How to Determine Air Brake Adjustment-Applied-Pry Bar-Mark & Measure

For both a road test & your daily pre-trip inspection you must determine if the air brakes are in adjustment. Watch the video! CDL IN-CAB Air Brake CHECKLIST: www.smartdrivetest.com/cdl-ai... SUBSCRIBE TODAY! ► / smartdrivetest
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Depending on where you're taking your CDL licence, you are required to check air brake adjustment. Either the pry bar or the applied stroke method will be required. Most jurisdictions use the pry bar method to determine if the air brakes are in adjustment.
Safety first: chock the wheels, release the parking brakes and ensure that the system air pressure is above 90 psi (620 kPa).
If using the pry bar method, you'll require a pry bar. Using a pry par, force the push rod out of the brake chamber. The push rod should not extend out of the brake chamber more than 3/4 of an inch, or the width of your thumbnail. In New York & the state of California, they allow 1" inch of travel using the pry bar method.
Other jurisdictions, such as Ontario in Canada, require that license examinees use the applied stroke method. Again, chock the wheels, release the parking brakes and ensure the system air pressure is above 90 psi.
Mark all the push rods at a fixed point - usually the face of the brake chamber. Apply the service brakes and hold - either get someone to hold the service brakes in the applied position or use a stick, or other device. After applying the service brakes, measure from the fixed point out to the mark on the push rod to determine if the air brakes are in adjustment.
With automatic slack adjusters on a Type 30 brake chamber--which are the most common--you are allow 2" of push road travel. In the rare case that you have manual slack adjusters, the push rod is allowed to extend out of the brake chamber 1 3/4" inches.
The amount the push rod is allowed to extend out of the brake chamber is determined by brake chamber size, and the size of the brake chamber is determined by its diameter.
If the brakes are out of adjustment, and the vehicle is equipped with automatic slack adjusters, you can attempt a "6-pack" to bring the brakes back into adjustment. Pump the system to maximum pressure, make 3 full, hard brake applications. Pump the system's air pressure back to maximum and make 3 more full, hard brake applications. Often this will bring the brakes back into adjustment. If not, the vehicle will have to be brought to a mechanic for repair.
Good luck on your road test!
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[@Mr222226]

If you do pry bar it's 3/4 in and if you do applied method it's 1. 3/4 in.?

[@smartdrivetest]

Yes - 1 3/4" inch on a Type 30 brake chamber fitted with a manual slack adjuster. Almost all slack adjusters in this day-and-age are going to be automatic, so it's 2" inches using the applied stroke method. See this chart for more info: www.smartdrivetest.com/cdl-air-brakes/chart-of-adjustment-limits Drop us a note if we can help further. Cheers Rick

[@edenfieldjared0]

@@smartdrivetest thanks for replying to his message. So I have no one to help me to perform applied stroke but thats what the dot does here, Sto see what they see on applied stroke with free stroke please give me the correlation. Two inches applied stroke equals how much free stroke? Lastly please give me the relationship or formula to compare applied and free stroke on my type 24 steer chambers. Please sir and thanks!!:)

[@smartdrivetest]

Cut a bit of board and jam it between the seat and the brake pedal. That’ll work. Find out if your state requires applied or free stroke my friend. Cheers Rick

[@frankyholguin3838]

@@smartdrivetest I’m confused in California can you do the applied pressure method to check if brakes are out of adjustment? And it’s no more than 2 inches?

[@rodan2852]

I'm training as a class8 tech and this video taught me more than my trainer did. Thank you for clear and comprehensible information that will allow me to do my job properly.

[@smartdrivetest]

Hi Rodan - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@franklinclinton8092]

Thank you , You might save some lives with this video. At the very least it will save me a bad DOT inspection. I got my CDL in Ohio. We were only required to know the tolerances, not demonstrate it. My schooling ( Clark State) also didn't teach it. The six pack thing wasn't even taught ! I will use this knowledge from now on. Thanks again from a newbie.

[@tonygalicia5906]

Taking a test to be a driver trainer (diesel bear)……you are the one that had the best answer,,, great to know you are teaching the right stuff. Guys follow this gentleman….

[@smartdrivetest]

Hi Tony Galicia - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@MrRavindersidhu]

Do it everyday in pre trip inspection. 4 hard brakes with pause before leaving. Never ever a problem.

[@smartdrivetest]

Hi Ravinder Sidhu - Thank you for your comment. And you're checking pushrod travel ensureing all the components are working and note damaged. All the best, Cheers Rick

[@NCC2087]

Rookie here. Thank you so much. Great video.

