As I said in my previous post, the maximum air pressure shown on the tire is 55 psi. I'd feel completely safe going to 45 psi. So far, I can't feel any bad effects in the ride--just a tad stiffer. I'd say it actually rides very well. Incidentally, running the tires on my Grand Caravan at 38psi makes for a better ride than the recommended 30.
What does it say on the sticker inside the driver's door jamb? On my '93 Accord, the recommended pressure specified by Honda on the sticker is 29psi, and my current all season tires specify a maximum pressure of 44psi. I usually put 30-32psi in them. But one time I tried it at about 35psi, and it felt too jittery for my liking. I didn't keep it like that long enough to see how it affected my gas mileage.
yeah, it kind of amazes me that there are so many "but it says 45 on the tire" people out there. do they also drive 120 because that's what is says on their speedo? logic dictates they should. fact is, honda, who know far more about the dynamics of their vehicles than i suspect do /any/ of us. not following their advice is going to have negative results. and /i/ can attest to that from recent experience. i have an 89 civic dx hatch, and have a set of si tires on it. what i didn't know, not /owning/ an si or the owners manual, is that the si tire pressures are lower than the dx's skinnier tires. so, having now applied the correct pressures i am pleased to report that i can happily drive a certain freeway on-ramp much faster than before because i'm not skipping and bumping as much on it's rutted broken hairpin surface! truly, correct pressures are a good thing.
I'm not finding any safety issues per se by inflating to near that which is printed on the side of the tire. The only caution is that overinflation may lead to greater wear down the middle of the tire than on the edges, so tires should be inspected more often. If wear down the middle is detected, reduce the pressure.
This has been quite an issue in the Toyota Prius group in Yahoo. The tires (at least on the first generation) are max inflation of 50 psi but Toyota recommends pressures of 33 psi front and rear. At those pressures the tires show serious underinflation wear. The gurus have pretty much settled on 42 front, 40 rear. The tires still show signs of underinflation wear, but it isn't as bad. Dunno about the Civic hybrid, but the Prius is an unusually heavy car for the tire size, which means it has to have XL (IIRC) load range tires. Those load ratings are only valid at maximum inflation; there is some arcane derating system as the tire pressures decrease. Mike
The Prius uses every trick in the book to increase fuel economy ratings, including many which have nothing to do with hybrid technology. Few people realize that narrow, tall tires give better fuel economy than wide, squat tires. The effect isn't huge, but it is there. John
Tire technology has developed amazingly in recent years. The rolling resistance of today's tires is way less than it was. I don't know, but I suspect Honda has done enough homework to have tires with low rolling resistance as OEM on its cars. I think it's more than the larger contact patch that affects mileage when tires are under-inflated--a low tire has MUCH more rolling resistance than a correctly or reasonably over inflated tire. At 40-45 psi, the LAST thing I'd worry about is heat buildup: most of the heat buildup arises from internal resistance in the tire. IIRC, that's called hysteresis loss
Oddly, the OEM Low Rolling Resistance tires operated at the recommended pressure give almost 5% poorer fuel economy than more standard tires at proper inflation. The most popular aftermarket tires for the current generation Prius are the Michelin Hydroedge, with maximum rated inflation (I forget the numbers) in the front and 2 psi less in the rear. The "bleeding edge" in fuel economy is a marketing issue, not a design issue. The Prius was originally designed to be a 21st century car from the ground up, and the revolutionary passenger capsule and suspension designs were the first considerations. The original design outline (in November 1993) only called for 50% better fuel economy than the equivalent Corolla and there was no thought to use a hybrid power train. It was only when the fuel economy spec was increased another 50% a year later that the team turned to what was then very experimental hybrid technology. See http://www.vfaq.net/docs/Prius_that_shook_world.pdf (note: more than 1 MB file size). Mike
You don't make any sense here. The proper inflation for ANY tire is what's recommended by the manufacturer. There is no different inflation value for a replacement tire than there is for the tires that came on the car. You must be thinking that the "max inflation pressure" listed on the side of the tire is some kind of "proper" inflation amount. It's not.
