Tire Pressure on Fuel Economy

ive got bridgestone ecopia and at 68k miles...

 

i had plenty of tread left at 48k, but one tyre was bad, and i really wanted to try the michelins.

 

Stay home on snow days. I kid you not, lol.

About a decade back (when we still occasionally got snow ) I needed to drive to a tire place for snow tires, on a day with a fresh/deep dump of snow, with well-worn Bridgestone Insignia SE200 on the car, the forerunner to the Ecopia EP20, has identical tread pattern (I'm guessing EP20 is your specific tire).

Once the tread depth gets low there is nothing but longitudinal grooves on them. I made it but it was nerve wracking. All was pandemonium at the tire place too: the plow that was supposed to clear their lot didn't get there, it was a mad house.

 

LOL... ummm its a prius.. im going so slow it dont matter!!!!!!

and fyi.. for snow ill take this out...

20160314_191200 by Jeffrey Riggs, on Flickr

 

Yeah that should do, lol.

 

yeah so when people make fun of me for driving a prius then later they see me driving the truck.. they are like woah...

full 1 tons, 4:56's, 40's, detroit lockers !!!!! hoping in march/april to get rid of the sb350 and go BB 496 (8.1L)!!!!

oh wait.. back to prius forums...

[/hijack]

 

The "sweet spot" for my car, seems to be no more than 2 psi over spec. Two pounds over doesn't affect the ride or suspension. (There seems to be a natural loss of 1 to 1.5 psi over three or four months, depending on temperature.)

The "Pearl" was really shining this morning.

 

Good to see the sun shining somewhere!

 

88 degrees for the next couple days. And the drought is terrible. I never get a free car wash.

 

Very mild and wet up here. Hit a high of 66F about a week back. Supposed to be getting a bit colder next week though.

 

There are some things I have come to the conclusion with car ownership, that become nearly ritualistic beliefs. And once people settle on what they think is best, it becomes nearly a religious act.

Oil change intervals.
Fuel Grade Usage.
Aftermarket Fuel Additives and "Beneficial" products.
Tire Pressure.

So I don't really even bother to argue or debate it too much.
If you think inflating your tires way above the Toyota recommendation is "The Right Thing" to do? Nothing I say is going to change your mind.

My personal foray into the inflate to greatness movement lead me to these personal beliefs.

Not worth it.

Increases in Tire Pressure did NOT result in my case, into huge advances in MPG. It did result in much harsher ride, and I think more trauma on the entire suspension...as well as my butt.

Given The Prius is a highly computer controlled vehicle, employing Regenerative Braking, Traction Control, and numerous systems that are directly tied into feedback that the vehicle gets from tire and pavement, it felt dangerous to me to severely alter the feedback created by pumping my tires up to marble floor levels of low rolling resistance firmness.

Given I thought the supposed benefit of increased inflation...greatly inflated...my decision was to keep the tires inflated at the recommendation.

My gas mileage was always good/great and the ride was also good. And I felt I wasn't putting stresses on the suspension that should be avoided.

Having said that? I know my opinion will be met with negative religious fervor by those that keep their Tire Pressure gauge on a rosary bead chain, and mutter prayers to the 40+PSI god.

My only concern to newbies in the decision making process?....Safety First.
I also assume...Toyota as the manufacturer balances their decision based on engineering factors only a manufacturer might include.

 

All of that true but main reason for Toyota (and all the other manufacturers) to give low tire pressure specifications is comfort. And at least I’m willing to trade bit of comfort for MPG and sharper handling. Higher tire pressure should also decrease tire wear.

With tire pressure above 40psi (above 2.8 bar) traction is still good on (even on) snow and ice. And testing on race track on ice all the systems including stability control system seem to work fine with higher pressures.

 

^ This bit concerns me too.

Best tact I figure, as has been mentioned a few times, is set pressures higher, but very slightly. This assumes there's decent buffer when Toyota set pressures, and also allows you to slack off for a while, if pressures drop a pound or two.

 

Lots of Prius owner run those high tire pressures and the still isn’t a lot of suspension stuff that needs replacing. Actually I would say that there are less suspension parts replacements needed than on average car. So from that we know that the effect on suspension parts is small.

Rear springs breaking is due to rust and design I don’t think it has much to do with tire pressure. Tire pressure might have some effect on front bearing lifetime but it’s hard to tell. Somebody would need to make a statistic on pressures and bearing life. And if bearings wouldn’t survive the life of the car anyways then does it really matter?

 

Can anyone recommend a good tire pressure gauge? I have three different types, and I get three different PSI readings. They can vary by as much as 4 PSI.

 

id say take it to the dealership and have them set it.. then test your gauge around that setting to see how yours rate. i would assume that the dealership is held to a more strict accurate reading... but I maybe incorrect.

 

so Saturday morning I got my Hankooks installed. $428 out the door vs $625 for the michellins I was looking at.
Cant verify if my MPG has changed at all as Friday was 61F and finished my round trip commute of 135 miles @ 65mpg. Following same speeds on ride in resulted in a way lower 58mpg but @ 37-28F !!!!! I ranged it that way as my house (car in garage and car said 60F) changed to 37F after 12 miles then almost at work was down to 24F!!!!!! I know in the cold I usually get about 55MPG. if we get a warmer day I can have a better comparision.

 

how is your mileage on that car? When I was in for my oil change last the dealership said they had a salesman getting 80mpg !!!!! I do not know the details but only that and have not looked into this new body stile and mpg...

 

i have 3 pencil gauges, all within a pound of each other. because i keep tham above recommended, i'm not concerned about being exact. when you see how little air it takes to add or subtract a pound, hard to believe it makes that much difference.

 

I'm thinking to pick up a few Milton S925, for myself and Xmas stocking stuffers. It's a pencil style, reads up to 70 psi, good reviews. There's a few other Miltons to consider.