Brake lock up LXI

[al perna]

the other day our tag axle wheel locked up on us . prior to stopping the tire was hot enough to boil water when placed on it .

My question is how much damage has been done to the parts and what should be replaced ? upon wheel removal and visional inspection there appears to be no visual deformation or evidence of burning ? The tire did not explode and with repeated water baths along the remain 60 miles we arrived at Mark s & Ginger's . The wheel is removed and we are searching for a mobile mechanic here in Yuma . any advise is appreciated .

[davidbrady]

Hi Al,

T6 aluminum can begin to lose it's temper and strength at 400 deg F, pyrolysis of the tire rubber begins at around 475 deg F. Tire rubber will vulcanize at around 350 deg F. The trick is estimating how hot the tire got. Generally anything over 200 deg F is hot enough for tire damage. Aluminum and rubber don't like heat, your steel will fare better.

I had a similar situation with my LXi right after I bought it. The right side tag axle brake hung. I had mechanics replace the brakes, drums, rollers, etc several times, but the problem persisted. I finally fixed it myself by replacing the slack adjusters. Remember that brakes should be done in pairs, both sides of the axle at the same time, including slack adjusters. I believe you're running Crewson Brunner slack adjusters. I can get you a part number in a minute. Automatic slack adjusters are finicky, the installation has to be correct and the brand needs to be the same on both sides of the axles. Mechanics mess them up by adjusting them manually.

Al, during our WaGu rally I mentioned that your brakes consumed excessive air pressure. Sitting in your driver's seat I applied the brakes and the air pressure dropped greater than 12 psi which usually indicates out of adjustment slack adjusters. Did you have anything done to the brakes since then? Were there mechanics monkeying around with your SA's?

[RetDA]

Al, David:

This seemingly has been a very important discusstion among 'bird owners. While I am always conscious of brake safety, things can happen.

I make it a point when I am traveling to stop every 75-100 miles, visually inspect my tires and "shoot" each tire with my IR themometer. This discussion has led me to think that perhaps I need to not just shoot the crowns of my tires but the brake assemblies and axle end as well. It appears a few extra minutes could save some grief on down the road.

For us techno-challenged people, like myself, anything else to do while making these routine traveling stops?

[mpierce]

If you do not have a "gun", your hand works well. Just touch the tire, and the hub. Do them all. They will feel much alike. If you feel one much hotter than the others, need to look for a problem.

The tires on the sunny side will be a little warmer than those on the dark, even when running down the road.

[davidbrady]

Hi Tommy,

I wholeheartedly agree with Melvin and I think you have a good habit developed: an IR thermometer or a touch of the palm is indispensable for checking heat at tires, wheels, and hubs. I also got to know my coach's coasting abilities. Even with a toad connected, when on an almost imperceptible incline if I shift into neutral and let off the service brakes the coach will freely roll (forward or back). Once a day or so I do this to see if the coach is freewheeling the way I think it should. Another tip-off to issues is the use of a tire pressure monitoring system. If there's a hot tire you'll see an anomalous increase in pressure on that one tire; some TPMS have a built in temperature sensor. Also, we do want to periodically carry out the DOT air brake test to check for air leaks and brake safety. I learned somewhere along the way that a full application of the service brakes should cause only a small drop in tank pressure. With my LXi a full brake application dropped the gauge reading by 2.5psi. This is a sign of well adjusted automatic slack adjusters. If a single application drops more than 7 psi then the adjusters aren't adjusting. Malfunctioning automatic slack adjusters can also tighten up and cause brakes to drag. Been there, seen that!

In addition to checking temps you also want to inhale deeply for signs of unusual heat or burning odors, also visually scan around the entire sidewall of each tire to check for defects or damage, look for a starburst pattern of greasy oil streaking out from your tophats which might signify a hub fluid leak, listen for clicking and other sounds that might signify extreme heat expansion and contraction. Over time we all become familiar with the normal appearances, sounds, smells, and temperatures of our buses; nothing beats a periodic walk around with all five senses on alert for possible issues. (Okay, maybe we don't want to lick our buses, LOL)!

[al perna]

There is much to share and when able mark and I plan to put this together with Pics. Turns out the slack adjuster on the street side was the cause of the brake lock up . we were lucky as it was determined that only the brakes, slack adjuster, seal and Tire needed to be replaced . the brakes did not weld themselves to the drum and it was determined the drum was not damaged . as to the curb side the seal, adjuster and brakes were replaced .
It was brought to our attention that the slack adjusters have been improved , we will post and detail these findings on a future post . In the morning we plan to replace the front slack adjusters which are different from the Tag . This could be due to my tag being a steerable . Parts numbers will also be posted .

The bottom line here is this can happen to anyone no mater how often you walk around with your IR or back of your palm . the best cure would be to change out your SA with new ones. IMHO.

All mechanical work was done by a reputable and highly recommended shop . we will post contact info upon job completion .

[RetDA]

Thanks, y'all - a good and timely series of posts.......

David, I do all those things you suggest, except the "roll test", which I will start doing periodically. Also, I quit using the TPMS sometime back because the system I had seemed to "lie" from time to time. Get a warning, alarm sounds, pull over, remove the tire sensor, check the pressure, and nothing is wrong.

Maybe I need to find a new system, especially one where the sensors have a flow through valve.

Martha sometimes complains that my stops are too frequent and it takes too long to check the tires and brakes.

FYI, one of the first things I learned in flight training many years ago was to listen for odd and unusual sounds, especially during takeoff. A "funny sound" while climbing out could portend a major incident in the making.

[davidbrady]

Thanks for the report Al. Now that we have two documented cases of LXi tag axle slack adjuster failure resulting in dragging brakes and excessive heat its probably a good idea to add this to the list of "known" LXi issues. (There are probably more undocumented cases).

My failure occurred in 2005 when the coach was only 3 years old. I bought my coach and immediately drove from Florida to California and I fought tight brakes on my curbside tag axle the whole way. It was obvious the wheel assembly on that axle location ran hotter than all the others. When I returned to my garage and disassembled the brake assembly I could see that the SA was over-adjusting itself to the tight side. Al's failure appears to be more sudden and catastrophic.

Tommy, the air pressure loss test is a good one for testing slack adjuster functioning. Start the engine, build up full air pressure (let the air drier spit), shut down the engine, and apply full service brake pressure. The air pressure drop at the front/rear brake pressure gauge should be less than 7 psi. In my case, with my LXi, the pressure drop was considerably less, only 2.5 psi with each full application of the service brakes. Although this test may not identify a tight adjuster, the fact that you have loose adjusters is reason enough to pay them some attention.

[al perna]

David, the mechanic who is the owner states up to a 7 lb drop is acceptable 12 lb as was my case was not . he also stated the stock slack adjuster which is still available , is know to fail . a SA should last 150,000 miles . There is a zerk fitting and on mine it was filled, so maintenance was not the cause of the failure . we have switched over to the new design and have changes all on board . Mar plans to replace his SA prior to his Summer escape from Yuma trip .

[davidbrady]

(04-11-2014 10:42)al perna Wrote:  David, the mechanic who is the owner states up to a 7 lb drop is acceptable 12 lb as was my case was not.

Thanks for the correction Al. Is everyone listening???

Max brake air gauge pressure drop on full service brake application: 7 PSI

Al, I'm going to edit my post above to remove any confusion. Thanks for the update! Lucky for us, post editing on WaGu is allowed!