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Greetings,

I am on a quest to discover a load chart for any of our commonly used tires. While it is true that the CHrysler placard indicates that the correct PSI for the vehicle is 35PSI, that is based on the curb weight of 4987lbs. Our max gross weight is listed at 6300lbs. In commercial grade tires, load/PSI charts are readily available. The basic principle is that the greater the load, the greater the PSI, up to the max PSI and load rating for the tire itself.

When I chatted with the folks at Michelin about this, since I did not have corner weight or axle weight values for the Pacifica, the only recommended PSI values they could recommend were 35 PSI for no load, and 44 PSI (max for the model of tire) for max gross load. Not super helpful!

Anyone seen load/PSI table for any tire in sizes common to our vehicles?
 

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I havent seen what your looking for but I might have some ideas that can help.

I have successfully used commercial transport wieght station scales after hours without issues (they seem to leave the scales on).weighing the front and rear axles seperately isnt as good as corner weighing but divide by 2 it is pretty accurate (to a couple percent) and can help you provide the correct numbers to the manufacturer for help.

The second idea is one I use and have had excellent results with over the years for setting up tires with unknown specs.

On light pickups with lifts and big tires like a lifted toyota on 36" tires, 30psi is likely excessively over-inflated because the rated load for a single tire exceeds the entire vehicles weight. The correct pressure could be as low as 15psi.. remember its deflection that causes heat not the pressure. Like folding a paperclip.

And race tires (R compounds) need heat to get sticky so 23psi cold runs a correct patch at opperating temp for my setup.

This trick is easy, needs only common resources and some common sense but could take some time. Heres the gist: use the tread print to determine the contact patch then compensate for tire heating/cooling.

This "print" is not the same thing as the tread patch pressure distribution and does nothing more then indicate an over inflation condition down to a full contact condition. Which is useful by itself because the correct pressure for a tire produces a full contact patch at opperating temperatures (typically - more on this later).

Edit: The tread patch pressure distribution is directly related to the tires shape so can be inferred. This has been happening long before pressure plates where invented ;)

This does not however indicate an under-inflation condition because the tires pressure distritbution changes so that the rubber wears rapidly on the outer edges but the center blocks remains in contact.

Make or find a puddle and set your tires to an obviously overinflated psi. You can start at the max load recomended psi on the sidewall if you cant ballpark an overinflated psi value mentally. Then simply drive through the puddle (slowly) and read the resulting track.

Directly out of the puddle the tire is too wet and the track is blotchy but soon becomes very clear before being faded. Obviously read the clear spot. Deflate by 5 psi until close then 2-3psi until the entire patch is printed in the track.

So knowing the pressure at which a full tread contact print occurs clearly gets you in the ball park but still will be a higher pressure in the center tread region due to the pressure distribution than you want but this is pretty close to the max range we want to set for the tire at. its the high side of the normal operating temperature. Most tires increase around 4-5psi under highway usage depending on the tires carcass construction and resulting deflection (ie: load rating and speed rating).

Setting the tires 3-6psi lower after a full contact print is found will produce a even to under-inflated pressure distribution that allows for tires to heat normally and be close to the ideal pressure distribution during normal useage much like the factory specs on the placard. This should be recorded and used as your new cold inflation pressure.

A prefectionist will want to monitor the tread landmarks for even wear rate (nipples, nubs, flashings, even dust and colour differences can use used) for a couple days and trim the psi accordingly to fine tune the wear. For customer vehicles I like to see them back around the first oil change when the vehicle has seen a full normal "life" conditions and use the average wear that is just begining to show its pattern to trim and fine tine the psi in a convenient manner.

Note that not all tires are a square contact patch and some have less tread thickness on the shoulders then the center blocks. If the tire is setup to wear evenly then this type of tire will wear the shallow shoulder bald prematurely.

Tuning for wear works but needs a basic understanding of whats going on with the tires.
 

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I will say FCA tends to ship with tire pressure ~44PSI, so do check and adjust.
In the section about Storing the Vehicle, the Owner's Manual states:

"Inflate the tires at a pressure of +7.25 psi (+0.5 bar) higher than recommended on the tire placard and check it periodically."

I suspect they are setting it up assuming that it will be sitting for a little bit, so by all means, a new owner should check it. I did check mine when I picked it up, and the pressure in all four tires was in that ballpark.
 

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Its common practice for transport because prevents flat spots from sitting around and should have been adjusted at PDI..

But its faster to do said PDI if you skip checking everything! If theres a problem the customer will report it anyway right? - being cynical here - my instrument cluster was delivered with a large crack in the lens.

