Staggered Wheel Setup on a GTR - will this combo work?

[judasentinel]

I want to learn about the front/rear difference threshold for running a staggered tire/wheel setup on an R32 GTR (while keeping the AWD running). What is the primary cause of concern - diameter of the rim or the total wheel/tire diameter? If I measure the total diameter for back and front and they are the same (even if the wheels are different width), will this work ok? I am noticing that there is a constant 8-10% power being diverted to the front wheels under most conditions. This doesn't seem normal. Here is the setup:

Rear
Wheels - 17 X 9.5
Tires - 255/40ZR17

Fronts
Wheels - 17 X 8.5
Tires - 235/45ZR17

Do you guys think the above setup is alright for ATTESA or is the difference too much? If someone knows how to calculate the difference (if any), please let me know.

I am not sure if pulling out the AWD fuse from the main fuse box (in the engine bay) is a good idea and what ramifications it might have on the car in terms of front diff/driveshaft being impacted negatively or what not.

Thanks,

Munib

[Dragon Humper]

I am running something similar and have no issues. 245 45 on the front and 275 40 on the rear. These tires are ment to be together right from the manufacturer. If you measured the circumferance and they were the same, or slightly bigger on the back, you should be fine. However, when I was driving around on the tires that came with the wheels I bought, the rears were quite a bit smaller than the front and the torque meter was constantly showing some power transfer. Drove around for a month or so with the ATESSA disabled, and do quite a bit now because its too much fun, and no ill effects to the transfer case in 2 years.


As a test, try running 40psi in the rear tires and 20psi in the front and see if the torque meter is still showing transfer. With those pressures your effective tire radius should be much shorter in the front and should cut out all power to the front in normal driving.

Jon.

[Daryl @ RightDrive]

I strongly advise against running a staggered setup on the GT-R.
The car was never meant nor designed to be run with a staggered setup. It was meant to run with the same size wheels and tires on all 4 corners.
On a GT-R you can run 255, 265 or even 275 tires on all 4 corners, what do you think you could possibly gain by running a staggered setup? It doesn't make any sense.

The difference is the overall circumference of the tire. Since they are different that is why you are seeing the AWD system getting confused and constantly directing power up front. This will destroy the system.

Every AWD vehicle is designed with a specific wheel setup by the engineers, who know a billion times more stuff then we do, because they designed the vehicle. When you start playing with wheel and tire sizes, you risk running into discrepancies, which could damage and destroy the gearing of the AWD system. If the front wheels are turning slightly faster than the rears, the gears will constantly be chasing each other, and eventually wear out and destroy themselves.

The GT-R has been designed with a specific wheel setup and the suspension has been designed around that. Changing to a staggered setup will upset the balance and geometry of the system.
Just do it properly. If you are doing it because you can get a deal on a set of staggered wheels, then pass it by. It's not worth ruining your car over.

[Voodoo_ChildR32]

X2^^^



Sent from my iPhone using Tapatalk

[bobbo]

Do not do it. Or if you're bent on the idea and you're a fashion over function type pull your ATTESSA fuse and neuter your car.

[judasentinel]

Guys, let me clarify here: I HATE staggered setups on an AWD car. This particular GTR came witha staggered setup and being the purist that I am, I wanted to know how I could get away with driving it safely while I save up dough to buy the same size tires on all four wheels. My concern is primarily due to the pulling out of the AWD fuse, if doing this would cause any mechanical damage.

I myself fully endorse putting on the same size shoes on allfour corners....just that due to funds availability, I have to wait until I buy the same sized rubber for the fronts as the rears.

Assuming the tire size is the same, can I get away with 9" in the rear and 8.5" in front?

[Xeno-Vibe]

Takes longer for attessa to kick in so you can get a better entry angle. I believe Kyoseki and Taisan Advan ran higher aspect ratio rear tires.

[bobbo]

^^^ that may be and is surely fine on a car with a big budget but if you look at how ATTESSA works you'll be scrubbing the clutch pack.
Also why would they play with tire sizing and risk xfer case damage to engage the ATTESSA sooner when all you have to do is get an ATTESSA controller?

As for the original posters issue I was in a similar situation when I got my car, realized there was an issue when the torque split gauge was always off the pin and did some research both on here and on the web and realized the safe thing to do was pull the fuse.

