Before you over inflate watch this.

Discussion in 'Fuel Economy' started by ALS, Jul 2, 2008.

  1. ALS

    ALS Super Moderator Staff Member

    ABC News report on old tires being sold as new. :eek:

    abcnews
     
  2. Damionk

    Damionk DWL Lover

    I just called my girlfriend and had her look and the only ones she can see are the ones on front and if shes reading the right number they were made in '91:eek::(
     
  3. the_ghost

    the_ghost Active Member

    you folks shouldn't be overinflating anyways, it's outright dangerous and bad for tire wear. The money you save is offset by the $250-400 you will be spending to replace your tires when the tread is gone in the middle but still there on the outside (called cupping)... stick to maximum recommended PSI.

    Best,
    Ghost
     
  4. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Errr... NO. Tires will last LONGER, not shorter.

    Try Wayne's accord with 100,000+ miles on the original tires and completely even treadwear.

    This is what happens when you use Toyota's recommended pressure for the Prius. I've seen similar results on my Civic at Honda's specified pressure.
    [​IMG]

    The pressure you should use is the sidewall rating: 44 psi in most cases. If you want to go higher, you can, but we don't officially recommend it.
     
  5. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

  6. the_ghost

    the_ghost Active Member

    I am referring to overinflating PAST sidewall maximum pressure... which IS dangerous AND causes excessive treadwear (i.e. cupping)
     
  7. kwj

    kwj I hypermiled this

    Hi Ghost. First, what do you mean by "overinflation"? We need to see what your definition is, as that has been a good topic lately.

    Second, how many tires have you worn out by overinflation versus underinflation? My tires have always had to be replaced because they were worn on the outside and/or inside edge of the tread. Way back when bias ply tires were popular, you could wear out the centers with too much pressure, but it is my understanding and experience that this is not a problem with modern radial ply tires.

    My current philosopy on our family cars, is to go to max sidewall pressures. On my commuter, I have gone over that for the last 15,000 miles. I don't have any wear on the sides of the teads, and they appear to be wearing evenly across the treads. This is what I expected after reading the article with the San Jose Police Pursuit trainer. An underinflated Radial tends to roll on its edges in cornering, whereas a tire inflated to the max sidewall tends to keep all the tread on the road. Better traction, better wear.

    Go to: http://www.officer.com/article/article.jsp?siteSection=19&id=27281 to read more about this. It's a very interesting counterpoint to what we backyard mechanics have always been told.
     
  8. the_ghost

    the_ghost Active Member

    My definition of overinflation is 60PSI (COLD) when sidewall maximum pressure is rated at 44 PSI.

    Anything BEYOND SIDEWALL MAXIMUM pressure is dangerous in my opinion.

    While this will help economy, it will throw off your overall milage slightly because it is doing the exact same thing as putting in a lower final drive gear, so instead of say a 3.27:1 final drive, you are dealing with what is equivalent to a 3.25 final drive ratio at the expense of a reduced tire contact patch and thus more wear because one specific part of the tire is doing all of the road-gripping work.

    I have seen a number of tires come in that way from a few years ago when I worked at a Goodyear retailer, and I would check out what was wrong with the tires that were being thrown out (so I could salvage tires in my size for things like autocross, drifting and burnout contests).

    There weren't many but when overinflated tires do wear more on the center of the tire and tend to cup-- haven't you ever read any of the stuff posted around the tire store or on tirerack?

    I got the information not only from experience but from industry information as well.

    Best,
    Ghost
     
    Last edited: Jul 2, 2008
  9. Ophbalance

    Ophbalance Administrator Staff Member

    It's there, however, it can also be hard to trust the source in these matters at times. TireRack has an objective, and that would be to sell tires (yes, I know, in addition to other components... but it is the TIRERack). So, some of us are a bit skeptical when it comes to drinking the koolaid. And as I posted earlier, I get that we're a statistically small bunch at the moment, but at least one member here has had OEM tires go beyond 100k inflated at/above the number stamped on the tire.
     
