Tire pressure after changing tires?

[Alfalfameister]

Switched from "passenger tires" to "light truck tires". Same size (185 R14).

Question, do I use the same tire pressures as on the "passenger tires" now that I have "light duty truck/van" tires?

FWIW, vehicle is Suzuki APV. Recommended tire pressures are 29 front, 35 rear; 32 front, 44 rear if fully laden.

Reason I ask is the guys at Goodyear (I got Cargo G26 tires) pumped the rear to 50 psi.

[bloowolf]

I always follow the recommended cold tire pressure.

[dr. d]

Switched from "passenger tires" to "light truck tires". Same size (185 R14).

Question, do I use the same tire pressures as on the "passenger tires" now that I have "light duty truck/van" tires?

FWIW, vehicle is Suzuki APV. Recommended tire pressures are 29 front, 35 rear; 32 front, 44 rear if fully laden.

Reason I ask is the guys at Goodyear (I got Cargo G26 tires) pumped the rear to 50 psi.

many tire shops pump in higher pressure than "recommended". dunno why.
and for lack of any "rule" , i just do the recommended pressures as usual.

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Switched from "passenger tires" to "light truck tires". Same size (185 R14).

Question, do I use the same tire pressures as on the "passenger tires" now that I have "light duty truck/van" tires?

FWIW, vehicle is Suzuki APV. Recommended tire pressures are 29 front, 35 rear; 32 front, 44 rear if fully laden.

Reason I ask is the guys at Goodyear (I got Cargo G26 tires) pumped the rear to 50 psi.

many tire shops pump in higher pressure than "recommended". dunno why.
and for lack of any "rule" , i just do the recommended pressures as usual.

[SkyFlakes88]

I just put in 30 psi on all 4. Just right for me. Not too bouncy

[bloowolf]

The safest rule to follow is the recommended pressure written on the tag on your cars driver side door. Problem is, when I have my tires checked, it isn't cold anymore, so the recommended pressure is different. I will usually put in 2-3 psi more & check again in the morning.

[Alfalfameister]

Yes, I agree that following the recommended pressure is good, but the recommendation is based on original equipment (OE) tires.

I changed from the OE tires (which were "passenger" tires) to light truck (LT) type tires... so does the recommendation of tire pressures on the tag on the door still hold?

[red_one]

You can set tire pressure between what's recommended on the car door jamb and the Max PSI rating marked on the tire sidewall. Example,

Door jamb = 30 PSI (Front), 36 PSI (Rear)
Tire sidewall = 40 PSI Max

This means you can set tire pressure to any value from 30 PSI to 40 PSI (Cold Tire Pressure), whichever works best for you.

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You can set tire pressure between what's recommended on the car door jamb and the Max PSI rating marked on the tire sidewall. Example,

Door jamb = 30 PSI (Front), 36 PSI (Rear)
Tire sidewall = 40 PSI Max

This means you can set tire pressure to any value from 30 PSI to 40 PSI (Cold Tire Pressure), whichever works best for you.

[Alfalfameister]

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

From what I am gathering at the interwebz, the LT-rated tires are heavier, ride rougher, but tougher, and better at carrying full loads. P-rated tires ride smoother, more pliable, more fuel efficient.

Since I am not getting a definitive answer yet regarding tire pressures of P-rated tires vis-a-vis LT-rated tires, I will stick to the higher end of the spectrum on the sticker on the door jamb (i.e., use the laden recommended tire pressures) for these LT-rated tires.

[Alfalfameister]

Sino meron APV carry or Panel Van (where the original equipment tires are the LT-rated tires -- 185R14C)?

Ano nakasulat na tire pressures doon sa door jamb? (yung sticker)? Thanks!

[bloowolf]

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

[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).