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Bigger tires, increase ground speed?

Discussion in 'Lawn Mowing' started by Wayne Offiler, Mar 31, 2001.

  1. Wayne Offiler

    Wayne Offiler LawnSite Member
    Posts: 113

    Just got a 1997 Bunton 52" hydro WB, 16 HP Vanguard. Will use a Proslide sulky with it, and want to mow at best possible speed. BUT, seems to me that max. speed is only aboout 4 MPH (I can walk about that fast)
    How to increase ground speed? has 6.50x13-6 tires on it now; if I went to 6.00x15-6 tires, would my top speed increase enough to make it worth while?
  2. Runner

    Runner LawnSite Fanatic
    Posts: 13,496

    I'm not exactly sure, but I think you're looking at about a 14% increase with the figures that you gave. Just make sure that you have enough clearance at the deck for this. Other than that, you won't really have to worry about the blade pitch as this increase in the back of the mower will not be the same distance the the back of the blade is lifted as the back of the blade is still forward from the axle height. Also, keeping those babies pumped right up increases the diameter and decreases the roll resistance. The only holdback is that you have a bouncier mower with less traction and it is a bit harder on the equipment. Hey, 5 more posts to a thousand!
  3. Gear drive toros have a ground speed of 4.5 in high gear with 13" tires and 5.2 mph with 15" tires.
  4. smburgess

    smburgess LawnSite Senior Member
    Posts: 469

    Runner... Good work!
    Lawrence... Huh?
  5. jeffyr

    jeffyr LawnSite Senior Member
    Posts: 876

    Increasing tire size on a truck without changing the ring and pinion gears will lower the engine RPM which in turn will allow you move faster. However, it also slows the acceleration speed and hill climbing ability. I would imagine this holds true with mowers. The rpm's will not be effected as with a truck, and your ground speed will increase, but it may not climb the way you remember if you have alot of hills. By putting the larger tires on you are effectively changing the gear ratio (similar to the speed up pulley that walker offers, only you are changing the tire diameter instead of the pully).

  6. The 15" tires are a must when using a stand on fixed position two wheel sulky. They also are easier on the turf.

    The 13.5" tires ride REAL rough. Plus you get better mowing performance with the rear of the deck raised up a bit more.
  7. little green guy

    little green guy LawnSite Senior Member
    Posts: 955

    Try adjusting the hydro liknage. One of my scag hydro's was kinda slow when I first got it but I adgusted the setting and got it up to speed. Thats kinda wierd though that it only has 13" tires, I don't thing I've ever seen a hydro with less that 16" tires.
  8. Chopper Lover

    Chopper Lover LawnSite Senior Member
    Posts: 288

    Switching form 13" tires to 15" tires will raise the rear of your mower 1" at the axle. How much it will change your blade angle/height depends on the angle change from front to rear of the mower deck... Probably not enough to worry about.

    Yes, it should go faster because the taller tires will travel a farther distance for every revolution the wheel makes.

    Will it go faster? That depends on how much load is already on the motor. It takes more engine effort to turn the bigger tires. If you are already maxed out with your power it may be more detrimental than going slow was originally.

    Will it work? Not being familiar with that size mower/engine combination I do not have an answer.

    Good luck and let us know what you do!

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