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The following questions and answers represent actual situations and are intended to help users of the Foundation Brake Analyzer to use the tool effectively. If you have followed the product's instructions and studied the following questions and answers, and still experience difficulty using the tool properly, please contact us at info@hubtechsystems.com. 

1. Reg from Saskatoon, Saskatchewan:
I have just done a brake job on a trailer. It has 16 1/2" brake drums with standard brake linings and standard S-cams. I checked the S-cam rotations on all of the wheel ends and have found that three wheel end rotations are 16 to 17 degrees and one is 35 degrees of S-cam travel. The gauge tells me that at 35 degrees the drum is worn out. What is happening? 

The 35 degrees of S-cam travel is an indication that there is a component that you have re-used that is not within minimum specifications. For example if you have re-used the S-cam. Did you check it for wear? It is critical that when you assemble a brake system that you are sure that all components are up to spec. Reg found that in this case the S-cam that he had re-used was out of spec so it was replaced.  

2. Peter from Estevan, Saskatchewan:
I have done an S-cam rotation on a 1997 Mack power unit. It is equipped with Q+ S-cam and Q+ linings. I have 60 degrees of S-cam rotation and 19/32 of brake lining left. The gauge tells me that 19/32 is 60 degrees of S-cam travel. So 60 degrees of total S-cam travel minus the 60 degrees of brake lining wear equals 0. Can this be right or what does this mean?  

When we see values where the remainder is 0, or a negative number. It is an indication that there is something prohibiting us from getting a total s-cam rotation. This could be a dirt buildup in the S-cam lands or something inside the brake drum that is wearing abnormally. In either case the brake drum must be removed and all components inspected. Peter removed the brake drum and found that the spider was bent. The linings were 19/32" when measured through the inspection holes, and on the inside edge of the brake linings they measured 1/32". The brake drum was also tapered.  

3. Terry from Calgary, Alberta:
I have just bought your foundation brake analyzer and have just done a test on a brand new trailer. The trailer has a Q+ assembly on the wheel ends and according to the tool I have 20 degrees of S-cam travel and a new lining. If you have 20 degrees of travel and a new 7/8" lining the drum is .047 thousands worn already. Is this right? 

What we have to consider is that when we use the tool we have to measure all the dimensions that we are inputting into the tool. The total degree of S-cam travel in this case sounds right although the lining thickness doesn't. The manufacturer of the brake lining tells us that they manufacture the Q+ lining to .850 thousands of an inch thickness from new. The 7/8" thickness that was used translates into .875 thousands of an inch. A measurement of the brake lining must be done and the values recalculated. Terry re-measured the brake lining thickness and found that he had 27/32 of lining thickness. So if we have a look at our foundation analyzers with the red discs in place. The total of 20 degrees of S-cam travel minus the value beside the 27/32 lining thickness, which is 6.7 degrees, the remainder of 13.3 degrees would reflect a more normal dimension.

4. Abe from Winnipeg, Manitoba:
The first time I tried to use the foundation brake analyzer, I went out to a unit that I had just completed a brake-job on and attempted to use the tool. I have followed the instructions and I have measured 18 degrees of total S-cam rotation and I measured 3/4" brake lining thickness. If I am correct, this tells me that my brake drum is .025 thousands of an inch oversized. I am struggling with this because I replaced the brake linings, the S-cam, the hardware kit and the brake drum was brand new. I checked the brake drum prior to re-assembly with my brake drum gauge and it was fine. Any suggestions?   

The dimensions that are given here are not abnormal. What we have to look at is a couple of issues. The first issues being that the manufacturers of brake drums build the brake drums to a specific tolerance from new. This specific tolerance I have not been able to nail down with the manufacturers yet, although I have measured several different brake drums made by different manufacturers and have found that the size of brake drum could range from 16.5" to 16.530" depending on the manufacturer. The second issue that must be considered is the type of brake drum gauge that we are using and how do we calibrate it. If we are using a new brake drum to calibrate our brake drum gauge, consider the possible size range of new brake drums. The practice of calibrating your brake drum gauge to a new drum could cause you a major problem. Abe was calibrating his brake drum gauge to a new brake drum. He calibrated his brake drum gauge to 16.5 inches and re-measured the drum. Abe found the brake drum to be .020 thousands of an inch oversized from new.


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