[@smartdrivetest]

Hi NCC2087 - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@kentkirkpatrick7953]

My truck is as old as this guy is, so it has manual slack adjusters all around. Nearly 80 years old and they still work great!

[@smartdrivetest]

Perhaps I didn't communicate effectively - it's not manual slack adjusters that aren't reliable, it's training and the driver that have led to crashes. Some unfortunately very serious. We're happy to hear that your "big iron" is still rolling my friend. All the very best, Cheers Rick

[@michaelarthur6271]

Thanks Rick. Rejoining the "roadrunners" helping out though more on the older side. Running a haul truck with manual adjusters and keeping it tidy and on spec. Thanks for the info on auto adjusters and the "applied stroke" tests. Like recurrency on my pilots license. God speed.

[@matbsaccounting1056]

Keep up the great work! we need more insturcture like you on the youtube

[@smartdrivetest]

Hi MATBS Accounting - Thank you for your excellent compliment. And you are most welcome my friend. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@Greg3070]

I got my CDL in 93 and I was taught that to check the slack adjusters you tightened the nut all the way down and backing it off by 1/4 turn. I never knew about measuring the rod. I have always worked for companies with maintenance schedules so I never had any trouble. Now I'm buying my own, I am reviewing some of these things I will be ultimately responsible for. I appreciate your video.

[@smartdrivetest]

Hi Gregory Peterson - Thank you for your comment. And congratulations on getting your own truck! All the newer trucks are fitted with automatic slack adjusters so you won't have to adjust them up anymore. And for the purposes of liability, you probably don't want to do more than keeping these greased and measuring the push-rod travel my friend. All the best, Cheers Rick

[@j79kf]

That was a very good video. Thank you for posting it. It will definitely be a big help for not only new drivers but new techs.

[@smartdrivetest]

Hi jason - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@delventhiels4564]

Use a two inch piece of material instead of a tape measure. It’ll act as a go or no go gauge, so if this clearance fits your out of spec.

[@tobydulanski3000]

I'm learning a lot from your videos, Your PDF Air Brakes Simply Explained and the NYS CDL Manual. In the NYS manual it does state that the this test can be done by hand. The first thought was "Yea, if you are 21 years old and that strong, sure you can". Not so easy without tools. Learning something new is challenging to say the least. Thank You Rick for your demonstration on the CDL Air Brake Check.

[@smartdrivetest]

Hi Toby Dulanski - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@elroyjelinek9308]

Thank you, so very much for your time and shared knowledge

[@MrCoopersdad]

Great information, thank you putting this video together.

[@arthedrick6638]

I enjoyed the video , I was trying to find out about brake adjustments, so this six pack should work. Thank you I look forward to more.

[@smartdrivetest]

Hi Art Hedrick - Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@shabroopsingh9625]

@@smartdrivetestshould we check the airbrake adjustment whenver we have new trailer?

[@pauljimenez6984]

Very helpful and clear instruction!! Thanks keep up the great videos!

[@smartdrivetest]

Hi Paul Jimenez - you are most welcome my friend. All the best, Cheers Rick

[@driverbank6563]

Good job on this illustration, keep up the great work!

[@smartdrivetest]

Hi Driver Bank - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@baclieustud]

Hi Rick, Thanks for a refresher video, very educational, watched 3 times already, My test Tomorrow 2nd try. I forgot to mention the 2" free play, but I won't forget tomorrow. So many things to remember. Thanks again.

[@smartdrivetest]

Hi Bruce - Apologies for the late response. Thank you for your comment. How did the test go? All the best, Cheers Rick

[@baclieustud]

Smart Drive Test I pass the pre trip, but on the road, I failed again,,this time for going too slow. 3rd try tomorrow. DMV in Fontana, CA. are Anals. Still Thanks.

[@chromesurf9]

Well done! Answer is every day!!!! During pre trip Every day!!! Again, nice work thank you.

[@smartdrivetest]

Thank you my friend. Drop us a note if we can help further. All the best, Cheers Rick

[@cliffp.8396]

Excellent tutorial, thanks for this.

[@u812chevy]

Great job love the way you teach. God bless !

[@smartdrivetest]

Hi kenneth rippy - Thank you for your comment and flattering comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@veronicacalloway2795]

Thanks I really think this will help a person seeking getting a CDL license

[@smartdrivetest]

Hi Veronica Calloway - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@marshmallowblaster]

Thanks for the great video! I'll have to start doing a six pack as part of my daily PTI.

