Tire pressure - tire wear

Clink clank clunk.... I sure heard the suspension, and he or she was not happy. Now it feels like I'm riding in someone's Lexus.

 

My decision to go by manufacturer vehicle recommendation wasn't really based on concern about the tires themselves wearing out significantly faster but more about concern it being tougher on the suspension, possibly reducing braking. I keep the Honda Fit inflated to the manufacturer recommended PSI, it's just the philosophy I've decided to embrace.
But when I owned my Prius, I felt it was even more important. With ABS regenerative braking, and a suspension system that IMO is very urban driving based, I thought harder tires just wasn't wise.

When I first got my Prius, I did experiment a bit. I never really found that increased PSI really resulted in MPG gains that seemed worth it to me.
I did feel the vehicle rode harsher, and was more apt to skid.
That just didn't seem good to me.

 

I see, most people here just talk about how they feel about the issue. I the industry I work for, everything is about evidence based. Looks like this thread is one big waste of time.

 

FWIW, here is a paper on effect of under inflated tires on suspension.

The influence of vehicle tyres pressure on the suspension system response by applying the time-frequency approach - IEEE Conference Publication
The results show that, when the tires were under-inflated by approximately 35 percent, it was significantly increased the vibration of the car body by up to 30 percent.​

I did not want to pay $33 just to read the entire paper, so I read abstract only. I don't know if the paper discuss effect of OVER inflated tires on car's suspension or not.

EDIT: Found a copy of full article PDF for those who care to read entire paper. Does not seem to mention anything about the influence of OVER inflation of tires on suspension system.
http://eprints.hud.ac.uk/id/eprint/18552/1/icacinfluence.pdf

 

You need to weigh the consequences. For example, I'd be fine with hearsay and rumour, for the consequences of smoking, not using seat belts, asbestos removal, stuff like that.

Here's what I've got:

1. Toyota spec's a certain pressure. I'm ok with that suspect it's somewhat a compromise, maybe weighted a bit in favour of a cushier ride and suspension longevity.
2. Tires do get firmer, less able to deflect over speed bumps and pot holes, as you raise pressures.
3. My tires invariably hit ten years before they get even close to minimum tread depth.
4. Bearings and suspension components do not come cheap, and they can be royally rusted, hard to deal with.

 

Three thumbs down for that dude.

 

Here is another paper I found by searching on-line, showing relationship between Tire Pressures on Vibrational Transmissibility in Cars. Not surprisingly, they concluded:

Vibrational transmissibility will continue decreasing as pressure is reduced
https://avestia.com/ICMEM2014_Proceedings/papers/145.pdf​

And another paper concluding similarly:

Shock-absorbers efficiency decreases with increasing the inflation pressure in tyres.
http://archiwummotoryzacji.pl/images/AM/vol64/64_KEMZURAITE_27-36_en.pdf​

They are direct opposite conclusion of the paper I cited on #24. So, maybe there is no universal answer to this question of relationship between tire pressure and car suspension function at this time. It all depends on what car and tires and driving conditions, as well as how they are being measured.

 

I use the manufacturers recommendations as the minimum tire pressure. I don't ever remember people saying they run less than the manufacturers recommendation.

 

I only know what I feel.... and hear. And my Prius definitely has a better & smoother ride when I reduced the pressure back to factory specs. No more groans from the suspension. And gas mileage has not been affected. It's win-win.

 

From what I can figure out, in general, there seems to be more of concern about UNDER inflated tires on the road than OVER inflated ones, maybe because of suspected safety issues?

That said, yeah, I run mine always a few pound higher than recommended. I like to make it bit higher so I have a room for loosing some air over time before next tire pressure check.

 

Same here, 2~3 pounds at most over.

 

Well because this was the question as first posed.....

....I really didn't feel I needed a double blind scientific study to defend my opinion.

Besides, in the automotive world, in the realm of maintenance, and often operational minutia, a lot becomes peoples adopted rituals. And IMO most of them are based on perceived personal experience, and perceived personal results.

I've also been in threads centered around this issue enough times to know, that my opinion isn't really going to sway anyone convinced exceeding the recommended PSI is the way to go. They will still do it.

The Michelin Man could show up with blood shot eyes, a 3 day growth of beard and say "Man...don't inflate above the Manufacturers Recommendation"...and those that perceive benefit? Would still do it.

And finally, since my recommendation...or "thoughts on this" pretty much boil down to ....I recommend doing what the manufacturer recommends and what is actually printed and attached to the vehicle, I feel my thoughts and feelings on this, do come from at least a Toyota the Manufacturers- supported truth. It's not JUST my random thoughts and feelings...you could say, it's based on reading the owners manual.

 

I wonder what a Prius feels like, and sounds like, with 50 or 60 psi??? Some guys do that.

 

I run 45psi front and 40 rear. Doesn't feel overly harsh, doesn't skid or squeal. Ran same set up on my GenII.

 

Dude, I'm talking about 50 or 60 psi that some of these guys run.

I like what that guy said.

 

My most recent mileage:

That's with reduced tire pressure back down to factory specs. (Nice smooth ride)
AC on constantly.
Driving briskly in PWR mode.
And Mobil 1 5W-30 synthetic oil.

Hand calculated, it came out to 56 mpg by the time I filled up. I am more than satisfied with those numbers. I don't care if anyone else is getting 65 or 70 miles per gallon. I'm good! No worries, mate!

 

I think your car is broke.

 

17 inch tires on Gen3 and getting averaging 56.25 MPG is excellent. My Gen3 with stock 15 inch tires got ~52 mpg lifetime despite short. I only drove 2.5 years. As you know tire pressure changes with temperature. Both ambient temperature increase and temperature rise caused by friction of driving on them increases the internal pressure. I recently installed external TPMS that shows both tire air temperature and pressure real time while driving. In my experience both ambient temperature changes and frictional temperature increase of 10-20F cause 3-4 psi increase. Of course, frictional temperature increase will depend on how hard you drive and what surface you are driving on.