Technical > Wheels and Tyres

240Z & 260Z Wheel/Tyre Options, Offset, Backspace

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Toecutter:




People often ask about wheel options for Z's. You need to know 3 things to select your wheels/tyres;

1. PCD which is distance from center hole to center hole on the wheel stud holes. For the S30 it's 4 studs at 114.3mm.

2. Offset or back space which is explained in the diagrams above. The stock 240 runs ethier 0mm or +12mm from memory. Just keep in mind the higher the negative value the deeper the dish. For instance -20 gives you 20mm more dish than the same wheel with 0 offset. This would also mean that the wheel with the -20 offset would also sit 20mm closer to the wheel guards than the 0 offset when put on the same car. There is a limited amount of space between the stock guards and suspension. This space limits your wheel offset and size options. For instance alot of wheels on the market are designed for newer front wheel drive cars with a +35 offset. If mounted on a Z these wheels would rub on the suspension as they would sit too far in. One way around this is using a bolt on spacer that pushed the wheel out. These spacers can be made to order and bolt on to your existing hub. I've used them before and there is much discussion on the net about them. Installing aftermarket suspension like coil over gets you some more room as does installing flares but I won't go into that as there is much discussion on that in other areas on this forum.

3. Rolling diameter is based on the diameter of the stock tyres. Not sure what the 240's is but I think the tyres I'm running are about 620mm. To work it out just add the height of the tyre walls to the wheel size. Just remember a 225x50 tyre is 50% of 225mm so tyre wall height is 112.5mm. Apart from looking like crap getting the rolling diamter wrong can put your speedo out.

For those that have been down this road and would like to comment on wheels/tyres you have found to fit on a Z car please add your comments and pics. To help others out please try and include info like offset and tyre size etc

Years ago I came across a page on the net that had a comprehensive list and pics of stock wheels from other cars that bolt on to the stock Z car. If anybody has a link to this info please share!???

My contribution might not be helpful to many as I've got flares on my car but I'll try to kick start the thread with my set up.

I bought 3 piece ROH Venturo wheels in 17 inch. 17x8.5 (-6 offset) for front and 17x9.5 (-19 offset) at the back. 5-6 weeks to be made. I think tyres are 225x45 front & 255x40 rears.

Zeddophile:
Link to a very useful calculator for determining alternate tyre sizes (especially useful when changing rim size!).

http://www.miata.net/garage/tirecalc.html

nat0_240_chevZ:
heres my wheels.

simm's 16x9 rears and 16x7's on the front.

the front tire profile is a lil small and the rear a lil big but wait till i waste them and grab some better fitting tyres....

the rears poke out a smidge but i have about 5mm i can  off the inner of the wheel and get a tyre without rim protectors and drop dow to a 225 or 235 sould be good.

rear backspace is about 130mm and front is about 115mm
also the rear drums are off gives me another 6mm, as i will be going rear discs when i drop the lsd and cv's in!!! very soon hopefully next week!!! yaaa


nato

RUSSJZ-ZED:
Another picture thats worth 1000 words,PCD number is the diameter of the circle in mm.
PCD is pitch circle diameter, a PCD of 114.3(x4) is standard 240/260/280Z , 114.3 circle x 4 bolt holes.
114.3(x5) is same size circle, but with 5 bolt holes(this is PCD of Z32s, late Skylines, most Big Toyotas.)

NickF:
Dont confuse offset with backspace
Backspace
This is the distance from the back edge of the wheel to the hub mounting surface. To determine the wheel backspace:
Position the wheel face down.
Lay a straight-edge across the back of the wheel.
Measure the distance from the straight-edge to the wheel's hub mounting surface.
Offset
The wheel's offset is the distance from its hub mounting surface to the centerline of the wheel. To determine wheel offset:
Position the wheel on a flat surface and measure its overall width.
Divide the overall width by two, then subtract this result from the backspace value.
Offset = Backspace - (Rim Width ? 2)
8" wide wheel  with 3" backspace has a -24mm offset (deep dish)
8" wide wheel with a 4.5" backspace has a+13mm offset
8" wide wheel with a 4" backspace has 0mm offset

The offset of a wheel can be one of the following three settings:

Zero offset:
The hub mounting surface is even with the centerline of the wheel.

Positive offset:
The hub mounting surface is toward the front or wheel side of the wheel.
Positive offset wheels are generally found on front-wheel drive cars.

Negative offset:
The hub mounting surface is toward the back or brake side of the wheel's centerline. "Deep dish" wheels are typically negative offset.
 
Strange that the rim width is in inches but offset in mm

Nick

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