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

[Fred-R]

When I bought my GTR, it had 245/40/17 on all corners. When the tires came to an end, i've changed them with 245/45/17 again on 4 corners. The torque meter was suddenly acting sort of crazy: goin up and down even at regular speed!!?? Does anybody know what could do that?

These tires are now about to be replaced and already bought same 245/40/17 for fronts and 275/40/17 rears. Now I don't know if it's a good thing...

[Voodoo_ChildR32]

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.

Ok, I guess 5 years of training was for nothing, lol. Granted I haven't fully studied the GTR system, so I guess I stand corrected and textbooks are way off base. Thanks for the clarification.


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[Skym]

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).

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


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).

I agree with overall diameter (tire profile + rim diameter), as that affect's speedo to wheel speed as well. I run a staggered setup on my car with similar specs, which is wider on rear than factory by I think was 20mm, but a lower profile by 5 on rear like you have shown and had speedo checked on a dyno designed for checking speedo to wheel speed. It was only 1km/h out at certain speeds. They said it was the most accurate Skyline they have seen, as when doing 50km/h on dash it was actually doing 50km/h at wheels, exactly like a factory car using factory speedo cable, factory calibrated dash, but wider rear wheels, etc.

I run staggard for some very specific mechanical reasons and for personal preference, I can elaborate if you like.

Yes please.

One benefit I noticed with staggard vs non staggard setup is steering response when turning left to right, as felt alot quicker with staggard (like there was less understeer or weight on front of car).

[Voodoo_ChildR32]

Did some more digging and apparently you CAN run staggered. For example, 45 series on front and 40 series on rear as long as the rears are slightly wider than the fronts.


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[MarusGTR]

I would only run wider in the rear with the same rim hub offset from the knuckle as the front... fail to do so and I'm thinking there's some potential for geometrical issues.

It's nice to dream about the perfect setup...

Edit: But then what about high the effect of a high negative camber's contact patch which would make a same offset setup also be affected geometrically? The rear's contact patch would be more inside than the in the front. *sigh* just skip my post, move along.

[Dragon Humper]

Ok Skym, just because it's you and you even had a smiley face.


Let's first cover some GTR basic operating parameters. Firstly and foremost the GTR in R32, 33 and 34 guise is primarily a RWD car with the capability of AWD on demand. Like a basic anti-lock brake setup the transfer case will not engauge unless there is a trigger. In an ABS system it's a pressure swt inside the module, the ABS will not do anything no matter how out of whack the wheel speeds are front to rear unless there is some pressure in the system from the brake pedal. Similarly, the GTR and GTS4 will not feed any power to the front unless there is a measureable amount of detectable rear wheel slip, some say it's up to 1%. Mostly, I have noticed that it takes very little to trigger the clutch pack in the transfer case. That is why tire rotation and pressure is so improtant on a GTR, to prevent unwanted clutch engaugement. The G-sensors come into play as soon as the trigger is activated, no matter what the Gs are seeing, they can't activate the transfer case unless there is detectable slip from front to back....I have tested this rigorously (and just about filled my shorts a few times in the process.....lol).


The reasons for me running staggered tire widths on my car are varied, for one thing, I like the look of "bigs and littles". Having a big fat tire filling out the rear just looks too good. What I don't want to do is run a big, heavy, hard to turn set of wheels up front to match the rear because "that's how the car came from the factory so that's how it should be".

The mechanical reasons are:

1. I am making an assload of power and have a factory, open diff. in the front, that is the biggest reason. I don't want to pop it, smaller front tires will help that from happening. It all adds up, a wider wheel is heavier, the tire is heavier, all putting more stress on the front diff. Nissan put a smaller diff. in the front for a reason. Running a 295/30r18 up front while funneling up to 50% of 1000hp wasn't in the cards for these cars, they were pinching yen, even in the mighty GTR.

2. My car is setup for dragracing and as such the rear camber is zero at the level of compression during launch. This makes the car want to oversteer a bit more with the factory dogbones in front and I want to have the handling about the same as stock. The smaller tires also help to correct the oversteer. Once I do get the front camber dialed back the car will want to plow a bit, which I want. I can also minimize that by deleting the HICAS.