[@smartdrivetest]

Hi Irreverent Crawfish - Thank you for your comment. And you only have to do a six-pack if the brakes are out of adjustment. Most of the time these aren't going to be out of adjustment with automatic slack adjusters. Let me know my friend. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@ColtonBlumhagen]

I was taught to do 2 hard brakes when stopped at least a few times a day just in case you get stopped in my air brake course. Of course still pretrip them. Doing my class 1 MELT in Alberta next month.

[@smartdrivetest]

Hi Colton Blumhagen - that's a good technique my friend. That's awesome that you're off to truck driving school next month. Have you started look for a job? Have a look here my friend: www.smartdrivetest.com/employment/ Drop us a note if we can help further. All the best, Cheers Rick

[@teal94z28]

The truck driving school I went to stressed that checking your slack adjusters is always a part of your pre/post trip inspection

[@smartdrivetest]

Hi teal94z28 - Apologies for the late response. Thank you for your comment. It is law that you check the adjustment of the brakes everyday. However, since the advent of automatic slack adjusters, this is often overlooked and not done. All the best, Cheers Rick

[@MAYURGUPTA9]

Very nicely explained

[@TheCm900]

Great video Mr. White!

[@friedchicken1]

I'm loving all this

[@smartdrivetest]

Hi friedchicken - you are most welcome my friend. Have a look at this vid too: kzbin.info/www/bejne/mn7bmp-Xqbljp9k Drop us a note if we can help further. All the best, Cheers Rick

[@ryanmeana6170]

good thing you provide helpful videos, for Commercial Drivers.. this vid would be helpful if i get to set my brakes on a roadtest in a Trucking company.. so is it internationall for both canada & usa the adjustment is should no more than 1/2' to 3/4" inch..

[@smartdrivetest]

Hi Ryan - thanks for your comment. It the United States they allow up to 1" inch on a pry bar method. However, the manuals also state you can pull the slack adjuster with your hand; however, that's not possible. You're going to need a pry bar. The best measurement is the width of your thumbnail. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@marcocasillas5023]

Thanks for the knowledge I just bought a Rv diesel pusher with air brakes and I want to know about air brakes

[@smartdrivetest]

Hi Marco Casillas - Thank you for your comment. Congratulations on your new purchase. How many slides do you have my friend? These videos will help too my friend: kzbin.info/www/bejne/mn7bmp-Xqbljp9k Drop us a note if we can help further. Always happy to help. All the best, Cheers Rick

[@dennisramashka3526]

Great job on video!, like always!!👍

[@smartdrivetest]

Hi DENNIS RAMASHKA - thank you for your comment and compliment. It is greatly appreciated. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@nathanausten4445]

This helps so much. Thank you.

[@smartdrivetest]

Hi @nathanausten4445 - Glad you liked it. Drop us a note if you have questions. Cheers Rick

[@fatcattowing8990]

lots of people would say " I have automatic slack adjusters... they check them self and adjust" but the rules state in BC, Even trucks with automatic slack adjusters installed, Brakes SHOULD be checked each day as if you didnt have auto installed"

[@smartdrivetest]

Hi Fatcat Towing - Thank you for your comment. Automatic slack adjusters do not check their own adjustment my friend. According to law, you must check brake adjustment as part of your daily pre-trip inspection - as you stated. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@KaranSingh-eg4us]

Great Information

[@hdebesai3033]

Very helpfu & informative

[@smartdrivetest]

Hi H Debesai - Thank you for your comment. And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@turner593]

on the applied brake check being out of adjustment at maximum 2 inches, what is the minimum push rod stroke allowed at a 100 psi applied brake application ? or is that just minus the maximum allowable free slack being 3/4 of an inch making it 1 1/4 inches ?

[@mickeysettlemire5931]

Rick, thank you for your training program. The only method I recommend when checking air brake chamber travel by ones self is a process I believe you touched on and that is to use a wedge of some kind between the brake pedal and a point under the dash to apply the brake pedal to full application. Ensure wheels are chocked and on level ground and ensure the brake pressure is not over 100 psi. By either marking the pushrods or having the colored plastic tabs installed. Parking brakes to be released. Also info the applied angle is to be between 90 - 105 degrees in California.

[@smartdrivetest]

Hi Mickey - thank you for your response - that is great. I looked at your previous post and admit I didn't fully understand the reason for the air pressure not being over 100psi? Yes, here in BC, some person indicated that students no longer had to say that the brakes are applied because the push-rod and slack adjuster form an approximate 90° angle. And now students only have to say that the brakes are applied because the push-rod is extended. How the heck does a student know that? If the brake is installed correctly, the angle is going to be approximately 90° - it's simple physics. The best force generated is at 90°. All the the best, Cheers Rick

[@mickeysettlemire5931]

Keep up the good efforts. The public needs it.

