Tire OVERinflation...it really works!!!
 

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).

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.

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.

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

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.

Loss of traction and tire wear have been discussed here before

https://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.

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

Partial excerpt:

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?

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

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.

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.

But when they blow from a puncture they will really make a big noise much like a high pressure bicycle tire. Probably shread the tire into pieces too! But what the Heck - go out with a big BANG!

Eh, I've had two tires blow out on me after they developed weak spots in the treat that expanded/wore past the rest of the tread, as well as a complete wheel/drum fly off a spindle axle at ~60-70mph. No biggie. ;)

Ha Ha Ha Ha Ha No Biggie!! I Love It!! Badda Booom!

Maybe that would actually be good for the people I occasionally see driving around on totally flat tires. :confused:

Cheaper than a remote pressure monitoring system.

My neighbour drove arond town on a flat for long enough to damage her rim and cause the car to stall - automatic!

Yeah I saw a girl in the real estate office downstairs drive her car until the tire was completely flat which took several days - left rear which she should have noticed - eventually she destroyed the tire one night when she left work. Ahhhh if only they would be more sociable I would have offered to inflate it for her.

Hi krousdb

You said about excessive tyre wear with overinflation - ?and in my experience, I would respectfully disagree, as would the San Jose police department I would expect.?
https://www.officer.com/article/artic...on=19&id=27281

Over-Inflating - Causing rapid wear along the centre of the tread.
https://www.national.co.uk/products-tyres.asp

Overinflated tyres-
# Causes more wear in the centre of the tyre.
# Reduces the tyre's grip.
https://www.smartdriver.co.nz/Articles/Tyres.htm

HIGH TYRE PRESSURES. Over inflation is also highly undesirable with risks from blow out, uneven wear and a harsh ride.
https://www.tanvictyres.co.uk/pages/tyre_info/law.htm

Over inflation reduces the ability of the tyre to absorb road shocks, resulting in a much harsher ride. In fact, excessive over inflation may lead to impact fracture, or other casing failures. Over inflation will also cause excessive wear of the centre of the tyre
https://www.bridgestone.com.au/tyres/...care/facts.asp

Over-inflation
Over-inflation has resulted in the central tread area being forced into contact with the road causing rapid centre and worn shoulders.
https://www.dunloptyres.co.uk/ourTyres/car/tyreCare/

Over-inflation causes tyres to run hard, more vulnerabe to impacts, less grip due to reduced area of contact with the road and faster wear in the center of the tread.
https://www.michelin.com.sg/car/car_cat_tips.jsp#16b

From these sites that all say that overinflation will result in less grip and more centre tread wear.

Ime sure that police article you sited had a good motive behind it but I would rather go with advice from the tyre companies themselves and leave the cops for busing the coke dealers.

you think 40 psi is dandy? wait till you hit 60 psi, just don't hit that pothole! well I hit ones many times at nasty angles and my tires are still going on their originals! And yes these tires have quite a long history...

i can't wait to start a fresh set, and start from really high pressure from the beggining. I'm sure my tires will last WAY longer than what I had these for.

I have had high pressures in my tires for over twenty years. I have never had a blowout, nor have I experienced uneven wear, nor have I experienced any problems with traction. Hopefully we can agree to disagree about these points. YMMV of course. :D

Wow, another point to agree to disagree upon. I would much rather go with the advice of highly trained drivers who routinely take thier cars to the limit.

Hi krousdb

So , are you saying that these multibillion $ tyre manufactures dont know what they are making , or are they just lying , either way ..you got to do something about this scandle before someone gets hurt. :D

PS ,.i hope this overinflation issue isnt about going form 25 to 35psi.
35 is not over inflation , but 60 or more ide consider over inflation.

Hmm,
I don't see a scandal here. I just pointed out an article and conveyed information about my experiences with overinflation.

And after reading through your earlier post, it appears the we actually do agree on the subject. :thumbup:

Yes, I agree with you . So in my case, with a 44psi max sidewall rating, 66psi, we both would agree, would be safe. My tires are below 66 psi. :thumbup:

Well if you go read the articles linked earlier in this thread, you will see that there is conflicting data. You could argue either way I guess. But the last two sets of tires on the Prius were inflated to 60 PSI. Each set of OEM Goodyear Integritys lasted 37k miles, about 5-10k longer than is what is typically reported. Both sets of tires, at the time of dismounting showed perfectly even wear.

