Tire pressure question from newbie

Discussion in 'Start Your Journey Here' started by dare2be, Jul 2, 2008.

  1. dare2be

    dare2be Well-Known Member

    Hi, I just joined today hoping to get the most out of my 2003 Saturn Ion CVT for short commutes and in the hot Florida sun (A/C almost always required). I want to start with the tire pressure trick, but I'm having trouble finding the maximum sidewall pressure for my tires. The only thing imprinted on the tires is something about "Max load 500-ish kg yada yada yada at 44psi". Is 44psi the number I should be going with?

    I've read up on the HM techniques which most were already common sense to me (minimize braking / acceleration using terrain and traffic/signal timing to my advantage). I love my CVT transmission as it gives me pinpoint control of my rpms and throttle with simple adjustments of gas petal pressure, allowing me to find the right balance of efficiency and power. My main complaint of my CVT transmission is the automatic engine braking / downshifting going downhill, which makes downhill coasting much more difficult without a lot of neutral shifting.

    Curt
     
  2. run500mph

    run500mph Well-Known Member

    Hey there dare2be, you came to the right place. You will get some super high numbers soon. Read Wayne's article "Beating the EPA-The How's and Why to Hypermile" on the top right of the home page. Yes inflate to the MAX side wall rating which in your case is 44 psi.
    This will net you a gain in fuel economy immediately. Then practice all the techniques one by one till your numbers make your friends jealous. You seem to be doing great already.
    I have only been doing this 3 months and have gotten to the point where my last tank was a full doublel of what my car is rated at (23rated-46 by hypermiling).

    Welcome and ask many questions.
     
  3. dare2be

    dare2be Well-Known Member

    Thx.

    Yes, I did read Wayne's article which is what I was referring to as my common sense tactics. Minimizing A/C use is almost impossible in Florida between the months of April - October. There aren't many hills either, so coasting is limited. I will try to increase my P/G activity and slow down on highways.

    Funny, I was recently on a long 12-hour drive home from a vacation and I tend to be one of those 5-10 MPH over the limit drivers just to save time, fully knowing I was sacrificing mpg for time. However, for me, many times on long trips like that saving a few mpg isn't worth adding an hour or two of trip time to my already long journey.

    Anyway, after stopping off at a rest area, I found myself cussing out an extremely slow driver I was behind as we both merged onto the interstate, who slowly got himself up to 50mph when he finally merged into the right lane of the 70mph highway. Perhaps he was a hypermiler. I'll be more tolerant of slower drivers from here on out knowing what I know now (except for those that hog the left passing lane lol). I was mostly concerned about the 20mph (or more) differential between us and the rest of the moderately heavy traffic.

    I may not turn out to be a hardcore hypermiler, but I sure will take what I learn here to find my own balance of efficiency, speed, and time on the road. And I'll try to post any results that may be of consequence.
     
  4. Nanci

    Nanci Well-Known Member

    Hi Dare2be! I just asked that tire pressure question myself! I just emptied my second hypermiling tank- the first tank with no speeding, and my mpg went up 3 mpg! (That's a lot for my vehicle). I have trained my speeding brain to think of slow drivers as an excuse to go slowly myself. Now I'm hoping max tire pressure will get me a similar increase.

    Nanci
     
  5. LL3

    LL3 Well-Known Member

    We need a bumper sticker That says, "Hypermiler on Board - Please stay back 200 feet or 20 feet ahead" :D

    GL on your techniques in Fla. I hope to be joining you there soon!

    When I changed my tire pressure to 44 from 36, I noticed about a +3 mpg difference.


    LL3
     
  6. Hello, I have a concern about inflating your tires up to the recommended tire pressure. You all do realize that by overinflating them you are increasing the wear and tear on the center of the tread? Has anyone calculated the mileage increase vs. the price of your new tires that you will have to purchase sooner because of the high psi? I am guessing that the mileage increase is worth it when compared to the decreased lifespan of your tires. The only other concern I have is that we are assuming here that everyone maintains their tires properly, by wearing them unevenly with the higher psi you are losing traction (think of rain and oil spots at stoplights/signs). What are ya'lls thoughts on this???
     
  7. mr. blue sky

    mr. blue sky Member

    noone here is talking about overinflating tires, instead the recommendation is to inflate to maximum sidewall pressure that the manufacturer states on the tire itself. This pressure rating is the maximum safe pressure, which as far as I know does not change the contact patch of the tire itself(as long as your tires are correctly balanced and you have a proper allignment done on your car when you bought the tires). That is why the manufacturer sets it as a maximum, which means that above that point there is danger of what you mentioned, and other problems will occur above that point. I hope that made sense, I have not slept in 24 hours.
     
  8. I guess this is just my noob mentality here, but I always thought that by going over the recommended psi (from the inside of the door/manual) would be considered over-inflating. Generally, tires are rated up to those higher psi's so that you can inflate them for heavier loads, but under normal driving conditions for the best wear possible the psi should be at the psi noted in the inside of the door/manual. This is just what my understanding of those recommendations are, I am a noob here so take what I say with a grain of salt.
     
