Poor Fuel mileage - typical?

I would say these tires definitely contribute to your lower than expected MPG. A quick search on Amazon.com (this brand did not show up on TireRack.com) shows this is a run-flat tire and not low-rolling resistance. Run-flats have beefier sidewalls than standard tires, and thus are also heavier than standard.

 

What about her mention of a lot of "3 minute" trips? That's gotta be a killer.

 

apparently, you can't cite a source for your 'knowledge'.

 

I missed that but I saw "less than one mile to work". Definitely a mileage killer!

 

This is what I tell people.
That MAX PSI on the tire, is the max PSI of which the tire manufacturer says the tire can be inflated.
It's the tire manufacturer MAX recommendation for the tire. The tire manufacturer has no way of knowing what vehicle the tire is going to be going on, it's a generalized MAX warning. It is NOT.....

..not the recommendation of the vehicle manufacturer. The vehicle manufacturer which is familiar with the design, suspension, braking system of the vehicle.
IMO, I thought the best PSI was to simply follow the vehicle manufacturers (Toyota's) recommendation which should be on a sticker in you drivers side door jam.

I would highly recommend lowering that PSI. Others will know and remember, but I always went with the PSI as stated on the door jam sticker.
But IMO 50 PSI is way too high. To the point of being potentially dangerous.

 

I always figure a "few" pounds more is good, because:

1. The manufacturers tend to favour ride comfort, and likely want to baby suspension components as much as possible, at the possible expense of a few mpg.
2. Slightly higher pressure gives a bit of a buffer.

Operative word being "few". For third gen Prius with 15", they say 35/33 psi (front/rear) do they not? With our 15 X-Ice in winter I use 38 all around. Then for our 17" stock all-seasons, where Toyota says 33/32 (f/r) I use 36 all around.

I don't go higher, for a couple of reasons:

1. The aforementioned possible detriment to suspension components, as you raise pressures.
2. MPG improvements seem to diminish as you continue raise pressure, I suspect they're overrated.

Plus I don't much the filling-loosening ride, at extremes. Especially with the 17's.

 

This hasn't always been true. When Ford Explorers were rolling over from defective Firestone tires blowing out, killing many people, one of the numerous contributing factors was that Ford door jamb sticker having a too-low recommendation.

My 1986 Honda Accord also had a too-low recommendation, exacerbating tread wear and propensity to hydroplane. The later is a significant hazard in my climate.

 

My experience inflating to 42 / 40 during during the summer, all tires psi expands 4 to 5 lbs more after 10 min of driving therefore that's another reason to not push it a bit over or even on the dot.

 

I have always understood the sidewall max label to be a cold rating, with allowance for that driving warmup built in.

 

I would say, those are dangerous exceptions to the rule.
Manufacturers don't want lawsuits, they don't want injuries and deaths associated with their vehicles. They designed the vehicle, and have reason to offer a PSI recommendation that is both safe and efficient.

The tragic Firestone/Ford situation had Ford blaming Firestone for poor manufacturing-tread separation, and Firestone blaming Ford for a low PSI recommendation.
In any case, I would site that very specific situation as a dangerous exception to the rule, not as a example of a reason to NOT follow manufacturers recommendations.

Having spent a lot of time at Prius Chat, I know that many owners agree with that approach.
And I also know like oil change intervals, and gasoline octane recommendations, once someone has an embraced approach or ritual, I'm not going to be able to change your mind.

My personal opinion, and my personal experience, is it's just best to keep inflated to recommended PSI.
I just didn't return an appreciable benefit from being a "few pounds over".

I also felt that if I inflated to recommended PSI on a cold morning before the vehicle had been driven, once the vehicle had been driven and warmed up, I probably WAS driving a few PSI above recommendation through the natural physics of warm air expanding.

So...for me, even today with my Honda Fit...recommended PSI is what I recommend.

 

I tend to treat the manufacturer's recommendation as an absolute minimum. Since many people do not stay on top of monitoring tire pressures (me included) and they tend to drop over time, it is common to let them get well below the door jam recommended. Therefore, I typically try to fill to the middle point between the door jam number and sidewall number.