  10. the_ghost

    the_ghost Active Member

    well, I figure it this way, there is a reason that it is listed as the MAXIMUM PSI... these companies have laboratories to test these things and exceeding the limits can make bad things happen. I have heard horror stories of tire techs going to 160+ PSI on a tire rated for 1/3 of that when trying to seat the tire's bead and then having the thing explode or otherwise injure them when the bead pops into place...
     
  11. kelly.cardona

    kelly.cardona Well-Known Member

    So if you find yourself in a situation where your tires are brand new but were made 6+ years ago can you go and get your money back? Or what can a person do?
     
  12. the_ghost

    the_ghost Active Member

    Depends on where you go, I reckon you could demand a new set. Talk to the manager (assuming you haven't put too many miles on this set yet) and say "hey, I thought I was buying NEW tires, and these clearly aren't and I don't feel safe, and I feel like you gypped me." Or something like that. Try being nice first, and then if that doesn't work, get LOUD and insistent and write a letter to the owner of the service station you bought them from and send it via certified mail and post the tire retailer on consumerist. Back to the original post, inflating older tires past sidewall limit is definitely dangerous because after only a few years the sidewalls will begin to crack and dryrot.

    Best,
    Ghost
     
  13. HAFNHAF

    HAFNHAF Well-Known Member

    i just replaced my tires after 45,000 miles/3 years. they only had a treadwear rating of 380, so i didnt expect great treadwear out of them. i ran them at 50 psi (s/w rated at 51) the whole time. perfectly even tread wear. never needed a re-balance since new. i think the placard says 34 or 36. something like that.
     
  14. hawkgt647

    hawkgt647 Well-Known Member

    Let's see if I'm understanding you correctly - more pressure in the tire will increase the diameter of the tire, changing the effective ratio. Wouldn't that benefit mileage? Lower profile tires (smaller diameter) were promoted as a cheap gear reduction in the early '70s. This would be the opposite, I believe.
     
  15. CarlD

    CarlD Well-Known Member

    I think he was referring to odometer mileage being less than actual due to slightly less revolutions/mile with a larger diameter tire. Makes the warranty last a few miles longer, though........
     
  16. the_ghost

    the_ghost Active Member

    yeah I was kind of vauge I guess, I mean that overinflation will increase mileage slightly by slightly increasing the diameter of the tire but at the same time this will also be offset because the odometer will read incorrectly (as will the speedometer)

    but in short my point is inflation past sidewall max is bad for tire wear and is dangerous.
     
  17. Chuck

    Chuck just the messenger

    It's not good form to go around telling us what is and is not good hypermiling on the 1st day.... ghost, read Beating the EPA - The Why’s and how to Hypermile.

    On tire pressure - I'm at 60psi or so the past 30,000 miles and my tread looks better than the one in the Prius picture (has more tread on the sides, although the center is still thicker).

    For comfort and legal parnaoia reasons, the max psi is 4-5x less than the bursting pressure.

    I realize it might be different on a vehicle other than a Honda Insight and/or bad weather.
     
  18. LL3

    LL3 Well-Known Member

    I don’t think anyone here would question that 160+ PSI for a 44 PSI max is over inflating.

    Companies that put the “MAX” on anything are under calculating what the limits actually are. For example, when you see a road sign before a curve that says “Max Speed 35” – It does not mean the curve limits are 35 MPH and you will run off the road if you go over. An engineer for building roads could tell you that the max speed limit for the curve is much higher, but they will post a lower limit for CYA reasons when someone does go off the road at 70 mph.

    It is the same for tires. There is a rating so if you’re above their rating and the tire does blow up, you can’t go back to them with a legitimate complaint.

    Excellent topic,

    LL3
     
  19. 99HXCivic

    99HXCivic Well-Known Member

    Yeah, overpressure is bad for OLD tires. 2 old tires on my HX bulged after I put 50.5 psi on them.
     
  20. LL3

    LL3 Well-Known Member

    99,
    This does make sense. Depending on what “old” is and what the psi was on prior, it more than likely would bulge. Another analogy:
    If you took a balloon, (like one of those long ones to make shapes) and put a little air into it, then manipulated just a section by stretching it, when you put more air into it, that section you manipulated would bulge or change shape in that region. I know this is a corny example, but that is kinda what happens to tires as they wear in a spot.

    LL3
     

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