  9. atlaw4u

    atlaw4u Well-Known Member

    slowdown - pumping your tires to the max psi listed on the tire's sidewall (probably 44psi in your Ranger) will result in increased fuel efficiency and improved tire wear. Do a few searches in the forums hear as this topic has been discussed at great length.
     
  10. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Here's what happens on a Prius if you use Toyota's recommended tire pressure. I've seen similar results on my Civic, too.
    [​IMG]
     
  11. Until now, I have always kept my tire pressure at the recommended psi (manual/inside door) and have had excellent treadwear. Obviously, it depends on the vehicle; I will try the 44psi as per the sidewall instructions and see what happens. Thanks all!
     
  12. mr. blue sky

    mr. blue sky Member

    another thing that came to mind is that most low profile tire users already use the max psi on the sidewall(including myself) without any negative side effects.
     
  13. kwj

    kwj I hypermiled this

    Welcome SlowDown, good name. Tire pressure is an interesting topic here. The site promotes use of at least the Max Sidewall (see www.tiresafety.com, and go to maintenance and then pressure). This is a Bridgestone site, and they mention going up 3-5 PSI for extended highspeed driving (like Interstate), but they also mention not to go above Max Sidewall.

    Since you lose pressure over time, we also recommend that you check it once every week to two weeks. Any longer than that, and one or two tires can get way different. I just checked a friends tires. Door placard was 30 all around. She had 18-20. I tried to explain how that causes tire failures.

    I run my tires above Max Sidewall. In 15,000 miles, I notice only even wear all around, and nothing off the sidewall edges despite cornering hard. I'm just testing a theory, and am keeping a good look for wear. In the old days of bias ply tires, center wear was a problem for some, but I've never worn out a set of tires in the center, only on the outside edges. I'll keep you posted, but so far so good.
     
  14. jimepting

    jimepting Well-Known Member

    I've been curious as to the actual payoff of running high tire pressures for a while, so I did some testing. On a calm day, on a lightly used section of level road, I tested mpg at 70, 60, 50, 40, 30 and 20 psi. These results are for a Toyota Echo fitted with Goodyear Viva II LRR tires.

    The mpg improved significatly up to 44 psi, the max load spec, but slowed down at higher pressures. The improvement was less than 1 mpg between 50 and 70 psi. All this said, the "curve" was still slightly on the rise at 70 psi, so it is reasonable for the ultra hypermiler, or the competitive hypermiler, to go on up 80 psi. I have no idea of what the risks might be in doing so.
     
  15. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Jimepting:

    ___Your results are exactly what we have posted here for a few yeas now. Problems at 80? Not many but it is going to be a rough ride ;)

    ___Good Luck

    ___Wayne
     
  16. dare2be

    dare2be Well-Known Member

    Did I miss a posting of the entire results somewhere?
     
  17. jimepting

    jimepting Well-Known Member

    dare2be,

    No, I have not posted the entire results in tabular form. As others have noted, it is extremely difficult to gather such fine grain data as this. I have done the testing on two seperate occasions and have had some problems with wind gusts on both occasions. In the most recent case, some slight windgusting influenced my 60 lb. psi data. The rest of the data was consistent with a smooth curve. Similar results on my first set of tests.

    As you can probably deduce, even minor wind gusting can have a significant effect. Other factors such as temperature also impact the data. For example, with my testing methods, the test take place over a period of around two hours. Unless the time of day is picked carefully, temperature variations can distort the tire pressure data.

    All-in-all these are difficult tests to conduct. I feel confident in the observations I made above, but I don't want to offer up data which is not fully credible. I hope to repeat the tests under more ideal circumstances, but given the near universal agreement by those with experience, it harly seems worth the waste of fuel. It is the engineer in me coming out;)

    As Wayne noted, my observations are consitent with prior data gathered by others.
     
  18. kwj

    kwj I hypermiled this

    I have personal proof that pressures above Max Sidewall net additional fuel savings. That much I know.

    As I understand, some risk is introduced, but no one has been able to quantify that for me. simply driving is a risk/reward endeavor.

    If I inflate my tires, at some unknown point, their ability to safely absorb shocks may be overcome, and the suspension takes a bigger hit.

    Road hazards can become more pronounced. BUT, I also drive more slowly than before, and am more aware of potholes and things that would affect MPGs, and that definitely decreases that risk. So, what's the bottom line? I am comfortable with my current risk/reward, just like I'm comfortable with driving on the highway with apparent fools.

    For those who deal with risk, can you please attempt to quantify my risk and the offset due to more aware and slow driving?
     
  19. Yep again here is another example of "ASSIMILATION"

    It used to be before 2 lanes merged I had to be in the lead. Now I am thinking maybe I can get behind that truck and draft, or if it is a car going slow... I won't be the one holding things up. Hypermiling is a drug..... YOU WILL NOT LIVE WITHOUT IT
     

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