Re: Tire inflation and gas mileage
 

Look, there a lot of guys running Civics in the street classes at SCCA autocross events. That's probably a better starting place to judge what would give optimal grip on your HCH than a police article on Crown Vics, no? As you've pointed out, you're not running the same size tire nor is the car the same size.

What you run your tires at is your choice and I'm not going to tell you to lower the pressure, but you have to concede you've made a sacrifice.

Re: Tire inflation and gas mileage
 

Not many of us will concede to that. This issue has been beaten to death over and over again... for years already. :embarass:

It would be a net sacrifice if the negatives outweighed the positives. Let's see:

Undeniable positives of running higher tire pressures:
- awesome fuel economy potential due to lowest road resistance.
- tires wear better and last longer
- improved handling
- greater safety under many adverse situations - hydroplaning , etc.
- lower tire temperatures. A cooler tire is a safer tire.

Possible negative(s):
- harsher ride.


Cheers;

MSantos

Re: Tire inflation and gas mileage
 

40 psi isn't over-inflation. It's well within the safety margin of the tires.

Talk to a real pro at a tire store. He'll never tell you to inflate more than the manufacturer's spec because he doesn't want to be responsible for moving you out of spec. But tell him you're inflating to forty and you'll see him nod in approval. The only reason cars in America are spec'ed at 32 psi is because the manufacturers think we're all soft in the tush. 32 psi is about low as you can go without starting to squish the tires.

Improving the MPG by 10% means that the gas savings will pay for my replacement tires as long as I own the car. And as a byproduct it means I'm driving a greener car. Any HCH owner should appreciate that.

Re: Tire inflation and gas mileage
 

- At high speed, tires run hotter, increasing the tire pressure and the chance of damage
- Easier to damage by potholes or debris
- Can't isolate road irregularities. Uncomfortable ride and more noise
- Could be found at fault in an insurance claim on the grounds of operating the vehicle outside of manufacturer's recommendations


Questions: Why do you always remind everyone of the cyclic nature of the forum? Why not put your energy instead towards getting topics merged? Have you tried navigating all the search results of redundant topics?

Re: Tire inflation and gas mileage
 

Keep in mind that the Dunlops, at least, are rated for 45 psi(?) max cold. 50 is still high, obviously, but the 32 that is recommended is too soft and the tires handle poorly. On the flip side, I noticed a marked decrease in traction this winter with my tires at 40-42 psi.

Re: Tire inflation and gas mileage
 

32 is definitely below ideal high-speed performance or fuel economy psi for normal temperatures.

Getting tires up to operating temperature in cold weather is tricky business. If you don't drop a few psi, you'll find you never get quite the right amount of friction or keying.

Re: Tire inflation and gas mileage
 

Good points spinner.

But since you brought it up and to be more specific: all tires will run hotter at higher legal speeds. However, the ones that sport lower inflation values will consistently run hotter due to the added friction.
So even if speed is factored in, the probability of tire failure due to heat build-up remains statistically higher with lower tire pressures. That is why I simply love direct TPMS systems since that seems to be what's need to reduce many of the tire failures that occur in our highways.

Yes and yes. A "harsher ride" will implicitly mean that the road imperfections will be transmitted to the suspension components and those in turn will work harder and less effectively in reducing road noise and comfort. If one drives on many cobble-stone roads or roads loaded with pot-holes then running the tires at Max Pressure is not going to be nice at all. That is why we often recommend people raise the pressures gradually until they find a good balance of FE and comfort that is suitable to them.

The "insurability" and liability aspect is a good one, but that too is not a universal concern for everyone. As an example, my provincially managed insurance policy does not regard higher tire inflations as being a meaningful determinant for failure. Notice my use of the word "higher". However it does refer to under inflated tires as a significant attribute impacting safety and even liability.
While there are definitely limits as to how "high" is too high, the best approach for most folks is not to exceed the max pressure rating for the tire. Calling your insurance company and asking does not hurt either.

The good thing about these forums is that we all have the opportunity to discuss, debate and share knowledge that while useful to some may not necessarily apply to everybody. If you notice, my previous post was not qualified by "all-inclusiveness" either.


Cheers;

MSantos

Re: Tire inflation and gas mileage
 

Because people are lazy and would just start a new thread anyways.

Re: Tire inflation and gas mileage
 

Suspecting that my tires came back from the dealership with low pressure, plus thinking tire pressure might be accounting for a little rear wiggle, I have been pumping it up a bit. My 12V portable says 40psi. Tires feel a little more wooden but still plenty comfortable.

Re: Tire inflation and gas mileage
 

More sidewall flex at lower psi will cause higher pressure changes due to the heat generated (and the fatigue generated.)

I would rather hit a pothole at 50 psi than at 30. The lower pressure will probably cause more damage to the tire, and is much, much more likely to damage the wheel itself.