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Increasing tires too much?

Discussion in 'Gen 2 Prius Fuel Economy' started by Hokie-Dave, Apr 14, 2005.

  1. Hokie-Dave

    Hokie-Dave Member

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    Do you think that there may be people driving Hybrids that are TOO obsessed with fuel mileage now? I know with fuel prices rising like they are, people are inflating their tires a bit more to try and reduce the rolling resistance. I know that this is a trade-off to tread wear since an over inflated tire wears just the center portion of the tread instead of evenly accross the whole tire.

    The main reason I ask is that while driving to work this morning, I saw two cars changing flat tires. One was a newer Civic Hybrid, and the other was a Prius. Probably just a coincendence, but thought I'd throw it up for discussion.
     
    #1 Hokie-Dave, Apr 14, 2005
  2. paprius4030

    paprius4030 My first Prius

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    I would think if they were fairly close to each other maybe they hit the same thing on the road. I don't think many people here are overinflating their tires. If your thinking that many of us run 42/40 instead of what Toyota recomends it's because alot of our Prius mechanics recommended that anddit does decrease tire wear at least with the Integrity tires.
     
    #2 paprius4030, Apr 14, 2005
  3. efusco

    efusco Moderator Emeritus
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    Hmmm, maybe they were running their tire pressure to low and thus were more at risk to tire damage from road debris.

    Also, although OVER inflating can, indeed, cause uneven wear in the tire center todays well built steel belted tires can support much higher pressures without distortion or concern about uneven wear. Now, you assume that higher than OEM recommended pressure is 'over inflation'...I don't think that's the case...I think the problem begins once you surpass the maximum inflation pressure on the sidewall.

    So no, I don't think your coincidental spotting of two hybrids having tires changed is likely, at all, to be related and may, very well, be that they were under inflated.

    As to the question of whether we obscess too much...yea, some of us probably could be putting our collective brain power to some better use. But for me it is entertainment and I won't need therapy just b/c my mpg drops below 45mpg for a tank.
     
    #3 efusco, Apr 14, 2005
  4. jayman

    jayman Senior Member

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    Well, even running my OEM Goodyear Integrity and Michelin Harmony tires at maximum cold inflation pressure, the most I ever gained was around 2-3 MPG. Usually there was no difference, except for the bone jarring ride.

    Thanks to all the potholes and frost heaves around here, the local dealers tell all owners, not just Prius owners, to *not* inflate beyond the manufacturer recommended inflation.

    A tire at the maximum inflation on the sidewall is much less resistant to impact damage (Pothole or object on the road) than one aired down a bit.

    I run mine at 35F/33R.
     
    #4 jayman, Apr 14, 2005
  5. Hokie-Dave

    Hokie-Dave Member

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    All good points. It was just something that popped in my mind as I saw two Hybrid owners changing tires in the left shoulder of the road this morning. I'm sure it was probably just a coincedence. Didn't look fun to change that front right tire on the left shoulder though.. Yikes!

    I've noticed the center tread wear on a few friends Mustangs that were running their tires up close to 40psi, but there is quite a bit more tire to bulge out at the center of a 245-265 tire, than a 185.

    I too have also noticed the obsessive behavior I've gotten into staring at the monitor while driving seeing how different techniques will play a role in MPG.
     
    #5 Hokie-Dave, Apr 14, 2005
  6. galaxee

    galaxee mostly benevolent

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    Heck I run my tires at 42-40 and had to change one... because I got a construction screw jammed in my tire. That's what I get for driving through construction to take a shortcut.

    There are way too many variables to assume 2 people on the side of the road had their tires too inflated and that's what caused their flat tires... just my thoughts. :)
     
    #6 galaxee, Apr 14, 2005
  7. raintree

    raintree New Member

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    I had been running 42/40, but found the bone jarring too much and have lowered the pressure to 38/36. Gas mileage has not moved down, but the ride is MUCH more comfortable.
     
    #7 raintree, Apr 14, 2005
  8. 200Volts

    200Volts Member

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    On tire wear I have 36,000 miles on my stocks and they are ready to be replaced. I've had my pressures between 42/40 for the first 15k miles and 38/36 for the rest and the most wear is the OUTSIDE of the tires from the FRONT drive-steering. The outsides have now worn down past the wear indicators (small lines/pits) on the outside 2 inches. I only have about a 1/8" of tread left evenly across the rest of the tires.
    I'm probably going to try the Tire Rack's Bridgestone G009 in the same size or 195/60-15. I'm not sure which to try.
     
    #8 200Volts, Apr 14, 2005
  9. gschoen

    gschoen Member

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    The sidewall max psi assumes a cold tire, so it allows for thermal expansion as well as a safety margin, so overinflation occurs when going past the tire's rating. Hazards due to underinflation are far more common. The guidelines I always follow:

    -Never go below the car maker's psi or above the tire maker's psi.
    -Keep whatever differeence between F&R the car maker recommends even if you're using a higer pressure for handling.

    I'm currently at 42/40 on the Integrety's and am going to try lowering in 2psi increments until at Toyota's recommendation to see if the ride will get a little better, a last resort before I buy new tires. I'm all about feeling the road, but I've only got one tooth left and losing it on another pothole will make me cry. :cry:
     
    #9 gschoen, Apr 14, 2005
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