Tips & Information

How to properly measure leaf springs & u-bolts...

One of the challenges we here at Niagara Spring Service Limited face is incorrect dimensions of springs and u-bolts.

So please use this guide as a template when collecting information about leaf springs and u-bolts.

Leaf Springs

There are several types of leaf spring assemblies, some are single leaf suspensions while others are multi leaf suspensions.  Some have two spring eyes, while others have one; as in a "slipper" leaf spring.  Some springs are paired while in other vehicles as in 1994 Buick Regal are known as a "transverse" leaf spring and travel from rear wheel to rear wheel.  Regarding these styles of leaf springs they all are measured in the same manner. 

Multi/single leaf springs are made up of several components.  These are a Main leaf which will have two eyes, each eye located at each end, a centre bolt, retaining clips and spring bushings (located in the eyes).  

There are four dimensions associated with measuring a leaf spring: spring width, spring arch, short end length and long end length.

Dimension A - Spring width - This dimension is the actual width of the spring.  Most likely it will be 1-3/4", 2", 2-1/4", 2-1/2", 3", 3-1/2" or 4".  These widths are commonplace in the suspension industry and relate to how the steel is milled for production.

Dimension B - Free arch - This dimension is the unloaded height of the leaf spring and is measured by drawing and imaginary line from the centre of one eye to the centre of the opposite eye (or top of the leaf if measuring a "slipper" end leaf spring) and measuring from that line to the top of the main leaf.


Dimension C - Short end length - This dimension relates to the length on the short end of the leaf spring, usually the front. Measure from the centre of the spring eye on the short end to the centre bolt following the arch - not straight across. This is a misconception when measuring leaf springs.


Dimension D - Long end length - This dimension is similar to the short end measurement but relates to the long end of the leaf spring.  Measure from the centre of the rear eye to the centre bolt, again following the arch

Measuring U-Bolts

U-Bolts like leaf springs come in different shapes and are categorized by their bend. The different styles of u-bolt are full round top, square top,semi round top, semi square top and forged top.  We are able to make any u-bolt for any application given the dimensions, except for forges top, these must be ordered.

To measure a u-bolt, there are four dimensions to consider; the type of bend, rod size (thread size), inside width and length.