Understeer
 

How much understeer would a 265/295 tire combination have on the track? I am asking because I am trying to decide on a good tire and tire size that can be used on the street and light track work until I can afford a dedicated track set up. I plan on taking a few driving courses so I can have real instruction on how to drive, up to now its just been autox events. Wheels are SSR Type F 19x9.5 et22 F and 19x10.5 et15 R. I am still pretty new to this so it may not be an issue at all. I would like to fit a 275 up front since I am looking at ADVAN AD08's but I can get RE-11's in 265/285. I am investing in tires, brakes (AP brakes from a member) and instruction at this point. Its a base 370z so the brakes are no where close to the task. Wheel to wheel racing with this car is not in the cards anytime soon, just HST and autox.

Just as a reference we are 245 front and 275 rear by the rules.
It's all in the way you set it up :)
I would search what most track guys in here run and use that as a starting point as well as looking to see what is available for $$ track tires in those sizes.
Dwnshift

I run a 265 fr and 285 rear it grips really well and it is the set up also, you can get anything to push at some point

I'd focus on getting best tire you can either RE11 or Hanckook RS3 for street tires. Consiider ditching the 19's in favor of 18's. Then you can get 275 front and 285 rear RS3 setup that works pretty nicely on the track and AX. Look into getting at least 275 up front. While I agree its mostly about setup stockish cars need more tire up front. You likely dont have luxury of dialing in suspension and bars like a race car can. FYI I run 295 rears and 285 fronts on the track on same width rims as you. For AX I run 315 rears and 295 fronts.

If you are doing AX no amount of dialing will offset front end push if you are under 275 so go bigger in front by default for AX for sure.

Shamu, any issues with rub up front with the 295's? Also what wheels and offsets are you running these on?

Run 285 up front and 255 rear.. your car will never push again

Bwaaaahahahahaha
;)

hahah I got a flat so I had to put my spare rims on. 275/35/18 Front and 255/40/18 rear hahahah No pushing here. PS.. I know I could flip them to be a better stagger, but the wheels that the 255s are on dont clear bbk.

OP I would consider running 275/35 all the way around. That is what I run for my track setup.

Any thoughts about a 255/305 set up? I have a swift spring too.
But I noticed while I put in the power on the way to 120miles I started to loose road feedback in the front and the front feels loose like having no grip!

Is this a lack of downforce issue or alignment issue my casters are at Max in front with -1.4 camber and 0 toe.

With OEM sport wheels and oem springs got it off at 140 and it hugs the road like glue very stable.

Can you share inputs. Thanks.

How do the 275's fit? I thought about those but I have no clue if they will rub. My suspension is stock.

I'm running 275/295 on 18's, and it's a very stable setup, almost too stable. It can be a bitch to get the back to push a bit when you want it to, even with the Hotchkis rear sway set at full stiff. Next time I buy wheels+tires I'm doing either 275 or 285 all around square.

With stock suspension you should be fine. My 295s in front only rub plastic fender skirt occasionally (little scuff in plastic) and my car is almost 2 " lower than stock. Remember im on 18s and run 295/30/18. I run 275/35/18 front Nitto Nt05 on street with no rubbing at all.

If 295's only rub a little, then 275 will have zero issues. I haven't bought my wheels yet, ordering them next month. I was planning on going with 18's but Vivid checked brake clearance with he AP's on the type F and said the caliper would hit the barrel. He did say that they noticed the printer didn't print the template out in a 1:1 ratio so that could have been the problem. Worse case, I can order the 18's and check their fit over the brakes before having the tires mounted. Looks like I will be going with either a 275/285 or 275/295. Just need to determine my wheel size then brand of tire. Thanks for the help.

I run 275 all around at the track car feels great


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I am here: http://maps.google.com/maps?ll=33.890729,-118.309364

I'm running RS3 275/35/19 square I love it car feels very neutral the turn in is great now. Still a little bit of under but it's okay. I tried 305's in the rear and had zero issue with rubbing with -2.0 camber so with the proper camber 295 will be no problem.

I've tried many staggered tire combinations on this car.

245/275 stock
275/305 RE-11
275/315 NT-01
315/345 V710 - For the extreme guys :)

On all the setups I've dialed the car in to feel pretty balanced, but front tire wear is twice that of the rear. I'm considering a square setup next to see how that goes for front tire wear.

As far as understeer goes on track it can often be driver induced, such as trying to combine too much turning and acceleration. With Auto-X it's inevitable, you just have to manage it.

