Have recently bought an 300zx import, and its got 17" wheels with 235/45 on the fronts and 255/40 on the rear, but I have no idea what the pressure in them should be.

 

I've got 32psi in them at the moment, but the ride feels abit hard to me, any ideas at all?.

If i were you id run 30 all round - you cant really go wrong on that mate

If i were you id run 30 all round - you cant really go wrong on that mate

 

Thanks for that, I'll try it out this weekend.

Have always ran 30 on most cars I have had, zed is no different....

I'm running 265/35ZR18 on the back @38psi and 235/40ZX18 on the front @36psi. Anything else gives bad tread wear across the width of the tyre. They say 2psi increase for each step down in sidewall size.... 36psi in the rear and 34psi in the fronts should be about right for yours. The stiffness of the ride shouldn't really be controlled by the tyre pressures, only the shocks and springs..... :)

I'm running 265/35ZR18 on the back @38psi and 235/40ZX18 on the front @36psi. Anything else gives bad tread wear across the width of the tyre. They say 2psi increase for each step down in sidewall size.... 36psi in the rear and 34psi in the fronts should be about right for yours. The stiffness of the ride shouldn't really be controlled by the tyre pressures, only the shocks and springs..... :)

 

Andy, I know you are the man when it comes to knowing the Zed but 38psi!!!

 

I have the same rears and I find 38psi hard as fVck!!! Do u have any teeth? :rofl:

LOL :D Like I said, the softness should really be in the suspension and the tyre pressures set for even tyre wear - this also means equal pressure on the road from the tyre, equating to more grip ;) Because the tyres are so wide, they need the extra pressure to hold the centre of the tread out.... I think :D

Hi Sheppard

 

I have the same tyre sizes as you and find it OK on the stock pressure settings for a UK car - 32 front and 34 rear IIRC.....

 

....plus Andy is dead right, the ride firmness should not be adjusted by altering tyre pressures as it's all down to suspension settings. These cars have quite a firm ride anyway, more noticable if you have come out of an "ordinary" car. Plus the ride will get firmer as you step up the tyre sizes - 255/40 on 17 inch rims will be a lot firmer than stock wheels on 245/45/16s. Alluminium alloy is less flexible than rubber ;)

 

Experiment with varying pressures and see what has the most positive and secure feel, ignoring the firm ride. You don't want them too low as the tyres will flex more at high speeds, overheat and could go bang :nono:

 

HTH

 

Richard :)

Hi Sheppard

 

I have the same tyre sizes as you and find it OK on the stock pressure settings for a UK car - 32 front and 34 rear IIRC.....

 

....plus Andy is dead right, the ride firmness should not be adjusted by altering tyre pressures as it's all down to suspension settings. These cars have quite a firm ride anyway, more noticable if you have come out of an "ordinary" car. Plus the ride will get firmer as you step up the tyre sizes - 255/40 on 17 inch rims will be a lot firmer than stock wheels on 245/45/16s. Alluminium alloy is less flexible than rubber ;)

 

Experiment with varying pressures and see what has the most positive and secure feel, ignoring the firm ride. You don't want them too low as the tyres will flex more at high speeds, overheat and could go bang :nono:

 

HTH

 

Richard :)

 

 

Thanks for the all extra and scientific info on tyre pressures all you guys, I'll just have to play around with the pressures, but I'll start with 32 front & 34 rear and work from there I think.

One other thing. You really will be amazed at how much difference even 1psi affects the handling of the car ;)

I've found slightly higher psi settings then stock improve handling no end.