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Discussion Starter #1
I have been getting very useful advice in another thread about what tyre sizes are right for a R32 GTR.

This car is definitely and R32 GTR and not a GTS

This is the sticker on the door pillar

Lee.


It shows front being narrower and higher profile ( I think)
So could all R32 owners please, please, come on I am begging now, let us know what tyres are fitted to your car, and what does the sticker on the door pillar state.

OH, and no guess work please!!!

Thanks in advance everyone
 

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225/50 16 = height 24.9
side wall 4.5
width 8.9

205/55 16 = Height 24.9
side wall 4.9
width 8.1

My GTR is gone right now, as soon as it gets back I'll take a look and see what the door says.
 

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Oh and this is not guess work:)

I looked for the pics you were posting, but I could not find them, can you post a link, thanks.

Tony
 

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That sticker is stating at what pressure the tyres should be inflated to. There is no mention which one is in the front or rear. The third tyre listed is the spare.

Hope this helps
 

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R32 Gtr came out with 225/50/16 inch tyres on 16 x 8 rims.
205's would be too small on 8 inch rims.

Autech 4 door gtr however, came out with 205/55/16 inch tyres as did the Gts-t's and Gts-4's.

I am guessing the sticker in the door pillar is to cover all R32's that came out with 16" wheels, not just the gtr. I also think front and rear is split vertically rather than horizontally as in 2.3kg/cm front and 2.3kg/cm rear.
 

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As of my knowledge you should NEVER mix tyre sizes on a 4WD Skyline. Especially not between the rear and front.. The difference in wheel rotation speed will fool the ATESSA computer to activate the ETS-clutch thus quickly wearing it down.

Regards
Lars B.
 

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Discussion Starter #7
Thanks, should have thought of that realy, its the same on scoobies, it justy shows tyre pressures front and back for each tyre size - makes sense.

This does not help me out though, what tyres should I fit on the front with 17" rims??
 

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Depends on the width of your wheels. The standard wheels are 16x8 and I used 225 50 tyres and I now have 18x8 and use 235 40 tyres. I guess that I will use either 225 or 235 45 when I fit 17's if they are 17x8. Hope that is of some use.
Dave
 

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Lee,
I think we are all missing the obvious answer for you ;)

Fit the same width and profile front and back.

Fit 245x45x17 all round on the 17" rims and you'll be fine, assuming that your 17" rims are all the same width.
 

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Right, just so you are really confused you must also look at the tyre load rating, it should be uprated to allow for the lower sidewall height, you can see this exemplified in the last figures shown i.e. 88V/92V(?).
For 17" wheels you must uprate the side wall strength otherwise the car will be a bit wauward under braking, the 'number and reference' are important, so 245/45×17 92Y is the minimum, a 94W would suffice but it would be a lesser tyre, going upto a 96Y (if you can find one will put you in a good position to do trackdays with impunity.

Edit...rim width, if you go for 8" that will be a minimum for 245s' better will be 8½" as that will give a more alert feel due to the more 'vertical' sidewall profile.
 

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Discussion Starter #14 (Edited)
Brilliant, thanks for all the help guys.

I would like to point out that although this is our first skyline we have been working with WRX's / EVO's for quite a while now so give us a bit of credit eh.

Yes the obvious answer is to fit the same alround, no need to shout that one out. The question is that I have spoken to some traders and exporters in Japan and they often see GTR's both 32's and 33's with larger rears fitted, perhaps the Japanese are ahead of us LOL.

On any permanent 4wd car the over diameter of the wheel must be the same:-

225/50/16" rims (standard) = 631mm
235/45/17" rims (my fronts) = 643mm (1.9% variance)
255/40/17" rims (my rears) = 636mm (0.7% variance)

Not enough there to worry me.

SO the fronts are a fairly good match for the originals.
The question I am asking is if the wider rears are better than orginals.

From a standing start I would say yes, but cornering is more complex. The lateral Gee sensor would come in to play before the rears break free, making the car less volitile. After all the more advanced R33 system works much quicker. But would this induce more understeer?

Now I could fit fatter fronts, expensive and less comfotable around our roads.

Comments please.

ps Emre great comments m8 thanks. I Should have worked that out really.
 

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wrx.co.uk said:
On any permanent 4wd car the over diameter of the wheel must be the same:-

225/50/16" rims (standard) = 631mm
235/45/17" rims (my fronts) = 643mm (1.9% variance)
255/40/17" rims (my rears) = 636mm (0.7% variance)

Not enough there to worry me.

SO the fronts are a fairly good match for the originals.
The question I am asking is if the wider rears are better than orginals.
Lee,

I'm sure you know this really but the GT-R is not a 4wd drive car in the same way as the Impreza and Evo are. The Attessa torque split control WILL be affected if you go down the route which you seem hell bent on. Even different compound tyres will affect it let alone different size tyres. The choice is yours obviously, let us know how you get on.....

Here's a 'brief' explanation of the system courtesy of Mario:

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"ATTESA 101.

Sorry if people know this, but from the brief read through of this thread, it appears it is the usual signal to noise ratio on most chat boards - 95% opinion (ie: bullshit) to 5% factual (ie: correct) information.

Here we go:

The GTR is predominately a RWD car. All power, be it a Vspec model or not, is transferred to the rear wheels.

The 4WD control system is called ATTESA. In true Japanese style, this acronym stands for "Advanced Total Traction Engineering System for All wheel drive".

This system is used by Nissan on a majority of their 4WD cars and off roaders (Shogun, Pajero, whatever you call those behemoth things driven aroung by posers that usually never see a spot of mud or an offroad track in their lifetimes).

