Tire OVERinflation...it really works!!!

[Brian D.]

Wow, unfortunately I can't yet post actual numbers, but I have to say that I am extremely impressed with the results from taking my tire pressure from the standard 32psi to 40psi. WOW!! Well, that and the fact that I swapped out my bad rear shocks & noisy, feathered rear tire. It looks like I'm well into the 50MPG neighborhood...where this car is supposed to be. ('89 CRX HF). Thanks for the tip. Now how much more can I inflate these tires before I need to start worrying? And are there any other tricks of the trade that are as generously MPG-yielding as this? (excluding the engine kill at lights...that doesn't interest me).

[onegammyleg]

Hi Brian

A very experienced tyre man should be able to tell you.

The maximum presure would be a combination of what the tyre is , quality of construction wise and also the seating properties of the rim.
Some rims will allow the trye to blow off at a lower presure and some higher., they and tyres are not the same.
I would guess that 50% over maximum would still be safe but bear in mind that when using excessive presures you will lose grip as the tyre starts to ride in the centre rather than across the whole width of the tread face.

You will probably find far greater wear of the tyres in the middle of the tread, which will also cost you with more tread wear.

Also note that any accident involving your car with overinflated tyres on (even if it wasnt your fault) will probably be blamed on that - and you.

[GasSavers_Ryland]

what have you done to your car already?
a compleat tune up, with things like new spark plugs (ngk v power seem to work the best) new air filter (K&N don't seem to help, and they let dirt in) oil change to synthetic in both engine and tranny (calls for regulare motor oil, altho honda MTF works, so does synthetic MTF) clean your fuel injectors, you can pull them out and with a toothbrush scrub the tips with a little bit of solvent like carb cleaner, or sea foam, check the timeing with a timing light, jack up each wheel, and check for free spining, and exsessive play in stearing and suspention linkage.

beyond that, you can do things like a grill block (search this site, or check out what svoboy did) belly pan, buy or make smooth hub caps or better yet, get some honda insight wheels.

[light-foot]

With my chevy cobalt I noticed an increase from my normal 25 mpg city to 29-30 city mpg after inflating my tires from standard 30psi to about 37psi. I also set it neutral going to a stop and i won't go anything over the speed limit by a couple mph

[Brian D.]

Well, that's one thing that I made sure to keep constant; my highway cruising speed. Unfortunately with my gearing in 5th I'm still at ~2500RPM when I'm doing just 60MPH or so. That's very unfortunate. I'd really like a gearset / Tire-wheel size combination that will bring me into the neighborhood of 65MPH @ 1900RPM. I just wonder if my little 60HP 8-valve engine will adhere to those demands.

[krousdb]

Originally Posted by onegammyleg

Hi Brian

A very experienced tyre man should be able to tell you.

The maximum presure would be a combination of what the tyre is , quality of construction wise and also the seating properties of the rim.
Some rims will allow the trye to blow off at a lower presure and some higher., they and tyres are not the same.
I would guess that 50% over maximum would still be safe but bear in mind that when using excessive presures you will lose grip as the tyre starts to ride in the centre rather than across the whole width of the tread face.

You will probably find far greater wear of the tyres in the middle of the tread, which will also cost you with more tread wear.

Also note that any accident involving your car with overinflated tyres on (even if it wasnt your fault) will probably be blamed on that - and you.

Loss of traction and tire wear have been discussed here before

http://www.gassavers.org/showthread....light=san+jose

and in my experience, I would respectfully disagree, as would the San Jose police department I would expect.

http://www.officer.com/article/artic...on=19&id=27281

Partial excerpt:

Myths about pressure

Let?s put to rest some common misconceptions. The tires will not balloon out creating a peak in the center portion of the tread when tire pressure is above 35 psi. There is a steel belt that prevents this from happening. Also, you are not overstressing the tire with higher pressure, and the tire will not be forced off the rim with higher pressure. The picture above is Bobby Ore of Bobby Ore Motorsports driving a Ford Ranger on two wheels. The tires on the left side have 100 psi in them, and they happen to be tires and rims from a 1999 Crown Victoria! This is a dramatic example of how pressure holds the tire in shape, and how much stress a tire can handle.

Performance

If you were able to watch a tire as it travels across the ground at high speed, you would see that it deflects to one side during cornering. The faster you are going through a corner, the more tire deflection you get. As the tire deflects over onto the sidewall, you get less traction and more of a tendency to understeer or oversteer. This could spell disaster when negotiating a corner at high speed during a pursuit or a Code 3 run. Higher pressure keeps the tire from deflecting onto the sidewall as much, which keeps more of the treaded portion on the road.

A good demonstration for EVOC instructors is to have students drive a high-speed course in a vehicle with 32 to 35 psi. Then have them run the same course with 44 to 50 psi in the tires. The student will experience a marked difference in performance. Having officers experience this difference in vehicle performance is much more effective than just telling them to check their tire pressure.

[Sludgy]

My normal tire pressure is 85 psig. But the tires are load range E. Do you suppose that I could go to 100 psig safely?

[Hot Georgia]

Tire recommendation from Honda is 32PSI.
I've heard car MFG's like the softer tires for selling a smoother riding car and is primarily why the 32PSI figure.
I have Dunlops with sidewall cold max rating of 51PSI. I've ran them 50-55PSI since new.
Back when they were new I did a skid test on a Sunday night on a vacant mall parking lot in an extremely heavy down pour with lots of standing water and measured my skid by landmark going 50MPH and full braking. 5 Runs produced about the same result.

I dropped my pressure to 32LBS and did 5 exact runs again and could not tell any difference at all.
My Civic tires have been rotated every 15,000 miles and at 76,000 miles is ready for replacement. Tire wear is uniform across the tread according to the wear bars.

We've ran tires the same way on my old Dodge Spirit, Two Grand Caravans and not seen odd tire wear except the 1st set on the Spirit which ran 40,000 miles with no rotation. (Neglected maintenance)

If I don't tell the dealer to keep max sidewall they'll underinflate to 32PSI. After being used to rock-hard tires it feels like sloshing through deep mud and if allowed to continue drops my MPG by a few.
-Steve

[diamondlarry]

I would have to agree with Hot Georgia and krousdb. I have ran 60 psi in my tires(44 psi max on tire) for a year or more and have not seen the middle of the tread wear more than the rest of the tread. I don't think you would see this type of wear on a steel belted radial tire. The sidewalls will flex less but the belts keep the tread basically flat. I have heard that tires have been tested at well over 200 psi with out bursting. For insurance purposes the manufacturers and exact pressures won't be revealed. At that pressure though it would be like riding on steel wheels. I also think that somewhere around 60-70 psi the rate of mpg increase starts to dwindle.

[omgwtfbyobbq]

I think the cold pressure rating is a function of what's considered to be always safe at the tire's maximum rated speed during a really hot day on a rough road, plus some safety cushion. Since most of us won't drive on rough roads in 120 degree weather at 80mph, doubling the pressure at lower speeds should be safe.