Slack adjuster check

The other thing to check is the angle between the push rod and the slack adjuster when the brake is applied. It should be a ninety degree angle. Worn bushings, "s" cam, shoes, or wrong length of rod on a replacement chamber could result in something other than a ninety degree angle. In that case, part of the application force will not go to the shoes because it is effectively applied against the bushings rather than rotating the "s" cam. Of course, in a worst case situation, the "s" cam has rolled over and will not move the shoes at all.

 

The proper way to check brake adjustment (as you are asking in your question) on equipment manufactured after 1995 is to look at the brake adjustment indicator. This is usually a strip of paint on the brake chamber pushrod (usually dark red or dark blue). If you can see the colored strip on the pushrod in it's entirety with the brakes set the brakes are out of adjustment. If you can't see it, or just see a little of it the brakes are still legally in adjustment.

And with the self adjusting brakes you don't need to back up to adjust them. All you need to do is allow the air pressure to go to maximum pressure on the gauge, then release the brakes (push both buttons in), and pump the brakes hard. Then set the brakes & check the pushrod again. If you still see the indicator they're still out of adjustment & you need to repeat the cycle. If they're still out of adjustment then the self adjusters are broken & you should call the company to see how they wish to correct the problem. Self adjusters quit working predominantly so due to lack of maintenance (they need lots of grease in the grease zert).

Self adjusters can go out of adjustment primarily because of the way they're used. There must be a certain pressure application in order for the self adjusters to work.

From a retired federal DOT official.

 

Auto slack adjusters arn't suppose to be adjusted. If they fail and are out of adjustment they probably need to be replaced.

If you adjust a auto. adjuster you could be giving yourself the illusion that the problem is solved. It could and probably will go out of adjustment faster again, and there could be more problems.

There could be a worn out S cam bushing, broken spring, cracked drum.... Get the truck (or trailer) in a good shop and have it gone through..

 

The play is dependent on the type of brake chamber. You are correct with a clamp-type C-30 chamber though. The C-30 brake chamber is used more often than not however some companies that travel the mountains exclusively sometimes use C-16's & C-12's. But other size chambers have different allowances for the "play". Your J.J. Keller (green & white book issued by the carrier) will show you the limits for all brakes in the rear of the book.

The chamber type is stamped on the brake chamber.

 

Yes auto slack adjuster aren't supposed to be adjusted by anyone if they fail to adjust themselves replace them.

I just had to do this to one of my trucks due to them not adjusting themselves.

 

The best way is to have a mechanic check them . Unless you are certified you're not allowed to adjust them

Good read here on reasons why automatic slack adjusters could be out of adjustment . http://74.125.47.132/search?q=cache...ed+slack+adjustment&hl=en&ct=clnk&cd=14&gl=us

 

I wouldnt be suprised if i was taught wrong or taught stuff from ages ago...

 

Rickg is right you need a ticket to adjust brakes (I have one) the proper way to adjust the autos is to pump the brakes while stopped at least 12 times you can't do this at one time 2/4 times than wait for the air to build I usually do it in towns or cities where there is a string of lights when I stop at a red I pump 3/4 times and go on to the next light and repeat don't worry they wont over adjust the ratchet will only "click" when it goes over the adjust point. The 90 degree tip is pretty safe when brakes applied 90 degrees between adjuster and rod and as for free play pretty sure it's 1/2'' the dot will get you to press the brake and hold it while they measure travel pretty sure thats 2". Other posters are right about manually adjusting autos you shouldnt need to but you still need to check them. What I do (may not be the best way) is tighten the adjuster all the way and back off 1/2 turn (manual adjusters) you can do this with some autos there is a tab you need to pull out befor backing off this releases the ratchet. Please pardon the long winded post but this is one area that even I don't frig with and not because of the rules

 

The rule to which you refer is 396.19. The title of that rule is "Inspector Qualifications. This rule has nothing to do with brake adjustment, but rather complete/annual inspections. Clearly in the first sentence it tells you this because the first sentence tells you the rule is related to annual inspections and does not even mention brake adjustment. After all, the title of the rule is not "adjuster qualifications". It is the requirements for an inspector who performs annual inspections. This person is usually also the person that repairs the brakes. If it were illegal for a driver to adjust brakes then how could a driver use self adjusters? There is no exception in 396.19 for self adjusters. That rule has been in effect since 1972 (memory serve). If your theory is/was correct, then how could drivers prior to July, 1994 (when self adjusters became mandatory) manually adjust their brakes?

It's too bad that some of these idiot state inspectors don't understand that. These state inspectors need to take a better look at the title of the rule, and to what the rule refers, because the title relates to what that rule is about and nowhere in that rule does it mention brake adjustment. But these idiots use this rule to tell a driver that he/she can't adjust brakes.

And your statement is incorrect Re. pumping the brakes. So long as you have minimum brake pressure (before the safety valve cuts in & sets the brakes), and can apply at least 30# pressure (the pressure at which the safety valve kicks in & sets the brakes, memory serve), there is enough air pressure to adjust self adjusters. You should look at the NHTSA (National Highway Traffic Safety Administration) rules that tell exactly how self adjusters are made & work. NHTSA is the USDOT entity that determines how all items on a commercial vehicle work.


Sec. 396.19 Inspector qualifications. (a) It shall be the motor carrier's responsibility to ensure that the individual(s) performing an annual inspection under Sec. 396.17 (d) or (e) is qualified as follows: (1) Understands the inspection criteria set forth in 49 CFR part 393 and appendix G of this subchapter and can identify defective components; (2) Is knowledgeable of and has mastered the methods, procedures, tools and equipment used when performing an inspection; and (3) Is capable of performing an inspection by reason of experience, training, or both as follows: (i) Successfully completed a State or Federal-sponsored training program or has a certificate from a State or Canadian Province which qualifies the person to perform commercial motor vehicle safety inspections, or (ii) Have a combination of training and/or experience totaling at least 1 year. Such training and/or experience may consist of: (A) Participation in a truck manufacturer-sponsored training program or similar commercial training program designed to train students in truck operation and maintenance; (B) Experience as a mechanic or inspector in a motor carrier maintenance program; [[Page 474]] (C) Experience as a mechanic or inspector in truck maintenance at a commercial garage, fleet leasing company, or similar facility; or (D) Experience as a commercial vehicle inspector for a State, Provincial or Federal Government. (b) Evidence of that individual's qualifications under this section shall be retained by the motor carrier for the period during which that individual is performing annual motor vehicle inspections for the motor carrier, and for one year thereafter. However, motor carriers do not have to maintain documentation of inspector qualifications for those inspections performed either as part of a State periodic inspection program or at the roadside as part of a random roadside inspection program.