They get paid flat rate after all and its a customers responsibility in the end ;)
 

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paRegistered to this forum to give you an answer.
Live and was born in The Netherlands and end 2007 got hold of the official formula and system to calculate pressure for a sertain load ( and speed) on tire, and went runing with it.
Got wiser in time and now call myself "pigheaded Dutch selfdecared tirepressure-specialist".

Risking being banned from this forum I begin directly with giving a link to a map on my public map of Onedrive that belongs to my hotmail.com adress with same usernname as in this forum ( so you can combine if you want to mail me, spamm robots cant this way.

Got the message that I cant give a link yet so will give it when I made enaugh posts



In this map pressure / loadcapacity -lists for the most important tirekinds and Loadindexes.
Made with my own extra save formula , even saver then the European one , I got hold of, so gives higher pressure advice then the official system.
Given per tire , per axle single and dual, so you can use your preference.
Use it like this: find onn sidewall the loadindex ( and speedcode ) or the maximum load and loadranche.
Then look in te PDF for your loadrange for the loadindex/maxload, and in that list the weight you want to know the pressure for.
This weight is the most tricky part in it all, and that is the reason why tire- and car-makers are not that eager to give you advice, also the reason why advices are that high nowadays.
So if you use other then advice from carmaker, you yourselves are responcible.
So determine the load on the axles as acurate as possible, and mind that its not total weight devided by 2 , only driver mostly front more then rear, and fully loaded mostly rear more then front.
Add 10 % to that for reserve for unequall weight R/L etc.
Then look this axle weight up in the list at the loadindex of your tires in the PDF given per axle.
Or if you want to use the american system , devide by 2 and look in the PDF givenn per tire.

Speed is also a factor, and the official system had a way for highening up the reference-presssure( is not the maximum cold pressure) for speed higher then reference speed. .
But I determined my own system wich I nicked from the tiremakers .
This is simpler and goes for every kind of tire, up to trucktires even.
For every 10km/6.5m diferent maximum speed used( and wont go over for even a minute) > 1 Loadindex step diferent.
Lower speed >Higher loadindex
Higher speed > lower loadindex.

You probably use in this forum only Standard load -tires , and those are sometimes called B-load /LRB or Eur system 4PR( Plyrated).
Those Are mostly speedrated Q or higher , and have reference-pressure AT 35 psi ( EUR 36 psi), for this pressure the maximum load is calculated for up to 160km/99m/h.

Can be that you have XL/reinforced/Extraload P tires and they have AT 41 psi in USA system and 42 in EUR system. Also Q and up speedrated, so reference-speed 160km/99m/h.

But the Americans think bigger is better, so sometimes swich to E-load/LRE tires AT 80 psi , and
on sidewall in this notation ( AT 80 psi).
Those mostly lower then Q speedrated, so mind if they are allowed for the maximum technical carspeed of your car.
N speedrated is for up to 140km/86m/h and then you have to do the LIstep-system going from that reference-speed.

Now you have the system , use it wisely , because you cant hold the tire- and car-makers responcible, also not me.
If you want me to help, give the needed data, and I will use it as example.

Greatings from Holland
( ja dat is) Peter
 

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Discussion Starter #9
35lbs is my starting point, but that's for an empty vehicle. With the family of four, dog, and supplies for a weekend, I bet we are adding 1200lbs or so. I want a chart that shows me what the PSI should be for that kind of load.
 

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Both gas and hybrid have the same recommended tire pressure, despite hybrid's additional weight. I chose to drive with 42PSI. Extra stiffness is good with the tall 17" tires.
 

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Both gas and hybrid have the same recommended tire pressure, despite hybrid's additional weight. I chose to drive with 42PSI. Extra stiffness is good with the tall 17" tires.
Good for mileage but what you save you pay for in tires. It might be ok - watch for the signs..
 

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The recommended front pressure is way too low

I have a 2017 Pacifica Hybrid Platinum with the 18" wheels and Michelin Premier A/S tires. The front tires have been kept at 36 psi cold since I got the vehicle (new), and the tires have not been rotated. At 28,000 miles, the front tires were worn out on both outer and inner edges. Clearly, they are underinflated. The rear tires do not appear to be unevenly or heavily worn.

I was expecting to get 60,000 miles from a set of tires. So 28,000 was a disappointment, especially given the wear pattern. I find it annoying that the recommended inflation pressure seems to be suboptimal.

I found no psi vs load charts for these tires, but I did find a similar load chart for Toyo tires in the same size here: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Basically, Toyo wants an additional 3 psi for every 88 pounds, which suggests a contact patch size of 29.3 inch^2, which sounds about right. I called Michelin (866-866-6605) to confirm this information, and they would only say to use what's on the door jamb. I'm pretty sure the door jamb recommends the same front/rear tire pressures because they figure some people are going to rotate their tires, and forget to check pressure when they do that, and will end up with underinflated tires on the front.

