tedboss1

I find the even in Comfort driving on our terrible roads in Montreal the ride can be quite harsh.

I looked at the tire pressure label and it recommends 33psi for front and 31psi for the back.

My actual pressure was 2 - 3 psi higher.

Is it safe to go lower?


Here is the tire pressure label that is located on gas filler door.l

jadatis

Viewing the high speed for wich the advices are given, for speeds below 99mph the pressure can be lower safely.
Pressure advice is to give the tire a deflection that wont overheat any part of it riding constantly the speed it is determined for.

I am able to calculate a safe pressure for the tires.
Give me of car GAWR's and GVWR, empty weight and the way you load it( so also persons).
Then max speed you use and wont go over for even a minute.

Then from tires 3 things .
1 maxload or loadindex
2 standard load or XL/ reinforced
3 speedcode.

I suspect by the advices that your tires have a comfortable reserve, so low pressure could be completely safe. But let me calculate it.

BAMBAMODA

Im no expert but...
I run 33/32 F/R

Because the veh is all wheel drive you want it about there. In a turn the *** pushes the front outside wheel hard you don’t want to get the tire pulled off of turning on transitioning pavement or any road condition that’s gonna put excess pressure on a tire edge during turn. Like a simple pothole. The 33/31 is a public use safety buffer because you could fill it on a super ***** hot day right after driving (hot tire) say in Phoenix AZ then drive up to flagstaff had have 80deg temperature change and if you have 21” wheels and hit a pothole at 22psi then yeah that’s gonna be bad which 32psi might save you from and also maybe hit ice slide then your under inflated tire grabs pavement and a pothole and it’s a bad day that maybe extra pressure would save you from.

So id recommend staying where it says for your application. And watch for tire wear on sidewalls. But if you were a racer you’d go even lower than 30psi on your tires for best performance. I like 33/32. I’m sure some dudes are lower. But I’m sure anyone who haven’t adjusted it from the dealer or got new tires is at 44 and that just makes a crappy ride.
If you track your car then up to 4psi is a general rule but that’s what hot tires.
For desert truck racing you want beadlocks for below 20psi. But we’re not racing on sand

your sidewalls will wear fast below 30 I think as well as your MPG will suffer.

BAMBAMODA

Good read on getting proper tire pressure.

Need a a thermometer tho.

http://www.turnfast.com/tech_handlin...ling_pressure3

gfish

I watch tire wear and adjust accordingly. I have 36 in my front and 32 in the rear because at lower pressures there was a lot of wear on the inside edges of the tire in the front. I had an alignment and yes it was toed in too far from the factory. My tires are wearing pretty even across the tread at this pressure. I have the 21in option

scotchy

Do you have 20" or 21"?

tedboss1

My tires are 21-inch diameter.

Joe biker

Go by the tire pressures in the drivers door jam
Set the pressures when the tires are cold as they will increase once the tires get hot.

tedboss1

Tire pressure label in the door jam shows cold pressure of 42 psi in the front and 41 psi in the rear which seems high to me.

Joe biker

The tire pressure in the door is for the size of the tire on your vehicle.
The gas door readings are a general tire pressure.
These vehicles have different options for wheels and tires.
My 43 with 21in tires is 35 front 38 rear
Make sure your tires are cold when checking or setting your pressures.
Try 40 front and rear
I just wouldn’t go much lower my that’s my opinion.

jadatis

This plate shows 105 loadindex in front and 107 in rear. And Y speedrated. Also extra load so front 925kg At 290kPa upto 160kmph/99mph to my system. But official european system, to wich America stept over as late as

2006, upto 220kmph.
Your GAWR's you gave in PM are F1300kg R 1330 kg. But can yust not be read in this new picture.
Payload of a good 400kg would indicate emty weight or driving ready to be 2600Gvwr minus 400 payload is 2200 kg and not the 1800kg I determined, so the advices I gave have to be reviewed.
My quess is that they used 270kmph to calculate for your 250kmph advice, to build in some reserve, and the upto 280kmph they used the full 300kmph calc for same reasons.

Have to look back, but will recalculate and show it here.

ZR , a man from Dutch education centre of VACO made me wiser about it. Nowadays ZR in the sises , means that the tiremaker did something offstandard in the design of tire( fi other treathwidth then standard for H/W division) and for that reason has to give system for calculating pressure themselfes.
Mostly they then also put W or for your tires Y behind it, and then you can use the system for that speedcode.

The paint image I gave, is what the reference- pressure has to be highened up for the speed, before putting it in the official general formula.
30kmph below maxspeed ( 300- 30 Is 270 kmph) the maxload acording to loadindex , has to be lowered 5% per 10 kmph.
I conversed that in the image to mph and psi .

If interested, I can sent you the official european calc by mail, if you mail me at my hotmail.com adress with username jadatis. Combine yourselfes, spamm machines cant this way.

Later I made my own system, wich is simpler and closer to laws of nature, and I lower maxload by 1 LI step for every 10kmph= 6.3mph , in fact the official system uses that too for the last 30kmkh. And for LT and Trucktires, this is also used.

Will give in next mail the official calc for 250 and 280kmph and the fully loaded and normal loaded, as on the plate, and what I would calculate.

KingMonkeyJr

I am 40/41 with PS4. They have a very delicate sidewall so running low pressure leaves you open to puncture in that area.