Well Jerry can speak for himself but I suspect his "calculation" is experience which he has a bunch of.
Tire pressure calculation
- Thread starter Stockli
- Start date
Tire shops routinely over inflate tires. It's not so much that they are "clueless" as some like to claim with smug superiority , but instead as a defense against Ford/Firestone type lawsuits claiming personal injury and wrongful death as a result of purposely under inflating tires to improve ride comfort at the expense of consumer safety.
For this reason many if not most tire chains will refuse customer requests to inflate tires to less than the pressure specified on the door sticker or the tire sidewall, or in the case of vehicles with TPMS less than the pressure required to keep the warning light off.
I can't count the times after having tires installed or serviced that I've pulled out my tire pressure gauge and deflaters and reduced tire pressure in the tire store parking lot to my preferred pressure. It's just the way it is in our over regulated and litigious society.
BTW, and in order to keep this thread on track, on my 2006 LJ I run LT315/75R16 Mickey Thompson Baja ATZ P3 tires ("metric 35's") at 26 psi around town and 28 psi on long Interstate runs. My door sticker specifies 33 psi cold for the 245/75R16 factory supplied tires.
For this reason many if not most tire chains will refuse customer requests to inflate tires to less than the pressure specified on the door sticker or the tire sidewall, or in the case of vehicles with TPMS less than the pressure required to keep the warning light off.
I can't count the times after having tires installed or serviced that I've pulled out my tire pressure gauge and deflaters and reduced tire pressure in the tire store parking lot to my preferred pressure. It's just the way it is in our over regulated and litigious society.
BTW, and in order to keep this thread on track, on my 2006 LJ I run LT315/75R16 Mickey Thompson Baja ATZ P3 tires ("metric 35's") at 26 psi around town and 28 psi on long Interstate runs. My door sticker specifies 33 psi cold for the 245/75R16 factory supplied tires.
Jerry and Mots,
Thank you both very much. My tire store guy is actually an experienced international racer. He runs in the 24 hrs of Lemans and a bunch of other stuff. I found it a bit odd that he recommended such high pressures. I'm going with you guys on this one. So far this thing is a beast to drive when it comes to handling and braking. It locks 'em up in a heartbeat on dry pavement. In the rain its an accident waiting to happen. I spoke with the guy at Black Magic Brakes and he talked me out of buying his brakes!! he said that I don't have a brake problem, I have a traction problem. I was originally thinking about installing an anti-lock system. Any thoughts on that?
Thank you both very much. My tire store guy is actually an experienced international racer. He runs in the 24 hrs of Lemans and a bunch of other stuff. I found it a bit odd that he recommended such high pressures. I'm going with you guys on this one. So far this thing is a beast to drive when it comes to handling and braking. It locks 'em up in a heartbeat on dry pavement. In the rain its an accident waiting to happen. I spoke with the guy at Black Magic Brakes and he talked me out of buying his brakes!! he said that I don't have a brake problem, I have a traction problem. I was originally thinking about installing an anti-lock system. Any thoughts on that?
They're not that much heavier than a TJ, I'd go for the usual 24/26 psi. That works for my fairly heavy TJ with lots of armor, tools, spare parts, etc.
Do you mean Antirock? And yes, Blaine @mrblaine the founder/owner of Black Magic Brakes is good about not recommending his products unless they're appropriate.
Robnfl
Member
Thx Mots, my "X" has 30x9.5's on it, and I was wondering what pressure I should be running. The PO was running 36 PSI in them, I knew that couldn't be right.
Sent from my SM-G950U using Tapatalk
I'm that guy. What I was trying to explain to you is how to get a rough starting point.
Goodyear has a tire that has 50 psi max for 2535 pounds max load. Divide 50 into 2535 and you get 50.7 lbs per psi. Divide your estimated corner weight of 1000 lbs by 50.7 and you get 19.7. Round that to 20, add a few pounds for safety and you could likely keep that tire at 23-24 psi forever if it wasn't too squirrely in the turns.
Not AR, ABS to try and prevent lock up. He doesn't have a braking problem, he has a traction problem and my stuff will only make it worse.
Many thanks again to all of you. mrblaine was a great help. I bookmarked your website for future brake purchases.
The ambient air temp is in the 30s - 40s here in Maryland this time of year through March-ish. I just dropped my tires down to 27 psi/front x 26 psi/rear. I'll keep you updated as to how it works out.
Cheers
Tim
The ambient air temp is in the 30s - 40s here in Maryland this time of year through March-ish. I just dropped my tires down to 27 psi/front x 26 psi/rear. I'll keep you updated as to how it works out.
Cheers
Tim
I got some BF Goodrich All terrains, 33x10.5r15 C load on my 01 TJ sport. Tire shop mounted them and put them at 38 psi. After looking around this forum I'm guessing that is way too high? What psi should I run for everyday in town driving?
jeepndogs
TJ Enthusiast
Here is a tire chart from Cooper. My 33 x12.50 SST Pro is still rated for more than my Lj weight at 25 PSI. I have been running 21 in mine for over a year and close to 10K. Just did a toys for tots run where I had to travel 280 miles each way on the expressway to get to it. Set the cruise at 75 and rolled along.
FYI - That page from Cooper is excerpted from the Load and Inflation Tables published by the Tire and Rim Association and applies to all tires, not just Coopers.
You can find it here: https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
You can find it here: https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
jeepndogs
TJ Enthusiast
It’s been about as close to flat as I think it would get. I was measuring tread depth for the first few rotations (3000 miles) and it was even across the tire. The outside 3/4 was not showing much wear. I stopped measuring them a while back because they were always pretty much on the money.
So with my 33x10.5 r 15's i was way high on the psi until you guys helped me out. Mid 20's definitely made for a much better ride in town. But I was wondering what the pressure should be for long high speed driving. I hit the interstate the other day, going between 75-80 mph. I felt like I was white knuckling it much of the way. it was windy but i was wondering how much the tires were affecting me. Any thoughts?
Thanks Jerry- I just purchased a set of Falken Wildpeak M/T, 31x10.5x15 for my stock 2003 Freedom Edition. The dealer set up at 42 pounds and I adjusted them down to 30 pounds. Your advice really helps.
What pressure do you recommend for these tires when airing down for running in sand or hills?
Thank you
Thank you
Might look here, it's a good starting point
https://wranglertjforum.com/threads/airing-down-discussion.26719/