A common cart setup will have four casters (4-wheel diamond pattern shown), but keep in mind that 3 points make a plane. So, if you have an uneven floor, expansion cracks, or pitting, your carts could have only three casters on the ground at any given time. An everyday example would be a grocery cart with one wheel off the ground and freely spinning as you push it. This is why adequately supporting your load if only three casters are touching is crucial.
Determining a safe weight capacity.
This brings us to the topic of accurately determining capacity. Since the weight of a cart isn’t always distributed across all four casters, always include a margin of error. We recommend an additional capacity rating of 33% to the load weight for safety. Adding the extra weight capacity allows more pressure to go on one wheel and lessens the chance of failure.
For example, your caster may have a weight capacity of 3,000 pounds, which would equal a 12,000 lb. cartload with four wheels. However, by adding in the safety factor of 33%, you might end up needing a higher capacity wheel. So the weight capacity stated on our catalog or website is correct. But adding in the safety factor may push your needed capacity higher. This means the recommended capacity you get from your sales rep may be different than the caster’s stated capacity.
Whether you talk with me or anyone else on the sales team, we take this factor into consideration. However, we may not always explain our thought processes. Occasionally our customers will tell us that we are trying to “up-sell” them or sell them something that is more than what they need. I assure you this is not the case. The reason we are doing this is to make sure that your caster is not going to fail you.
Read more: Why Is The Listed Weight Capacity Different Than What You’re Telling Me?