I just ran outside and measured the difference. The front is less then a 1/4" taller then the back.

 

Rim-Volk Gt-7 1890 5-114.3 GM w/GT cap
Rim Volk GT-7 1810 5-114.3 GM w/GT cap
Tire-Nitto NT555 245-40-18 Front
Tire-Nitto NT555 275-35-18 Back
Mounting and balancing


That is what was on the description for my tires/wheels...
Hope that might help out...
I did measure the top portion above the rims on my car, and
they were the same size....

Came back from Nissan, and they said they couldnt find anything wrong with the car, and they test drove it, nothing happened....
very odd!

 

They were probably not pushing the car as hard as you do. You might have to take one of them for a drive yourself while you demonstrate.

 

This isn't Nissan's problem. It's people like you who waste Nissan's time when they could be helping people who legitimately have problems stemming from their product.

Go to the people that sold you the tires, or buy new ones. What do you expect Nissan to do? Re engineer the car just to accomodate some guy who purchased tires the wrong size?

 

According to the tire sizes you listed above, you should have:

25.75" diameter in front
25.50" diameter in back

Yikes! That means your front tire has a taller diameter than your rear tire! According to what I've read around here, that could very negatively affect the performance of your VDC and/or ABS.

Of course, rim width will also affect tire diameter. The wider your rim, the more it pulls out on the tire, making the tire's diameter smaller. That's why the tire manufacturer's always list what they call a "measuring rim width" in their specs. That is the width of rim they used to measure all the numbers listed in their specs. If your rims are wider or narrower than their "measuring rim width", than your numbers will be different. For example, you could use a front rim that's wider than recommended, and a rear rim that's narrower than recommended. This will make your front tire have a smaller diameter than expected, and your rear tire a larger diameter than expected.

 




Ralphus,

You don't have to be rude about this, my goodness!!!! I came here to ask a question not to be persecuted!!!! And NO im not asking them to re engineer the car, you are so far fetched!!!! Taking things to max... typical male if you ask me!
Im not the one who chose the tire size for car. I fig. these guys do this everyday and would know what they are doing! So if you want to be rude and belittling, take it else where b/c I don't tolerate that kind of crap... go some place where they do.

As for jrieter, should they switch the tires then, put the front on the back and the back on the front?

Thanks

 

I wasn't being rude or belittling, I was telling you that it's not Nissan's problem and you should get some new tires from the place that sold them to you. What's wrong with that idea?

 

No, you definitely don't want to swap the front and rear tires! The sizes would be all wrong. You want your rear tires to have a slightly taller diameter than your front tires (for the sake of VDC and possibly ABS), but you generally want your rear tires to be a bit wider than your fronts, also. Some folks around here have found that you get better handling balance by having the front and rear tires the *same* width (due to the understeering nature of the stock suspension), but I'd probably avoid that unless you are hardcore about road racing events. Just stick with the rear tires being slightly taller and wider than the front tires.

Honestly, I would think your best bet (like I said in one of my previous posts up above) is to just replace your rear tires with 275/40/18's, but keep your 245/40/18's up front. That way you only have to replace the rear tires, not all four.

For what it's worth (to anyone interested), I did some calculations previously to find out which combination of tire sizes would result in a front-to-rear diameter ratio that was as close to stock as possible. The *ideal* tire size combos were:

245/40/18 front
265/40/18 rear

OR

255/40/18 front
275/40/18 rear

Not only do those combos result in front-rear ratios that are extremely close to stock, but they also would help reduce understeer in the car. Unfortunately, 255/40/18 and 265/40/18 are both very rare sizes that aren't available in most of my tire brand choices. Oh well.

 

I have been following this thread to prepare myself on what to expect from VDC when I put winter tires on my Z (225/55/17 on all 4 corners)

And now I am confuse because, if I understood it correctly, having all 4 tires the same size (according to this thread) will advance VDC activation. However, what I found is the exact opposite; that is, VDC with my winter tire setup is now retarded (to a point where I think it should have been in the first place)

And I like the result, now the Z allow a little more wheel spin/slide before VDC activates (as compare to my stock 18" setup), ABS/TCS still work as good as before ( I just went for a test drive on unsalted snow covered road - yes, SNOW ! to people who is lucky enough to never have to drive on it) - and it felt great on the slipery stuff.

So what am I missing ? Can any expert here shine some light on what I'd observed ? Why did I found VDC being retarded while other reported VDC (SLIP light) comes on much easier ?

 

Hey.......I'm really glad to see that you guys are getting it.

Shorter Front....Taller Rear....or ALL The Same, you'll have no fear.

Well I'll be.....that's sort of a rhyme or a chant.

Let's ALL try it:

Shorter Front....Taller Rear....or ALL The Same, you'll have no fear.

Once again............................


Happy Motoring

 

Ok figure this. I installed Michelins 225/40/18s on all tires. I don't have VDC but still the slip light comes on with the TCS and again acceleration is locked up until it comes off...The slip light comes on even on dry roads....HELP

 

premium

resurrecting an old thread.
you have purchased the wrong sized tires. read the post above yours.
you may not have VDC but you have TCS and it's looking for the staggered tire sizes.

pp

 

Well there seems to be some question about that....there is some confusion as to whether TCS recognizes different tires as opposed to the VDC which apparently does.
I have heard from other Z owners that their vehicles also slip on cold surfaces so I am not in a great hurry to replace the rear tires....especially since I am due for four new ones in the spring.

 

premium

yes, most discussion is about VDC and tire sizes, but i don't think there is any confusion...

from the factory service manual
page BRC-48 and 96
"TCS function: the wheel spin occurance is detected by....wheel speed signals from all 4 wheels...."

page BRC-96
"VDC function: driver steering amount and brake amount are detected....and the vehicles driving status....is determined by yaw rate sensor/side G sensor, and wheel sensor"

both edited for brevity
TCS uses wheel speed sensors. it is expecting your front/rear wheels to be traveling at different speeds given the factory stagger. your tires do not have that stagger. VDC also uses wheel sensors but uses several other inputs as well.

hope that clarifies
EDIT : btw. you can just turn off your TCS to avoid it actuating

pp