Tire pressure after changing tires?

[bloowolf]

Try posting in Tamaraw FX thread. Those AUV's also use similar tires.

[red_one]

The LT-rated tires have a 65psi max. I guess the P-rated tires would be 50?

It depends on the spec of the tires.

The Michilin LT265/75R16E is rated 80 PSI max. This is an "LT" tire.

My Yokohama A.Drive is rated 44 PSI max while my Dunlop SP Touring tires are rated 40 PSI max. Both are "P" tires.

Truck tires (LT-metric) have more rigid sidewalls, and typically feature stronger construction. They’re rated for higher pressures and are specifically designed to withstand the considerable weight of a fully loaded rig, along with potentially severe towing demands. They enable you to maximize control over your vehicle when operating it under load.

In comparison, P-metric tires are typically designed for a quiet, smooth ride – the kind of ride you want in the family sedan. They’re rated for lower pressures, are lighter, and maximize handling and fuel economy.

[Alfalfameister]

I'm doing my research (unfortunately, post-purchase) re LT vs P tires.

All the info here is well and good, but maybe I should rephrase my question:

When using LT tires (when van originally had P tires), should one still follow the psi recommendations as listed on the door jamb sticker (which were meant for the P-rated tires)? Or should one use a higher psi?

[red_one]

Yes, you can still use PSI recommendations on the door jab, but you can also vary the tire pressure depending on your load.

Example, Tire Inflation Chart for Michelin LT tires. You can set tire pressure from 35 to 80 PSI depending on your load.



http://www.classbforum.com/phpBB2/do...ile.php?id=617

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Yes, you can still use PSI recommendations on the door jab, but you can also vary the tire pressure depending on your load.

Example, Tire Inflation Chart for Michelin LT tires. You can set tire pressure from 35 to 80 PSI depending on your load.



http://www.classbforum.com/phpBB2/do...ile.php?id=617

[Alfalfameister]

*red_one

THANKS! That's the answer I was looking for.

EDIT: Off topic. Bakit dito sa tsikot.com, palaging nagdo-double post (that's why I'm editing this post)

[Alfalfameister]

Excerpts from Tire Types: Tire Load Capacities & Pressure for Euro-metric, P-metric Tires

LT-metric tires were specifically developed for use on light trucks and have a number of characteristics that differentiate them from P-metric tires. An LT tire is built more robustly than a P-metric tire, primarily to handle heavy loads under adverse conditions. Heavier body plies and larger bead bundles allow LT tires to be inflated to higher pressures, increasing the tire's load capacity and allowing them to carry a heavy load continuously (not just occasionally) without overheating and failing.

ypically, LT tires are made of higher quality materials than P-metric tires, and their construction is much more robust, with heavier sidewalls and denser, higher quality steel belts.

The trade-offs for these strengths include significantly higher weight, a stiffer ride, increased rolling resistance and reduced fuel efficiency. The differences in load capacity and required inflation pressure prohibit mixing LT-metric tires with P-metric tires. It also creates problems when trying to replace P-metric tires with dimensionally equivalent LT-metric tires, and vice versa.

Size-for-size, compared to P-metric tires, LT tires require higher air pressures to carry equivalent loads.

[emphasis mine]

Because of the higher inflation required by LT tires, they often are not appropriate replacements for OE P-metric tires due to ride harshness caused by higher inflation pressure.

As an example, consider an OE P265/75R16 114S with a maximum load of 2,601 lbs. at 35 psi. If a LT265/*75R16 Load Range C is to be used as a replacement, to carry an equivalent load the LT tire must be inflated to 50 psi. Even an LT265/75R16 Load Range D or E tire must be inflated to 50 psi to carry the load the P-metric tire carries at 35 psi.

[emphasis mine]

From another site:

If you replace passenger car tires with light truck tires,
replacement tires will require a significant inflation pressure
adjustment in order to carry the same load as the original
equipment size. Passenger tire load carrying capacity must be
reduced by dividing by 1.10 for LT applications. For example:
P235/75R15 which has a maximum load capacity for passenger
vehicle application = 2028 lbs. For a light truck application,
using the formula, the maximum load capacity would be 2028
/ 1.10 = 1844 lbs.

[emphasis mine]

I'm now gonna do the math and come back here to post...

[Alfalfameister]

This is Suzuki APV specific:

Kerb weight is 1300 to 1340 kilos (2860 to 2950 lbs).

Gross vehicle mass weight rating is 1950 kilos (or 4299 lbs), or about 1,350 lbs of passengers and cargo.

(hmmm... about eight 170lb people with no cargo; medyo "heavy duty" na mga malusog din iyon of average height people, LOL).

