This whole thread is about "square" tires sizes, not wheel sizes. You can put the same size wheels on all four corners and still use a staggered tire setup. Some of the 03-05 Z's came with 8x18" wheels yet 225/245 tires.

 

You answered the question I just posted on this OLD thread! Took me a while on *search* though. BTW, this isn't a true *square* set up, since the rears are still 8.5" wide vs 8" up front and the profiles are still different. I really think a a 245/40 up front will dial out understeer nicely.

 

Yes, a 245mm wide front tire will mitigate understeer, unless the rear tires are wider (maybe something like 275mm on the rear).

My wheels for the all-square setup are 8" wide, front and rear. The tire profiles are different, but have the same width.

--Spike

 

AHHHH..OK. So you're running same exact size then. I see why you would then have a bit more tendency for oversteer (still not bad), because my stock set up gives me 8.5" rims in the rear for slightly better grip rear vs front in my case. That extra 1/2" spreads the tire section width a bit more, given the same size tires. Actually, having the 40 profile up front (vs the 45 rear) will give the front tire better turn in as well with the stiffer side wall.

 

Update. I have Square set up now with 18X9.5 WHEELS, but TIRES are 245F and 275R. I do get oversteer with this..the rear can snap out without warning if I'm powering down into the turn. Handles great, but breaking rear traction WITHOUT WARNING (no tire noise) can be a bit alarming. I do have a very modest rear bar on (Tanabe non adjustable). I also have Nismo S tune shocks and springs. Wonder if others are experiencing this with same size rims all around?

 

I'm guessing that your problem is unrelated to the tires and is a result of suspension setup. With those tire sizes, you should have the same understeer as the OEM setup. I run 265s in a square setup on the track and have never experienced an oversteer problem.

Keep in mind that when you left off the gas, the weight transfers forward effectively lightening the rear. That is the classic way to invoke oversteer. Maybe you need to learn to get your braking done before starting a turn.

 

Hi ronn1, Thanks for the update. 245 F/275 R should not produce appreciable oversteer; in fact that setup is more likely to result in understeer. As mentioned by others in this thread, your suspension can influence a deviation from neutral steer. You do name the components in your suspension, but I don’t have experience with this suspension setup.

What brand/model tires are you running? --Spike

 

It's not on lifting..this is power oversteer. I do brake going in, but if I'm turning sharply and start applying power the rear can snap loose. It actually takes LIFTING to catch it! In sweepers, car is dead stable even if I feed in power. Never had this tendency with stock tires and rims (same suspension set up)..but it pushed a hell of a lot more. I suppose I could add some rear camber..right now I have -1.8* each side. Prolly should go with 2.5*.

EDIT:
Just found this tidbit in a post here..seems to be my situation

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Even when drag racing, you want camber in the rear. When the rear is loaded under power, it squats, causing positive camber. Having some negative dialed in while the car is "static" will give you better traction.

 

I have VERY sticky tires..Cooper Zeon RS-3S..Ultra Summer. But that works both ways..front sticks too! I have 245/40s on 9.5 rims..that's the MAX limit for wheel width on that size tire (245/40), so the side walls on the front are very stiff and optimal for grip! On the rear I have the SAME wheel width, but with 275s, which are the MINIMUM width for that wheel width..allowing more *flex* than the front. SO>>>even though I have a *stock* staggered TIRE spread,
the FRONTS are getting relatively more grip here.
What do you think of adding more Neg camber in the rear? I now have -1.8* each side and I'm thinking of 2.5* (I still want to keep tread wear optimal).

 

Thanks for the thorough reply. Your last report eliminates tires and tread wear along with your driving method as probable suspects for the oversteer problem you report. And, I don’t believe having the same width wheels front and rear is the cause.

The next possible culprit is suspension. You describe your suspension components so we have this information. I don’t have experience with your configuration so hopefully someone who knows this can help here. I’m not sure about the camber. I do know some owners state that different sway bars can make a noticeable difference.

You report a problem that appears to be unique to your setup; it’s probably a good idea to begin exploring until you find a solution. Oversteer that you cannot control is dangerous. --Spike

 

I don't even know where to start, but i will start with the junk tires. Crappy tires with soft sidewalls and you try to heavily load them and they break loose. A 10.5 rear wheel may help a lot. Next we have your swaybar situation, the tanabe mystery bar. Do you only have the rear bar or both, how much stiffer are they than stock? I would just go buy Hotchkiss bars reading your sig it says only the rear. I run the hotchkiss bar full soft 80% stiffer than stock out back and 20% stiffer up front, what are you up to the GayDM mystery bars? Last is the camber issue , not much more than -2 is needed for an NA Z. What track to your run on? I would only run that much camber on high speed flowing track like Willow Springs. How much front camber do you have? I suspect you have around -.8 front, that would give you mad understeer vs proper front camber of -2 plus.

