PSI for ztr tires?

Discussion in 'Lawn Mowing' started by EagleLandscape, Nov 27, 2007.

  1. EagleLandscape

    EagleLandscape LawnSite Platinum Member
    Male, from Garland, Texas
    Messages: 4,350

    What psi should I run in the rear tires of my 48" emark ztr? thanks!
  2. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    Well funny thing about Z's. You don't really go by PSI's. It goes by loaded circumference. This way, your travel is straight when both drive sides have equal power going to them. The way they say to do it is lift the back of the mower, and use either a soft tape measure (like they use in the tailor shops) or a string or twine, and use it to measure around the center of the tire all the way around. Adjust so they are the same. then, when you are wide open on a smooth level surface, your machine should track straight when going full open on the hydros. The reason for this, is that many of these tires, when molded, come out different. Some are bigger, some are smaller....yes,...enough to make a difference on the drive when used on dual drive machines such as the Z's.
    Now, how do I do it? If my drive is a little off, I inflate or deflate a side a little bit to compensate. I usually get it dialed right in rather quickly.
  3. EagleLandscape

    EagleLandscape LawnSite Platinum Member
    Male, from Garland, Texas
    Messages: 4,350

    Right, I do that. But I'm worried about rutting out the turf. We are mowing perennial rye now, which doesn't abuse as well as our warm season grasses.

    I might deflate them a little to get a bigger surface area.
  4. lawnman_scott

    lawnman_scott LawnSite Fanatic
    Messages: 7,547

    Personally, I would look at the rear tires for the awnser.
  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I always fill my tires to the max psi printed on the side.
  6. Nosmo

    Nosmo LawnSite Bronze Member
    Messages: 1,216

    Runner's advise seems very reasonable about the circumference of the rear tires. I know some of them can have a bulge and others don't.

    One thing I'd say before you do any measuring on those rear tires is to warm them up first. Drive the mower around to round out any flat spots .

    If you guys like a firm and bouncy ride inflate them to the maxium on the sidewall. I run 8 lbs. in the fronts and rears . Where did I get this idea ? I believe Envy was the source.

  7. delphied

    delphied LawnSite Silver Member
    Messages: 2,067

    If the tires are low on pressure, you can run them right off the rims if you get on a curb or bump just right.
  8. tacoma200

    tacoma200 LawnSite Fanatic
    Messages: 5,426

    I run 8-10 psi in every tire on every ZTR I've owned. I have never had a problem and it rides "much" better. If you have air filled front tires you just have to be careful on curbs. Just me personally, not speaking for anyone but myself, I would never run the maximum pressure on the side wall. There are a lot of us that run regular tires at the 9-10 psi level with out problems. 15 psi and up is bone jarring to me, even with a suspension seat. Run a Super Z with 8 PSI and flex forks and man is it ever smooth. You can ask Puppypaws about that. My Exmark Lazer and Turf Tiger both have 9 psi in the rear. No problems.
  9. delphied

    delphied LawnSite Silver Member
    Messages: 2,067

    I will try it
  10. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    That ALSO brings up a good point. When you bring your tire pressure down, iy is mathematical that you are going to lose ground speed - or ARE you? Yes, top end on smooth surface is going to be decreased, BUT the result of the softer tire will both enhance the quality of the cut by smoothing out the plane of travel, but most importantly, will allow faster ground speeds per rough area, and with less fatigue. The mowing is not usually done with sticks full out, SO, with a smoother ride, the ground speed is compensated by a little more forward action on the sticks. Bottom line, it is my opinion that a bit of a smoother ride is more productive than a rock hard ride. Now, the front tires, this really applies on this. While I don't actually measure the psi on the front, I do step down with my foot and compare cushion on each wheel.

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