How to check Brake Stroke on a truck
To check brake free stroke on s-cam brakes:
1)Be sure that the air system has above governor cut out pressure. (above 125 psi.)
2)Block the wheels on a drive axle to avoid truck to roll.
3)Release parking brakes
4)Check each brake for push-rod length using a ruler or measuring tape, while the brakes are NOT applied. (i use the mounting surface of the brake chamber, and the center of the clevis pin)
5)Record your reading of the push rod length
6)Next you want to check the stroke, this is how far out the push-rod would travel when brakes are applied. Using a heel bar to check stroke is not the same as using the system air, or actual brake application (when using the system air you can see what is the capability of producing brake application)
7)Record your reading of how far out the push-rod traveled. Make sure to measure from the same place as in step #4
8)Depending on the brake Chamber size/type, there is a specific maximum allowable stroke. I have uploaded a picture to assist.
9.)Take both your readings and determine if you are withing specification. (in my case push-rod length: 2 3/4", push-rod travel:4 1/4", so my stroke was 1 1/2" and a type 24 chamber has a allowable stroke of 1 3/4" so i'm well in specification )
*if stroke is not within specification, the slack adjuster will to be adjusted. On the slack adjuster there is a 7/16 head bolt, some might have what is called a locking collar, that requires to be pushed in before turning the bolt. Some adjusting bolts turn clockwise and some turn counter-clockwise so you need to pay attention what rotation brings the brake shoe to the brake drum. Turn the bolt until you notice the brake shoe moving towards the brake drum. You need to make sure there is a slack in between the brake drum and brake shoe of .020", you don't want the brake shoe contacting the brake drum because its like the brakes are being already applied. Re-check your stroke and do adjustment as needed.
1)Be sure that the air system has above governor cut out pressure. (above 125 psi.)
2)Block the wheels on a drive axle to avoid truck to roll.
3)Release parking brakes
4)Check each brake for push-rod length using a ruler or measuring tape, while the brakes are NOT applied. (i use the mounting surface of the brake chamber, and the center of the clevis pin)
5)Record your reading of the push rod length
6)Next you want to check the stroke, this is how far out the push-rod would travel when brakes are applied. Using a heel bar to check stroke is not the same as using the system air, or actual brake application (when using the system air you can see what is the capability of producing brake application)
7)Record your reading of how far out the push-rod traveled. Make sure to measure from the same place as in step #4
8)Depending on the brake Chamber size/type, there is a specific maximum allowable stroke. I have uploaded a picture to assist.
9.)Take both your readings and determine if you are withing specification. (in my case push-rod length: 2 3/4", push-rod travel:4 1/4", so my stroke was 1 1/2" and a type 24 chamber has a allowable stroke of 1 3/4" so i'm well in specification )
*if stroke is not within specification, the slack adjuster will to be adjusted. On the slack adjuster there is a 7/16 head bolt, some might have what is called a locking collar, that requires to be pushed in before turning the bolt. Some adjusting bolts turn clockwise and some turn counter-clockwise so you need to pay attention what rotation brings the brake shoe to the brake drum. Turn the bolt until you notice the brake shoe moving towards the brake drum. You need to make sure there is a slack in between the brake drum and brake shoe of .020", you don't want the brake shoe contacting the brake drum because its like the brakes are being already applied. Re-check your stroke and do adjustment as needed.
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