[@owenja7708]

Thanks for the info 👍 helpful it was.

[@smartdrivetest]

Hi owen Ja - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@truckercamionero846]

Excellent video, thanks so much

[@smartdrivetest]

Hi Trucker camionero - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@Brute750]

Great video Rick.

[@smartdrivetest]

Thanks Paul - how's the job search going? Thanks Cheers Rick

[@laurencebelanger3978]

Thanks rick vary well explained 👍 any videos on how to properly determine axle weights on super bs

[@smartdrivetest]

Hi laurence belanger - And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@grantskinner6713]

All man thanks so much for the info buddy

[@smartdrivetest]

Hi Grant Skinner - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@jerrycasana1157]

Thanks for sharing Sir very informative tutorial

[@smartdrivetest]

Hi jerry casana - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@ivanmadrigal1395]

Always nice videos

[@scotthooper5127]

Adding another 2 cents worth... In Ontario the "applied method" is referred to as "Mark and measure". Exactly the same process as you demonstrated, just has a different name. Great videos, keep 'em coming!

[@smartdrivetest]

Hi Scott - Thank you for your comment. I believe the authorities thought they were being clever with the alliteration - 'mark & measure' sounds more cool than 'applied stroke method.' That is great information I'll add to the title and search tags. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@g41thomas]

Such an awesome 👌 instructor 👏👏👏👏👍👍👍👍

[@smartdrivetest]

Hi GETREAL! - We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@kcrobin7456]

On a tractor trailer, truck only how many slack adjusters are there? I am guessing for two for the stairs, take exit Miami on the right to choose for each drive axle on the inside of each axle beside the tires on the inside.

[@cztrucking1559]

I’m from California and every inspection I’ve gotten in California they used the applied brake test

[@smartdrivetest]

Hi C & Z Trucking - it's not just CA my friend. Every DOT inspector in all the states is going to use the applied stroke method. The reason is that they have 2 people, which makes it easy. They just put a radio in the cab, and when they're ready to measure, they tell the driver to apply the brakes. And the applied method is way more accurate than the pry bar method. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@cztrucking1559]

@@smartdrivetest I found this video do to problems with trailer brakes. I’ve replace (i do all my work myself) the chambers, drums, pads, s-cams, and slack adjusters and no matter adjustments I make, the applied stroke goes to the maximum 2”. So I’m trying the 6 pack method you said in your video now to see if that works. And it’s all four on the trailer that go to the 2” limit

[@smartdrivetest]

I'm not a technician, but it could be a couple of things: 1) the pushrods are too long; 2) the slack adjusters need to be adjusted manually. If you can't get it to work, I would counsel you to take it to a shop and have a mechanic have a look. All the best, Cheers Rick

[@felipeserrano8528]

Thanks dude. Great video.👍

[@smartdrivetest]

Happy to hear we could help out. All the best, Cheers Rick

[@karterdedo3334]

Great video 👍

[@ericbrule4465]

We have alot of trailers in our fleet that run on longstroke chambers (square ports) which allows extra half inch. We're phasing out and all new ad of 2011 are air disc equipped. My question is whats the difference between the two and why does one allow half inch more than the other. Hope to hear from you soon.

[@smartdrivetest]

Hi Eric Brule - Thank you for your comment and query. The reason that the long strokes have another 1/2" inch of push rod travel is owing to the bigger chamber, which allows for a full 3" of travel before the plate inside hits the bottom of the chamber. For safety however, the push rod is only allowed 21/2" of travel. In other words, it's the depth of the brake chamber that determines the travel of the push road and its legal limits. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@ericbrule4465]

Smart Drive Test thanks for the reply. It always baffled my mimd and couldn't find the amswer. I learned about 10 years ago on how to tell the difference between the 2.

[@smartdrivetest]

Hi Eric Brule - you are most welcome my friend. Glad we could help. All the best, Cheers Rick

[@courtneyhoggard8168]

@@smartdrivetest I was looking for the link to the chart you was talking about but not able to find it in the comments

[@andrewtattooske697]

Thanks Bud !

[@smartdrivetest]

You are most welcome! All the best, Cheers Rick

[@ryandouglass4]

Where can I buy the push rod tabs? This would be very useful for our fleet.

[@jhoefernandez976]

Thank you very interesting.

