SM brakes grabby

FarmerSid · Jun 13, 2011

Having a problem with a Super M and one brake grabbing and jerking the tractor when the brake is applied. I have both sides apart and the grabby side is missing a spring. I have another but is a bit smaller. Would this be the problem or are they out of adjustment? Can I sand blast the housing and the disks that hold the 5 balls in place? Rusty but not too bad. I don"t think the amount of rust in there would cause this but you never know.

Wardner · Jun 13, 2011

I had the same problem on a SMTA many years ago. I would have to back up to release it. I think I only sandblasted the expanding discs and drum. May have replaced the fiber discs. The spring is available from OEM Tractor Parts and others.

FarmerSid · Jun 13, 2011

The disks are in great shape with lots of life left. They were changed some years ago but the tractor hardly gets used. The brake instantly releases when you take your foot of the pedal. Even when you tap the pedal lightly, it grabs and yanks the tractor.

sflem849 · Jun 13, 2011

I test drove a SM like that. I put the tractor in fifth and HAMMERED on the brakes and it fixed it right there. The guy said that is how he usually dealt with it and it worked!

Are the brakes oily? Not sure how oily brakes will work, but an oily clutch grabs REALLY hard, instantly.

FarmerSid · Jun 13, 2011

Everything is nice and dry inside. Slightly rusty but the balls should move freely. Not enough to cause them to jam.

Ludwig · Jun 13, 2011

Sounds like the spring to me, they're still available new. I got mine from the MPG dealership in Presque Isle, Maine, took my '52 Super M from having zero brakes to being real decent.

1468 Chris · Jun 13, 2011

Just went through all of this with my super M. But with all the power your making im surprised that the brakes will hold it. The balls and the actuators have to be spotless, i don't think that i would sandblast the actuator, Makes sure that there is no lip in the ramps on the actuator for that will cause the balls to bind, don't ask me how i know. I really shouldn't be giving my compition any tips! haha

Janicholson · Jun 13, 2011

They are servo brakes, meaning they self apply when the expander opens one of them is held, and the other spins in the direction of the disk (CCW going forward) this wedges the balls farther up the ramps assisting the operator (in this case way too much)
I would wear on them some get the grabby brake hot (not glowing) and do it again after cooling. I also recommend getting the ramps very smooth, if they have any dips or worn spots in them, it will be lockup city. Jim

FarmerSid · Jun 14, 2011

(quoted from post at 18:37:19 06/13/11) Just went through all of this with my super M. But with all the power your making im surprised that the brakes will hold it. The balls and the actuators have to be spotless, i don't think that i would sandblast the actuator, Makes sure that there is no lip in the ramps on the actuator for that will cause the balls to bind, don't ask me how i know. I really shouldn't be giving my compition any tips! haha

Hey Chris! How's things? Having fun getting seed in the ground? I can't remember filling silo and planting corn at the same time. Anyway's, the spring you gave me some time ago is a little smaller than the one's I already have. Do you have anymore springs by chance? Same length but wire size is a little smaller. Maybe I will wire wheel them instead of blasting them.

mkirsch · Jun 14, 2011

Um.... MISSING SPRING!

This is one of those hit-yourself-in-the-shin-with-a-hammer-and-wonder-why-it-hurts moments...

Fix it...and it's got to be the right spring, not just "a" spring. Clean everything up, NO LUBE.

If it still grabs, replace the disks. I don't care how new they are, replace them.

SM brakes grabby

FarmerSid

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Wardner

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FarmerSid

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sflem849

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FarmerSid

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Ludwig

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1468 Chris

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Janicholson

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FarmerSid

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mkirsch

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