There is a further refined variation of this system, known as ATTESA-ETS. Where ETS stands for "Electronic Torque Split". This is used in the GTR.

Then, there is an updated version again, known as the ATTESA-ETS Pro. The Pro spec version is used on the Vspec (it stands for Victory specification, in honour of the many Nissan motorsport victories, BTW).

There are other versions (ATTESA-ETS Pro ELITE, used in motorsport and not commercially available, as there are undoubtably others).

The two important ones to this thread are the ones as used in the GTR and the GTR Vspec cars.

The difference between the two versions is that the Pro version has control over the torque split between the left/right rear wheels (via the A-LSD rear diff) - in addition to the standard versions front/rear lockup (which is performed via an electically pumped, fluid filled, transfer case arrangement).

There are also other differences in how the torque transfer is performed front/rear. Namely to do with the ramp speed of the pump (which affects the progression of the lock up) as well the monitoring of various extra sensors.

The sensors used by ATTESA-ETS are a three dimensional G-sensor and the ABS wheel speed sensors. The Vspec variant will take into account deceleration and vertical G's in it's torque split bias, whereas the standard GTR will not.

Both versions will take note of road speed differences (via the ABS sensors) and cross reference them with the G-sensor input. If ATTESA detects a loss of traction at the rear, it will proceed to gradually lock up the transfer case (by increasing the pressure of the fluid with the electric pump) until it achieves a full 50/50 lock.

Depending upon the quality of the fluid, the state of the pump, the state of the clutch pack arrangements in the transfer case, you might not get a 100% lock (ergo a 50/50 split) and this is usually the case on older cars that have been thrashed.

Basically, put the car onto some wet grass/dirt, Vspec or not, and dump the clutch at 8000 RPM in 1st gear. If you don't get 100% lockup within a second (a full 50/50 split) your ATTESA system might need some attention. As Vspec or not, your transfer case should be locked.

More on the differences between Vspec and non-Vspec. The Vspec cars will take into account the vertical G's, so if the front of the car is dipping (due to a decline in the road) or under heavy braking, 10% is immediately transfered to the fronts (your torque transfer gauge should show this). Also on the Vspec, if you are in a hard turn, with the rears braking traction (drift) ATTESA should detect that you are in a moderate to high G sustained corner and not take action (the normal ATTESA-ETS will in this case). The Pro version will limit torque split to the fronts until such a time as your input from the steering wheel indicates that you wish to terminate the slide (by counter steering) at which point it will immediately transfer gradual lock (in correlation to the speed of your steering input, via the HICAS computer).

The system is very complex, but there is more to it than the usual dealer story that 'there isn't much difference'. The truth of the matter is that most people will never push the car hard enough to find the differences, in conjunction with the fact that alot of second hand GTR's have 'loose' transfer cases and the 4WD system has suffered.

Mario."

**********************

And:

"I might as well add to that before I go:

ATTESA requires that all the wheels and tyres are idential. The same grip level and rolling diameter.

One of the common mistakes that people make is using different tyres (grip levels) and different sizes (your fronts and rears should be the same size, width and height) as any small changes will drastically affect how ATTESA interprets its input.

Tyre choice is also important. If you use crap tyres, don't be surpsied to see the 4WD system doing strange things. You bought a performance car, so go out and use performance tyres.

Enough for now. I shall now go eat, for real.

Mario."
 

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Great info from Mario and within it is the clue to the 'idea' of using different size rear/front tyres, if the system is a little bit degraded then making the front wheel smaller than the rear will compensate for the degradation elsewhere. The logic being that any transfer to a smaller radius wheel will result in a higher apparent torque delivery at the contact patch.

This is how I read the logic of the system, but I accept that I may be under-estimating the ATTESA system so feel free to take the above to pieces.
 

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Just have a read of the below links dude...

Thread 1

Thread 2

Thread 3

R32 Gtr's only differ from the later models electronically. Running mechanicals are the same and the difference in the rolling diameter will harm your clutch packs in the transfer case and possibly more in long term.

Don't forget... %0.7 will be magnified when you are doing 100kmh+ on the motorways.

EDIT: Except the 6 speed getrag ofcourse.
 

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Mycroft,

Was this the part you were referring to?

"Depending upon the quality of the fluid, the state of the pump, the state of the clutch pack arrangements in the transfer case, you might not get a 100% lock (ergo a 50/50 split) and this is usually the case on older cars that have been thrashed."

If so, surely you'd want more grip up front to compensate as you're not getting as much torque to the fronts...?

Also, doesn't your statement fly in the face of your thread about grip levels not being dependant upon tyre widths/contact patch area or do I still not understand what you said?

Peter.
 

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My 'thinking' runs as follows;
The power to the front wheels is 'switched' on and because (I assume) the ABS sensors are used to detect wheel speed that circuit is also activated*.
The reading from the front would show some 'slip' as the front wheel is rotating faster than the rear for any given speed, this would tell the system that there is too much torque being applied to the front and would shut it down again, when the rears are travelling faster than the front, ie the rears are sliding/tramping the system works fine but allows a bit more rear wheel steering than normal as the differences are slower to manifest themselves and quicker to disappear, the car would feel more RWD than P/t AWD.
This is what I mean by 'apparent' torque, if the front wheels are powered and rotate faster than the rear and the car is travelling forward then the system has to 'back off' the torque to the front' it is being fed info that they are slipping.



*I doubt that it would be switched on or off it would just be ignored when not needed, in a manner similar to the O2 sensors inputs during acceleration, still 'there' just not effecting the system)
 
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