OC4 poor steering performance

[bcgofo]

I’ve got a 1201A with the oc4. New pads from spryte improvement, to4 spec oil.

When cold wet brakes function well enough. Wants rear end warms up, less than a mile, steering performance tanks severely, to the point I have to reverse to make a turn. They become soft and squishy to the point they don’t even bite. Performance is maintained in reverse for some reason. Once it cools, basically back to normal.

The rearend is not over heating and I am pulsing brakes like you’re supposed to

My thoughts are it’s gotta be the oil. From those more experienced with tearing these oc4 s apart, what else could it be?

 

[redsqwrl]

Im putting my $.02 you have your bands *internally* adjusted too tight.

 

[bcgofo]

Tried backing off the bands via exterior adjustment. No change. Works well enough cold but quickly becomes squishy after 1/2 mi to the point they are useless.

I’ve got to head back down the hill but will consider pulling cover when I get back

 

[redsqwrl]

if they are internally too tight I am not sure the outside matters. but yes a quick peek is in order

 

[zspryte]

Might the same be said if they are internally too lose?

When peeking inside see if the bands fully conform to the drum. Relined brake bands are hard to get tight enough initially. Once used for a while and the band conforms to the drum, they become easier to (internally) tighten.

When the brakes at applied going forward, the friction between the brake lining and drum decreases the tension in the brake band and in reverse it increases it (might have the forward & reverse swapped). Speculation here - if the bands are too loose maybe when the oil is cold its viscous enough for the lining to grip the drum when going forward and brake but not after it warms. Since the band tension increases when braking in reverse, the oil viscosity may not matter much.

When you figure this one out please post what you discovered.

 

[bcgofo]

Ok, couple thing’s after talking with Pat a bit at spryte improvement:

-not a common problem to have after installing new brake bands
-any t04 oil should be just fine as far as no problematic additives
-really difficult to over tighten internal adjustment
-should notice slight amount of play on external adjustment by hand before band firms up
-check external threaded rods for signs of bending. This is indication of improperly adjusted bands
-check master cylinder. Should bubble/squirt brake fluid up from reservoir when handles pulled gently
-when handle brake controls are FULLY released, should be small amount of play about master cylinder piston indicating full piston extension
-brake handles should tighten up at about 50% pull
-some after market master cylinders have a stop that won’t allow lever to be pulled back all the way
-many of these vehicles steer better in reverse, not sure why
-brake bands will expand slightly when warm
-most dramatic improvement he ever saw with braking was with 10 weight oil. Not recommended of course due to lack of protection for other internal components

My brake handles hit my wiper motor when fully released so I’ll have to make sure this isn’t the source of the problem. Also my problem isn’t necessarily with the masters (I believe they are original) internally as left and right braking are affected equally.

 

[redsqwrl]

I have had a situation after changing bands with a delay in turning, I pull back to a firm pull on stick, and the rig doesnt respond right away. I wrote it off as new shoes need to break in. I guess I will pay more attention. I have two imps to compare and the rear ends charicteristics follow the diff, What this means is diff A went into machine B and the turning experience was same with new/ different masters ( I had swapped rear diffs ahead of an outing) I use a shell 50 w aeroshell product.

 

[bcgofo]

Ok, I had a chance to go through the machine this week. Here’s what I found:

-cylinders are working perfectly and bled to perfection
-confirmed no gl additives in oil
-no apparent interference from levers contacting dash
-oil level in diff was good however one side drop box had excess. Pat said this isn’t uncommon and has seen a Dropbox fill to top without consequence provided the oil level in the diff is maintained
-pulled cover and the new bands had loosened a bit after break in. I was able to tighten each side another 3/8”
- drums are scored but not particularly worn when compared to portion that doesn’t contact pads
- pads still look new

Refilled with 10-30w for now, tightened external brake adjustment and took for a spin.

I had a modest improvement in cold braking but condition of soft brakes returned after 3/4mi of driving. Rearend was too hot to keep a hand on it for more than a few seconds. I noticed that the problem seemed to worse in harder snow conditions.

Turns out a big part of my problem was modifications I made to my groomer setup. I added a cutting implement to my packer bar this year. I don’t have a pivot steer setup. The teeth on the cutter work like an anchor when trying to turn. When elevated problem resolved. Which is why in soft snow I had less of a problem. Glad it was simple solution but surprised it wasn’t immediately obvious to me.

Cutters work well in a straight line with very little resistance. Will have to adapt how I operate in these conditions and likely modify my setup for next year.

Thanks guys for chiming in