outside diameter) tires front and rear, I would recommend staying with the same diameter wheels fore and aft. Otherwise you can/will run into issues with brakes/ABS, etc. Plus, if you get into an accident, you will find that any insurance you had will magically disappear once they find out about your mismatched wheels & tire combo.

That said, you can certainly get 19x8.5's in the front and 19x9.5's in the rear and be okay. You will want a minimum offset of 40 for whatever wheel you consider, otherwise you can run into problems with rubbing, depending on what width tires you choose.

Wheel size has no bearing on outside diameter, get the proper sized tires that have matching diameter front and rear and you'd have no problems. 245/40/19 fronts and 275/30/20's on the rear should be the same diameter.
How can you even claim having different size wheels will void your insurance??? Vettes have been running staggered rim sizes for many years now from the factory.

Wheel size has no bearing on outside diameter, get the proper sized tires that have matching diameter front and rear and you'd have no problems. 245/40/19 fronts and 275/30/20's on the rear should be the same diameter.
How can you even claim having different size wheels will void your insurance??? Vettes have been running staggered rim sizes for many years now from the factory.

For a wheel & tire combo to look right, the proportion of tire sidewall to wheel diameter necessarily dictates that the rear outside diameter be a larger number than the front outside diameter, if you are using different diameter wheels. If you use 19's in the front and 20's in the back, the sidewall height will need to be the same front are rear in order to look aesthetically correct. This means your OD in the rear will be larger than your OD in the front.

In your example (245/40-19 fronts and 275/30-20 rears), although your ODs will be the same, you will have 3.9" of sidewall in the front, and 3.2" of sidewall in the back, which will look pretty stupid. No one does it this way who does it at all. To look right, you need 275/35-20's in the back (for 3.8" of sidewall), which would make your rear tires an inch bigger overall than your fronts.

Although you are correct in stating that Vettes do this from the factory, you fail to mention that the Vette's computer is programmed this way, and can account for this idiosyncracy in making all of its ABS calculations. It is designed this way. Unless (1) your car's computer is capable of this type of programming, and (2) you actually make these corrections, setting up a different overall diameter front and rear setups is ill-advised.

And finally, to address your last question - if you get into an accident and happen to get an on the ball inspector who notices your out-of-spec wheel/tire combo, not only could you end up voiding your own policy (and having your own vehicle not covered by insurance), you could end up liable for damages to all other people, vehicles, and property. Not something you really want to mess with.

Well, you must not pay attention to the F body community because MANY people are running staggered 17/18 combos and some running 18/19 combos with the same diameter front and rear tires. I didn't say it looked good, just that you can do it and keep the same diameter front and rear.
If you really want to get technical, even going from a factory 18 to aftermarket 19 wheels could void your policy since they are larger than the factory equipped wheels, even though 19's were a factory option(some insurance companies explicitly state that larger than stock wheel/tire combos will void your policy). You take your chances with customizing your vehicle and pick a good insurance company that won't nitpick and screw you on every little detail.

Unless you have access to program the computer for different OD (outside diameter) tires front and rear, I would recommend staying with the same diameter wheels fore and aft. Otherwise you can/will run into issues with brakes/ABS, etc. Plus, if you get into an accident, you will find that any insurance you had will magically disappear once they find out about your mismatched wheels & tire combo.

That said, you can certainly get 19x8.5's in the front and 19x9.5's in the rear and be okay. You will want a minimum offset of 40 for whatever wheel you consider, otherwise you can run into problems with rubbing, depending on what width tires you choose.

So if I went with 19x8.5's front and 19x9.5's rear, what size tires would I need to get? I'll be honest, I have no idea when it comes to tires/wheels except what looks good on what car.

Looks like the Penta's don't have an offset of at least 40 for 19x8.5's. So now I'm looking at these Beyern Mesh Black wheels.

19x8.5 w/ 40 offset 1.5" lip
19x9.5 w/ 45 offset 3" lip

http://www.1010tires.com/wheel.asp?wheelbrand=Beyern&wheelmodel=Mesh+-+Black&pc=1995BYM455120B72

Correct me if I'm wrong, but these should work with the right tires, right?

Looks like the Penta's don't have an offset of at least 40 for 19x8.5's. So now I'm looking at these Beyern Mesh Black wheels.

19x8.5 w/ 40 offset 1.5" lip
19x9.5 w/ 45 offset 3" lip

http://www.1010tires.com/wheel.asp?wheelbrand=Beyern&wheelmodel=Mesh+-+Black&pc=1995BYM455120B72

Correct me if I'm wrong, but these should work with the right tires, right?

That's an excellent combo and will work just fine for you. For tires, if you get 245/40-19's for the front and 275/35-19's for the back, you will have the same overall diameter as stock (front and rear) and will need no computer re-programming.

Looks like the Penta's don't have an offset of at least 40 for 19x8.5's. So now I'm looking at these Beyern Mesh Black wheels.

