Umm, why would you stick with 19's? What you want are 18x11's.

Agreed!! You get better handling characteristics, lighter wheel/tire combination and the cost of tires is less.

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I like the gearing offered by the 19 tire sizes. To run the 18’s I lose 3 mph in 2nd which would seldom be an issue at autocross. But I loose 6 mph in 4th which is a big problem for me at two spots on my local track (ncm). I don’t want to ha e to do a bound up dogleg down shift creating turn 16, which is off camber decreasing radius with an entry of 120+ Mph. It’s also not like there are a lot more wheel options in 18. The goofy offset up front makes for very few options. One of the great things about the 350 was 18x10.5 on stock suspension, cheap light available.

It is your choice to do with your build whatever you want too and be for warned if you come hear asking for opinions or just posting whatever you are going to get feedback that you may think is harsh, rude or whatever. Now that that is out of the way your logic goes against pretty much everything that has been posted in the track section on the best wheel selection for track or autocross. Most run 18x10.5 with a NA build with a 275 35 tire. A few of us have stepped up to 18x11s and there are smaller number running 18x12 or 19x12 (those running 19x12 run a staggered setup). The handling characteristics of the 18" tire is much better than 19's so you gain on turn in and exit. Also on a NA car 18's have the same impact as changing your gearing to about 4:08 but probably not that much. After running tire size through a calculator there is only 4 mph difference in fourth gear. You will also gain time in acceleration because you are running a smaller wheel and tire diameter.

I guess if you want to do something different than every highly successful 370z time attack or racecar more power to you, it is your car and your fun! Good luck and let us know how well it works out for you.

I’ve used the internet before, my feeling aren’t hurt ;)
11” width is max allowed in Stu so 12 wide are irrelevant. The 315 width was new in 2019 and very few seem to be run the z34 at nationals and they’ve not been overly successful. Only one bested the fastest z33’s in 2019 (no 2020 nats).
I built my own speed calculator using revolutions per mile and the gearing correct to my car. The 315/30/18’s get me only to 117.73 mph in 4th and the 285/35/19’s up to 123.8 which meshes with my gps data, the 305/30/19 will only get me to 120.99mph which might be worth the sacrifice.

On track I think mine was the only 370 at Time Trials Nationals. So there isn’t a lot of people running these cars at solo nats or TT nats.

What's goofy about the offsets? I slapped on the same set of 18x10.5s from my Z33 after I switched cars. One and done! Got 4 lovely pandemic events in time to need something else 🤣

The OE wheels on my nismo are 19x9.5 +40, the rears are 19x10.5 +23. As opposed to my 350Z (GT) 18x9 +30 and 19x10 +30. I ran my 18x10+23's up front on the 370, they fit due to the smaller diameter of the tire but stuck out from the body a bit. My 10.5 +15's would have been worse up front but fit pretty well out back.

To each their own I suppose! I've always run 18x10.5 +15 square and I couldn't recommend it more for the sake of ease. The 315 rule is probably going to bring a change to 11s at some point, obviously, but still.

I'm not finding many choices in the 11" width in either diameter.

You are going to have to go custom if you want wheels in 19x11. Volk, Enkie, Konig and Wedssport all make 18x11 in a size that will fit a Z.

fify

It's pretty easy to run 18x10.5 or 11 up front but I'm not sure what you mean by goofy offsets. If you are on stock suspension you will get some poke. Once you lower the car and add the appropriate amount of negative camber you shouldn't have any fit issues. I run a +24 up front with room to go to maybe a +18 comfortably. A stock offset wheel actually might have inner clearance issues when you add camber.

I run Enkei NT03-M 18x10.5 +30mm offset square. With 5mm spacers in rear and 20mm in front. Plenty of room and you can comfortably fit 295-30s on them. They do protrude out past the fender in the front and I’ll be installing splats soon to help that. They fit nicely with OEM Sport calipers and to my delight fit over my new Stoptech Trophy Rs. And they are affordable you can get a rain set and also replace them when you bend them (I’ve destroyed three already in off-track adventures).