[@smartdrivetest]

Hi Jhoe Fernandez - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@Luneytoons]

What a great video! Very informative and he's easy to learn from. I'm glad to see Tommy Lee Jones is keeping busy when he's off the silver screen! ;)

[@smartdrivetest]

Hi Dylan Lunenburg - Thank you for your comment. And you are most welcome. We're happy to hear we could help out. I like to think I'm better looking than Tommy Lee... 👍 All the best, Cheers Rick

[@chrisquintino559]

With the pry bar method are there differences in free stroke travel between brake chamber types as well as standard stroke to long stroke? I just noticed that the width of the thumb is sort of a generalization. I'm from Ontario but now working in alberta. Just trying to learn the pry bar method now.

[@smartdrivetest]

Hi Chris - nope, so long as it's not more than an inch, you're good to go. Ontario is the only province or state that I'm aware of that does the applied stroke method for measuring push-rod travel. Every other jurisdiction does the pry-bar method. See this vid too: kzbin.info/www/bejne/o2bVZIepmbaEh9k Drop us a note if we can help further. Oh yeah, in Alberta, the leak test is 2 minutes my friend. All the best, Cheers Rick

[@osbornebay944]

Great Vid! Is that yellow plastic called stroke indicator? My single axle dumper only has one pod with it.

[@smartdrivetest]

Yes, those are stroke indicators my friend. They won't stand up in a DOT inspection, but they do help with the daily inspection if you know these are set right. All the best, Cheers Rick

[@Arbitrageur_]

Great video.

[@cotes42]

I see that 2" is the maximum range before adjustment, what is the minimum? Surely the push rod must move a little as it applies the brakes, how much does it move minimally when the brakes are new and adjusted? Thanks

[@peterohmart5954]

IMPRESSIVE!!!! QUITE THOROUGH. THANK YOU. WHERE CAN I SEE MORE VIDEOS YOU HAVE PRODUCED?

[@handyomarv]

Great video!

[@smartdrivetest]

Hi Omar V - you are most welcome my friend. All the best, Cheers Rick

[@robertross8565]

Where did you buy your pry bar. How long is it? I live in Vancouver.

[@mrbrnard]

great video. very informative. Do you have a video where you adjust air break because it really needs adjustment? Im reading air brake adjustment book, i would really love to see it in action. Im trying to get my DL Class1.

[@smartdrivetest]

Hi Bernard Mallari - Thank you for your comment and query. And this is the video you seek: kzbin.info/www/bejne/oZ_FmJmrmaiNeZo&list=PL0x-bChcUvwG2bSWReQWnk9Tm92L7WN_O If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@firstname6208]

if the brake chamber rod is not the correct length it will affect how the ASA works. especially that type of slack on the trailer. the double yolk has lots of wear being outside in the elements, and that slack is about a 6 in reliability anyways. some slacks adjust on the push stroke and some slacks adjust on the return stroke. so your six pack method only works on some slacks not all.

[@smartdrivetest]

Hi First Name - Thank you for your comment. And you are correct my friend - it's not going to work all the time, but it's worth a go before taking it into the shop. All the best, Cheers Rick

[@antsara9218]

great info, thanku!

[@smartdrivetest]

Hi Ant Sara - Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@rezamoghadasianrad7743]

thankul

[@smartdrivetest]

Hi Reza Moghadasian Rad - you are most welcome my friend. All the best, Cheers Rick

[@mikegrazio5376]

if your s-cam bushings are wore out, your automatic slack adjusters will exceed the 2" on the applied. So its not always the slack adjusters issue

[@smartdrivetest]

Hi Mike grazio - Thanks for the information. Can't say I've every had equipment old enough that it wore out the bushings. All the best, Cheers Rick

[@aperez8601]

Good information

[@smartdrivetest]

Hi Aperez - Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@bdr4212]

I am reviewing the MTO Ir Brake Handbook and see no reference to using a pry bar.

[@smartdrivetest]

In Ontario you have to use the mark and measure my friend. Drop us a note if you have further questions. Cheers Rick

[@brandookie79]

Thank you for the vid and the chart

[@smartdrivetest]

Hi brandon thomas - Thank you for your comment. And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@mickeysettlemire5931]

Just watched your video and want to say I appreciate your program for teaching air brakes issues to watch for. However I also teach air brakes and was DOT in Calif for many years also. I want to add a little info with your permission. The diameter alone isn't the factor for the travel allowance. Additionally the depth of also is a factor meaning is it identified as a LS or long stroke chamber. the long stroke allows 2" travel where as the non LS chamber allows only 1 3/4 "on a type 30. I like to advise in my classes a slight modification to your method of using an object to apply the brakes to actually be able to observe the applied travel. I recommend this method along with starting with the air pressure below cut in pressure and with the brakes applied to build the pressure to between 90- 100 psi. The brakes travel measurement are not out of adjustment when exceeding 2" if over 100 psi if they are within the 2" when not exceeding 100 psi. I have seen that process done at inspections which will then be written as a violation when per CVSA standards and manufacturers standards it is not. That then produces a brake violation on a drivers record which is a point and one half . Other than that you are doing great. Oh and the thumb nail measurement is only a recommendation.