19x8.5 w/ 40 offset 1.5" lip
19x9.5 w/ 45 offset 3" lip

http://www.1010tires.com/wheel.asp?wheelbrand=Beyern&wheelmodel=Mesh+-+Black&pc=1995BYM455120B72

Correct me if I'm wrong, but these should work with the right tires, right?

This is probably not an issue with the 19”s, but the Beyern Mesh has spokes that turn back toward the car (you will notice that the stock 19"s push away from the car). The wheel fits great (you’ll need hub apapters (I got my from discount tires for $15 even)), but the spokes may hit the calipers. I had this problem with the 18”s. I was just going to do the spacer thing ($80+ for 2) when Mr. Sandog suggested that I modify the calipers instead. I ground them down a little and now they fit without touching the calipers.

I think that they look awesome!

This is probably not an issue with the 19”s, but the Beyern Mesh has spokes that turn back toward the car (you will notice that the stock 19"s push away from the car). The wheel fits great (you’ll need hub apapters (I got my from discount tires for $15 even)), but the spokes may hit the calipers. I had this problem with the 18”s. I was just going to do the spacer thing ($80+ for 2) when Mr. Sandog suggested that I modify the calipers instead. I ground them down a little and now they fit without touching the calipers.

I think that they look awesome!

You know the drill - PICS!!!

This is probably not an issue with the 19”s, but the Beyern Mesh has spokes that turn back toward the car (you will notice that the stock 19"s push away from the car). The wheel fits great (you’ll need hub apapters (I got my from discount tires for $15 even)), but the spokes may hit the calipers. I had this problem with the 18”s. I was just going to do the spacer thing ($80+ for 2) when Mr. Sandog suggested that I modify the calipers instead. I ground them down a little and now they fit without touching the calipers.

I think that they look awesome!

I knew it was too good to be true, damn. When you say, "modify the calipers," what exactly are you doing to them?

I knew it was too good to be true, damn. When you say, "modify the calipers," what exactly are you doing to them?

He had to shave some off of his calipers to get a set of 18's (that he had from another vehicle) to fit...you won't have to do anything with the 19's, they'll fit just fine.

I've got to say, so far this forum has surprised me a lot. Friendliest and most helpful I've ever been on.

I have one more question for ya. Any suggestions on what brand of tire to go with. I'm in Southeast Coastal Georgia, drove my car from Chicago down here. Pretty sure I won't be needing the all seasons they put on back home.

Thanks Mr. Sandog.

He had to shave some off of his calipers to get a set of 18's (that he had from another vehicle) to fit...you won't have to do anything with the 19's, they'll fit just fine.

Sandog - I'm not doubting that you are correct, but why would the 19"s be different? The specs are the same 9.5" wide with a 45 offset. Is it because they are 1" larger in diameter, so the arch angle would be less severe? I'm a little confused and would like to understand more. Initially, I planned on getting the same wheels from Discount Tire which the specs they provided are the same ones that I found. If the Mesh wheel didn’t bend backwards, there would be no issue.

Sandog - I'm not doubting that you are correct, but why would the 19"s be different? The specs are the same 9.5" wide with a 45 offset. Is it because they are 1" larger in diameter, so the arch angle would be less severe? I'm a little confused and would like to understand more. Initially, I planned on getting the same wheels from Discount Tire which the specs they provided are the same ones that I found. If the Mesh wheel didn’t bend backwards, there would be no issue.

That's the only thing I could think of as well.

Sandog - I'm not doubting that you are correct, but why would the 19"s be different? The specs are the same 9.5" wide with a 45 offset. Is it because they are 1" larger in diameter, so the arch angle would be less severe? I'm a little confused and would like to understand more. Initially, I planned on getting the same wheels from Discount Tire which the specs they provided are the same ones that I found. If the Mesh wheel didn’t bend backwards, there would be no issue.

Theoretically that should be correct...but I just realized you are dealing with 1010tires and not Tire Rack (that has vehicle-specific and guaranteed fitment), so you should call them just to make sure that this wheel will work with the G8.

I got ya!

A few years ago I bought a set of MB wheels from Discount Tire for my 2WD 99 Yukon. Everything was supposed to fit properly, but once I got them they didn't fit. The problem was the center bore was like 1mm too large for the wheel. I ended up sending them back and just got my money back. They were really cool about the return, but I was surprised at the money they ate from shipping because of the minimal difference. I would have figured that it would have been tested prior to my purchase.

It appears that there are nuances with each wheel type that may cause problems. Again, the wheels I have are of the same specs as the ones that Discount Tire would guarantee. I guess the difference would be if you go with Discount Tire/Tire Rack or whomever guarantees fitment, you can always send them back.

Does anyone know if the wheels that they list are from tests or from measurements? It would appear from my experience that they are from measurements only.