Unfortunately one of the rules of stu is that the top of tire can't protrude past the fender so no f1 fitments.

So, I'm trying to decide on a good 18x11 option. The waaaay cheaper option, but still a good quality lightweight wheel is the Konig Hypergram, but I'm worried about a +15 offset. Many of you here are saying this should be fine, but math shows that these will stick out 14 mm further than my 19x10.5 +23 that I'm coming from which fit perfectly flush on the front with -3.2 degrees of camber. It would seem that running around a +25 would be best. Wheels available there would essentially double or triple the price over the Konigs, though. Anyone have good picts of 11's at around a +15?

There may not be enough back spacing to run a +22. I run +18 and it is really close.

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Don’t know if this is helpful. But this is a pic showing flush at the top with -3% camber. Theses are:
Enkei NT03-M 18x10.5 +30mm offset (relatively cheap)
With 295/30/18 Toyo RR‘s
And 5mm spacer

Is it the steering knuckle I have to worry about? Currently, I have about 3/4" of clearance, I'm estimating. Going down an inch in diameter will move the wheel slightly closer to the knuckle. I'm guessing it'll give me another 1/2" to work with. Total guesses, though, without actually measuring.

I think I'll be taking a bit of a plunge on behalf of the current thread topic. Looks like I'll be picking up a set of 18x11 square Forgestar F14s (or Gramlight 57T, haven't decided yet).

Probably going with a 18x11 +25 all the way around, with a few different sets of spacers to give me options. Per the math, I need +21 to match my current fitment and would expect that to give me about 7.5mm clearance inside at the narrowest point to the arm, depending on how the 315 tire itself sits out from the lip. That's based on a rough measurement, so I'm trying not to get down to the millimeter on the inside.

I figure if a spacer is necessary, with a 5mm spacer I'll be only millimeter off of my current setup in the front, and even with the extra tire meet it won't be looking like a formula car. If I have to run even more spacer, well I'm already rocking #44 so maybe it'll just be another silver Mercedes.

On the rear it's obviously not as much of a concern, and 10-15mm of spacer will probably get the aesthetics handled.

Fingers crossed. I've been talking to Brendan, but if anyone else has measurements that make me crazy, speak now or forever hold your peace.

Good luck, man. I was planning on popping a front wheel off tomorrow and throwing one of my new 315s under there with a rather cheap *** fitment jig I borrowed. I'm hoping it'll at least get me close.

I didn't take the time to set up a jig or anything, but I actually created a rough mold of the negative space by making some putty in the kitchen and then jamming it between the wheel and arm. I found I had 21-23mm of space depending on whether I measured at the edge of the wheel lip or at the edge of the tire. The space for the tire gets easier as you go up.

So I went ahead and ordered Forgestars with a +22 offset, which will put me 0.65mm inset of my current setup on the outer edge, and 13.35mm inset on the inner edge. That's the wheel of course, and the 315 tire will be a bit puffier so I'm hoping it doesn't take up more than 7mm of the space inside. I can use a 2.5 or 5mm spacer from Z1 to fix that right up if it does, and I'll use a 5 or 10mm spacer in the rear anyway. Will obviously update everyone with they arrive in hopefully 2mo or less...

TL;DR: YOLO hope these things fit

I couldn't trust the measuring I did on Sunday. I do have access to a legit professional fitment tool. But I would need to drive to Portland to get it which is a 4 hour round trip. I may consider it this weekend.

