MissFairlady_Z

Hi Guys,
So I have been searching all over the forums since yesterday and I still can't find a question to my answer. I even resorted to the 350z FB page and just got trolled but I need some help.
I just got new wheels (ESR sr01 18x9.5+22 fronts and 18x10.5+22 rears) and mounted them on the car yesterday but had some problems when I drove down the street. So on my old stock set up, I had 225/45/18 in the front and 245/45/18 in the rear. I used the 245/45/18 on my fronts since my tires were practically new. I went to get some 275/45/18 but no one had any so the closest I could get was 275/35/18 for the rear. Now I already know this isn't a good size to run together, but I want to know first off. should I be changing the rears to 45's or the fronts to 35's? (I did this so I could get the wheels on my car until I could get proper ones ordered online for the following weekend.)
So after those went on the car, my slip light immediately came on every time I shifted (my wheels weren't actually slipping though). Then, in 3rd gear, it went into limp mode and I couldn't accelerate past 2500 rpms. I need to know what exact wall size I need to be running front to back to make it happy and then also if I turn off VDC will that do any damage? I turned it off and the car drove just fine but I don't want to be driving down the freeway and start slipping. Also thinking maybe it's not even a tire issue? I read somewhere else that someone changed the size slightly and it didn't help. I am just confused because an hour before mounting the tires, my car drove amazing! Has for the last year of me owning it.

I know this post is every where and probably hard to follow but any help is appreciated.

MicVelo

Not hard to follow at all. You've put the car into "Help me, I'm spinning out mode." (From this, presuming you've got something other than a Base model with VDC.)

Here's your stock ref sizes (same ratio applies to OE 17s, 18/19 Nismo stagger):

....Size......Diameter (in.)
225 45% 18 25.97
245 45% 18 26.68

Here's what you have on:
245 45% 18 26.68
275 35% 18 25.58

Your car's wheel speed is registering as too fast in the rear as compared to the front wheels (outside of the 3% delta it's expecting F-R, hence triggering VDC on). You're at about 4% differential.

You need:
245 40% 18 25.72 Front
275 40% 18 26.66 Rear
(Or 255/285 to maintain the wheel speed differential)

MissFairlady_Z

MissFairlady_Z

MicVelo

Not safe (unless you've disabled VDC *completely* according to instructions on this site).

You do NOT want to go into VDC-enabled mode when you need to make an emergency maneuver or anywhere there's other cars that don't anticipate your car suddenly slowing.

Just put your old tires/wheels back on for the moment.

MissFairlady_Z

MicVelo

Good call.

terrasmak

iTrader: (8)

I would order 275/40-18 to run out back and install the 275/35-18 tires up front. That is your best solution at this point

MissFairlady_Z

MicVelo

Here's what you end up with:
245 35% 18 24.75
275 35% 18 25.58

Technically MIGHT work. 3.2% is still outside the 3% delta but it might be enough to satisfy VDC.

But then, there's the overall size difference to consider...

Again, the OE reference sizes:
225 45% 18 25.97
245 45% 18 26.68

Compare that to the proposed above. You'd be dropping about an inch in overall diameter, which, IMO, just looks silly. Kinda defeats the purpose of getting nice wheels in the first place when the tire is so short.

To do it right.... stay within the 97%/100% ratio. Buy the 245/275-40s (or 255/285, sell the 275/35s to someone running a squared up 275/35 setup, call the day, done.

terrasmak

iTrader: (8)

Worst case, do a 245/40-18 front , and turn off TCS every time you drive. At least it will be drivable