The overall height or load height on a caster is the vertical distance from the top of the caster to the bottom of the wheel. In other words, this is the distance from the ground to where the unit sits/rests once mounted to the caster. Load heights are absolutely critical in many applications. Often times this is a measurement that gets overlooked. When overlooked, this measurement can have drastic implications.
The overall height issue starts with one question – “Are you replacing 1 caster or 4 casters?” If you are replacing all 4 casters in a non technical application the overall height most likely means nothing to you. However, if you are replacing 1 caster of the 4, there is a good chance the overall height on that one caster is going to be different from the other 3 if they are from different manufacturers. This difference in height can cause the unit to be slightly uneven. Depending on the distance between your casters 1/16″ or 1/8″ is not going to be very noticeable across the length of the table or cart, but some overall heights can vary from 1/4″ to 1/2″. This is where the difference might be noticeable. Whether it matters to your application or not, this is something you should be
Applications where load heights matter:
– Food grade applications. Many items are spec’d into a food plant and have to have the specified load height to keep the machines functioning exactly for their design. If a cart or table fit into a slot under a conveyor there is no room to increase a casters load height so these must be exact. Also, certain OSHA requirements specify how tall a certain item can be throughout food operations which is another reason these load heights are critical.
– Laboratories sometimes have carts that are mounted to the wall via a safety clip or bracket for safe storage and six sigma reasons. With these brackets being mounted to the wall they are fixed and non-adjustable. If you were to change out the casters on these carts and the overall height changes 1/4″ in either direction these brackets are no longer functional to store the carts safely. This is a BIG issue.
Lastly, overall heights can vary on casters from the same manufacturer due to manufacturing tolerances. All manufacturers have a tolerance range their tooling operates within when drilling their axle holes. Depending on the tooling of the machine, these tolerances can vary in different ranges, and if the axle drop is measured with a precise caliper these differences can easily be noticed.
Again, whether it matters to you or not, this is a very important measurement on a caster that you need to be aware of. Please contact one of our experts if you have any questions or concerns about the overall heights on any of your casters.