Tire pressure question

Post by **Big Tone** » Sun Apr 30, 2006 2:37 pm

Ok, I plugged my first tire today! I had a nail in the front driver side, and since the people at Pep Boys had me standing around for 5 minutes without anyone trying to serve me, I decided to try my hand at tire repair. It worked!

Now that it's done I began to wonder what my tire pressure should be. The other three tires were set at around 36 or 38. The size is 225/40Z/R18. I set them all to 40 and the ride seemed to be ok, but is that too high?

Post by **DominickJ30** » Sun Apr 30, 2006 3:00 pm

Yea, that way too much. Most tires specify on the sidewall, but the max I would keep it at is 35, I have mine at 30 right now, the recommended spec for a J is 29 psi.

Post by **driverdriver** » Sun Apr 30, 2006 3:33 pm

Stick to the tire manufacturers recommended PSI rather to anything in the Infiniti manual.

Post by **Big Tone** » Sun Apr 30, 2006 4:27 pm

driverdriver wrote:Stick to the tire manufacturers recommended PSI rather to anything in the Infiniti manual.

Where on the tire can I find that information?

Post by **DominickJ30** » Sun Apr 30, 2006 4:44 pm

Some have it written right on the sidewall, just to be safe I would keep it at 32 and call it a day.

Post by **93j30t** » Sun Apr 30, 2006 5:30 pm

um not in the J... it's actually in the arm rest, open it up (between the two seats) it's plastered on the top of it in big letters

Post by **driverdriver** » Mon May 01, 2006 5:04 am

Big Tone wrote:Where on the tire can I find that information?

Most tire manufacturers websites have this information also. Look under "specification".

Post by **Big Tone** » Mon May 01, 2006 5:23 am

driverdriver wrote:
Most tire manufacturers websites have this information also. Look under "specification".

Thanks!

Post by **RussA89** » Mon May 01, 2006 7:21 am

I lowered mine to 29psi per the J specs listed under the center console lid, but I'm running the stock size 215/60-15s. It seemed to smooth things out a little more, not quite as harsh on bumps.

All the stuff I've read says you're supposed to set the pressure when the tires are "cold", because tire pressure increases as the tires warm up.

Post by **gr8scott72** » Mon May 01, 2006 5:45 pm

I adjust my tire pressure to match my tire's wear. If they are wearing too fast on the outside edges, assuming that the alignment is ok, then I up the pressure some to get the inside tread to wear some. I think I'm up to about 35 or 36 on my 215/65/15 Falkin Ziex.

Post by **Q45tech** » Tue May 02, 2006 1:36 am

The oem tire placard COLD inflation is just the minimum they found safe for oem as built and delivered tires. It is not valid for any other brand or size!

44 psi tires are tested at 35 psi in lab COLD. The PROPER way to calculate inflation is to divide the loaded tire weight plus the gain in peak load from cornering and set up a ratio with the max inflation pressure.

If a tire sees 1400 pounds peak and has a 1521 pound max load 1400/1521= 0.92 x 44 psi = 40.5 psi AT THAT LOAD!

Same with a 51 PSI tire = 0.92 x 51= 47 PSI AT THE PEAK LOAD NOT COLD which might be 40 PSI.

Post by **elwesso** » Tue May 02, 2006 3:03 am

Q45tech wrote:The oem tire placard COLD inflation is just the minimum they found safe for oem as built and delivered tires. It is not valid for any other brand or size!

44 psi tires are tested at 35 psi in lab COLD. The PROPER way to calculate inflation is to divide the loaded tire weight plus the gain in peak load from cornering and set up a ratio with the max inflation pressure.

If a tire sees 1400 pounds peak and has a 1521 pound max load 1400/1521= 0.92 x 44 psi = 40.5 psi AT THAT LOAD!

Same with a 51 PSI tire = 0.92 x 51= 47 PSI AT THE PEAK LOAD NOT COLD which might be 40 PSI.

Thats very intriguing information about tire inflation

Post by **Big Tone** » Fri May 05, 2006 9:34 am

Ok, after squinting and turning my head almost upside down to read the small print, I finally saw something regarding psi. It says the max should be 40, but I didn't see a suggested psi. What gives?!

Post by **NismoChi** » Fri May 05, 2006 10:14 am

Big Tone wrote: but I didn't see a suggested psi. What gives?!

Because the tire manufacturer wouldn't know waht kind of car you are going put their tires on. And you can't just go follow the car manufacturer for the suggest tire pressure either, according to "the man" Q45tech, Vehicle placard only applies to as delivered tire brand and size........change either and all bets are off as to what is correct COLD PRESSURE for a different tire.As i would do is as long as you keep the tire pressure under the max pressure, in this case, 40psi, you will be save/alright. of cause, the higher the psi(still <40psi) the rougher the ride would be. try different tire pressure setting and go for a ride to see what tire pressure you like the best, i set my 235/40/18 at 36psi and like it that way. Of cause different tires even same size have different stiffness of the side wall too, so my ride w/36psi may be softer than your ride w/36psi.

Post by **Big Tone** » Sat May 06, 2006 4:44 am

Gotcha. I went with 36 for now. So far so good. We'll see how that works through the weekend.

Tire pressure question

Tire pressure question

Re: Tire pressure question (Big Tone)

Re: (driverdriver)

Re: (Big Tone)

Re: (Big Tone)

Re: (driverdriver)

Re: Tire pressure question (Big Tone)

Re: Tire pressure question (RussA89)

Re: Tire pressure question (gr8scott72)

Re: Tire pressure question (Q45tech)

Re: Tire pressure question (elwesso)

Re: Tire pressure question (Big Tone)

Re: Tire pressure question (NismoChi)

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