Wayne Gerdes, founder of hypermiling, started with a Honda Accord

High tire pressures resulting in better handling / braking seems counterintuitive. Tires are the first part of your suspension and allowing them to deflect around corners and during braking is what I presume the engineers accounted for when designing the car to handle safely.

I'm not sure why Wayne would put that down. The only benefit to high tire pressures is better rolling resistance and turn response. Otherwise higher tire pressures = less grip = less performance.

I personally do not like to put too much air in my tires. But to be very specific, the current tires on my car now has maximum psi on the sidewall as 51psi. So, I am sure that means the manufacturer is saying if that tire is filled up to 51psi "cold",it is ok to drive with it.

And remember when we drive the tire heats up and that 51 can quickly get to 55 or more. I am sure the tire manufacturer is aware of that.

It's not so much the blowout pressure; the problem lies in significantly reduced performance and a large NVH increase. All that extra NVH in overinflated tires is transferred directly to the suspension components. Any small imperfection that was soaked up by the tires at door sticker PSI is now significantly increased and transferred directly to the suspension as well as tramlining and bump steer are now more noticeable.
 
Wayne Gerdes' advice on psi for serious hypermiling; "MAX sidewall is what I would recommend for most as it is well within the safety limits of your car and tire and allows better Fuel Economy than the pressure listed in the driver’s side door."
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I don't know what you guys think about this.

I think its pretty ignorant. Max sidewall pressure is the acceptable maximum pressure for that tire for its load rating, but not necessarily what is acceptable or safe for *any specific vehicle*. Those specific limits are in that cars owner's manual or the door jamb placard, and those numbers aren't just there for occupant comfort, the way some of these hypermile people act like on the forums when you run into them. That particular tire may fit a multitude of very different cars that may have significantly different weights. A tire that fits a 3800 lb car may work fine at 40psi, but that same tire at 40psi on a 2900 lb car would be grossly overinflated. Not a problem for that tire, its a problem for that CAR and how its going handle during braking and around curves with rock hard tires with a greatly reduced contact patch.

Grossly overinflating a tire can dramatically reduce the amount of footprint the tire has, which can create very unsafe braking and handling. Great gas mileage sure, but at what cost to safety. Overinflating a tire is defined by the vehicle manufacturer, NOT the tire maker's maximum sidewall pressure.

Do what you want, but you go sliding through a wet intersection in your Prius with your tires pumped up to 58psi and T-bone mom and pop killing them both, in this day and age don't go around thinking your grossly overinflated tires wont be used against you.....
 
It doesn't have to be slower over the whole journey. You can coast towards a stop light and get green before you are there vs maintaining speed, braking and sitting there stopped for 30 seconds. In both cases you cross the intersection at the same time.
If there is traffic, that does often slow down the traffic. The coasting, makes the vehicle behind, cover less ground, and the vehicle behind that one, and so on, with many of them losing speed by applying brakes because they didn't expect to be coasting so long. The result in denser-city traffic is then that more vehicles don't make it past the prior stop light too, further backing up traffic.
 
I changed my oil this morning with 0W16 and a Fram TG 7317. I then went and got my tires balanced and rotated at Discount Tire and psi set to 45psi.

Oil change, Balance and Rotate tires and psi set to 45psi! Time to experiment more hypermiling...

Let me try a bit of hypermiling and see how that goes. I normally hypermile in city driving with 40psi (instead of oem 33psi), but this is my first time asking them to put 45psi in my tires. Let me try this for a month and see what I think.

I left Discount Tires to Costco to fill up my gas tank. I then went ahead drove around this morning running some errands. No freeway driving. All city driving with top posted speed limit of 50mph. This is my mpg so far.
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Overinflation depends on the max load rating of the tire vs the load per axle of the vehicle. The higher the load rating of the tire vs the axle weight, the lower the point where a tire becomes overinflated.

I usually like to run about 10% higher than the door jamb sticker for stock size tires (closer to door jam for larger than stock tires), but never higher than the tire sidewall max PSI spec.

With modern vehicles, manufacturers are trying to eek out a little higher fuel economy and will spec closer to a good compromise (leaning towards fuel economy), but older vehicles sometimes even had too low a door jamb spec. For example '90s Ford Explorer with 26PSI, was way too low for a vehicle with a ~5000lb tow and (~ 800? lb) cargo rating. Those tow and cargo rating #'s may be off a bit but still, not off enough that 26PSI is going to cut it.
 
