Preparing for a roadtrip

Most passenger cars have mfr recommended pressures in the low 30 psi range.

 

How does running the tire at its max sidewall indicated pressure mean running low to you? I specifically said 38 lbs. Thats max manufacturer recommended pressure. Not running pressure. MAX.
Read your tire.

Don't sweat pressure rise at high temps?

As tire temp increases so does tire pressure. Alot. If you start out at 42 psi on a 45 degree day and run it hard on asphault for hours into a 70 degree day, tire temp could cause pressure to rise as much as 10 lbs. Maybe more. You started at 4 lbs over max tire rec pressure.
Even 8 lbs more puts you at 50 psi. Your 25% over inflated past max tire pressure.

For what to save $1 the whole day of driving.

Actually you should run your car at door placard pressure. That pressure takes all travel variables into consideration. And is safe.
And is close to the average SAFE OPERATING inflation pressure for most passenger car tires in the US.

My 2007 Prius says 35/33 on door placard.

Which is exactly the pressure I would run on a very long trip. The tires will be safe, quiet and provide a smooth ride. Check them off your list.

Long trips are very dangerous.

 

Setting your tire pressure to 42 is definitely okay, and well-documented in this forum. I've been doing that for over 25k miles and no problems yet.

Saving $1 a day is a lot. You save 50 cent here, you save 50 cent there, pretty soon you have $1. You go to dollar store and buy something.

 

Ed is pretty clueless when it comes to tires. The 10 psi increase he talks about would require the tires to be about 100F above ambient temperature. That hasn't happened since the days of overloaded bias ply tires. 40 years ago after a long drive at 70 mph on a hot day, bias ply tires got too hot to hold your hand against. Modern radial ply tires typically only heat up 40 or 50 degrees on the highway. LRR tires heat up a bit less than normal tires.

It's the heat, not the pressure that damages your tires on a long highway day and the lower starting pressure you use, the more the tire heats up. There is no problem starting a trip at the marked sidewall pressure on the hottest day of the year.

 

On all the tires in my household, that is max COLD pressure, not max running pressure. And while my 80s' era Honda had tires with a max rating of 35 (car placard recommendation of 26), everything remaining in this household is rated 44 psi.

I wish Toyota gave me one of the other tire models rated 51 psi.

So what? That increase is already allowed for in the max COLD pressure stamped on the sidewall.

 

I run my tires the same for local driving but if I was taking a cross country trip under less than ideal conditions and was seeing temps go from 35 & possibly colder to possibly very hot road conditions all in one day I would lower the tire pressure a little. That was my friendly and safe recommendation.

Richbrvd1987: I've driven cross country from here to LA twice. 1-10. Years ago before GPS. Texas is a trip. First time from here driving through texas you think you'll never ever see El Paso.
El Paso being the point where Texas ends and possibly civilization begins please god please... while your thinking for hours how big can this freakin' state be?
Last time I went got caught in a really bad dust storm in Texas.
Saw this wall of white miles away and never having seen one before
was not sure what it was till it got close. No where to hide side of road.Filled the car up with dust. Scratched the hell out of the paint.
Scary. Engine started to get hot few hundred miles later. Had to get the oil changed.

Western part of Texas is an incredibly long drive over super deserted highway and the hardest part. Take good care of your tires and best of luck to you.

 

Thats exactly right.

 

That sounds like cheap entertainment.:rockon:

It's close to 1 psi per 10 deg F. It's a simple calculation using the absolute temperature and absolute pressure of the air in the tire. The real increase will be a small (probably insignificant) amount below that because the tire also expands a little bit.

The outside skin of the tire will be cooler than the inside of the tire, but probably not by much if you are quick with your measurements.

5 psi sounds reasonable. I usually see a 5 psi (so 5 degree) increase or less on my two cars with TMPS systems that have a pressure readout for the driver.

 

Yup, out there weather can change very, very quickly if the conditions are right. I snapped these two pictures about an hour and one cracked windshield (hail, no place to hide) apart on I-10 in west Texas this last May.

 

Nice shots. Thats what it looked like. I had no idea what it was till pebbles & rocks started hitting the car. Came up really fast too. Destroyed my car's paint.

The sheer size of Texas is hard to understand unless you've driven it all the way across. It does not end. And the shot from San Antonio to El Paso is unreal for the volume of nothing. Miles and miles of nothing. Bring cooler with lots of food & drink! And stop at every gas station and top off alot.

I mentioned to the op to lower tire pressure as the best side benefit is a nicer ride. The thought of driving across Texas in a Prius makes me wince as this a not a comfortable car for all day driving. I love my Prius but the seats suck and its tight.
I hope the OP's are young & in shape. Its a trip they'll never forget!