According to the sticker, unladen weight (29 psi front, 35 psi rear) is the kerb weight plus a maximum of four people (laden weight would be the aforementioned full of eight people, and would necessitate 32 psi front, 44 psi rear... on P-rated tires).

From another site (Toyo tires)...

For P185/75 R14 (closest I could get to P185/80 R14), maximum load per tire is:

26 psi = 1,113 lbs
29 psi = 1,168
32 psi = 1,235
35 psi = 1,290

(x4 na lang for four tires, more or less)

Now, using LT-rated tires (again, from Toyo), 185/75 R14 (again, the closest I could find to 185/80 R14)

35 psi = 1,040
40 psi = 1,140
45 psi = 1,240
50 psi = 1,355

That would mean, unladed P-rated tires at 29 (front) psi should be about 42ish, and laden 35 P-rated "should" be 46-48 psi at the front, but gross axle mass weight rating of front is 2,425 lbs, then 44 psi should be enough.

Rear (P-rated 35 psi to 44 psi) would be, on LT-rated tires: 46ish to ??? But, since gross axle mass weight rating of rear is 2,690 lbs, 49-50 psi would be enough.

Shortcut conclusion: with LT-tires, front should be 40-44 psi, and rear would be 45-49 psi.

So, mukhang tama nga yung Goodyear technician in putting 50 psi at the rear.

BUT, harsher ride nga lang (and heavier, and less fuel efficient than P-rated). But, since my APV will be used mostly full of people, puede na rin LT-rated tires (after all, the APV carry (same exact chassis, etc) was spec'd with LT-rated tires in other countries that have it).

[TireWhisperer23]

The information user 'Alfalfameister' posted seems the most legitimate on here, so I don't know what happened to them. Maybe the links?

The resources I consulted - a website with exhaustive tire pressure and load tables - bears out what alfalfa was saying.

For an example tire size: 205-70R15, the load capacity for the 'P'(passenger) designation at 35psi = 1,433lbs.

For the LT(light truck) tire, same size, the load capacity at 35 psi = 1,260lbs.

So for the LT205-70R15 to match the P205-70R15 load capacity of 1,433lbs, it must be inflated to around 43psi.

Even if that size is common to both cars and light trucks, I would recommend using only a Metric or P-Metric class tire on a car(sedan, hatch, coupe), because the higher pressure required for the LT tire to match the load capacity of the passenger metrics would probably not work with the spring rate of the suspension on the car. IE It might end up riding like a pulpwood wagon, even if the tire fits.

Also remember: Even if you replace the tires on your vehicle with tires of a much higher maximum load capacity than the originals, your vehicle ultimately determines the gross/ maximum load it can carry, as specified on the stickers located on the door frame, or in the owners manual. Exceeding vehicle max load, even with XL/XD or LT tires, will result only in a rough ride, bottoming out of the suspension, and potentially other vehicle handling and damaging issues.

[mikhadelacruz]

To ensure you have the correct tire pressure after changing tires, follow these steps:

1. Refer to Manufacturer Recommendations:
Check your vehicle owner's manual or the driver's side door jamb placard for the recommended tire pressure. This information is specific to your vehicle's make and model.

2. Use a Quality Tire Pressure Gauge:
Invest in a reliable and accurate tire pressure gauge. The reference you provided emphasizes the importance of using a quality gauge. Ensure that the gauge is suitable for the type of tires you have.

3. Check Tire Pressure When Cold:
Measure the tire pressure when the tires are cold, as driving can heat them, affecting the readings. Wait at least 3 hours after driving before checking the pressure.

4. Remove Valve Caps:
Remove the valve caps from the tire valve stems. These caps protect the valve stems from dirt and debris.

5. Attach the Pressure Gauge:
Press the tire pressure gauge firmly onto the valve stem to get an accurate reading. The gauge will display the current pressure level.

6. Compare with Recommended Pressure:
Compare the measured pressure with the recommended pressure values from your vehicle manual or door jamb placard. You have the correct tire pressure if the pressure is within the recommended range. If it's below, add air; if it's above, release some air until it reaches the correct level.

7. Repeat for All Tires:
If applicable, check the pressure of all four tires, including the spare. Ensure that each tire is inflated to the recommended levels.

8. Replace Valve Caps:
After checking and adjusting the tire pressures, securely replace the valve caps to protect the valve stems from dust and debris.

9. Monitor Regularly:
Regularly monitor your tire pressure, ideally at least once a month and before long trips. Temperature changes can impact tire pressure, so ongoing monitoring is crucial for optimal performance, fuel efficiency, and safety.

By following these steps and consistently monitoring your tire pressure, you can ensure your tires are correctly inflated, promoting vehicle safety, longevity, and optimal performance.

To learn more about tire pressure, this resource might help – Tire Pressure Defined: From Passenger Cars to Construction Heavyweights.