[@smartdrivetest]

Hi Mickey - thank you for your comment and information. You are correct that the depth of the chamber is relevant to overall allowable push rod travel. Yet, in all the manuals that I've read, it only refers to the diameter and not the depth of the chamber - which in my mind makes more sense. LS brake chambers in my experience are rare, and were a product of the 1990s when authorities revamped the air brake course and required drivers to check brake adjustment. They were also a product of the transition to automatic slack adjusters. Finally cost precluded the widespread use of LS brakes chambers. Companies simply weren't going to pay extra for a brake chamber that only gave them another 1/2" of travel. I would like to know how drivers can observe push rod travel if they're alone and have to apply the brakes? Thanks again for the comment. If there is anything further we can do, drop us a note. All the best, Cheers Rick

[@serhiyryabtsev4762]

Good video Thanks

[@smartdrivetest]

Hi Serhiy Ryabtsev - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@edmourgagnon1504]

Hi. I am in BC. In theirDriving comercial vehicule book, page 188, at the bottom... I got confused... They wrote: "Pry method of free stroke measurement". Now... I believe they meant to say: Pry method...or... Free stroke measurement... Rrrrrrr.

[@LordTimelord]

Good Video, Thanks for uploading it! I never was taught the "Six Pack" technique. If you do a normal 4-Point Brake Test every day, and engage the brakes all the way down on the pedal on each push. Shouldn't that also make the slack adjusters move? Although after watching your video I'd bet that the air pressure would be below 90 PSI too quickly, and it might only get the brakes partially adjusted. And I must be a brute, because I can pull the slack adjusters out with my gloved hands. :-) Although I will be picking up a small pry bar like you used in the video to make it easier! LOL

[@smartdrivetest]

Hi LordTimelord - Thank you for your comment. I suspect you are a brute my friend if you can pull the slack adjuster out with you hand. ;0P And yes, if you're making 4 hard brake applications every day, that will adjust up the automatic slack adjusters, so long as these are being greased every couple of weeks. Also, you are correct - you can only do 3 hard brake applications before you have to pump the air pressure back up to 90psi. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@CONTENDER791]

Question. On a steer axle pry bar check (air brakes )with the brakes applied should the push rod be able to be pulled out an inch? Or must the brakes be released during the pry bar test to check the push rod play?

[@smartdrivetest]

Hi CONTENDER791 - Thank you for your comment and excellent query. For the steer axles you don't have to have the parking brakes released. There aren't parking/emergency brakes on the steer axles due to the fact that you don't want these to lock up in the event of an emergency. Yes, you can do a pry bar on the steer axle pushrods without having the parking brakes released. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@tomgoldy9027]

CON5TENDER791

[@johnkavalchuk5927]

I have a problem with air brakes in rear of an RV with 20,000 lb axel. left hand wheel was making an unusual sound when applying brakes. I chocked the wheels .had air pressure between 60 and 90 psi, released park brake marked the push rod with marker and my wife applied brakes while I measured the stroke. The problem wheel only had one in. stroke and other was just over 2 in. I also did the pry bar test per video instructions and both rods had 3/4 inch stroke. any ideas what is going on. We are from canada but in calif now and have to wait one week to get it checked would like to try something else in mean time.

[@smartdrivetest]

Hi john kavalchuk - Thank you for your comment. If you have a push rod stroke more than 2", little doubt the brake is out of adjustment. I would suggest trying a 6-pack. Chock the wheels, release the parking brake, and build system pressure to maximum. At maximum, the air dryer will purge and the air gauge needle will be between 100 and 135psi. Make 3 full hard brake pedal applications. Let the pressure built to maximum again, and do 3 more hard full brake application. Remeasure the push-rod stroke. If it's still out of adjustment, you might be able to put some grease to the slack adjuster and try the 6-pack again. Some times these seize up because they haven't been greased in a bit. When you measure the push rod stroke using the applied method as you did, ensure that the system air pressure is at maximum. If that doesn't work, you may have to replace the slack adjuster. Let me know if that works. All the best, Cheers Rick

[@topdogvic]

How do you determine if it’s an automatic Slack adjuster or not?