Another point about the sidewall max pressure: if you look closely at the words associated with it, it says the max load is tied to the max pressure. So, if you are carrying increased loads in your car, you should also increase the tire pressures accordingly, up to the max sidewall number, if needed.

What causes under-inflated tires to fail is heat build-up in the sidewalls due to excessive flexing. So, if you are carrying more load, this also increases the sidewall flexing. Thus extra tire pressure at higher loads keeps the sidewalls stiffer.

 

Again as I posted above, I realize those that embrace the few pounds more, or more PSI is better philosophy aren't going to be swayed.

But the manufacturers recommendation is not an absolute minimum....it's the recommendation.

Sometimes I muse at the justifications and reasons people create to NOT simply inflate to the recommendation.

I tend to think whatever recommendation Toyota offered, you would always have people that for whatever reason, believe they know best, and would avoid the target.

If the recommendation was 33 PSI...they'ed be inflating to 36 PSI...if it was 36 PSI...they'ed be inflating to 39 PSI....

The temptation to believe they've discovered a better "sweet spot" is just too alluring.

So I'm not really going to waste too much more time arguing it.
For purposes of this thread and to the OP...I'm going to clearly say 50 PSI...is IMO way too much.

 

I saw it as a pattern, not an exception.

They also want to offer a comfortable ride. Tire PSI choice is a compromise between multiple conflicting goals, and I have come to feel that the door jamb labels have been too overweighted in the comfort direction for my tastes, underweighting other factors I value.

Firestone 'forgot' to include one of the components called out in the design specifications for that tire model.

Ford specified a too-small tire, recommended a too-low PSI, and did not correctly tune the suspension for the tire-vehicle combination.

Then drivers let the pressures fall even lower, overloaded their vehicles beyond the rated load capacity, and went speeding well over posted speed limits in very hot climates.

Add all these together, and Boom!

There are two manufacturers involved here, not just one. I take one label as a minimum, the other as a maximum.

Also, one of my past tire set sidewall labels was quite clear that the sidewall pressure number was also the minimum pressure required to use the tire's rated load capacity. I.e. lower pressures demanded lighter loads. Combine this with the common multi-pressure labels on the European rental cars we have used -- the heavier the load in the car, the higher the recommended pressure -- and I can no longer adhere to the PSI scheme viewpoint you describe here.

 

Like I said, I've hung around Prius Chat and other automotive forums enough to know that on some topics debate is useless.
But citing European Rentals, Changing Load Capacity...
All falls under IMO making justification for simply NOT following the manufacturers recommendation.

What PSI do you run on a daily basis?

Again, yes we all know the Firestone/Ford Explorer tragedies were a failure. But not typical. My opinion on the whole matter is that BOTH entities probably failed. That is the tires had abnormal-sub-standard tread separation, and perhaps Ford was wrong about their recommendation for PSI or tire size. Both parties to this day, blame the other. But as far as using the case to justify the idea that manufacturers recommendations are wrong? I think false. In 99.9% of cases, that recommendation in the door jam provided by the manufacturer is going to be the PSI you should use, for daily driving. And your tires will not have tread separation, or explode.

I think there is far more potential for danger or creating risk, when one takes it upon themselves to self diagnose what they think is the best PSI for their vehicle. Especially when they cater that decision based on what the TIRE manufacturer presents as a MAX pressure-for the tire and not what the vehicle designers recommend for daily usage for the vehicle.

I think this thread is a example of that truth. The OP...read the tire sidewall, and pumped their tires up to 50 PSI because the tire said the Max was 51 PSI.
IMO way too high...and not good for either the suspension of The Prius or the safety in most driving situations.

If the OP had read that label within the door jam, and followed that recommendation, they would be much safer on the road IMO.

 

Did we ever figure out if worth while mpg gains were achieved at 50psi? Nothing I'd do. Lol

Posted via the PriusChat mobile app.

 

I wonder if Fred Flintstone’s tires are still available.

 

I thought we covered that already.
Did you miss a few posts ??

 

I was caught up in the safety talk. Don't think I saw any numbers. Lol

Posted via the PriusChat mobile app.