I don't know if they are lying or not but, they used to say that you couldn't use a tire on the left side of a car that had been on the right side and vice-versa. This was said about all tires, not just the directional treads. After that myth was disproved you started seeing the recomendation of the diagonal rotation pattern you see now.

I'm not going to get into the argument over whether cops who trust their lives to a solid tire or companies who do nothing but spew crap to make more money have different amounts of validity to their arguments, but I will say that hot georgia should introduce his or herself to the forum so we know all know who he or she is, ;)

Yes, ride quality definately suffers. Over a year ago I did some testing on the Prius marathon course with the Prius. At 35 PSI, 96MPG. At 50 PSI, 97 MPG and at 60 PSI, 98 MPG. Those gains are quite small but may be worth it to some drivers. The ride quality really suffers between 50 and 60 so 50 seems to be a good compromise.

Ive ran my tires at max side wall psi for years. I always get good tire wear and milage. I got 57k miles out of the Rangers OEM AT Wilderness self changing recall tires. I chose to keep mine. :) Then I put a cheapy set of Dougles Wal-Mart tires on it and got over 50k miles again out of them. So i put another set of heap cheap tires on it and doubt I'll ever purchase tires for it again.

Its looking like the OEM tires on the Hondas will make 40k pretty easy then be changed out for LLR tires and again be set at max side wall.

I prefer the ride of my cars to be on the firm side.

Im not a fan of inflation above max side wall psi. I dont like the way cars handel when psi is pushed way up there. Except for when auto -xing on very smooth surfaces. It helps with rolling the bead off the rim if you get hooked up real good. :)

Other wise the rear ends seem to get loose as a goose on me at certin times. Like when on a clover leaf on ramp with bad expansion joints. There comes a point when suspension cant react as fast as a small amount of side wall flex. Resulting in the rear end wanting to kick out on me at every joint.

That reminds me ,,,, I need to check my psi this am. :)

Hi all..

One point that hasnt been touched on much is the handling degradation due to over pressure.(and no , ime talking about over 60psi - not 35)

The tyre manufacturer knows the saftey limits of the carcase (tyre structure) as far as air presure is concerned , and I would guess that this is A LOT higher than what is printed on the sidewall.

I would not be worried about tyre failure from presures in the mid to high 40's at all.
I think its quite safe.

But even at these presures handling and braking probably are compromised.

When racing we use tyre pyometers to measure the temperatures of the tread at different points.
Assuming 0 degree camber and 0 toe setting a tyre that is overpresurised will show higher temps in the centre of the tread.
A racer knowing this will liklely drop the pressure to the area where the tread has equal temperature across the face.
This will be in the zone of maximum grip.(suspension setup and steering angle complicate this , but this is a simple explanation)

If tested with a pyrometer normal road tyres can show overinflation but its less of a problem (structually) for them as they (by comparison to race tyres) are not so fragile.
They are quite duarble but low performing as far as tyres go.

But really , if you notice that in the wet you are more likely to plow through a corner than turn it when using higher presures then really it is already too high.
This is easily tested and doing it in the wet simulate what its behaviour would be in the dry but at a much lower (and safer) speed.

As ive said b4 , ime all for saving gas and money , but when the line of safety gets crossed I dont see any saved value at all.
I think my safety and the saftey of my friends and strangers is more important than the few extra cents in my pocket.

My presures are around the low 40's where I feel that its a good safe compromise.



PS :theres been some good posts so far on this thread - Thanks :)

SVOboy wrote:
Thanks. Here is more than you'll care to know:
https://www.gassavers.org/showthread....6185#post26185

Well f0rks, it's in the wrong forum!

i like to deal with tire pressure the lazy way, set them real high and don't have to check with them for a long long time! I think its been two months since I checked my pressure but before I did I set every tire above 60 psi, so by the time I check them they should be around 40 and that's when its time to pump them up again!