TrailerTech: Reusing Tie Plates

Welcome back to TrailerTech!

We all know you shouldn’t re-use u-bolts when servicing or modifying your trailer’s leaf spring suspension. Tie plates though, aren’t as cut and dry. There are obvious qualitative observations that can be made, such as the presence of rust or total failure. Structural integrity is a much different story. At a casual glance, tie plates often appear unchanged after a use or two. In this TrailerTech article, we’ll take a closer look.

Lateral bending is one of the biggest concerns when assessing a tie plate’s structural integrity. The tie plate flexes across the leaf spring, bending towards the u-bolt’s clamping force. The photo below shows an unused tie plate on the left and a tie plate torqued down only once on the right. Notice the slight circular markings from the u-bolt washers.

A keen eye will also notice the slight arc in the tie plate on the right (a 1mm rise). This might not seem like much, but if we graph the result, the deflection is much more apparent.

Naturally, the proper care must be taken when re-using tie plates, as lateral bending is not always visibly obvious and a closer inspection is necessary. If you have any doubts about your existing tie plates, the safest thing to do is to replace them along with other one-time use parts, such as u-bolts.

We hope this TrailerTech article is helpful when making your assessment.