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Replacing worn out or broken air springs? Need help indentifying which air springs or air bags you need for your heavy duty truck, trailer or bus suspension? Review this guide or call 1-800-358-4751 to speak to a firestone air spring specialist.
How do I identify and find out what air spring is on my vehicle? This is a frequent question that is asked of our parts department team members. Finding out what spring you have and getting the correct one the first time around can seem like a daunting task when you are looking at an old, dirty air spring with hundreds of replacement options to choose from. One of the first things you should know when attempting to find out which air bag you have on your semi-truck, trailer, motorhome or RV is that they are not vehicle or application specific. Air springs are put on vehicles by variety of suspension manufacturers after a vehicle leaves the factory. Firestone and other air spring manufacturers do not have a master list that we can reference that shows the part number that was used by aftermarket manufacturers. Air Springs are sold by cross referencing the existing part number or by measurements and in the video and content below we give you some tips and show how this can be done is a few easy steps.
The easiest and fastest way to identify Firestone air springs is by the part number located on the sticker on the top of the air bag. All Firestone air spring part numbers will start with W01 or W02, ex. W01-358-9082. If the sticker with the part number is not present, look for the bellows number stamped on the rubber. The bellows number is normally molded directly underneath the Firestone logo and typically with start with 1T, ex 1T15M-6. The bellows number can typically be seen with the air bag still on your truck or trailer.
If you know the part number, enter the last four digits of the part number into the search box on our site. If you have just the bellows number, enter that in our search. If nothing comes up, try entering the 1st four or five digits. If you do not know the Firestone part number or bellows number, you may enter and search using other parts numbers such as: Goodyear Part Number, Goodyear Bellows Number, Triangle Part Number, Triangle Bellows Number, Manufacturers number (Hendrickson, Neway, etc.).
Measure and compare dimensions. The cross sectional view of the Airide spring shows dimensional information in inches on uninflated diameter, maximum height, and collapsed height. Measure the bead plate diameter and molded (uninflated) diameter of the rubber bellows (please note that the molded diameter can grow slightly with years of service). Then measure from the bottom of the piston to the top of the bead plate while the part is uninflated and extended.
First determine whether it is a single, double, or triple convoluted style. A double convoluted air bag is shown in the picture to the right. Then measure the bead plate diameter and the diameter of the bellows, with the air bag deflated, across its widest area and compare these dimensions with those given in the bellows index. Once a match has been made, proceed to step 4.
Many Airide springs include a rubber bumper inside the spring. To determine if one is present, compress the spring to its minimum hieght and measure from the bottom plate or piston to the top of the bead plate.
Compare this compressed hieght with the pictures in the appropriate bellows section that was determined in step 2 (1T style) or step 3 (convoluted style). Proceed to step 5 if you have a 1T style spring or step 6 if you have a convoluted spring.
Identify the top (bead plate) and bottom (piston) of the air spring. The same rubber bellows is used with many different combinations of bead plates and pistons, so be sure to check closely. Compare the bead plate and piston with the pictures from the “Cross Section View”, “Bead Plate Top View” and “Piston Bottom. You can view the images of the top plates and pistons by clicking on the “more images” button on the air spring product page. The piston can be further verified by reading the identification numbers inside the pistonand comparing these with those shown in the “Piston Bottom View”.
The same bellows is used with many different combinations of bead plates. Compare these bead plates with those diagramed in this guide under the "Bead Plate Bottom View" columns for the specific style convoluted plate that was previously determined and find the unit with the identical hardware, measurements and alignment (top bead plate mounting in reference to lower bead plate mounting). Once a match has been determined, the corresponding assembly order number (e.g,. W01-358-7135) can be used to order the part.
The bellows number (number 1T15M-6 in step 1 ) is the number of the rubber that is used on the air spring and is not the actual part number used to order an air spring. The same bellows number can be used on multiple air springs. It is very helpful in narrowing down the search, but is not the actual part number. The part number (assembly number) is a combination of the top plate, bellows and piston numbers and will typically look like W01-358-9082 is step 1.
Below are symbols that are used by Firestone to differentiate the air inlets, mounting studs, etc. They are shown on the top plate and bottom plate images on our website.
Threaded Hole 3/8-16 Blind Nut on Bead Plates 1/2-13 in Pistons.
Bolt or Stud 1/2-13.
Air Intel 1/4 N.P.T.
Combination Stud/Air Intel Stud Outside Thread is 3/4-16
Studs Inside Thread (Air Intel) is 1/4 N.P.T. Exceptions will be noted on Part View as