smaller diameter/wider tires in the back...

[1BADGTR]

I've run different sizes on my GTR for four years with 0 issues. I never see any torque to the fronts at any speed. Currently running 225/35/19's and 265/30/19's. Just make sure you use a calculator and keep the overall diameter within a couple mm. Tread wear differential could be up to a few mm front to back.

[bobbo]

I've run different sizes on my GTR for four years with 0 issues. I never see any torque to the fronts at any speed. Currently running 225/35/19's and 265/30/19's. Just make sure you use a calculator and keep the overall diameter within a couple mm. Tread wear differential could be up to a few mm front to back.

That ratio is closer than ours. The difference in your sidewall is about .75mm mine is about 3.75mm. That's probably why you're not having any problems.
Good to know though!
I'm sure the ATTESSA will allow for a small difference but perhaps 3.75mms is too much as McFly says.

[DarkCaporaL]

I've run different sizes on my GTR for four years with 0 issues. I never see any torque to the fronts at any speed.

Broken/disabled ATESSA/gauge?

You ARE suppose to see torque to the front sometimes (when you floor it, while cornering, etc.)

[mcfly]

That ratio is closer than ours. The difference in your sidewall is about .75mm mine is about 3.75mm. That's probably why you're not having any problems.
Good to know though!
I'm sure the ATTESSA will allow for a small difference but perhaps 3.75mms is too much as McFly says.

The system may have a tolerance as to when it activates, but that doesn't change the fact when it is engaged it will be working harder.

GTR's can easily fit huge tires all around. Use the wheel well space for meaty tires, not 235/19' ricer plates.

[bobbo]

GTR's can easily fit huge tires all around. Use the wheel well space for meaty tires, not 235/19' ricer plates.[/QUOTE]



So at this point one could assume that the ATTESSA may be engaging prematurely and the xfer case clutch would be getting scrubbed more then normal?

Simply trying to find out how critical it is to go and sell my wheels (or having them modified) or if I'm safe. I wouldn't do it on my Soobs but this system is SO different.

I'm curious about the tolerances the sytem has before the ATTESSA light flickers or shuts down.

[bobbo]

any other input on this one? Spoke to a machinish that can graft another 1" to my front wheels to be able to run 255s all the way around but I would really like to make sure this is really required. I'm pretty sure I know the answer...
Thanks for any and all input!

[mynameishigh]

alright well thanks to everyone for their input. i have put my old wheels back on for now. and i guess i will probably just sell the wheels. i think that having the 265/40/17s would do the trick. but im not sure if i want to have staggered wheels on my gtr anymore. it would be nice to be able to rotate the fronts with the backs.we'll see.

[BlackAura]

That being said, does the ATTESSA use wheel speed sensors front and rear (like a Sub) or does it only use the G sensor. How does it decide how when to send torque to the front diff?

You ARE suppose to see torque to the front sometimes (when you floor it, while cornering, etc.)

Interestingly enough, ATTESA uses a few different systems to determine how much torque to apply to the front wheels.

It has 3 g sensors...under the center console...behind the ebrake I believe...can't remember if two are lateral and one is longitudinal, or vice versa, but they're all built into the same unit.

It also uses wheel speed sensors (the same ones used by the ABS system to determine when your brakes lock).

One neat thing regarding how ATTESA works...as g's on the lateral g sensor increase, it applies less torque, causing some oversteer. There's an article out there (linked below)...someone did some testing and found that if they put 2.5v through regardless of the lateral g sensors reading (they read from 0v to 5v, with 2.5v being no motion detected), then the car had quite a bit of understeer through the corner. But with the default Nissan settings, they found the car had too much oversteer when flooring it out of the corners. They found that adjusting the voltage level so it was a combination of the wet and dry signal (wet being through the g-sensors, dry being 2.5v), they got the perfect setting for their R32.

Anyways, what I'm getting at is that "while cornering" is false, and the original ATTESA system pushed less torque to the front diff while cornering. Also tried to answer Bobbo's question about what sensors ATTESA uses.

Godzilla Tamed - Original article detailing lateral g-sensor adjustments

[bobbo]

Thanks Kevin!
I did manage to find all that info out. That "Taming the GTR" article I actually posted a couple of days ago. I found it while trying to learn if I'm causing any problems with my wheel/tire set up.
There is not enough detailed information to find out if a 1.5% difference in front/rear tire diameters will negatively effect the system.
I've come to the conclusion that although there is a difference it's not significant enough to bother the xfer case clutch but I'll still toast these tires as fast as possible, go to a 265/40 rear which will make the difference about .8 of a millimeter front to rear, equating to about a .5% difference.
Of course I'd love for someone to correct me if I'm wrong in this.

[mynameishigh]

umm, the wheels i tires up front on mine(which i have already taken off) are 235/45r17s and if you put 265/40r17s on the back, its like .1% difference(too slow), which the computer cannot even tell the speed difference. but as for me, i decided im going to go another route with my wheel set up. i dont want to bother with having fatter wheels in the back and not being able to rotate.
good luck with the new tires man!

[mcfly]

Thanks Kevin!
I did manage to find all that info out. That "Taming the GTR" article I actually posted a couple of days ago. I found it while trying to learn if I'm causing any problems with my wheel/tire set up.
There is not enough detailed information to find out if a 1.5% difference in front/rear tire diameters will negatively effect the system.
I've come to the conclusion that although there is a difference it's not significant enough to bother the xfer case clutch but I'll still toast these tires as fast as possible, go to a 265/40 rear which will make the difference about .8 of a millimeter front to rear, equating to about a .5% difference.
Of course I'd love for someone to correct me if I'm wrong in this.

any difference has an effect on the system as that it is just how it mechanically works.

[bobbo]

any difference has an effect on the system as that it is just how it mechanically works.

I'm hoping for something a little more technical. I've got an engineering back ground and "that's just how it works" doesn't give me warm feelings.
I really appreciate your input McFly, I figure you're probably one of the best sources for info around here.
Probably need a design engineer to really fill us in on the precise tolerances of the system and the effects this 1.5% difference could have.
Regardless I'm gonna put the wheel and tire package up for sale and see what happens.

[mcfly]

you can psychically feel a 1.5% difference as the car has a very specific and constant lurching under acceleration.

Though I cannot provide you with the engineering answer you are after I can give you personal experience

[bobbo]

Hmm, I don't think I can say I've felt that. I'll have to be cognisant of that next time out. Thanks now I've got something else to be paranoid about .

Anyone want a really nice set of Volk GT-Cs?

[BlackAura]

Thanks Kevin!
I did manage to find all that info out. That "Taming the GTR" article I actually posted a couple of days ago.

Haha, saw that post as well....about....3 minutes after replying to this one

Said something like "oops, just posted that article to the other thread, but I guess you've already seen as per your link here."



Sorry I couldn't help answer your other question, I've only heard anecdotal evidence that you want the tires the exact same size (and that was all from McFly, and he's already posted here )

Good luck!