| Author |
Message |
James Robinson (Jjrbus) (209.26.169.76)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2001 - 9:49 pm: | |
The rear brake drums on my MCI5C have multiple small cracks across the braking surface, at what point do these drums become unserviceable, the bus had been well maintained with recent brake work, I would not have found this but had to pull drum to replace a couple stripped lugs.
work/play safely jim Robinson |
Mark Domeck (Prevost3406b) (64.12.104.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2001 - 10:17 pm: | |
As a bus/truck mechanic, I have learned that the drum cracks are ok as long as they do not exceed 1" and not very deep. The way to check for dangerous cracks is use a good pinpoint flashlight and look for wide or long cracks. Also check for heat stress. The drums will have blued areas if they are heat stressed. Also check for out of round by using an inside micrometer if you can find one available. Any machine shop has one. If you have any other ?'s, feel free to email me at FreightlinerDude@aol.com. |
lukebonagura (63.24.146.78)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2001 - 10:33 pm: | |
Hi Jim:
Small cracks across the face of your brake drums are not an indication of a problem. The nature of drums is such that surface cracks will begin to appear in any new drum in a short period of time depending upon who is driving and in what driving conditions.
More important than the surface cracks is how smooth the face of the drum is so that you have full brake lining to drum contact.
The life of the drum should be cast in its face, which will be indicated as a MAX - ID. Unlike cars and many trucks, bus drums can be cut on a drum lathe out to the MAX - ID, as indicated. The drums when new are 14 1/2" in diameter. They can be cut out in 1/8" increments, up to the MAX-Id as indicated. When this is done, over-sized brake lining is installed which is also available new in 1/8" increments.
In our shop we always turn drums on our brake lathe so that when a brake job is done, the customer has full contact between the lining & the drum, which provides maximum brake force for stopping.
You didn't ask all this, but I know many others read this Board and just wanted to provide what input I could for the benefit of all!!!!
If your lining is smooth and your drum face is smooth and the wear line still shows on the inside of your shoes, then you are good to run. Remember that your drums were 14 1/2" diameter when new and your lining would have been 3/4" thick when new.
The wear mark which is an indication of (time to replace) is approx. 5/16" of lining left.
I hope this HELPS!!!!
LUKE@USCOACH |
Steve Fessenden (63.27.88.152)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 21, 2001 - 9:18 pm: | |
For a GMC 4905 I was told that the wear lines are meant to show through a site hole in the drum and the linings can be worn out with lining still showing beyond the wear line when looking at the shoes directly. Had a camover with that exact situation. The wear lines were below the window. (Luke or Mark please verify this or ask Ian to strike it if not true.)
Cardinal Bus Lines, Indiana showed me that on the Prevost you can wear them to the wear lines.
My Prevost has heat checked brake drums which were said to be fine. |
Luke Bonagura (Lukeatuscoach) (63.24.146.23)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 27, 2001 - 9:20 pm: | |
Hi Steve:
I tried to answer you last week but could not post. Ian now has it fixed ( a computer deal I Guess??).
I like to get right back to folks where safety issues are involved.
The info. Mark & I gave to you is correct.
The info. Cardinal Bus gave you is corect, however, it makes one assumption!!!
And that is that whoever did the last brake job for you matched the lining to the inside ID of the drum!!!
If not, you could look at the wear mark and see that you have plenty of lining above it and then cam-over and wonder what happened!!!! Perhaps that is the situation you had with your 4905.
If brake work on a coach is performed by a truck shop, in general they will not be aware of our ability to cut drums!!! Why!! Because in general on larger trucks, their drums are thinner on Day #1 and oversized lining is not available.
Best bet for brake work on a COACH is to have it performed by a BUS shop, or at least be informed of this topic if you are dealing with a truck shop and so advise them. You might get some feed-back, but stand your ground!!!!!
I hope this helps!!!!
LUKE @ US COACH |
James Robinson (Jjrbus) (209.26.169.227)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 28, 2001 - 9:56 pm: | |
How would us non bus mechanic types tell if the brake shoes were not matched to the drum? MY bus appears to havve been very well maintained by gray lines in Washington, The brake shoes are almost 3/4 in and the drums appear to have been turned, but how could I tell if I had the wrong shoes? I tried to send you a thank you but it came back as undeliverable so THANKS.