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If there is traffic, that does often slow down the traffic. The coasting, makes the vehicle behind, cover less ground, and the vehicle behind that one, and so on, with many of them losing speed by applying brakes because they didn't expect to be coasting so long. The result in denser-city traffic is then that more vehicles don't make it past the prior stop light too, further backing up traffic.

Only if the coasting car can avoid the red light completely, which isn't a given. AND it starts from a speed greater than 0 if the light does turn green again in time.
 
It doesn't have to be slower over the whole journey. You can coast towards a stop light and get green before you are there vs maintaining speed, braking and sitting there stopped for 30 seconds. In both cases you cross the intersection at the same time.
Leave enough gap someone will jump in and make you have to hit brakes anyway.

Unrelated to the above post: Honda Fits have really thin, narrow tires.
 
If there is traffic, that does often slow down the traffic. The coasting, makes the vehicle behind, cover less ground, and the vehicle behind that one, and so on, with many of them losing speed by applying brakes because they didn't expect to be coasting so long. The result in denser-city traffic is then that more vehicles don't make it past the prior stop light too, further backing up traffic.
For the geometric efficiency (i.e. how many cars can you squeeze on the street before the traffic light) to matter, you'd be very close to gridlock.

In anything other than inner-city rush-hour traffic, coasting to a red light and reaching it the moment it turns green actually increases car throughput. The reason is that once you pile up a lot of cars at a red light, individual reaction times add up... 5 cars and with distracted drivers and start-stop functions of modern cars, and the last guy won't be able to start moving until the green light is already lit for 10 to 20 seconds. If 5 cars had been coasting to the light and reached it at just the right time, the last car would already be over on the other side of the intersection.

What is indeed inexcusable is not getting into gear fast enough and then accelerating at a snails pace and drving slow enough that you yourself manage to reach the next traffic light at the very last instance that it shows green, but everybody after you has to stop. Mostly oder people or females guilty of this.
Hypermiling requires attention to traffic and forethought. If you cannot understand driving as a system composed of many different components such as cars, bikes, pedestrians all miving on specific vectors at specific speeds, then you have no business bragging about your accidentally low fuel consumption. Then you should not be driving at all.
 
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Anything over what the door jamb says.
Some of the door jamb pressures are quite low and left not enough margin for error for a slight under inflation(Ford Explorer...). I would always take the door jamb as the minimum safe pressure, and sidewall max as the maximum safe pressure. The manufacturer as many conflicting factors to picking a door jamb pressure, and they don't tell you which factors they chose. The ideal pressure for grip is different for every model of tire anyways and a sidewall max inflated UHP is still better on pavement than almost any all season...
Car performance and tires in general fall within a broad performance range of "good enough", so a Prius with 44 psi is allowed as is a truck with barely legal mud tires that have no wet grip at all... Either driver can exceed their vehicles limits and cause an accident.
Just like anyone in the rust belt cruising around on all-seasons in the snow. Clearly snows are safer but all-seasons are legal and not a basis to be sued alone.
 
Hrm. I remember reading a Popular Mechanics article, bemoaning about how pulse and glide was hard to do, as it was "illegal" to coast in neutral. Brakes were just that good, what was the problem? It was a good way to get every last mile per gallon.

The problem was, it was written by Thom McCahill, back in the mid 50's, you know, back with non-power assist 9" drum brakes and all.

I live in a semi-rural area so coasting to most stops is pretty easy; my vehicles tend to sit at EPA highway mpg, in all but the dead of winter. But there is something to be said for going with the traffic. What was it that George Carlin had to say about it?

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Imagine how much gas this Wayne gerdes fellow would save, if he stayed home, instead of doing all these drives, trying to get good mpg.

As a truck driver, I sometimes see people following me extremely close. Even as I crawl up hills slowly, they don't pass. Can only assume that they are drafting me, to get better fuel economy. But its a dangerous game they play, and also impossible for me to see them in my mirrors.
Why not instead buy a small motorcycle, and really use less gas.
 
For the first time in my driving history of roughly 37 years I have started running the tires in one of my vehicles above factory spec. But not for hypermiling, the Falken tires we installed on the Outlander about a year ago just feel way more squishy on turn in than the OEM Toyo at the door jamb recommended PSI of 35. If I put them up to 40psi, it feels much more like the original tires, confident turn in going into corners. So I've kept them this way for the last 8 or 9 months. I don't notice any detrimental effect.
 
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