tire pressure question, again?

Bob,
There was a lot of conversation on this subject over a year ago when I started using 40 front and 38 rear. I quickly got used to the firmer ride and have not experienced the handling or tire wear problems that many have mentioned on this board.

Johns site mentions running 42/40 as normal with some running 44/42 with no problems.

To answer your question, NO, there is no danger running 40/38 though it might require some softer pillows in the back seat!

 

IMHO - unless your roads are absolutely smooth - the ride harshness is *not* worth the 2-3 MPG you *might* gain.

I experimented with both the OEM Goodyear Integrity and the Michelin Harmony replacements, with inflation pressures right up to 44 psi. At city speeds under 80 km/h, there was *no* difference in my MFD or tank average fuel economy.

At Trans Canada speeds, a couple of times I gained 3 MPG. The "gain" was usually under 2 MPG, with many instances of no gain whatsoever.

BTW there is no difference in fuel economy between the Integrity and the Harmony, at least none that I could detect.

With all the potholes and frostheaves around here, I refuse to shake the car to pieces. The ride is *much* more civilized at 35F/33R.

 

I run 42/40 as per my prius tech and others recommend here. I notice increased thread life and an increase in mpgs. Lower pressure really causes the tires to wear prematurely. I like a firm ride so i don't really notice a harsh ride and the increased pressure

 

I agree with jayman... a couple of mpgs are not worth the harsh ride and the multitude of rattles produced by overinflation; 35/33 is an excellent compromise between economy and quality.

 

<div class='quotetop'>QUOTE(jayman\";p=\"80301)</div>

Potholes? frost heaves?? please explain.

 

<div class='quotetop'>QUOTE(TonyPSchaefer\";p=\"80365)</div>

I would hazard a guess as to weight bias towards the front of the car. So extra to carry the heavier load.

 

<div class='quotetop'>QUOTE(TonyPSchaefer\";p=\"80365)</div>

Toyota specifies a 2 pound differential between front and rear.

 

Frank:

Grrrrr ... must be nice to live in an area without frost that sinks down almost 6 ft. About the only thing worse would be Permafrost.

For the benefit of those lucky enough to live in an area where if the temp getting to the freezing point it is a FEMA emergency: a "frost heave" is a nasty ripple effect on pavement caused by the frozen ground "jacking" the pavement up.

AKA "frost jacking" and can really bugger up pavement and cement. Usually, the frost heaving will create 1-2 inch tall sharp ripples. Hit those babies just right and you either pop a tire or fly off the road. Like Speed Bumps from Hell.

Jay

 

Tony:

Beats me. I've tried reversing the bias, having no bias, etc. There was no difference in highway handling that I could detect, even on exit ramps or on ramps.

Jay

 

im sure it has to do with suspension tuning and the additional front-end weight. on another note, unlike most people, i couldnt detect a noticable difference in ride comfort from 35/33 verses 40/38 (what i ride at normally)

i have the "disadvantage" *sic* of living in the state capital where roads are generally much better condition than elsewhere so that may contribute to my not noticing the roughness of various road surfaces.

 

don't worry Jay this was a bad year for frost heaves here as well. Lots of broken pavement Cold snap back in January with day time showers made it icy and wrecked a lot of pavement. I also lived in Dawson Creek, start of the Alaska Hiway and I know what 6-8 feet of frost is all about.

 

Hi all -
Stupid question - I really do not check my own tire pressure but 3 weeks ago, Goodyear checked it and said the tires were 35 all around.

Today, 4/17, I went to an Amocco station and tipped the guy to check the tires - he said it was 30 in the rear and 32 in the front - I had him make it 33 rear and 35 front. However, since the Amocco station is 1/2 a block from the Goodyear tire place - why the difference.

How can I tell if I over-inflated my tires and why such a difference.

The outside temperature was the same (almost) both times - around 72 degrees.

thank you.

Mary Lou
Miami

 

difference can be as much as 5 psi just from cold to warm tires. the difference you mention could be simply how warm the tires were. the best time to check your tires is first thing in the morning after the car has sat all night. you want to measure it at the coolest part of the day. so early morning is best. may not be the coolest part of the day, but will be close enough

 

Thank you. 72 degrees was first thing in the morning and the coolest part of the day here in Miami - probably will not be that cold again until November.
Hopefully my tires are okay.
I think I will have to get one of those tire gauge things and measure it myself before driving it.

BTW - You live in a great place. I am considering a re-location to Portland Oregon.

 

Someone posted that their expensive guage was way off compared to a cheapie and the pressure monitor they installed.

So, I would say that it is possible that either Amocco or goodyear have guages that are reading incorrectly.

 

Every tire has a specific pressure for the load it is carring. I have always weighed my vehicles to determine what each tire is carring both loaded and empty. I then look at a load chart for the tire and set the pressure for the load it is carring. That along with rotating the tires every 10,000 miles or less will get the maximum mileage and performance from any tire. My 02 Avalanche has 63,000 miles on the OEM Good Year Wrangler ATS tires. The truck weighs 6300#s with me in it. The tires had 16/32" of tread when new and they now have 8/32". The wear has been even all the way around. Most of our vehicles recommended pressures were for maximum load as I think most are. We are rarely at max. load, so my pressures are rarely at the mfg. recommended pressures. I haven't weighed the Prius yet, so I don't know where I'll be, but I'll trust the weight charts to be correct.

Doug