Jonny K

Hello,

I've highlighted the good stuff in bold in case you want to skip ahead.

All winter I've been researching rims and tires. My web browser has 40 tabs open, I've viewed thousands of posts and pictures, read all the forum FAQs and guides, have played with the calculators, and even talked to actual people. I'm still stuck and with the cost being so high I'm afraid to buy until I figure it out. I need some pro advice from you guys. I'm looking to upsize the tires and move to extremely light rims with the intention of increasing grip without compromising drivability. I don't want to roll fenders and I don't mind keeping the wheels a bit tucked to accomplish that. I don't think I'll lower the car much, if any, but suspension isn't a thought right now. My car is a daily driver in a city.

I've got a 2005 350z Anniversary Edition, absolutely stock featuring Brembo brakes, TCS, and VDC. Stock wheel specs are:

Front - 18x8.0, Offset: +30mm, Weight: 24.4 lbs, Tire: 225/45/18
Rear - 18x8.5, Offset: +33mm, Weight: 25.8 lbs, Tire: 245/45/18

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Tires
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To maintain rolling diameters and keep the ratio of front to rear sizes consistent I was looking to go with the following tire sizes:

Front: 255/40R18
Rear: 275/40R18

Both of these tires are 30 mm wider than stock so I think the handling of the car shouldn't change too much in terms of over-steer and under-steer.

Question - Why do the recommended setups suggest 245/40R18 fronts with 275/40R18 backs? This diameter of 245/40 does not match with the stock diameter (1% smaller), and that's also putting more meat on the back than on the front compared to stock which would induce more under-steer, wouldn't it? And won't you throw off your speedometer? Why 245/40 instead of 255/40?

Performance is a priority so the new rims and tires must be as light and functional as possible. I know I can go stretched or chunky but I want to be in the best place for handling and feel so a flat sidewall or very slight stretch is ideal. I researched how to size tires to rims and found this:

https://motoiq.com/how-to-properly-s...r-performance/

In response to this article and discussions on forums I read I know that I need to pick my tire first before my rim. For tires I want the best I can get. I was looking at Michelin Pilot Sport 4S, which are supposed to be superb:

https://www.michelin.ca/en/pilot-sport-4s.html

Problem - They don't make a 275/40R18 size for the 4S. The old Pilot Super Sport comes in this size but is discontinued. Bridgestone Potenza RE-71R also doesn't come in that size. I'm having a hell of a time trying to find any high end tires in this size.

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Rims
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Because performance is a priority I've decided to get some light WedsSport wheels, specifically the new TC105X:

http://wedssport.jp/products/english/tc105x.html

Using this rim my ideal rim sizes (calculated based on the tires) are as follows:

WedsSport TC105X
Front:
18x9 +25 255/40-18 - Weight = 16.8 lbs
or
18.9.5 +25 255/40-18 - Weight = 17.52 lbs

Back:
18x10 +20 275/40-18 - Weight = 17.7 lbs

I'm favoring that 9" front rim to save that big chunk of weight but the tire will ultimately determine if I move to 9.5". I love the light weight of the rims and even with bigger tires I expect to trim weight when compared to stock. I think with these conservative +25 and +20 offsets it should be a little more aggressive without being out so far that anything will rub.

Question - It seems common for people to run 18x9.5 and 18x10.5 rims front and back. Given common tire sizes that seems too big and would stretch tires and add weight. Am I missing something?

Problem - The TC105X rims are so new that I'm struggling to find info about them, especially for the 350z. They come in different faces (the spokes are curved with different clearance) and I don't know if they'll clear my Brembo brakes. I have no existing examples of this rim to compare against. The Weds Japan people tell you to talk to your local dealer as they won't deal direct with the customer, but the local guys give me no confidence and suggested a crazy "stance" configuration to me as optimal.

Problem - I'm in Canada and everything is expensive. The local dealer wants $1100 per rim which is a crazy markup when these are selling for $500 US. The Weds people say they won't warranty unless you buy from a dealer.

Thoughts?

Thanks.

Chihuahuamaster

I will say that +20-25 offset will not be flush with the fenders, which is fine, if you do not want that.

I have those exact sizes in your title, Michelin pilot super sports, put them on late last year, but I guess they could be discontinued in your country.

Keep in mind different tires also run narrower/wider even though they may technically be the same width. The 255/40 I have on a 9.5" wide wheel is slightly stretched. The 275/40 rears are also on a 9.5" wide wheel and fit perfect, not stretched or bulged. And for reference the Pilot super sports run slightly wider than some other tires I was searching for.

If you're going 10.5" wide wheel in the rear, I wouldn't go less than a 285/40/18 tire. If you went this route I would personally go with a 265/40/18, front tire, on a 9.5" wheel.

As for the differences in width, i.e. 225 front - 245 rear, or 255 f - 275 r, this is usually done to keep from having traction control issues, as well as steering feel/ balance of the car. The larger the difference of width front to rear, the more the rear will 'push' the car when turning. Not very technical I know, but this gives you an idea of how changing certain aspects may affect the car.

Jonny K

So here's the new update:

I've found a tire replacement for the Pilot Super Sport: the Continental EXTREMECONTACT SPORT. This is a new tire they recently released to compete directly with the Super Sport and apparently it's pretty comparable. It doesn't come close to the Pilot Sport 4S, but it'll do, and it's less expensive.

I contacted Weds North America and spoke for a while on the phone with a helpful guy who knows the 350Z well. He told me the front wheels should have no issues with the Brembo brakes. He also suggested I go with an 18x10.5 rim on the back, even though the 18x10 would also do. I spent the night looking at fitment pictures and I'm still wanting the 18x10, the 10.5 seems to stretch the 275 tires too much and I dislike that rounded look. Lastly, he told me that it's likely Michelin will still produce a 275/40 size tire for the 4S, they just take time to release all the configurations.

So the plan is coming together now, 18x9.5 + 25 front and 18x10 +20 rear. I'm going to look into ordering soon. The Weds guy put me in touch with a US dealer to try and I'm going to consider shipping to Montana and then importing them via a local company rather than shipping direct.

Spike100

Hi Jonny. Your final decision on wheels sounds great. You could even go with more offset (20mm or even 15mm front, and 15mm rear) but the offsets you selected will work and look great. With those offsets and wheel sizes, you won't be able to drop the car more than about 3/4" or you will rub. You are in Canada, so I definitely would not roll the rear fenders.

I am running Continental tires now (and have run other models of Conti's in the past), and I really like Continental tires.

Jonny K

The offsets the rims come in already made my decisions for me. The 9.5" wide rim comes in +10, +25, +35, and +45 offsets. The 10" wide comes in +20 and +35. So, +25 and +20 it is. I can always do spacers later I suppose. All that said, both these rims will be pushing out another 35-40 mm over stock so I should still get a much more aggressive look anyway.

I'm not sure if I'll drop the car or not. As it is I can barely enter some of the parkades I frequent, so anything lower might make the car undrivable and that just won't do.

Spike100

I am lowered about 3/4" and do occasionally scrape. There are some places I cannot go.