No - the proper inflation is both application dependent and tire dependent. The load rating on the tire is only applicable at the maximum rated pressure, regardless of the vehicle. Car manufacturers state an inflation with the OEM tires that produces the ride they want with adequate inflation for safety with the tires they provide, but the tire manufacturers are not bound to the car manufacturer's recommendations when they offer a tire for that car. The good news is that people usually want wider tires, which increase the margin of safety between the car manufacturer's recommendations and the minimum inflation. My partner worked at a Discount Tire when he was young and absolutely rails about the folly of putting tire pressures in the owner's manual. Tire retailers have charts that tell them the proper pressure for the tire in a given operating load range, and he got no end of grief from people who said that didn't match the owner's manual... as though the manual had any foreknowledge of the tires that were to be used. The real test of inflation (as long as it is at least the required inflation for the load and no more than the max inflation) is tread wear. I don't bother with the tape test for inflation wear because I'm lazy that way - I choose an inflation and wait until they wear out, then look at the wear pattern. I've never seen a tire show overinflation wear. Mike
Ah. Now that I can consider the source, that your ramblings are insane at least makes sense. Discount Tire. Yep.
And your source is better?[/QUOTE] Than some guy who worked at Discount Tire? It's not hard to get better than that.
Than some guy who worked at Discount Tire? It's not hard to get better than that. [/QUOTE] You are certainly free to do what you want. The numbers in the owner's manual are not going to be dangerously far off for any tire that is suited to the car, so go for it. But I'm sure you understand that I will take the advice of the tire chain that has given me first class service for decades over your advice, your prejudices notwithstanding. And the "some guy" has proven his overall competence to me many times over the years while you are a variable source of opinion, so we are separating on this one. Mike
Very droll. As I say, no accounting for your prejudices... and still you offer no support for them. You are diminishing yourself in my eyes. Mike
Very droll. As I say, no accounting for your prejudices... and still you offer no support for them.[/QUOTE] I don't have to. I know the facts. And one fact I know is, you take your advice from some guy who used to work at Discount Tire--and you claim it to be the gospel.
As I pointed out, that "some guy" is my partner of 5 years. I have had good advice and stellar support from various stores in the Discount Tire chain for more than 20 years. In that time, I have seen or heard no complaints I can recall regarding Discount Tire. I have had exactly one in all these years: the mechanic failed to tighten the lug nuts on a wheel after a repair. And I never presented it as gospel, just as the most reliable info I had available. I don't know what you have against Discount Tire, and you still don't say - only that you "have the facts" you don't see fit to share. You don't know my partner but you assume he is less competent than you, particularly in the field of tires, a premise I find laughable. So who would you have me go with - somebody who has earned my trust or some random anonymous guy who offers no support for his ravings? Maybe I should listen to Alex, the "Toyota kills" guy, because he has less going for him than you do. Mike
Traded in an '04 Civic that pretty much ran 10% under the EPA mileages over the 1.5 year period for an '05 Accord Hybrid w/Navi. Mulitple tank average of the Civic's mixed local and up to 900 mile round trips was always over 40. The Accord's multiple tank averages are running 31 ish. Wife could not abide the highway 'feel' of the Civic (light-weight wandering in the lane) nor the 'slipping clutch' characteristic of the CVT. I must admit, I LOVE the power of the Accord V6. Has more get up and get than the non-hybrid V6 and even my old 72 Comet GT with the 302 V8 was a wimp (stock) compared to the Hybrid. Love the 'better' gas mileage. However, it is truly only an 'ego' or 'status' purchase with no monetary advantage over a standard vehicle. The premium is too high to recover unless gas prices get over $20/gal an as for being "green" the battery disposal is not. But... you have to breath air, you can bury batteries.
