When To Replace Liners?

[FlatHead]

Hello, hopefully this is an easy question for someone.

A couple of years back i replaced my liners because the DOT inspector told me they were almost on the rivets. Today they look fine to me but i also thought they looked fine back when he said replace them. Obviously you can't see the rivets and i'm unsure of how long the rivets are, so is there a measurement i can use to know when to replace them again? I'm unsure on the brand of shoes but i'd guess Bendix. The truck is a 1999 CH Fleetliner.

Thanks, Lee.

[other dog]

This reminded me of a great idea I saw once. I bobtailed to Alta,Fl. years ago to pick up a stretch trailer. When I got to the trucking co.'s yard that sold the trailer they were showing me around and one of the things they did was drill a little hole with about a 1/8 bit into the side of all their new brake linings just above the head of the rivets.

When a truck or trailer came through the shop it was easy to tell if they needed replacing.If the linings were worn down to the edge of the hole they'd put new ones on,no looking and saying "well,they'll probably go another trip or two".

[Underdog]

Many new brake linings now include a wear indicator groove molded in, much like that idea of drilling the hole, Tom. Most I have seen indicate 1/4" remaining thickness. At the roadside, it depends on the officer's judgement and mood at the time. Drum wear can also hide some of the visible lining thickness. I carry my own creeper on the road, so I am always willing to assist the officer in checking under my truck. Don't take their word for it, keeps 'em honest.

Gregg

[fjh]

Many new brake linings now include a wear indicator groove molded in, much like that idea of drilling the hole, Tom. Most I have seen indicate 1/4" remaining thickness. At the roadside, it depends on the officer's judgement and mood at the time. Drum wear can also hide some of the visible lining thickness. I carry my own creeper on the road, so I am always willing to assist the officer in checking under my truck. Don't take their word for it, keeps 'em honest.

Gregg

The best gauge of worn out ling and drums is a cam rotation !Back the brake off till the slack pulls away from the brake pot.mark the cam and turn the slack back till ith shoes are tight to the drum if the rotation goes past 90 degress of rotaion the lining is border line but still OK If the rotaion aprotches 120 deg of rotaion the lining and possibly the drum are done!Time to replace! Anything after 120 is pushing a cam over situation!

[Underdog]

The best gauge of worn out ling and drums is a cam rotation !Back the brake off till the slack pulls away from the brake pot.mark the cam and turn the slack back till ith shoes are tight to the drum if the rotation goes past 90 degress of rotaion the lining is border line but still OK If the rotaion aprotches 120 deg of rotaion the lining and possibly the drum are done!Time to replace! Anything after 120 is pushing a cam over situation!

Agreed, a good indicator of lining and drum wear. The problem nowadays is that many automatic slack adjusters can be ruined by repeatedly backing them off. Auto slacks are "set them and forget them" and should only be manually adjusted when lining is replaced.

Gregg

[other dog]

Agreed, a good indicator of lining and drum wear. The problem nowadays is that many automatic slack adjusters can be ruined by repeatedly backing them off. Auto slacks are "set them and forget them" and should only be manually adjusted when lining is replaced.

Gregg

A DOT man told us that if you adjust automatic slack adjustors manually they will lose the ability to adjust automatically.

[Underdog]

A DOT man told us that if you adjust automatic slack adjustors manually they will lose the ability to adjust automatically.

You are correct, Sir.

If your auto slacks need constant adjustment, they are either not functioning or they were not set up correctly when installed. Don't assume it was done correctly at the factory, either.

Another tip for maintenance of slacks and cams. Release the parking brakes on the axles you are greasing. Brake mechanical parts will take grease better, therefore last longer.

Gregg

[HK Trucking]

Worn brake camshafts & camshaft bushings can also prevent auto slack adjusters from working correctly.

[other dog]

truck drivers used to carry a 9/16 wrench and a hammer to set the brakes up with, if that was all the tools they did carry.

Whenever i'd go across rt. 60 from Charleston i'd always pull in the church parking lot at Boomer and set the brakes up before I went across Hawk's Nest, whether they needed it or not. This was before jake brakes were invented of course.

[Underdog]

truck drivers used to carry a 9/16 wrench and a hammer to set the brakes up with, if that was all the tools they did carry.

Whenever i'd go across rt. 60 from Charleston i'd always pull in the church parking lot at Boomer and set the brakes up before I went across Hawk's Nest, whether they needed it or not. This was before jake brakes were invented of course.

There aren't many guys out on the road anymore that would think to crawl under the truck, much less carry tools. I love the crazy looks and comments I get at the truckstop when I get out the coveralls, creeper and grease gun. Or better yet, "OMFG, he's changing his own tire!" I still consider it part of the job if you own a truck.

Gregg

[theakerstwo]

You are correct, Sir.

If your auto slacks need constant adjustment, they are either not functioning or they were not set up correctly when installed. Don't assume it was done correctly at the factory, either.

Another tip for maintenance of slacks and cams. Release the parking brakes on the axles you are greasing. Brake mechanical parts will take grease better, therefore last longer.

Gregg

I know your right.

[theakerstwo]

Worn brake camshafts & camshaft bushings can also prevent auto slack adjusters from working correctly.

Your right to.