I agree

This is my issue right now. :driving: I need to stop it..

I'd have to say with my Nismo it's rare case that I experience understeer in AX. On track never.

Maybe it's because I come from mid engine cars but honestly I rarely understeer with Z in AX. But I'm a consummate late apexer and have no fear of using power oversteer to rotate the car if needed.

But then I'm putting down a 295 Hoosier up front. When I go to 275 front and 285 rear street the car is an oversteering monster! But its very controlable oversteer. I just drift entire ax when I drive streets! Lol!

With the stock suspension and stock stagger, I don't think you can drive anything sideway unless you are stuck in the snow

At auto-x the car will only rotate under power if you have 2 things, enough front grip, and enough power to break traction at the rear. At higher speed auto-x is can be harder to break the rear-end free under acceleration especially when I run the 345's in the summer and they're nice and sticky :)

WOW 345's ChrisSlicks?! That's man's setup right there LOL!

With 295 A6s on the front, even pinched on stock wheels, you can make the car oversteer by tweaking shocks and tire pressures. It's never going to rotate like I would want it if I could change springs or bars but I wouldn't say it understeers.

Agreed and just think what you could do with some real negative camber and toe out up front. My car pretty much goes where I point it even if I do stupid stuff. People are amazed by my car in that respect so I have never understood anyone with some level of mods indicating these cars push. Never experienced it and with 315 Hoosiers I rarely find so much grip I can't goose it out of a slower turn but that's so rare it rarely happens to me.

The one thing the Z has as an advantage over EVOs and Porsches is it ability to turn like crazy. My issue is more with being able to put down my 450 hp lol! I leave two big strips of rubber out of slower sweepers.

I love the turn in speed with my square setup and your right Chris I'm running -3 up front and rarely find a push understeer unless I'm coming in too hot.

The car does turn hard once modified. With -3.5 up front it is extremely nimble in the slow stuff. Like I said I only get push in the higher speed 55-70mph maneuvers with too much rear tire. I'd really be better off with a square setup for auto-x.

You guys are lucky. With the street tires and my pathetic .9 degrees, I have to wait before i can turn. The slower it is, the harder it plows

With 275F and 315R, I can induce oversteer just by lifting a bit just before I hit the apex allowing me to throttle-out. Bare in mind I am AutoXing on A6's. As a point of reference, my next set will be 295F/315R A6's!!! I do run approximately 2-2.5 deg neg camber up front with stock ride height and 18's. Good luck!:driving:

Which front camber arms are you guys using? I've been holding off since I've heard mixed reviews about most options out there. My car desperately needs some negative camber up front...my tire shoulders can attest to that.

SPC right now, I'll upgrade to the Doran's or the SPL's when available. The SPC's get the job done, but if you do a lot of curb hopping or harsh tracks then they can slip out of adjustment. They are strong, but heavy steel, adds about 4 pounds each I'd guess. The ball joints in them lasted about 18 months, but at least the replacements weren't that expensive to replace.

^^what he said. To date, My camber adjustment hasn't slipped any.

There are so many factors to set up and making the car truly come to life....
Tires are great for overcoming issues...but they are truly a band aid.
Front ride height is major league critical.....and yes there is a to low.
Rear ride height can have a bigbeffect on apex out.
Spring rates and bars...... and def differential settings are vital to a well balanced car....
Even brake pads can be a very frustrating evil that will cause a huuuge understeer.
To truly understand understeer ....you need to know where the understeer starts in a corner and why.
Sometimes.....it can be simply driver induced.

AMEN :hello:

Haha I had a combination of going with the Eibach Front Sway Bar along with getting my corner entry right. Currently running 275/305 RE11s on the sport wheels and the Z feels great.

Would it be a good idea to add a larger power steering cooler when going to a 275 front tire? Summers in OK are in the high 90's to 100* and I am not sure of the stock cooler will be able to handle the added stress from the larger tire with the heat. Daily driving won''t be an issue I don't think but most of the track days and AutoX events are in the summer. I already have a 34 row oil cooler.

If you track then yes, an upgraded PS cooler would be a good idea (but certainly not mandatory). I changed mine to the Stillen since it was an easy swap, has about twice the cooling surface and a little more volume.

When refilling, fill the reservoir about 3/4 and have someone turn the wheel lock to lock a few times with the car running. Monitor the fluid level and top-off to about half-way full. The fluid expands a little with heat and sloshes around pretty good and since the cap doesn't seal that well you can get some overflow if it is too full.