[@smartdrivetest]

It's very unlikely that you'll encounter a manual slack adjuster, but just in case, see this video: kzbin.info/www/bejne/oZ_FmJmrmaiNeZo Drop us a note if you have questions. Cheers Rick

[@chrislareau8110]

Failure of automatic slack adjusters is not the only reason for out of adjustment brakes. You could also have worn brake linings or foundation brake parts issues that were not discussed in the video.

[@smartdrivetest]

Hi Chris Lareau - Thank you for your comment. That is true my friend. With vehicles that get regular maintenance it tends to be more so the slack adjusters than other things. All the best, Cheers Rick

[@davejames2015]

Great Video

[@smartdrivetest]

Hi Dave James - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@Qu3mao]

Awesome video, thank you!

[@smartdrivetest]

Hi Yuset Sanchez - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@josecarbajal1164]

!!!!THANK YOU!!!!

[@smartdrivetest]

Hi Jose Carbajal - Thank you for your comment and contagious enthusiasm. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@josecarbajal1164]

@@smartdrivetest 3 years later and still a great video!! 👍

[@robertross8565]

Awesome video.

[@smartdrivetest]

Hi Robert Ross - you are most welcome my friend. Drop us a note if we can help further my friend. All the best, Cheers Rick

[@nileedwards2466]

Do you do a 6 pack while moving or stationary? Thanks for the knowledge! Havent seen the applied method before.

[@smartdrivetest]

Park the vehicle in a safe location, chock the wheels and release the brakes. 3 hard applications, let the air build back to maximum and then 3 more. You should be good to go at that time. All the best, Cheers Rick

[@ajaugusto8]

The 6 pack while moving is called a seatbelt check.

[@smartdrivetest]

Going for a CDL, or higher class licence with a vehicle that is equipped with air brakes? As part of your road test, you are required to determine if the air brakes are in adjustment depending on your jurisdiction's requirements: either the pry bar or applied stroke method. Learn how to determine if your air brakes are in adjustment and correct the adjustment if they brakes are not in adjustment.

[@CarlosRamirez-vj4kz]

Smart Drive Test THANK RICK ,SAFETY FIRST👍

[@smartdrivetest]

Thank you Carlos - for your comment. If there's anything else we can do, drop us a note. All the best, Cheers Rick

[@truckintowardretirement686]

These methods were never demonstrated in my 2007 Community College CDL class. Now I’ve been driving for the big orange, mega carrier for a year. They never discussed or demonstrated this. If I’m going to be responsible for paying every fine I get as a commercial truck driver, then I need more education than just how to do a pre-/post-trip inspection. Any suggestions on training or suggested reading? I’ve looked at 49CFR regulations but there seems to be other publications to which these regs are attached. Here lately-while being a dedicated Wally World driver-I’ve flagged brake linings for borderline DOT failure, causing 1 reload already. Of course, I catch crap from my fellow drivers, telling me to just pick up the trailer and get going if I’m going to make more money. In the final analysis, I don’t want a fine and I sure don’t want to hurt someone, including myself. I appreciate your feedback.

[@sostrucking]

@@truckintowardretirement686 you are responsible for the safety of others and the load....screw those other super trucking idiots. They have a license to drive one vehicle at a time and yours isn't one of them. Being safe is a part of being a professional. All these wrecks out there put a target on our industry and that affects our pay. I haul bulk mail for a company and am home every night making 25 to 30 dollars an hour.

[@david-jh8rg]

Brake checks daily

[@smartdrivetest]

Awesome to hear my friend. You're one of the smarter drivers that looks after the equipment. All the very best, Cheers Rick

[@INTERVENTIONALRADIOL]

Great video, Rick. Where can you find those yellow push rod markers on the internet? Inquiring minds want to know. Thanks

[@smartdrivetest]

Hi Miguel Rodriguez - Thank you for your query. You might find them at a truck stop. I suspect that you would find them at a truck parts store. All the best, Cheers Rick

[@jjggggjj3053]

While performing 6-pack action it was stated that you need to push a pedal three times and then release spring brakes - does it mean that between these steps it should be applied spring brakes and then these should be released? and when spring brakes should be applied in these steps? after which in this algorithm?

[@smartdrivetest]

Full application of the brake pedal and then let the air pump back to maximum. There’s no application of the parking brakes my friend. Drop us a note if you have further questions. Cheers Rick

[@az5100]

thanks a lot

[@smartdrivetest]

Hi A Z - thank you for your comment and compliment. You are most welcome.If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@Peterbilt359]

I have a 95 kw and can't keep auto adjusters in. Changed them twice by good shops. Back up hit brakes. Nothing works would love to change them to manuals my trailers and other truck is old and check them once a week. Or every time I get in truck after been out of it for while.

