PSI adjustment for larger tires

.
32 psi is ok
34 psi is ok
36 psi is ok


Huh? So if your 215/45-18 recommends 36 psi, what should my 165/65-14 Honda Insight tires be inflated to? Like 12 psi? No, the manual says 38/35 psi front/rear.

Volume, not section! More exactly, volume provides load capability.
That's why heavier cars run bigger tires (taller and wider). However,
there's way more to suspension adjustment, tire choice and tire
pressures to any manufacturer. This task takes many many weeks if
not months.


The GTI calls for 39 psi and I round up to a nice even 40.

33 - 35 psi provides more traction to your GTI with two (one driver and
one passenger), in particular on wet surfaces. And better ride as a bonus.
.
 
The margin of error in a tire gauge may be more than that 2 psi.
I agree there are a lot of inaccurate gauges out there but I have a Longacre racing digital and a intercomp racing analog (from my autocross days). I bought them for their accuracy. There's less than a half psi difference between the two.
 
Earlier yesterday I emailed Tirerack asking them if they had a recommendation for tire pressure for my new Pirelli's. I gave them info about my car and the old tires as well but it seems they already had more than enough info to make the comparison (duh). Had a reply in my mailbox this morning (they must have bored employees manning the computers and phones on the weekend). Their recommendation based on Mazda and Pirelli info they had was 34 PSI. I think I'll stick with that for awhile.
 
There is a school of thought that says you should match the original pressure to keep the same spring rate in the tire so the suspension reacts the same.
That’s what I was going to suggest.

The difference between the two, a slightly increased width and slightly increased diameter, is so small, that a reduction in pressure won’t make a material difference. So, no need to adjust.
 
That’s what I was going to suggest.

The difference between the two, a slightly increased width and slightly increased diameter, is so small, that a reduction in pressure won’t make a material difference. So, no need to adjust.
I had to look up how a "tires spring rate" is calculated....:poop::poop: Wow, it appears to be even more complicated than psi calcs and not for mortals!!
 
I've been running the tires at 34psi for a month now and happy at this pressure. I did have an interesting experience a week ago. I drove from Colorado to Dallas to visit my son who just moved there. Started at moderate temps here (mid 70's) and quickly raised into the 100's once in Texas. Anyway once in Dallas and my tires had cooled a little my TPMS warning light came on. My son has a nice Joe's racing digital gauge (which I gifted him) to check with. My pressures were 31.5 PSI at all four corners! The drop was totally attributed to the elevation change between my home (5500') and the Dallas area (+/-600'). I wasn't aware that tire pressure changes 1 psi for every 1000' of elevation gain or drop. Also, I'm guessing the reason the tpms low warning didn't go on while driving in Texas was probably attributed to scorching pavements temps offsetting the elevation change. The reverse was also true on the return trip. I aired up to 34 psi at my sons home. When I got home it was close to 37psi! I was aware of elevation impacts on psi but not aware it would be so dramatic.
 
I would also like to comment on the new pirelli's. They changed my cars comfort levels dramatically. Much quieter on most road surfaces and rode so much better than the Dunlops that came on the car. The Dunlops were like rocks and screamed or rumbled on anything but the smoothest asphalt. Even though the Pirelli's come across as a great touring tire they have made my Mazda3 GT a Miata want-a-be contender (had one and miss it dearly). Should have made this change a long time ago but the Dunlops would not wear out. PS... love Texas back roads (we drove two laners most of the way on the return trip) 75mph speed limits are the norm!
 
Back
Top