Ideal weight ratios on a mid-mount ZTR

Discussion in 'Lawn Mowing' started by davidcalhoun, Sep 10, 2006.

  1. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Messages: 1,045

    We all know that if a mid-mount ZTR has too much weight on the rear of the machine, you will do a wheelie. Likewise, if you have too much weight on the front of the machine, you will suffer traction.

    If you see a mid-mount ZTR with a catcher added to the back, you often see some counter weights added to the front.

    I am sure that most manufacturers have a target (rear to front) ratio that they engineer to. Does anyone know what this ideal ratio is? Has anyone ever weighed out their mower (based on rear to front)?

    One other factor that must be factored in is that of the seat placement and the average weight of the operator.

    While we are at it, which mid-mount ZTRs do you feel hit or misses the ideal ratio based on your experiences.
  2. John Gamba

    John Gamba LawnSite Fanatic
    from ct
    Messages: 10,812

    Do you sell or make out front mowers??? Answer that first.

  3. barnard

    barnard LawnSite Senior Member
    Messages: 618

    No and No to answer your questions. As two tractors with the same ratio front to rear would behave differently if say the rear axle were mounted a few inches forward or further back than the other Also two machines with the same weights front or rear with different wheel bases would behave differently.
  4. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Messages: 1,045

    No John, I do not sell or build ANY mowers. I did not realize that I had to "Qualify" myself to you. Perhaps you should refrain from reading this tread if you are so skeptical.

    To all the others, I am just a end user without ANY ties to ANY manufacturer. I have used many brands of Commercial ZTRs over the last 20 plus years of mowing.

    I was hoping that this would be a information tread that all could share and learn from.

    Perhaps this tread would help someone who is experiencing a problem do to improper weight ratio. "Does your mower do wheelies all the time?". "Do you notice a lack of traction and cause a lot of rips in the turf when you slow down or accelerate?".

    My catalyst for this thought process came about after I talked my 70 year old father-n-law into buying a Gravely Mini (homeowners model) for his small yard. I notice that he was tearing up a lot of turf when he would slow down before a turn. I thought that maybe he was doing something wrong so I got on the mower. My weight actually made it worse since the seat is located quite a bit in front of the rear wheels. It became very apparent that this particular mower could use additional weight behind the rear wheels to provide the optimal ratio of weight. Some early commercial Snapper mid-mounts from the 90s also suffered this same problem.

    Finding the right weight ratio is a fine line. Some manufacturers lean toward the weight ratio more the front because of the inherent liability issues. Others have added wheelie bars to get more of the weight ratio to the rear.
  5. barnard

    barnard LawnSite Senior Member
    Messages: 618

    The tendancy for small z's to slide a wheel or tear turf is mainly due to small tires and the narrowness of the spacing between the rear wheels. The closer together you put them the harder it is for them to turn the machine.
  6. Scotts' Yard Care

    Scotts' Yard Care LawnSite Senior Member
    Messages: 343

    One thing I've noticed is that the small Zs tend to have powerful and very fast hydros which exacerbates this spinning and tearing the turf. The few large Zs I've run have very "soft" and progressive steering which seems to be much more modulated than the little machines. Obviously, I haven't run every Z out there.
  7. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Messages: 1,045

    Getting the ideal weight ratio will also help from putting too much weight on the front castor wheels. No one likes to have the grass pressed down so hard that their deck can't lift this area of the wheel path.
  8. WildLake

    WildLake LawnSite Senior Member
    Messages: 368

    two tractors with the same ratio would no longer have the same ratio, "if say the rear axle were mounted a few inches forward or further back".
  9. mowtech

    mowtech LawnSite Senior Member
    Messages: 252

    This is a good question. For most vehicles there is a definite ideal weight ratio. Mid-mount Z mowers are no different. What that ideal target weight ratio is, however, is not necessarily understood by all manufacturers and therefore not something to be shared. But what I will tell you is that since mid-mount Zs are dependent on traction for control, as you said the more weight on the rear, the better; however, up hill stability and wheelies become an issue if there is too much weight on the rear. The ANSI B71.4 safety standard which most manufacturers, but not all follow sets some limits. The requirement for up hill stability for a Z mower without ROPS is 30 degrees. That means the unit must be able to withstand rearward tipping up to 30 degrees. With ROPS, the requirement becomes 25 degrees. With a bagger attachment with full bag it is only 20 degrees. This tip angle is partly dependent on the weight distribution, but also is dependent on the wheel base and the height of the center of gravity. Because of this, the ideal weight distribution may not be obtainable on some units in order to meet the standard. Having said all that, what “Barnard” states about the small Z is true. The small tires and narrow tread width hurt the performance. Larger tires might help, but these would raise the center of gravity and hurt up hill stability and side hill traction. The equipment designer is always faced with compromises.
  10. lawnspecialties

    lawnspecialties LawnSite Silver Member
    Messages: 2,524

    Although they are fairly popular around here, I used to have a 2000 Cub Cadet M60 Tank. It was extremely front heavy. It even had a weight in the back but would still tear up some grass when doing z-turns. Yes, all ztr's will, but this was extreme. My SuperZ has a real good balance IMO.

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