3. Hydroplaning.....the wider the tire is the more it's going to float in the rain....this is a street car.

4. Wandering...again, this a street car, street ruts suck gigantic donkeyballs with a 275 and bigger.


Japanese people are pragmatic, they like to use things right to the very end. Having the same wheels and tires front to rear makes rotating possible to get the most out of a set of tires. This was not intended to be a "SuperCar" back in the day, it was a factory coupe that was outfitted to compete in a class of racing. At the time a 16x8 fully forged wheel was quite exotic in 1988 when the car was in the final stages of development. Getting fancier with staggered wheels was completely possible but not nessesary for what they intended the car to be.

Does this mean you can't run staggered at all? HELL NO, you just need to know what rules to follow. If you don't want to deal with challanges and solve problems then by all means leave this one alone. Really it's not that complicated, diameters MUST be the same or rears larger....period. The rears cannot be smaller......even the littlest bit.



Jon.

[Skym]

Now I have a grin.

Thank you for sharing.

Marus92, would need to measure track width of factory setup and staggered setup to see if offset is affecting track width??? -

http://www.ehow.com/how_5850001_measure-track-vehicle.html

Anyone got factory setup and willing to measure track width???? Or isn't there a catalogue photo with track width measurements on it??? They say track width varies from front to rear on any car, but by how much???

My car is basically setup exactly like you would see on F1 racecars that run a staggered setup -

[Voodoo_ChildR32]

I'm confused, lol. Time to do some homework. Wasn't trying to be a ****.


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[MarusGTR]

Skym; your picture makes a good point; a narrow track width in the back would increase the pivot effect while turning off throttle...with throttle it would be the opposite. So I could postulate that a high offset rear (with same total width as the front but wider tires) would increase turn-in response.

This thread really got interesting...

EDIT: But then a wild Deltawing appears

[Dragon Humper]

Another reason why my wheels in the back are 17x10 with a +42 offset. Front is 17x9 with a +18. Kinda gives it a bit of a "tubbed" look. Rim face is only battleshiped by about 3/4 of an inch.....much less than the factory 16x8 +30.



Jon.

[Veet-88]

Bit of a grave dig here but rather than starting a new thread just throw it up here. So picked up my R32 GTR and the front tires are fubared horribly weathered rears on the other hand excellent shape. Importer threw in a set to replace the fronts but the cuurent set up is 245,40r17 all round the replacements are 255,40r17 my thought was put the good rears up front and the wider out back. From what i have gathered from this thread is I should be good but if anyone has some further input Im all ears to it. Worst case I'll run it staggered and pull the AWD fuse till i can pick up a matching width

[steveo1502]

Try it, watch the guage, I had 235 and 255 and was a no go, but it was winter tires, I would just switch to 2wd on dry pavement.

[Dragon Humper]

You'll be fine with 255 out back and 245 up front, stagger the pressures (33 psi front and 30 psi rear) and the system won't even notice a difference.

A lot of people don't realize either that when the ATTESA is being used you are really putting the power to it. In that state more weight is on the rear than the front. If all things were equal and you had the same pressure front to rear in the tires, the rears would be shorter than the front......scrubbing the clutches in the transfer case and putting pressure on the system with different rotational speeds front/back anyway. But its for such a short time its just normal wear and tear.

That's why the ATTESA is so good, it can handle anything you throw at it....except for the rear tires being smaller while you are just putting around.

Jon.

[MarusGTR]

^ lol, spoken like a true dragger, all front to back accel, no lateral :P

But yeah your post reminded me I've forgotten what tire pressure I was running at with my RS-3s last year. My GTR currently has its tires overinflated to 40/40 (still in storage). I'm actually a little worried, I had it down to a tee for track/highway with something around 36/34 methinks.

[Dragon Humper]

You can change handling characteristics quite a bit with just tire pressure.....even laterally .



Jon.