Tag axle grease fitting

[MyPrevost]

1995 Liberty:

I wanted to share a recent discovery while working on the tag axle brake assembly. This picture shows a grease fitting that I found on the brake assembly of the right tag axle. Initially, we had an issue where the left tag axle brake wouldn’t release. While troubleshooting, I noticed that both the left and right sides were missing a zerk fitting, despite the fact that both steer axles had one. This lubrication point hadn’t been serviced in about 13 years, even with documented service from Prevost and various dealerships.

After installing the zerk fitting, we gave it a light shot of grease. A discussion with one of the knowledgeable members on the board confirmed that only a small amount of grease should be applied to avoid over-lubrication.

This experience brings me to a favorite theme of mine: many of us work on our coaches ourselves, some do a bit, and others prefer to leave it all to professionals. In my opinion, “enlightened amateurs” often deliver better work than professionals, whose primary concern can sometimes be the bottom line. While there’s nothing wrong with that, the enlightened amateur focuses on quality and getting things done right.

A big thank you to Jon for his assistance with this issue! And yes, I’ll be getting under there this afternoon to polish the slack adjuster.

[MyPrevost]

A1 Jon:

Looks like Jim Scoggins is at it again, posting some “dirty” pictures on the board—he claims you made him do it!

Well done, Jim! This is exactly the difference between an owner-operator and a service professional. We’re the ones driving these machines, with our families on board, so our attention to detail comes from personal investment. When it’s your own bus, there’s a whole other level of care and thoroughness. Professionals, while skilled, don’t face the same consequences if something goes wrong on the road.

Roger that!

2008 Liberty DS XL2
2023 Denali Ultimate
My 6th Prevost

[MyPrevost]

OK.

If this keeps up, with all the tattling going on, everyone’s going to have to turn off their computers and head straight to their rooms—no bus talk for you!

Good grief.

[MyPrevost]

Great advice on the S-Cam bushing maintenance! Properly maintaining these components is essential for keeping the braking system functioning well and reducing long-term repair costs. Your suggestion about greasing while the drum and shoes are off to check for any seal issues is spot on. Ensuring that excess grease isn’t contaminating the brake shoes is critical for safety and performance.

Limiting grease to 3 or 4 squirts, unless the seal is confirmed good, is a smart rule of thumb. It’s true that keeping the S-Cam bushings properly lubed can extend their lifespan significantly, making future brake work easier and less expensive.

Cleaning off grease fittings before servicing and washing away excess grease afterward is a good habit to minimize contamination and keep the undercarriage much cleaner. Doing this helps prevent dirt buildup, which can lead to wear over time. Your approach to preventive maintenance is thorough and practical—definitely the way to go for anyone looking to keep their coach in top shape!

[MyPrevost]

When I adjusted my brakes, I tightened the adjuster until the shoes made contact with the drum, then backed it off until there was no rubbing. Is that the correct method?

I also read Jon’s advice, which suggested backing off by a 1/3 or 1/4 turn after tightening, but when I did that, the shoes were still rubbing against the drum.

[MyPrevost]

Jon was right. While it’s important not to over-tighten, a slightly tighter adjustment is better than too loose.

After you’ve made the adjustment, check the slack by grabbing the slack adjuster and pulling on it. If it’s difficult to grab, you can use a vise grip to help. The adjuster should travel between 1 inch and no more than 2 inches. If the brake shoes lightly scrape the drum, that’s fine. What you’re aiming for is around 1 inch of slack at the adjuster.

[MyPrevost]

Since the S-Cam grease fitting is linked to the brakes and likely experiences higher temperatures than other chassis components, should a specialized grease (such as high-temperature, low-bleed grease) be used for these fittings?
Jim

[MyPrevost]

Joe, I will check the travel, thanks!

[MyPrevost]

Dale,

When I backed off by 1/3 or 1/4 turn, I didn’t hear any dragging; that was all it took to release them completely. If you’re experiencing dragging, check for an out-of-round condition. When the brakes are fully engaged, the slack adjuster arm should be positioned at a 90-degree angle to the brake push rod, or just slightly past it. This recommendation pertains more to the clevis adjustment on the end of the rod than the slack adjuster itself, as it optimizes the mechanical advantage for the brakes.

Joe,

I agree that if you’re working alone, you can check the slack adjuster arm’s movement. However, having someone apply the service brakes while you check the emergency brake provides a clearer idea of travel since you’re working against the shoe return springs and the brake chamber return spring.

For disc brakes, there isn’t an “S” cam. Instead, the slack adjuster moves a screw to push the piston against the brake pads. Over-greasing this area could prevent the piston from returning, causing the pads to drag.

Jim,

It’s unlikely that the “S” cam shaft or caliper piston shaft will reach temperatures requiring high-temperature grease. In fact, high-temp grease isn’t even specified for U-joints or drive shaft splines.

[MyPrevost]

Dale, if you’re using manual adjusters and have replaced all the shoes, be prepared to make another adjustment soon. As the shoes settle into the drums, they can loosen up quite a bit—sometimes significantly. Depending on your driving habits, you might want to check again after about 100 miles.

The initial 1/4 turn from tight serves as the static adjustment. Checking the actual slack at the adjuster helps you determine how loose or tight each hub is, so aim to make them all equal. One hub might need a 1/3 turn to reach the same slack as another that only requires a 1/4 turn.

Sometimes, there’s an extra hole at the pointy end of the slack adjuster. You can insert a bolt with two nuts in that hole, making it easier to grab and pull for slack checks.

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