::NISMO Wheels Thread::
07-15-2011, 08:17 AM
#1182
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I wanted to post tire PSI info as I saw a thousand different answers at different sites on what PSI to use. I just bought Falken 452's for my Z and emailed Falken to inquire on the correct PSI to use. NOTE: This is for the 18" LMGT4 only (8.5 front, 9.5 rear) using the recommended tires of 275/40/18 rear and 245/40/18 front). Here's their response for reference:
Our Bennett Garfield Tire Guide shows the original fitment for your car is:
F: 225/50R17 94 Load Index, at 35 PSI (= 1,338 lbs dynamic design weight per tire)
R: 235/50R17 96 Load Index, at 35 PSI (= 1,415 lbs)
(Both load indexes are Standard, not Reinforced)
If the data above is not correct, please let me know the Tire Information Placard data, normally found on the driver side door.
Assuming the sizes above are correct, our Load & Inflation Tables the air pressures for the replacement tires are:
F: 245/40R18 97 Load Index (Reinforced), which carries the design load at 38 PSI
R: 275/40R18 99 Load Index (Standard), which carries the design load at 31 PSI.
Having a lower pressure in the rear may seem counterintuitive, but remember load carrying capacity is based on tire interior volume times pressure (plus some other factors), so a larger tire volume needs less pressure for a given load. Also, a Reinforced spec (which you now have on the front) requires 6 PSI more to carry the same load as a similarly marked Standard spec, so sometimes it gets confusing. Probably the reason why different sites have varying recommendations; they may not be using the correct chart.
Our Bennett Garfield Tire Guide shows the original fitment for your car is:
F: 225/50R17 94 Load Index, at 35 PSI (= 1,338 lbs dynamic design weight per tire)
R: 235/50R17 96 Load Index, at 35 PSI (= 1,415 lbs)
(Both load indexes are Standard, not Reinforced)
If the data above is not correct, please let me know the Tire Information Placard data, normally found on the driver side door.
Assuming the sizes above are correct, our Load & Inflation Tables the air pressures for the replacement tires are:
F: 245/40R18 97 Load Index (Reinforced), which carries the design load at 38 PSI
R: 275/40R18 99 Load Index (Standard), which carries the design load at 31 PSI.
Having a lower pressure in the rear may seem counterintuitive, but remember load carrying capacity is based on tire interior volume times pressure (plus some other factors), so a larger tire volume needs less pressure for a given load. Also, a Reinforced spec (which you now have on the front) requires 6 PSI more to carry the same load as a similarly marked Standard spec, so sometimes it gets confusing. Probably the reason why different sites have varying recommendations; they may not be using the correct chart.
Last edited by 370zGatorman; 07-15-2011 at 12:07 PM.
07-15-2011, 12:32 PM
#1190
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thanks, I'm going with an LMGT4 owner then 
You have 18's right? I'll probably have the tires mounted this weekend and see how the ride is.
You have 18's right? I'll probably have the tires mounted this weekend and see how the ride is.
Last edited by 370zGatorman; 07-15-2011 at 12:34 PM.
07-17-2011, 01:11 PM
#1197
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Hey Waizzz, I got the Falkens mounted today and had them put 36 in the front and rear. They put nitrogen in for FREE to get me to try it out. It's normally $25 so I accepted and will see how they perform. At least I won't be scared to death in the rain now. I was on the expressway 2 weeks ago sliding all over the place and couldn't go over 45 mph for fear of hydroplaning.
07-17-2011, 01:38 PM
#1198
Hey Waizzz, I got the Falkens mounted today and had them put 36 in the front and rear. They put nitrogen in for FREE to get me to try it out. It's normally $25 so I accepted and will see how they perform. At least I won't be scared to death in the rain now. I was on the expressway 2 weeks ago sliding all over the place and couldn't go over 45 mph for fear of hydroplaning.
Let's see some pics!
07-17-2011, 03:21 PM
#1199
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Cool, I'll continue with nitrogen then and hopefully topoffs aren't $6 a wheel lol I'll take pics tomorrow as I'm tired now. I've been out there for 3 hours cleaning the rims, the interior, putting on leather cleaner, etc. Oh, and it was like an hour to get the tires mounted.
I was of course telling the manager these rims are special and expensive and to get a guy that is careful and takes his time. The manager had his silver 07' Z out there too so he was asking about my Eibachs, spacers, etc and of course drooling over the LMGT4's
while they mounted the tires. I told them to take as long as they needed and PLEASE no scratches so they were methodical and precise. That's why I got my tires mounted on a Sunday morning when they weren't busy lol
I was of course telling the manager these rims are special and expensive and to get a guy that is careful and takes his time. The manager had his silver 07' Z out there too so he was asking about my Eibachs, spacers, etc and of course drooling over the LMGT4's
while they mounted the tires. I told them to take as long as they needed and PLEASE no scratches so they were methodical and precise. That's why I got my tires mounted on a Sunday morning when they weren't busy lol
Last edited by 370zGatorman; 07-17-2011 at 03:23 PM.