Work Play safely Jim |
Luke Bonagura (Lukeatuscoach) (63.23.242.246)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 29, 2001 - 8:05 pm: | |
Hi Jim:
Thanks for your Thanks!!!!
If you had hit on my name at the beginning of the post you would have reached me. I just did it with a TEST MESSAGE & it came back to me
Out of resepct for Ian's rules I do not post a phone number or E-Mail address when I answer on his Boards.
Now to your question.
This answer makes the assumption that you or whoever else reads this has the availability of a pit or can otherwise safely be under thier bus to do the following!!!!!
(And for those reading who do not know what I am talking about, it is absolutely unsafe to crawl under a bus equipped with air suspension unless it is over a pit, or the wheels are up on ramps so that if something occurs in the air-suspension system that causes the bus to drop, you are not pinned to the ground, OR WORSE!!!!)
JUST TO REINFORCE THIS STATEMENT:
Back in the 60's I had a mechanic from my employers shop go out on a breakdown (non-suspension related) and he slid under the bus on a creaper. While under there a bellow let go and the bus came down right across his chest. Fortunately it was a hot summer day and the wheels of the creeper dug into the pavement and he survived, although out of work for some time.
And after the City of Philadelphia fire rescue came out and jacked the bus off of him!!!! In another instance, a very dear friend who owned a small bus company had his son (who had survived front line action in Viet Nam) changing radius rod bushings on the payment at his garage. The bus shifted, fell off the jacks (because the body was not supported properly) and his son went to his MAKER!!!!
I just can't emphasize enough to all who read this & other Boards how important it is to recognize that if you are not equipped to work under these buses, then don't!!!!!
Jim: I just had to pass along the above info.
Now again to your question:
The easiest way to tell, without pulling the drums and measuring them, which we do with a Drum Micrometer, is to go under the bus (READ THE ABOVE!!!), have someone apply the brakes and look at how far up the S-CAM the roller is riding. If it is riding close to the top (thinnest point) then the possibility exists that it will cam over as your brake lining wears. That tells you that although your have 3/4" lining, the drums are over-sized in realtionship to the thickness of the linings.
Now none of this may make sense to you unless you have seen the moving parts of your brake system or unless you have DA BOOK (as Fast Fred) says.
As I have said on another Board LET'S THINK ABOUT SAFETY.
BRAKES & STEERING work is best left to a professional or if you are going to do it yourself to have the advise of or better yet a professional with you who understands the system, when you do the work. I know the budget is a major factor for most as it is for me in my business and personal life. In the areas of safety, if the cost of a proper repair in the areas of steering & brakes is not in the budget then I suggest that the vehicle be PARKED!!!! until the funds are available to perform "FIRST CLASS REPAIR"
Don't mean to offend as I do not not know what you are capable of, mechanically!!!!!
I hope this HELPS!!!!
LUKE at US COACH |
steve Fessenden (63.25.54.13)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 01, 2001 - 12:27 am: | |
When you sell a bus, you can put in CAPITAL LETTERS in a bill of sale a warning about not going under the bus without blocking it up. I did that when I sold the 4905 and I left wood blocks with the bus.
I never sell a vehicle without getting the buyer to sign a bill of sale copy for me. Some jokers wait forever to change the title and I don't want some lawyer claiming I still owned it when an accident occurred.
A GOOD SOURCE FOR WOOD BLOCKS IS A SPECIALTY LUMBER COMPANY THAT MAKES LARGE WOOD BEAMS SUCH AS EXPOSED LAMINATED BEAMS FOR CHURCHES. THEY MAY HAVE CUT OFFS THAT ARE GREAT BLOCKS IN THE 6" x 8" x 18" size range. Companies that make semi trailer floors may have cut offs too.
Steve Fessenden |
Steve Fessenden (63.25.54.13)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 01, 2001 - 12:33 am: | |
The drum that had the camover was a new standard size drum. The (1980) 4905 has a window that the groove shows up in if there is usable lining left. If you look directly at the lining you may be fooled into thinking you have lining left because the maximum wear point is above the groove. Thats what the mechanic told me, and it sure cammed over with more than 1/8" of lining above the groove and standard, unturned drums.
Steve Fessenden |
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