shimmy at high speed

[Charlie Tango]

I have a 2003 Arctic Cat 500 Auto 4wd that shimmys at high speed on pavement.  Any one know what causes this and how to get rid of it?

[torpedoman]

the off road tires on pavement at high speed would be my first guess, you are asking equipment to do something it was not designed to do.   4wd is not stable on dry pavement because one axle is slightly slower than the other for steering and traction

[Old Syko]

Charlie this is usually a simple fix.  If you have a shimmy on pavement it's there when off road also just disquised by the terrain.  First thing to check is tie rods and other front end parts to be sure there is no excessive wear or bent wheels.  When you're sure all's well there it's time to balance the tires and not just the front either.  Balance both front and rear as a severely out of balance rear tire may also cause what you describe.  Lastly and the most overlooked is front end alignment which in most cases consists of toe adjustment only as long as nothing is bent and causing major geometry problems.  If your bike is full time 4x4 set the toe about 1/16" to 1/32" toe out.  If you have a switchable system that pulls by the rear wheels only when disingaged you want to set it about 1/16" toe in. 

The method most dealers use to set toe as described by the manufacturer isn't worth spit.  Find someone with a toe bar or build one yourself like I did.  It's amazing how much difference proper toe makes in handling both on and off road.  I've run over 70mph with both 27" and 29" 6 ply mud tires with no shake what-so-ever on a Kaw Prairie.

[30-30man]

When running any atv with knobbies on pavement, if you go fast enough the shimmy will turn into a flip over.  I once rode my atv down to the boat ramp at my lake house.  I hit 40 mph on my Yamaha Bruin as checked by my wife in the car...It was very squirrely and I would never do it again...On dirt it is rock solid.  Check it on dirt before you touch a thing...

[Old Syko]

When running any atv with knobbies on pavement, if you go fast enough the shimmy will turn into a flip over.

Not true at all.  As I've said here before, where I live it is legal to ride the paved county roads and at times you will see more 4 wheelers on the road than cars and trucks as it is a way of life here.  If you have a handling problem it is there whether you are on dirt or pavement.  It will only be more pronounced on pavement.  Either way it needs to be fixed.

The Bruin is probably like most.  It was set up with excessive toe in, in some cases as much as 2 inches, yet no one has taken the time to set it up properly.  Give your family car an extra 1/2 to 1 inch of toe and see if you can keep it on the road at speed.

[DCRthe3rd]

Depending on what he is referring to as a "shimmy" , it sounds like a front end/wheel problem

[oldandslow]

My experience parallels Old Syko's. I would check tie rod ends first and toe in second.

[gooser]

something not mentioned here is air pressure in the tires,make sure they are at specs, front and rear will most likely differ......just a thought.......