OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Ride On Mowers Questions on Greenfield Ride On Mower Frames Greenfield Disc Brake Problem

Hi all,

On late model Greenfield ride-ons there is a brake disc attached to the rear axle, which is used for a parking brake or emergency brake system. On my mower (from about 2009), play has developed between this brake disc and the rear axle shaft, and in its keyway, so the brake disc may rotate slightly while the axle remains stationary. This seems like a problem.



The brake disc sits on the axle with no set screws, just a long rectangular key preventing it from rotating on the axle shaft. According to the diagram from the manual I've attached, the brake disc is intended to slide along the shaft to compensate for wear of the brake pads. So the disc must be loose enough to slide along the shaft to compensate for pad wear, yet the shaft must transfer torque to the disc through the key when applying the brakes. If there is any play in the keyway, the key will begin to move around when changing direction which is not good.

The problem began when the brake disc was removed in order to replace wheel bearings. Previously it was seized to the shaft and wouldn't even slide along the shaft, but after removal and re-installation it has subsequently developed play.



I'm concerned the key will eventually fail if I don't do something about it. Does anyone have any ideas/recommendations for how I could fix this? As pictured I have the rear axle/differential assembly removed from the mower at present.

Many thanks,
RLP

Hi RLP,
Seems a strange way of doing things, was it working ok before you removed it seeing it was rusted solid as you would expect it to be. If it was wprking ok, I would be inclined to drill and tap the disc about half way along the keyway slot and fit a grub screw in it to hold the key and the disc solid, and then work out if it needed adjustment to take up for wear which I would imagine would be minimal

Hi Norm and RLP,

I'm just wondering if the key itself has worn and simply requires replacement. Only a few thou of wear on the key will give a fair amount of play on the outer radius.

This is the same issue we have on the Model 45 Scotty's and simply replacing all the key steel and woodruff keys certainly tightens most of it up, but as Norm has suggested adding a locking grub screw into the mix should alleviate and prevent any left over play issues.

Cheers,
BB.

PS. In some cases rust can be your best friend but in the long run it ends up being your worst enemy.

Evening All,

One brake pad is fixed and the other actuated. Locking it with a grub screw would be my last option.

I think I can see wear on the key in the photo. Changing that would have to be a good start.

How often do you use the brake in anger? Most of the starting and stopping is done with the transmission. If there is only a small amount of play and serious use is occasional then is a small amount of play a problem?it looks like a big key. 1/4 inch square?

Cheers,

I often wonder how the hydraulic disc brake I fitted to one some years ago is standing up to the terrible conditions they are subjected to down under these mowers. If I did another one I would fit one of the cable operated push bike type, would have to be a lot easier

Hi Norm, BB and prd,

It was indeed rusted solid prior to removal, and it did work fine at that point. I think the brake disc flexes slightly when you apply the brake, so if it is seized close enough to the fixed pad, then it still works OK.

I would like to replace the key but it is 1/4" by 3/16" which seems to be a less common size.

I have another possible method for tightening up the key. It is snug in the keyway of the brake disc - just loose in the key seat on the shaft. So I'm inclined to use a retaining compound like Loctite 660 which I have, just to hold the key to the shaft. That would tighten it up but wouldn't prevent the disc sliding on top of the key.

I rarely use the brake, it's mostly just a safety device should the drive belt or chain break. So a small amount of play may not matter that much. I just don't want it loose and rattling around too much as I drive along.

On the other hand, since pad wear will be minimal and I think the disc flexes, locking it in place with the ability to loosen the grub screw and adjust when needed might be fine too!


Cheers,
RLP

Hi RLP,
as you say the disc will flex so all you need to do is set the disc just kissing the fixed pad and it will be fine