The wheel spindles (not wheel axles) have three spring washers on the top under the nut used to control bearing preload. Does anyone know the preload setting on these? Thanks..

With new bearings on trailer, I certainly run them a tad bit more snug then 1/4" of wobble. More like half that.

And never had any run so hot that you cant keep your hand on the hub.

Quoting Removed, click Modern View to see

"So preload them like you would for a trailer bearing."

You PRELOAD trailer bearings?

Bearing manufacturers typical recommend several thousandths of PLAY, NOT "preload".

"Final Castle Nut Adjustment:
To make sure the hub is seated properly, back off the castle nut until it is loose.
Then tighten the castle nut snugly until it stops.
Look to see where the cotter pin hole lines up with one of the notches on the nut.
On hubs that use the tang washer or cage to lock the nut, you will have to do this by sight.
Then back the nut off one notch, so that the cotter pin will fit through the castle nut.
Install the cotter pin and then spin and rock the hub.
When you rock the hub you should feel the hub barely moving front to back.
Try experimenting by loosening the castle nut one more notch to feel the difference in the play in the hub.
Then install the wheel and rock the hub again.
On the outside edge of the tire, the movement should not be more than 1/4" inch.
Any play should be barely noticeable.
When you are satisfied with the adjustment, secure the cotter pin.
Push the pin through the hole on the end of the spindle and through the notches on the nut.
Then split the bottom of the pin to the left and right.

This quote is from "etrailer.com".

Quoting Removed, click Modern View to see

Yes, I was just mentioning that my blade spindle bearings use regular trailer hub bearings.

On yours since there is a call for preload they are evidently taper rollers with seperate races.

So preload them like you would for a trailer bearing.

Quoting Removed, click Modern View to see

I would ASSUME you snug them up enough to prevent the caster wheels from "fluttering" "at speed".

No but I would do them same preload as on trailer spindle bearings

In fact that is likely the same bearing as used for trailer hubs.

My mowers blade spindle use 1" trailer axle bearings.

NOT blade spindles. Spindles for castor wheels on front of deck.

These castor wheel spindles have three "spring washers" under the retaining nut. They are concave (not flat) and are stacked opposite of each other. First one down, next up and last one down. The book shows how to install but not the amount of "preload" Because the retaining nut is a "lock" type a torque wrench is not used. The setting would be something like "zero" lash plus a part of an additional turn of the nut. If too tight and they are crushed, break up, and pieces work down into the upper bearing causing damage. If too loose they fail to keep the upper bearing seated into the upper race. I have an owners manual but not a service manual. Anyone have one I could download. I have a 52" front mount. Take care and stay safe.

In my experience with belleville washers, they rarely crush and break up. Of course I'm sure it depends on the quality of the washer.

I have a five foot brush hog that uses bellevilles in the slip clutch. The adjustment on those are, tighten until flat then back off X amount.

If I were in your situation, I would tighten them until they are half way collapsed.

I found a crushed one in the tail wheel. That's why I am trying to find adjustment info. Thanks for your note. Stay safe. Merry Xmas

Got to talk to the head mechanic at Grasshopper. Very "low tech" method of setting preload. After cleaning, replacing parts as needed, fresh grease and reassembling, raise the deck to an upright position. Tighten top nut until the caster and wheel assembly stay in a 90 degree position. In small increments loosen top nut until wheel and spindle assembly rotate slowly downward. That's it. I expected a more sophisticated process. Stay safe and Merry Christmas