 

It's not the tires..they're BRAND NEW... the same as those used on Roush Mustang. Very stiff sidewalls. Might wanna to a search on Cooper Zeon RS-3S. Rear bar is 20% stiffer than stock..you DON'T want a stiffer rear in my situation. Yes...10.5s would be nice to eliminate oversteer, but these are new wheels and I don't want another set. I have run Willow Springs BIG TRACK numerous times when I had my 944T (does 1:32 give you an idea of what I was running?)...so I'm not a NEWBIE with this stuff. I no longer track my cars..this is a daily driver. I don't want to increase front camber...I have an OVERSTEERING car. Like I said..with 245/40s on 9.5" up front, ya have a very STIFF sidewall there. The 275/40s on the rear are not as stiff, since they're also mounted on the same size wheels as the fronts...THAT'S whats at the core of the problem here.>>>>

Again..I found this here:

When the rear is loaded under power, it squats, causing positive camber. Having some negative dialed in while the car is "static" will give you better traction.

Just looking for a little more rear grip...not much. That's why I would like to dial in .75* more camber there (-2.5*).

 

This thread makes me laugh a bit. Think 245's are an adventure....try running 285 or 315 Hoosiers on all 4.

Sounds like a combination of poop alignment and poop tires more than the fact that they are squared off.

 

Our cars gain negative camber under load. The stuff in red is false , drag Z's you want positive camber +0.5ish and the tires will go to 0.0ish under load.

 

I’m glad you find the thread entertaining.

Sorry to say I’m not impressed with a 40 mm (1+ inch) difference.

That’s probably a good guess, but not much more. Specific details (ie., the camber setting) are more useful.

--Spike
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EDIT: The OP describes his tires and they seem OK to me. The tires are not "squared off" as you falsely state. The OP's wheels are the same width.

 

Soften rear sway and/or stiffen front. Dial a bit of toe-in on the rear. 0 the front toe. Lower rear tire pressure, etc, etc, etc. All can help coral an oversteery rear of the car.

 

Also, 40-70mm of increase size in combination with running A compound hoosiers would boggle your mind if you haven't ever used them.

 

Rear bar not adjustable..I got it because I only wanted a modest increase in rear stiffness. This is 20% stiffer than stock..so further softening really isn't needed. I think toe and camber should help quite a bit. Going to try that.

 

not to challenge your driving, but take a class at a local auto cross.

once you figure out the power to weight, that set up should hold you over well, especially since your suspension is technicall better than stock.

im running 295/305 not but I ran a 255/295 for a long time with zero issues "after I learned how to drive my car" (first 6 months I ripped up tires and under and over steered the crap out of the car). I was all stock Sport G35 suspension.

my two cents.

 

So...you don't think going to more of a *square set up* doesn't induce oversteer on this car? I guess I have to keep repeating this...instead of having 225/45s on 8"rims on the FRONT, I now have 245/40 on 9.5" Rims. That's a HUGE difference!
Those rims are the MINIMUM APROVED WIDTH for 9.5".. stretching those 245 to their maximum optimum width for a very stiff sidewall (read GRIP!). Now the REARS stock were 245/45s on 8.5" rims and now they're 275/40 on 9.5" RIMS.....those are the MAXIMUM APPROVED width for the 9.5"..PINCHING the sidewalls a little and allowing for some *flex* (read *SO SO* GRIP).
Simply put I have MUCH more relative grip up FRONT now than stock set up.

"especially since your suspension is technicall better than stock"

Yes but what does that have to do with the BALANCE? I also have an upgraded sway bar in the REAR which also contributes to oversteer.

"but take a class at a local auto cross".

I'm willing to take criticism here and accept the fact that driving skills can always be improved given that I'm relatively new to this car. Having said that, I'm well experienced in tracking cars (Willow Springs...Sears Point..Laguna Seca..FireBird) and I campaigned a highly modded Porsche 944T for many years..I'm not uninitiated to racing and set ups.

I'm convinced I'm getting *SNAP* oversteer from powering down while turning in. Maybe I have to watch the throttle more carefully here. I'm gonna try and add an upgraded bar up front and maybe add some rear camber/toe. I'll report back on results when I do that.
Don't get me wrong..I appreciate all input here, but a lot of people assume some things that they shouldn't be.