Wheels and Tires

    I obtained some custom wheels and some large tires from Jim Biondo.  Jim upgraded to 300ZX 5 lug rotors up front and Corvette stub axles in the rear to get a better wheel selection as he wanted to change his wheel and tire setup.  Plus he now has stronger stub axles in the rear.

    The wheels I bought from Jim are 17x8.5 and 17x9  5 spoke light alloy wheels (From WRD, which is no longer in business).  The backspacing on the front wheels is 142mm and the backspacing for the rear is 149mm.  Note that on the rear, I have Jim's old brake setup that he had these wheel's custom made to fit.  The brakes are Arizona Z Car's old rear racing kit with drilled solid discs on aluminum hats.  The key is that the hat is 1/2" thick at the stub axle mating flange.  So this 149 mm backspacing will be too large if using the stock brake drum by the difference of the thicknesses of the stock drum and the 1/2" thick hat on the Arizona Z car discs.

    When I got the wheels and tires, the wheels had 235/45-17 (front) and 255/45-17 (rear) Michelin Pilot SX MXX3 tires.  These are the largest wheels and tires that will fit under the stock fenders with coilovers (in 17" anyway).  Be aware that if you go to another tire manufacturer or model, the tire sizes for a given designation (i.e., 255/45-17) change enough that the tires could be smaller or larger than desired.

    Just before the 2003 International Z Convention (New Hampshire), I bought new tires. The Michelins were old and hard. I had Toyo Proxes RA-1s installed, 235/45-17 front and 255/40-17 rear. I left them with the 6/32 thread depth. The rear tires fit easily, with more room at the fender lip clearance then the Michelins.

    The particulars are:

• Rear:  The coilover springs used with these tires must be the 8" free length version so that the adjusting collar does not interfere with the tire.  The springs must be stiff enough that they do not allow coil bind on large dips.  For a car with 600 pounds on each rear tire, a rate of 275 or 300 lb/in will give enough stiffness to not coil bind. I had 300 lb/in springs on the rear, but it was too stiff to my liking. I've since installed 225 lb/in springs on the rear and the ride is tolerable.

• The threaded coilover sleeve should be mounted at the highest location possible on the strut housing.  This maximizes inboard room for the 17x9 wheel, the rim being at the height of the very bottom of the threaded sleeve.   My strut tubes were shortened by 1.5".  With the threaded sleeve at the top of the strut tube, the collar is closer to the top of the sleeve than the bottom when the spring is adjusted.  Since the bottom 1 inch or so of the threaded sleeve is not used and it's added thickness to the strut in this area causes small tube to wheel rim clearance, the threaded sleeve can be slightly shortened so that it is above the rim lip height on the strut.

  The tire has more clearance inboard than the rim, but a section width of 10.55" is maximum.  The Michelin Pilot MXX3 255/45-17 tires, which are 10.5" at the widest point.  On Jim's car, these tires rubbed just a bit on a large dip on the outer wheel house.  Note that the top area (~4" on either side of the highest point) of the rear quarter opening must be "rolled" so that the short horizontal portion of the fender lip is bent at the outboard edge (still unseen from outside the car) in a straight up fashion.
   

• Front:  Any length 2.5" coilovers can be used in the front.  The max tire in 17" that will fit is a 235/45/-17 in the Michelin Pilot SX MXX3 (The Toyo Proxes RA-1 235/45-17 fits as well).  No fender rolling is necessary in the front.

Front strut with tire/wheel installed showing clearance at tire, wheel and coilover.  Click on image for larger version with dimensions.  1/8" at rim lip to spring, 3/16" from tire (at bead protector) to spring. (Picture taken when the Michelins were on the wheels.)   Click on the picture below to see the dimensions.