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How can I increase w/b speed?

Discussion in 'Lawn Mowing' started by shearbolt, Nov 22, 2001.

  1. shearbolt

    shearbolt LawnSite Member
    Posts: 171

    I have an Exmark 48 Metro and a belt drive 61" Ransome. Can I put taller tires on them? Are there a diferent pulleys available?
  2. Kent Lawns

    Kent Lawns LawnSite Senior Member
    from Midwest
    Posts: 870

    Yes and Yes.

    Bigger tires is probably the easiest, smartest way, especially if you need new drive tires. (Increase diameter by 2")

    As far as pulleys, it's easier to reduce the size of the one on the transmission. You'll need to find this at a supply outlet. You will also need a different belt. And keeping that belt tight can be a challange.
  3. Eng Mwr Guy

    Eng Mwr Guy Gravely Manufacturer
    Posts: 249

    A word of caution:

    If the machines are still under warranty you may want to wait on modifications as manufacturer's sometimes deny warranties if the machine is modified by someone other than a certified factory technician.

    If out of warranty.....party down.

    Gravely Guy
  4. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Posts: 1,544


    Taller tires (you mentioned 2" dia increase) will raise the REAR of your machine by 1" (half of 2"). The front, unless also raised, will remain at its original height.

    If you have 6" radius tires and go to 7", the circumference will go from 2*pie*6" to 2*pie*7", or 1.16 times the original circumference, or 7/6 for easy math. You don't need to get into the pie stuff because that factors out in the division.

    So if you max forward speed will go from maybe 5 mph to maybe 5.8 mph with the tires- NOT MUCH INCREASE considering your mower will ride ass-high like a trailer park Camaro.

    Get the pulleys- when your warranty is out!

  5. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    Albemarle Lawn wrote:
    NOT MUCH INCREASE considering your mower will ride ass-high like a trailer park Camaro.

    Oh come on now. I switched from 13 to 15 inch tires on my Gravely Pro 150 last year and you could even hardly tell the difference. For mowers that don't have an easy way to change the rake it's a very good way to add about 3/8 to 1/2 inch of rake to the rear of the deck.

    One of the minuses to increasing tire size is there is a percievable decrease in breaking power. This is because of the increased leverage over the break bands that the mower inertia has because of the increased tire size.

    One of the minuses to increasing pulley sizes is that you are increasing the rpms that the trans turns verses the rpms that the same trans would turn with taller tires at a given ground speed.
    Increased rpms equals higher temps and higher wear out time.
  6. You guys are barking up the wrong tree.

    Change the tranny. Lesco or your dealer should have one that will fit those W/B's

    One problem you will have on the Exmark, is if it has the 5 speed already. It is sapposed to go 6.2mph. Same as the hydro speed.

    The Bobcat I don't know off hand but you could try www.medartengine.com. for both even.

    Engine RPM. not a good option either, but check to make sure it is set at max by the MFG.
  7. jman00

    jman00 LawnSite Member
    Posts: 129

    has anyone put taller tires on a metro hp and had it go faster?

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