I ordered some 20' I-forged wheels and it is difficult finding a tire size combo that I like. I am not concerned about keeping the diameter of the tire the same as stock because I would be looking at a 30 series sidewall. That is way to small for my taste. Personally I would like a 40 series. There is only one brand that makes this combo Front 245/40/20 Rear 295/40/20 and it's about $1300.
If I select a different front tire than rear tire I would save about 500 bucks and still have the size I am looking for. Is this a big no no to do? Please no flaming.

 

dont worry about it, you really dont have to worry about performance any longer, thats already been toasted. as long as the tread holds you to the ground when cruisin down mainstreet, your in the clear.

 

I am having trouble understanding your post.

Did you just imply that performance has been thrown out the window by deciding to get 20's, or with different front and rear tires?

If it's 20s then I don't know what the big deal is?
So many are getting 19's, I don't see how going 1 inch bigger would drastically reduce performance.

Different front and rear tires was just a thought and I wanted to get feedback.
If that is where you are saying a dramatic performance lost would occur, then thanks for your post.

 

Ares was implying that the 20 inch wheels decrease performance, along with the fact that you said that you didn’t care if the diameter were same size as stock, and since you want 20" wheels and 40 series tires you not only would be putting on a heavier wheel but also a tire that is larger then stock thus raising your gearing and lowering you acceleration. Also, many hi-performance lightweight wheels are made in 19" but very few are made in 20" which indicates that you will probably be running a quite heave 20" wheel which will also decrease performance.

Hope that helps

 

Thankyou Throbber for your clarification.

I stated that the wheels are I-forged.
I ordered the 2 piece version which to my knowledge is lighter than the three piece.
The three piece weighs 25lbs for the front and 27lbs for the rear. I believe this to be a lightweight wheel.

Larger diameter would raise gearing. The downside to raising your gearing would be lower acceleration, but upside is higher top speed correct.

Although, my question still remains, what are the effects of having different front and rear tires? If there is a performance loss, is it dangerous, drastic, mild, or very slight? Thanks in advance for any feedback.

 

no, if by different you mean different brands, that is fine.

and no 27lbs is super heavy. light weight would be more like 17-19 for a 19" rim, you wont find light weight in 20". also the 20 puts its mass 10" from the center, where 19 is 9.5, and 18 is 9", yes that seems small, but it is a big difference.

also radius of tire affect gearing as was mentioned, youll increase your top speed since youll be going faster then the limiter thinks(meaning your speedo will be a little low, by how much depends on overall change of diameter, it will be little tho, maybe 3 or 4mph low at 100mph) acceleration will suffer.

as for those with 19s, that is fine, and they have their purpose, atleast they are still pretty light, but rotational inertia still comes into play(distance from center) as well as shorter sidewalls not being really optimal for anything(they ride rough, bad for traction, and risk your rim) 19s do allow a 15" rotor, but 14s are bigger than the Z needs, 15s are bragging rights I suppose.

anyway, nothing wrong with 20" rims, whos that with the chromy ones, cazzz or something? not sure, anyway, I like his. but its well known that 20" rims are very heavy and youll never see a car racing with anything near that size(ideally 17s are pretty good for pure racing, only that big so you can fit 14" rotors. smaller rims(lighter) are always better for straight line performance)