Depending on your wheels and budget you could look into getting your rear wheels sectioned ie. removing the extra width or you could temporarily put the proper size tire on the wider rim.

[GTR203]

I run a 10.5 in the rear and 9.5 in the front and used a tire calculator to get my diameter within 1% of each other, torque meter works the same as it did stock and I have not had any issues.

[judasentinel]

That's what I was looking for - tolerance level - you said 1%, so it pretty much limits my options.

Rear - 255mm -> 255/25.4 = 10.04 inches
Profile - 40% -> 40% of 10.04 inches = 4.02 inches
Doubling the profile to calculate the total diameter, we get 17 inches rim + 4.02 = 4.02 = 25.04 inches (assuming the tire wall is vertical)

Front - 235 -> 235/25.4 = 9.25 inches
Profile - 45% -> 45% of 9.25 inches = 4.16 inches
Total diameter for the fronts - 17 + 4.16 + 4.16 = 25.32 inches, assuming a vertical tire wall).

Difference is 0.28 inches, which is within 1.1% of the rear tire's height. However, since the fronts are sitting taller than the rears, this is destroying the whole ATTESA system.

If inflating the rears more solves the problem, we have a winner. Otherwise, I will keep the AWD fuse out until I can find a decent set of tires.

Any ideas what would be a good size to match up with the 255/40ZR17 rears (other than the same, hehe)? I did various permutations, but the only one that comes even remotely close is the one I have in front, within a 1% or so of tolerance. So I either have to change all four tires or go even smaller in the front and then inflate them a bit more to bring them in line with the rears.

[bobbo]

Don't know if you've seen this.

http://www.1010tires.com/tiresizecalculator.asp

Should help you out.

[Dragon Humper]

It's a little dishartening to see people useing personal preference to answer a technical, mechanical question. It doesn't matter whether you don't like the look of wider tires in the back or if you think that a staggard set of tires will messup the perfect balance that the designers of the GTR thought they had. It has no bearing here.

The FACT is that you can run whatever you want. There are only 2 rules: the tire diam. front to rear MUST be the same, and the rear tires can be larger in diam. by up to about 2% (any more and the ATESSA will get very sluggish to engage). I run staggard for some very specific mechanical reasons and for personal preference, I can elaborate if you like.

You cannot, in any way, have the rear tires smaller than the front, there is no tollerance.

Shame on some of you for perpetuating this mith with personal preferances and the lame-sauce answer of "the car came from the factory with the same size front to back, who are you to challange the engineer gods".



And to answer you sizing question, if you stick to a min. 30mm difference in width while staying to only a one step jump in profile (ie: a 225 45 17 and a 255 40 17) you should end up with the tires being at least the same size or the rears a little larger, depending on the amount of stretch (which I find stupid, but that also doesn't matter here).



Jon.

[Bossman]

If you want a tire size to match the rear tires then 225/45/17 will be better match then the 235/45/17 you have at the moment. You should also check the tire manufacturer's tire spec for the actural dimensions and available wheel width because not all tires are made to the calculated sizes. Incidentally my GTR came in the same wheel and tire size as yours and the front torque gauge did show to be active at 10%.

[Voodoo_ChildR32]

The main issue with running different size profiles is the ABS module will see a difference in wheel speeds between front and rear, if your car is equipped with ABS that is. This is especially critical in an AWD system where all wheels are monitored. Not to mention the added stress on the transfer case. Ive seen transfer cases split in half because the person ran a different profile front and rear. Come on guys, this is common knowledge. On a RWD system you would be fine.


Sent from my iPhone using Tapatalk

[Dragon Humper]

NO, THAT IS JUST BAFFLEGAB, and not even very precise. Profiles are only part of the picture.

If you don't know exactly how the GTR AWD system works then don't keep perpetuating this BS. You can even run staggard rim sizes if you want (17" front and 18" back) as long as you follow the only two rules I laid out. It's not really that hard to figure out either. The GTR system is the simplest, most robust and adaptable AWD capable (it's not really a traditional AWD system and really shouldn't be reffered to as such) system in the world.


$400,000 rediculously tempermental and fragile super/hyper cars run both staggard widths and rim sizes through systems that are 100 times more complicated than what is on a GTR, they do just fine.


Follow the rules, that is all.......



Jon.