Hi all,

After using the search engine... I didn't find my answer...but I read some threads plus I read in the top 100 common questions.

As you will see I'm not a tire expert but here's my question :

I own a 06 ZR with the stock : suspension / tires / rims :
225/45R18 front and 245/45R18 rear

If I keep the same rim (OEM) and I would like to change my tires for
245/40R18 - rear 275/40R18

1. Since the rim has the same width, the tire should not be larger right ? If it's possible to do, I'm affraid that with the stock splash guard I'm gonna chip and sandblast the whole side of my car because the tire might be larger...

2 Do I have to touch my fender ???

If any of you have done this, or can comment, your help will be appreciate.

Thanks in advance

 

Can you? Yes.
Should you? Probably not. The widest recommended tire for the 18x8" wheel is 245. While a 275 will fit, it is not the optimal tire width for the wheel size. Your handling and ride quality may suffer as a result of squeezing such a wide tire on.

 

The new tire sizes appears to be ok.

You can use the below calculator:
http://www.miata.net/garage/tirecalc.html

 

But, aren't the rears 18x8.5

 

You can, but I wouldnt. I think the best set up for stock wheels ( 18x8 & 18x8.5 ) is 245's front and 255s back.. or maybe 265s back. 245s and 255s is what I see most people use.

 

You are correct - that means that the max recommended is a 255.

 

Thanks for all your inputs.

your right about wheels Black Z Eddie and ZthirtyThr33 :

Front
Size: 18x8.0
Offset: +30mm
Weight: 24.4
Tire: 225/45/18

Rear
Size: 18x8.5
Offset: +33mm
Weight: 25.8
Tire: 245/45/18

So front rim to go 255 should be 8.5 - 10 in
Rear to go 275 should be 9 - 11 in
with these measure My OEM rim, Touring 18" v.2 won't fit.


But if my rims was larger a bit, the match was perfect for the ratio and speed difference roughly 1%
Black Z Eddie I prefer to use this calculator... http://www.1010tires.com/TireSizeCalculator.asp

About you DavesZ#3 :
I didn't wanna too large but I had a good price for these tire.

At this point I will keep the standard sizes. As per the calculator the other size in between won't fit as well.

I continu to read your feedback and I would like to thank all of you.

 

The smaller your wheel height and the greater the aspect ratio, the more flexibility you have when mounting wide tires (i.e., mounting tires with widths that go beyond the manufacturers recommendation).

To provide an example that takes this argument to its extreme: I found that I could easily mount a high profile 275mm width tire on my serious off-road 4WD vehicle equipped with 15x8” wheels. That works because the small diameter wheel uses a high profile (aspect ratio) tire. This arrangement (small diameter wheel with high aspect ratio tire) provides a lot of latitude when selecting a tire width.

On the Z, a 17” wheel is more forgiving when mounting various tire widths since the 17” uses a higher profile tire. You have some latitude here. Notice that many Z drivers successfully mount some pretty wide tires on 17x8” wheels.

But, going to an 18” wheel (and of course a 19” wheel is even less forgiving), the profile (aspect ratio) is smaller, to the point you need to respect the tire’s manufacture’s recommendation matching tire width to wheel width. A 275/40-18” tire on a 18x8” wheel (or even a 18x8.5” wheel) provides disappointing handling characteristics at best, and a totally bad arrangement at its worst.

--Spike

 

Got ya...
Thanks for having take the time to do the ''scientific'' explanation. That's more clear in my head and you won't see that often .

That's a good reason to stay with the stock measure. Security and handling. my car will be more predictable with 255....

 

The two most common questions here are

What's the biggest?

and

What's the smallest?

There is no correct answer. If you are interested in looks, do as you wish. If you are interested in handling, match wheel and tire width for the greatest surface contact print. That generally involves wider wheels for wider tires.

 

With 18x8 fronts, I'd do 245/40 18
With 18x8.5 rears, I'd do 265/40 18
Those are both assuming you are after width.

 

this thread ... https://my350z.com/forum/wheels-and-tires/325123-wider-stock-tires.html
talk about the same subject

 

By far… the best answer on this thread. You know, but I'm not sure readers will understand the subtle part of your message.

I would suggest a reader on the thread listens to your advice, and then searches… and searches again, and again… and then reaches Nirvana (the correct solution for the specific result they want).

I realize my advice (and yours for that matter) is somewhat vague, but there are just so many options, conclusions, and desired results (i.e., esthetics, performance, handling, etc.).

--Spike

 

I'm not speeding with the car, I use the bike for better feeling so that said I will go more for the look but I really wanna keep a safe handling !

Yes I am

Your right about so many conclusions but that why I asked for your opinions. I'm sure if I had said I'll go 295 for the rear most of you will kick me in the nu** it's alway good to have a lot of feedbacks and stay grounded with the answers

 

And I suppose if you *really* want to push the limits you could do a 255/40 18 front and a 275/40 18 rear, but I don't think I would go wider than the 265 out back. Maybe 255 front 265 rear for less understeer?

 

How would it effect my handling if I go with these measurements?

225/45 18x8 fronts
255/45 18x8.5 rear

 

You won’t notice any difference between front 225/45-18” and rear 255/45-18.5”
vs.
front 225/45-18” and rear 245/45-18.5”

A 10mm difference is not significant.

You will notice a difference if you go “all square widths”… front 245/40 and rear 245/45. This configuration provides nearly neutral steer.

--Spike

 

I've fit a 285 tire on an 8" wide rim before. However, with the small aspect ratio, the tire bulged and my contact patch with the road was actually less than it was with a 245 wide tire. If you're going for looks, it's one thing, but from a performance standpoint, not a good idea.

 

That is not correct. The 8" wide 5 spoke wheel didn't come to the "Z" until '06. You should have 6 spoke alloys that are *8 wide front and back. A 255 cross section is the widest tire that should be on that wheel. You can run 245/40/18 up front and 255/45/18 on back.

Lou

 

I don't know if your message is directed to me but I have a 06....