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Discussion Starter #1
This has been covered in various detail over the course of this board's history, but no one has really put their finger on the answer.

Just what is the correct offset for an R33 GTR?

The correct offset for Volk TE37s (18" x 9.5") is +12, I know that much. Takakaira, on the other hand, quotes all kinds of weird and wonderful offsets.

Is it the case that the offset changes dependant on the rim size?

Takakaira quotes the following:
Code:
8.0x17   +31 
9.0x17   +38 
8.5x18   +37
9.5x18   +42 
10x17    +20 
10.5x18  +20
..which doesn't sound right to me at all.

Can anyone shed some light on this?

Also - am I right in assuming that if you dont get the same width rims/tyres all around, it'll play havoc with HICAS?
 

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Discussion Starter #2
Durzel said:
Also - am I right in assuming that if you dont get the same width rims/tyres all around, it'll play havoc with HICAS?
Ignore that part - it stands to reason that different width tyres would cause havoc with the anti-lock brake sensors, and thus ATTESSA.
 

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Durzel

The width is not of importance directly really. What is, is the wheel circumference. They should not differ more than 1% (if I remember well) of each other. As long as you choose tires that are within this limit, you should be ok. Question is of course, if you can find these.

The correct offset for an R33 depends on wheel width and how far in or out you want these to be. The offset is measured from the centre of the wheel. Does that help ?

Andre.
 

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Discussion Starter #4
Sortof, thanks :)

Nismo seem to quote around +14 - +20 for their LM GT range, Volk TE37s are +12 as already stated - Im just wondering (generally because I wouldn't be buying any just yet) what the differences will be. I was always led to believe if you use an incorrect offset you put undue load on the wheel bearings, etc.

Would +35 to +40 be completely wrong for an R33 GTR?
 

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Durzel

That depends on the width. For 10J it would be, for 8J not I think. But that's a guesstimate; I would have to dive into that to get a better idea. I know that 10J with +22 offset are nice on an R33. If you take wider wheels, you want to have the outside on the same spot, meaning that the extra width has to be on the inside. This means that the ET has to increase with half the width of the rim width increase...
Try to work this out yourself; remember the offset reference point is the wheel hart line; and one J is one inch (puke) which is 25.4 mm for normal people.

Andre.
 

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Durz

This is something I understood when I was looking to buy wheels earlier this year. Whilst I think I remember the principles, I cannot remember some of the detail, but I'll try and explain as best as I can - its not that easy trying to articulate this in a note, but here goes.

The offset is the distance from the centre of the wheels width to the wheel hub where the wheel meets the car. By way of example, a 9" (225mm) wide wheel with no offset would mean that the centre of the wheels width (112.5mm in) would sit flush with the cars wheel hub and therefore 112.5mm of the wheel would protrude out from the hub, with the other 112.5mm going back into the wheel arch. The Skyline has an offset of 30mm which means that 142.5mm of a 9" wheel protrudes from the wheel hub and the balance of 82.5mm of the wheels width goes into the wheel arch. This allows room for the large brake calipers on the GTR.

In your examples, one of the 9" wheels has an offset of 38. If I've got things the right way round, I think this wheel would protrude outwards by 8mm more than a standard wheel (38-30). The wheel with an offset of 42 would (prima facie) protrude by 12mm more than a standard wheel (42-30). However, since this wheel is 1/2" (12.5mm) wider than a standard wheel, half the additional width (6.25mm) would also protrude outwards ie, a totalof 18mm more than a standard wheel. Many European wheels will not fit the Skyline because they have low offsets - which all other things being equal, means that the wheel will fit further into the wheel arch. This creates 2 problems, first the wheel may not accomodate the brake calipers, and even if they do, they tend to rub on the inside of the wheel arches. Both problems can be fixed by using wheel spacer which effectively increase the offset of a wheel.

I think I've managed to confuse myself, but I hope this helps.
 

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Sorry to butt in here but I hope someone can help me while they're on this subject. I have a set of standard 17" GTR wheels on my GTS and was wondering what offsets I would need for my car and if, as I suspect, the GTR wheels have different offsets can I change them?

Oh and finally just to set the cat among the pigeons, how much does it matter on a car only driving on the road?

Any help more than appreciated,

Matt
 

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Discussion Starter #8
Thanks Fred & somberg, that's cleared it up a bit.

Just out of interest, given (I presume) higher offsets are more desirable for GT-Rs, why is it that Nismo and Volk Racing supply their wheels with very low offsets? The TE37s (18 x 9.5) come in +12, and most of Nismos wheels are in the +20 region.

Surely with either of those wheels you're going to have to use spacers otherwise you'll have problems with inside arch clearance? Or am I confused? :)
 

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Durz, I don't think you are confused. I may have it the wrong way round ie, a lower offset would mean the wheel moves outwards. Therefore with a 20mm offset 9.5" wheel, the wheel moves outwards by 16.25mm compared to a standard wheel (30-20 +1/2 of 12.5mm).

Tim from SVS posted a very good post on this earlier this year and maybe you should speak to him to confirm. From Tims post, its appears that most wheels have higher offsets than the skyline ie, move towards the wheel arch. Hope I havn't caused too much confusion, but once you confirm which way a lower offset wheel moves the wheel in relation to the wheel arch, the rest is easy.
 

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Here are some thoughts, Durzel:

(1) Offset changes with the width of the rim.
(2) For a given rim width, offset changes with the style of the rim (eg. Volk Racing GT-C face 1 and face 2 rims).
(3) The lower the positive offset in a given rim style, the closer the hub mounting surface is to the center line of the rim.
(4) The closer the hub mounting surface to the center of the car, the more the rim protrudes out of the fender line (hence you get more of that cool "deep dish" effect).
(5) Large negative offset places additional stresses on the car's entire suspension and can potentially cause increased steering wheel kick-back.

On the spacer question, you don't need to use them for any of the Nismo or TE37 rims that are offset originally for a GT-R. The calculations have all been done already and they fit no problems - I've got TE37s on my R34.

Hope this helps.

Cya O!
 
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