MPG revisited

[Johnny Mullet]

Tire max is not over-inflation. Been this way since April and 6,000 miles ago with no wear issues or noticed handling/braking issues.

[Old3banger]

Maximum tire pressure is not "over-inflation" & the fuel savings garnered will probably pay for your next set of tires. Modern tires can last over 50K & maximum pressure will give the highest safe MPG. Since gas is $4 many vehicles cost nearly as much per tank to fill as a new tire costs! If you want to save money save gas. Running the maximum pressure makes it less likely to suffer low pressure which is unsafe & wastes gas. Running normal pressure means any loss of pressure results in unsafe low pressure which causes tires to overheat & compromises handling.

[Green_Swift]

Sorry, but you're just wrong. Do some research.

Running around on the max pressure is absolutely over inflation. The max pressure is the highest pressure the tire is designed to contain. It is intended for use only when the vehicle is loaded to its load limit. Unless your hauling heavy loads in your Swift/Metro on a daily basis, you are not at max load. So you do not need/should not run max tire pressure. If you are, the tire pressure is too high for the load you have. This is the very definition of over inflation. Consider also that as the tire heats up due to sun exposure and rolling friction, the heat generated will cause an increase in tire pressure by as much as 5-6 PSI. So if you start out at max tire pressure, you are now 5-6 PSI over that once they heat up. That's 5-6 PSI over the PSI what the tire was designed to safely achieve under load. This is absolutely over inflation, and dangerous. Your risk of a blowout with an over inflated tire is greatly increased due to the tires inability to absorb impact.

Run it that way if you want. The gas savings you get from it is not worth a blowout at highway speed in my opinion.

[Johnny Mullet]

I am not going to get into an internet argument about tire inflation or my safety. For God's sake, I am driving a Metro! The words Metro and Safety should never be in the same sentence.

I drive 55MPH maximum on my daily route and even on the hottest day, this little 55 horsepower 3 cylinder sure the hell ain't going to heat my tires up much. I am not one of those crazy dudes who pump 60 PSI into my tires, turn off the engine while coasting, pulse and glide, etc. I just have a great little car which gets better gas mileage than any car available to the American public without spending a fortune and I know how to drive it and tune it to get it's optimum fuel economy.

Did you know that all Metro/Firefly/Swift models have the timing "retarded" from the factory and with a proper ignition timing performed, a 1.0L Suzuki engine will gain 3-4 MPG right off the bat and this will also cause less carbon buildup in the combustion chamber and EGR ports which may or may not be the common cause of the "burnt exhaust valves" issue? Mine is set at 8 degrees advance currently and there is no ping or knock under hard load.

Did you know that lowering the air drag on a vehicle and weight reduction can get you an increase of 2-8 MPH on a car?

Did you know that driving 50-55 MPH in a Metro (or most cars for that matter) gets the best fuel mileage and going over that greatly reduces fuel economy?

Did you know that just doing proper maintenence like oil changes, tune-up, air filter, proper lubricants, checking tire pressures, etc will maintain your fuel savings and the life of the car?

Rolling resistance is another issue. When going out of gear, or coasting, I noticed the car would not gain much speed going down hills or rooling to a stop. I replaced all the wheel bearings, freed up the parking brake mechanism, cleaned and lubed the caliper slides and pad mounts, and used premium lubricants. The car had 130,000+ miles on it when I got it and noticed a slight bearing noise, so replacing them all only made sense. What an improvement that was!

Installing the vacuum gauge was one of my best gains in saving fuel. You can learn a lot from how much vacuum an engine draws through it's drive cycle.

[Old3banger]

I don't want to "get into an internet argument" either, but let me get this straight. Your "research" & belief is that "max pressure" is OK at a vehicle's "load limit"?

Originally Posted by Green_Swift

Sorry, but you're just wrong. Do some research.

Running around on the max pressure is absolutely over inflation. The max pressure is the highest pressure the tire is designed to contain. It is intended for use only when the vehicle is loaded to its load limit.

But "dangerous" & "unsafe" for light or normal loads?

Sorry, but you're just wrong. Please use some common sense.

If its safe at maximum load its got to be safer for light loads, just gives you a harder ride & better MPG.

Modern radial passenger tires often have single ply sidewalls. Don't be fooled by 2 ply ratings. Trying to maintain normal pressure means any leak results in dangerous underinflation. This all to common situation results in excess lateral flex & heat. When you add common sidewall parking abrasion & curb bruising to the mix you have the recipe for sidewalls to blow out. Higher pressure reduces sidewall flex & the heat produced.

The vast majority of cars are driven on underinflated tires, by folks who rarely check pressure, which compromises handling, reduces MPG & saps life out of tires by excess heat build up. Higher pressure reduces "rolling friction" thus reducing the heat. If I were you, I'd worry less about "the tire heats up due to sun exposure" & more about the thin sidewalls.

[Johnny Mullet]

I been working with motor vehicles of all sizes for most of my life. I know tires pretty well. If a tire blown on me for having max pressure, then it's my own damn fault.