Front Caster Shake

Discussion in 'Hustler Turf Equip (Archived)' started by mtmower, Jun 20, 2014.

  1. mtmower

    mtmower LawnSite Bronze Member
    Posts: 1,115

    I have a brand new 60" Super Z HD with flex forks and can't go much past half stick/speed on hard surfaces without caster going crazy. I've owned a early standard deck SZ which it was never a problem. I own a 66" XR7 SZ with flex forks and it was a problem until they came out with the poly bushing/washer to be added to the top of the caster. I demoed a new HD SZ and the rep said flex fork should fix it. It didn't. This is a fast mower but if the casters a flying back and forth the speed is worthless. It may have gotten a little less sever since I have 40 hrs. of wear on the ribbed tires now but not much different. I did verify that the dealer installed everything correctly when they installed the flex forks. Wondering if there is a fix and if not it a second poly friction washer should be tried?
     
  2. J&A Lawn Care

    J&A Lawn Care LawnSite Senior Member
    Posts: 437

    usually happens when one of you back tires has more air in it than the other which make that front corner of the mower lighter.
     
  3. hustlermidwest

    hustlermidwest LawnSite Senior Member
    Posts: 636

    Agree on the tire pressure. I would balance the weight up front before trying to apply more resistance. Sometimes it's not just tire pressure, some tires are softer than others and a measurement of the tire may be in order.

    Brian O
     
  4. ducnut

    ducnut LawnSite Bronze Member
    Posts: 1,569

    As I've stated elsewhere on this issue, there is an obvious reduction in trail with Flex Forks. The axle centerline is closer to the fork spindle, which results in the shimmy. My X-ONE has done it, from the beginning. No change in tire pressures will help it. At 7psi in the front, I managed to pop the bead on one, so beware if you try a pressure reduction to stabilize it. I'm thinking the poly washers are going to be the only solution, as they provide enough resistance to damp the oscillations.
     
  5. hustlermidwest

    hustlermidwest LawnSite Senior Member
    Posts: 636

    Should have been specific, I adjust the rear tires and keep the front the same. Washers as a last result. I would also triple check the correct flex forks are installed per you model number and serial number.

    Brian O
     
  6. puppypaws

    puppypaws LawnSite Fanatic
    Posts: 8,945

    I find it quite interesting that many of the Super Z mowers are plagued with shimmy, while many are not. I've dealt with shimmy on my 2006 with flex forks, what I did was add another white friction washer (now has 2), put Locktite on the bolt and tightened it to the point it would turn freely, but not too freely. I let the mower sit overnight so the Locktite could setup to hold the bolt at the tension I wanted, and I've never had a problem since.

    The big 72" HyperDrive has never attempted to shimmy at any speed, or on any surface.
     
  7. Steve_B

    Steve_B LawnSite Member
    Posts: 11

    My diesel Z had occasional front wheel shimmy. I didn't realize it was associated with pressure problems in the rear tires -- I was having a lot of trouble with trashing the big tires on the rough fields it lives in. When the pressure in one of them got low, I'd get shimmy in one of the front wheels. Replaced rear tires with some monster tires, front shimmy is gone too.
     
  8. hustlermidwest

    hustlermidwest LawnSite Senior Member
    Posts: 636

    Steve,
    You might have changed the pitch of the unit by putting larger tires on it. Not much different than the old days of jacking up the back end of my 74 Duster. Changed the way the front end felt.
    If you are doing field cutting you wont notice the cut, otherwise taller back tires you'll need to re-level the deck.
    Thank you also for the kind words on the other thread.

    Brian O
     
  9. Steve_B

    Steve_B LawnSite Member
    Posts: 11

    You're welcome (of course).

    I also put taller tires on the front, specifically for that reason, plus I wanted to go to foam tires instead of pneumatic. But the shimmy was -- at least in my case -- clearly related to rear tire pressure. When I'd air up the rear tires, there would be no front shimmy. If one tire got low, the shimmy came back.
     
  10. mtmower

    mtmower LawnSite Bronze Member
    Posts: 1,115

    A late follow up. I talked with my selling dealer and verified things were correctly installed on my machine and theorized on what could be done. I talked with Hustler direct and we decided to try the most basic thing we could think of which was installing a second friction disc to the fork assembly in the same location. This created quite a bit of friction to the point of tearing very wet turf when pivoting the caster. It didn't take but a few hours of use before the caster friction lessened and it's now a beautiful thing. Works wonderfully during normal mowing and I can now utilize full speeds even on hard surfaces. The only other challenge was the assembly is so tight that it blew both upper O-rings used to seal water completely out. I went to a hardware store and purchased square O-rings used for early style plumbing joints in sink drains and installed them. For us older people these square O-rings are also used on glass fuel separator bowls on old tractors. They also all but pushed out but are still providing sealing from moisture. As the friction discs wear these O-rings will possibly re-expand for a short time and continue aid in applying pressure along with the discs. For anyone with caster shimmy I'd highly recommend this. The O-rings and discs were only a few dollars and it takes all of 10 min. to install.
     

Share This Page