[@smartdrivetest]

Hi Scott coleman - Thank you for your comment. Every now and again I hear that about auto slacks. It's a perplexing issue I'm sure because all the components are mechanical. In other words, there aren't any electronic components that could foul up. If auto slacks are going amiss, it would lead me to think that manual slacks probably aren't going to solve the problem because there's something else going on. Do the technicians have any theories as to what causing the slacks to malfunction? All the best, Cheers Rick

[@rezamoghadasianrad7743]

computer is a good thing man plus all of your videos

[@smartdrivetest]

Hi Reza Moghadasian Rad - Thank you for your comment. And you are most welcome. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@Backthenwasgood]

How ofter should the driver do that , to check that .? Thanks

[@dano1234v]

I'm confused, you did pry bar and in usa manual is says inch or less is good, you would think that is for all brakes front back and trailer, but you are saying the type 30 brake pods are going to be 2" or less is that correct?

[@smartdrivetest]

Apologies for the late response. Using the "pry bar" method it's less than 1" inch my friend. However, it you're checking the brakes using the applied stroke--as the DOT will--then it's 2" for a Type 30 brake chamber with automatic slack adjusters. Applied stroke means you chock the wheels and push down on the brake pedal. See here for different measurements of different brake chambers: www.smartdrivetest.com/cdl-air-brakes/chart-of-adjustment-limits Drop us a note if we can help further. All the best, Cheers Rick

[@Respect_The_Hustle226]

Daily check them a lot of O/O check once a week would be cool if you showed how to check trailer brakes with the hand brake applied.

[@turboflush]

How much foot pressure to perform the chamber throw test? Even set at 100psi the if the foot pedal is pushed hard to floor (ohhshiz stop), the chamber brake throw will be very near the max stroke. On a normal application. It is within spec. I would just think that the 90-100psi would limit it.

[@smartdrivetest]

Are you talking about measuring pushrod travel with the applied stroke method, or are you talking about the leak test? If you're talking about the former - it's more than 100psi. If you talking about the leak test, it's maximum pressure because you have to first check to see that the governor kicks out before 135psi, or whatever the number is in your state. See this checklist for some help: www.smartdrivetest.com/pass-cdl-air-brakes-checklist Drop us a note if you have further questions. Cheers Rick

[@turboflush]

@@smartdrivetest Applied stroke is 90-100psi. How much foot pressure should be applied ( or can be). From what i have seen.. If the foot pedal is pushed hard to the floor it will make that applied stroke to the max. Jaming the brake to do this check one manned takes some footwork and often results in the pedal pushed farthur than a normal brake application. Point being one persons normal brake application can be different than another. Resulting in different measurements.

[@smartdrivetest]

Alright, I know what you're asking me. Nope, push the brake pedal right to the floor and hold as hard as you can. If you release the pedal and there is air leaking, the test is void. So make sure you hold the pedal tight, tight. All the best, Cheers Rick

[@zackbright8715]

@@smartdrivetest I only need 10-12psi to feel the brakes and slow down. Unless I need to stop now, may be 30psi. Never needed more. Dot said to hold it to the floor at 60-90 psi so he could check! Is that crazy?? When do you ever do that much?

[@CosgroveNotts]

What about extra long stroke travel type 24/30

[@garvinwatson7879]

I will like to know the difference between park brake an foot brake accuraters in a international ten wheeler truck ?

[@smartdrivetest]

Hi Garvin Watson - Thank you for your question. This video should answer your question my friend: kzbin.info/www/bejne/mn7bmp-Xqbljp9k If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@robertyoung7823]

Very good

[@smartdrivetest]

Glad you enjoyed it! Always happy to help out. Cheers Rick

[@govindchib7036]

Why push rode travel is different for applied method which is 2 inch and quarter an inch for pry bar method

[@smartdrivetest]

Hi govind chib - You can apply the same amount of pressure with a pry bar as can be applied with the air pressure my friend. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@esusekaw1598]

Tank you good vido

[@smartdrivetest]

Hi Esu Sekaw - Thank you for your comment. And you are most welcome. We're happy to hear we could help out. If there is anything further we can do, drop us a note. Always happy to help. All the best, Cheers Rick

[@sosexy9701]

Are you pulling the slack adjusters or push rod when the parking brake is released

[@helloneighbor11]

They are connected. You are essentially pulling both