mpfstew

Why didn't I do this sooner!?!?! I finally replaced my dumpy Stones with Kumho 245/40-18's all around, and the difference is very noticable. Road noise is about the same, but the ride quality is better, and the steering is much more precise and progressive than before. Meaning, the harder I drive the car, the more the tires hold the road. Of course I did put a little more rubber up front that stock. Anyone else experience this? I'm not an expert driver so I might not be explaining this correctly.

12 days to the next AutoX and 4 weeks until the Evolution school. Bring it on!

Happy Holidays!

mcclaskz

I will be interested in how they do at the track after 20 mins. Hopefully not as greasy as the re040s.

mpfstew

Well, I haven't been on a real road course yet, just AutoX. I plan to try road racing in the spring, so we'll see.

lowrider

iTrader: (3)

You've thrown off the stagger. Your "Z" must not have VDC. Do all "Zs" have traction control? Anyway, the OD of the rear wheel is 1" too small and it should affect handling in a negitive way.

Lou

J Ritt

iTrader: (4)

Good choice of tire...I'm running those in 245/275. They are a dramatic improvement. If you're starting with a marginal tire to begin with, tires will be the best starting mod 9 out of 10 times. Unfortunately, most people don't go this route...they would rather have something that looks pretty, sounds cool, etc!

mpfstew

Stagger? I don't have different

More importantly that is only a 3.6 percent change from OEM. Like I said, I'm not an expert. That's why I talked to people at Tirerack and Kumho before changing tires. They both said that the max acceptable percentage change for car tire size is 3-4%.

I wouldn't do it if they say it's a bad idea. We'll see.

kbomb

iTrader: (12)

Nice..i got them in 245/45 in front and 275/45 in the back in 18s. I felt a big difference as well. smoother and more responsive but the road noise seemed alil more though imo.

mpfstew

Cool. So does anyone else think that changing the rear diameter by 3.7% f$*#ed my car up? Feels fine to me. Should I have gone with a wider rear to get closer to OEM? That is not what I was told!

Thanks for the input.

Apexi350z

iTrader: (3)

if you still using track rims, then you can't go over 245/255 for the rear. also, by going with same diameters on front and back, it may have some effect on VDC. You should at least go with a smaller tires in the front, imo...

mpfstew

Well, for some reason I didn't see this thread when I did my search before I got the tires.

https://my350z.com/forum/showthread....0&pagenumber=1

UGH.

I should have asked you guys first.

FritzMan

I'm running 215/60/16 winters front and rear right now and I get no VDC issues despite zero stagger - and trust me with the freezing rain and snow around here lately the VDC gets a real good workout! It appears as though problems with stagger occur when the rear is smaller in diameter than the front.

mpfstew

Thanks. That's what I'm gathering as well. No problems with snow and ice out here in Southern Arizona. In fact, I don't think I have ever seen the VDC kick on. Thanks!

FritzMan

mpfstew, I'd love to see a pic with that setup (profile). Is there much wheel well gap in the rear? I've been thinking of running 245/40/18 BFG TA KD front and rear on Performance rims for AutoX B stock class. I'm hoping the 245 up front will cure some of the understeer as well.

mpfstew

That was exactly my idea by getting the 245/40/18 all around in the Kuhmo MX. I took the car out last night and it felt alot smoother and more precise. I wasn't really able to push the car to the adhesion limit however. The next AutoX is Dec 28th down here, so I get to test them out real soon.

By my eyes the car doesn't look any different. I'll work on the pic, but I've never tried to post a pic before so please be patient.

Audito350Z

iTrader: (1)

I have 255/40 on my rear Rays wheels, 245/40 on the front... Bridgestone SO2.

I had a 255/45 on the rear for a while, but the sidewall was noticably taller... looked like a truck tire and changed the grearing enough to make car slower at the track.

Todd@ProDyno

awww man, in my state and you didnt call me.

anyway, Im suprised TR sold you these. They are sticlers for going by the book, and Nissan USA advised everyone in this industry to maintain the stagger.

Beyond that, your new tire size choice should get you booted from the bstock class in auto-x if I am not mistaken

FritzMan

I don't blame you for thinking that, especially since it's a "stock" class. However, see the excerpt below from (http://www.cnacsolo.ca/rules.html):

January 1, 2003 CNAC Rulebook (Cdn Solo2 rules), Section 5.3/.4 (Stock Category) - D (Running Gear and Suspension).

"Any make, model and size of tire may be used, provided there is both a Department of Transportation (D.O.T.) approval stamp and approval number on the tire, except the following:
a) R-compound tires are a restricted modification, i.e.:allowed if the preparation point is taken.
b) When viewed from directly above the outermost edge of the fender opening (using the hub center-line as the viewing axis)from an angle perpendicular to the ground, no portion of the tread may be visible. This assessment shall be performed with the vehicle parked on a level surface and tires inflated to a minimum of 20psi. and not more than the allowable maximum pressure as stated on the tire itself.
iv) No alterations to the vehicle are permitted for wheel installation or clearance. No spacers may be used unless original equipment on that vehicle.
v) The suspension may be adjusted using the method authorized by themanufacturers only within the manufacturer's specifications for street use.

mpfstew

I can use any size tire a want as long a I don't change the rim size and the tire shop can phyiscally put the tire on. No problem there. Of course putting a 275 on an 8.5" rim might not be good for street driving!

mpfstew

Actually, Tirerack OK'd my choice and I was about to purchase from them, I called their recommended tire store to confirm they could install the tires, and the tire store made me a better offer. So I really bought the tires from the store. I talked to Kumho and they didn't seem to have any problem with what I did.

D'oh

Couple comments:

1. Auto-X - You can run any size tire that will fit on the stock size rims. R-Compound tires are acceptable as long as they are DOT legal (not racing slicks). These are the SCCA rules BTW.

2. My 265/35 race tires are mounted on 8" wide rims, and I know of at least one person that is running 275 race tires on 7.5" wide rims. This is for AutoX, where speeds are lower and competition is very tight. Everybody goes way outside the tire MFG recommended sizes in order to stuff the largest tire possible on their car. This may not necessarily be the best idea for a large track. Cornering G's in an AutoX will be similar to on a track, it is just the speeds that will be lower.

3. VDC - Your tire sizes may or may not cause VDC to misbhave. I run 245/40 in front and 245/45 in back on my street tires, but I run 265/35 all around on my race tires. I often drive 100+ miles to and from an event on my race tires, and I've never had any issues with VDC. However, others who have a stagger closer to stock (but still less than stock) have had problems, so who knows.

If you haven't had any problems so far, then there is really nothing to worry about.

Glad you like the tires.

-D'oh!