I think you might be in the sweet spot with the +22. I got hold of the fitment tool and set it to +25 and it appears the tire would be rubbing against the spindle just a little. +22 seems to give it a mm or two of clearance. The tool still probably isn't perfect, but it seems to give me a good idea. Now, should I take the plunge and pull the trigger on some wheels, trusting my results?

https://hosting.photobucket.com/imag..._155535(1).jpg

Do it

I was wrong about the fender rule. It doesn't say anywhere that you have to fit the tire under the fender. That should open up some options for 18x11. I mounted 315 on my current wheels today pretty easily. No rubbing and due to the shorter height, a little bit better clearance. I'll take some pics this weekend if I can get the prep on the car done in time

Here's some of the tires mounted
315 on 18x10.5
https://photos.app.goo.gl/QU9b3DN8rLGgWyox7

Finally got it to rub. I'm currently at -3 degrees of camber and my height is at 26.5 inches. I think I can raise the car another half inch and make it work. The rub happened going over a pretty huge dip in the road at speed and the witness marks are pretty minimal, so I'm hoping a little extra height will get me there.

Can we get some picts of them mounted on the car?

Quick album before I get to work on it

https://photos.app.goo.gl/buEqgziPE6cdQgfT9

Go for it! I thought the same thing based on measurements. My calculations suggested +24 would work, but with some uncertainty on the widest part of the tire -- so I figured if I'm going to potentially need spacers either way, I started at 22. I also have the Nismo flares so that helps (though only visually) with any poke.

I think I got it sorted. I'll get some proper photos later today. I will be interested to see what other folks 315 journey looks like. I'll miss the lower stance.

Issa monster truck now

https://live.staticflickr.com/65535/...6e866fd8_c.jpg_BES6507 by brendan sobers, on Flickr

https://live.staticflickr.com/65535/...303703c5_c.jpg_BES6502 by brendan sobers, on Flickr

https://live.staticflickr.com/65535/...5362ba2e_c.jpg_BES6498 by brendan sobers, on Flickr

https://live.staticflickr.com/65535/...4fc437c1_c.jpg_BES6490 by brendan sobers, on Flickr

I'm also back on my project to get a set of non-shitty-to-work-with and legal fuca for the z. I picked up these arms from gk-tech. The plan will be to buy some rod ends to replace the sphericals on the inboard side of the upper control arm. My first thought would be to replace them with the rod ends from the z1 arms which are actually pretty nice. Unfortunately the z1 rod ends appear to be rh thread and the gk-tech need a lh thread. So where I am is I will need a lh thread 3/4 16 rod end with a non metallic cylinder bushing. There seem to be a few off the shelf options available at speedway motors and summit racing but I am open to other sources and input from anyone with fabrication experience.

Before they allowed sphericals in SP I went through the same thing for the rear arms. I just got the rod ends from Speedway and they've worked fine ever since. I did need tp have a local machine shop make me a few sleeves and spacers though to match the OE dimensions though.

Hell yea. You inspired me to try this. So far this is my most promising lead

https://www.barnes4wd.com/Forged-Chr...ads_p_888.html

So not only will it have 4x4 ride height but actual 4x4 parts.
Can't wait to trigger stance bois.

So, I ordered some 18x11 +24 custom made Forgestars. I'm thinking +24 might be a tolerable rub. If not, I'll add some small spacers. We'll find out in 5-6 weeks. I'm hoping to have everything squared away in time for Crow's CT.

You guys. It worked. I'm so happy.
I will put a more detailed write up in my build thread but we have one more legal option for upper control arms.

With the right parts you might be able convert spl arms as well.

https://live.staticflickr.com/65535/...764f893c_c.jpgPXL_20210319_222049350 by brendan sobers, on Flickr

First event on the new tires. Photos showed I can go a bit lower than I had at the car. Also made some other tweaks to the suspension for the next time out. Grip is silly. This is from a practice event with a local club. I would have had ftd for my class if my buddy didn't decide to cheat and run an old set of hoosiers.

Measured caster on the new arms, actually not as bad as I thought. +7.2 which is still way more than stock. I also went to -4 degrees of negative camber since I couldn't even get closer to locking up these tires and wanted some more clearance than I had at -3.5

Figured I owe you guys some 315 / 18x11 snapshots by now.

I'm running straight second places at local events so far, 2/3 with class-winning scratch times by decent gaps but this extra tire is picking up cones ;)

We'll see how it goes nationally at Finger Lakes.

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