The Pacifica weighs 4987 lbs and has a 56/44 front/rear weight distribution. Add 500 pounds of people and 90 pounds of gas biased 40/60 to the rear, which is 60 pounds more in the rear. I estimate the front tires each have about 240 pounds more on them than the back tires. That suggests the front tires should be inflated with 8-9 psi more than the rear tires. I don't believe the tire optimal pressure scales linearly with load across that large a range, so I'm not going to set up with that large a difference.

Here is what I actually did:
* I bought Michelin Defender LTX 235/60-18 tires with a 107H load rating for the front. These have a maximum inflation pressure of 50 psi rather than 42 psi like the previous tires.
* I inflated the front tires to 44 psi cold.
* I inflated the rear tires to 38 psi cold.

I'll try to remember to check the tread depth at 10,000 miles and update this thread.
 

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I have a 2017 Pacifica Hybrid Platinum with the 18" wheels and Michelin Premier A/S tires. The front tires have been kept at 36 psi cold since I got the vehicle (new), and the tires have not been rotated. At 28,000 miles, the front tires were worn out on both outer and inner edges. Clearly, they are underinflated. The rear tires do not appear to be unevenly or heavily worn.

I was expecting to get 60,000 miles from a set of tires. So 28,000 was a disappointment, especially given the wear pattern. I find it annoying that the recommended inflation pressure seems to be suboptimal.

I found no psi vs load charts for these tires, but I did find a similar load chart for Toyo tires in the same size here: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Basically, Toyo wants an additional 3 psi for every 88 pounds, which suggests a contact patch size of 29.3 inch^2, which sounds about right. I called Michelin (866-866-6605) to confirm this information, and they would only say to use what's on the door jamb. I'm pretty sure the door jamb recommends the same front/rear tire pressures because they figure some people are going to rotate their tires, and forget to check pressure when they do that, and will end up with underinflated tires on the front.

The Pacifica weighs 4987 lbs and has a 56/44 front/rear weight distribution. Add 500 pounds of people and 90 pounds of gas biased 40/60 to the rear, which is 60 pounds more in the rear. I estimate the front tires each have about 240 pounds more on them than the back tires. That suggests the front tires should be inflated with 8-9 psi more than the rear tires. I don't believe the tire optimal pressure scales linearly with load across that large a range, so I'm not going to set up with that large a difference.

Here is what I actually did:
* I bought Michelin Defender LTX 235/60-18 tires with a 107H load rating for the front. These have a maximum inflation pressure of 50 psi rather than 42 psi like the previous tires.
* I inflated the front tires to 44 psi cold.
* I inflated the rear tires to 38 psi cold.

I'll try to remember to check the tread depth at 10,000 miles and update this thread.
I'm clearly not a tire expert but isn't the inner and outer ware you experienced on your front tires cause by the friction of turning?

I've always thought vehicle manufactures recommend a tire pressure based on a compromise of comfort, handling (safety) and gas mileage. Sure higher inflated tires will yield improved gas mileage, but will it not also be a bumpier/stiffer ride?

It will be interesting to see your results at 10,000 miles.
 

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Well, it's been about 10,000 miles, so here's the update.

The front tires have gone down to 42 psi cold, and the rears are at 38 psi still. I should have been better about keeping those fronts at 44.

Those tires started with 0.375" tread depth, and now have...
Center: 0.30"
Shoulder: 0.25"

These numbers were measured with a micrometer and are probably accurate to +/- 0.01".

Well, fooey. I extrapolate to 29,000 miles of anticipated tread wear, no better than the previous pair. If that actually happens, I'll talk to Michelin, as these tires have a 70,000 mile treadwear warranty. Maybe the shoulder started with a bit less tread depth, in which case the extrapolated lifetime from the center should be more like 50,000 miles.

We have noticed that my wife can now drive to and from work most days without using the ICE. She used to run out of battery coming home about 2-4 miles short of the house. This is probably just the higher tire pressure up front. I can't back this claim up with any numbers, as we don't track electricity consumption and see a lot of variance in gas vs electric miles, so we have no overall measure of gas+electric energy consumption vs miles.
 

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I have a 2017 Pacifica Hybrid Platinum with the 18" wheels and Michelin Premier A/S tires. The front tires have been kept at 36 psi cold since I got the vehicle (new), and the tires have not been rotated. At 28,000 miles, the front tires were worn out on both outer and inner edges.
@lain McClatchie, Rotate your tires bro.. the reason we do it is for even tire wear that makes them last longer.

 
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