I liked your setup, but you're the boss

 

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.

 

are those hot or cold tire pressures?

 

Someone buy the 19x9.5's and 19x10.5's LMGT4's in the marketplace! I would but cannot afford at the moment.

 

+1

I would love to buy them and paint them black!

 

He didn't say. Also, I edited the PSI amounts as I wrote him back with the PSI placard info from the car and it changed the values a little.

 

Hmm I'm not sure about 38 PSI cold. That would expand to 43+ and probably cause uneven tire wear.

I think I will stick to 35 PSI since it's worked for nearly 4 years.

 

Waizzz, that's front and back? I'll probably follow your info as you've had LMGT4's longer than me.

 

Yeah all around, I have had no problems after nearly 40K on that setup.

 

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.

 

I have 19's but it shouldn't make a difference IMO.

 

Haha that actually ran through my mind when I saw them for sale. I wondered how they would look if the rears were painted black with your setup. The would look pretty great, but then again you can't go wrong with any LMGT4

 

Please don't encourage me Dan, I'm trying to save money!

 

black lms with the red and white stickers ftw! thats what i have

 

I know how that goes. Every time I start saving money, I have an urge to buy more mods. But sometimes its just irresponsible. Your car looks great as is

 

Saving money FTL

 

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.

 

Nice, I've been running Nitrogen for about two years as well. Since I live near the ocean we get wild temperature drops at night and I have noticed that the nitrogen keeps the PSI much more constant than air. The only problem with nitrogen is that you can't just stopby the gas station to fill-up and need to go to a place that has it.

Let's see some pics!

 

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

 

Aww...look what I found. Waizzz knows what it is.