In severe motorcycle wrecks, the front forks often get bent. How much bend each leg is subject to is dependent on a number of variables, such as what the bike hit and how hard it hit. In addition, unless the impact was in a perfect straight line - which is very rare - one leg will be bent more than the other. In most instances, new fork legs will be needed to replace the damaged items, especially if the damage was substantial.

But occasionally, the legs may only be bent slightly and can be repaired with a bit of effort.

Replace or Repair?

After an accident, as a general rule, if fork tube material has creased on the inside of the bend, the legs should be replaced. Each case is different, and the novice should seek professional advice about their particular situation.

If you feel confident enough, you can follow a few steps to check on your own. One method is to hold the front brake on and depress the forks as far as possible. The action must be smooth and free from any stiction.  If the fender moves from side to side, the fork legs are bent or they have rotated in the triple clamps.

Another method of checking them is to put the bike on its center stand and then place a straight edge against each extended leg in turn.

Areas to check include the unsupported section below the triple clamps and above the slider, just below the lower triple clamp. The latter is a typical location for the legs to bend at.

A light bend can be detected after the legs have been removed from the bike by rolling them along a known flat surface.

If the legs are bent, the ends will raise and lower as they are rotated.

Repairing the Legs

The fork legs must be removed from the bike and the legs separated from the sliders in order to straighten them. The legs should be cleaned then placed into a suitable lathe to perform an accurate assessment of their condition. One end of the fork leg should be located inside the lathe’s chuck, and the other supported in the tail stock with a revolving center attachment. 

To find the location of the bend, the fork leg should be rotated against a permanent marker securely located on the cross feed. This operation is best done with the lathe out of gear and by turning the chuck slowly by hand. The mark will taper at either end indicating where the fork leg begins to bend and be at its widest at the point where the leg is bent the most.

With the fork leg’s bend location marked, the leg should be now placed into a hydraulic press supported in ‘V’ blocks which are spaced an equidistance out from the end of the permanent marker’s mark. Pressure should now be placed on the leg via the press tooling until the leg bends slightly below straight—there will be a certain amount of spring back in the fork leg material.

The markings should be removed from the leg and the entire process repeated until the leg is straight. A tolerance of between 5 and 10 thousandths of an inch (o.1 to 0.2-mm) is acceptable in most applications.

Once the fork legs are straight again, they should be returned to the lathe and polished with a fine grade of Scotch-Brite™ pad.

As with any accident damage, the mechanic must check the entire machine. In particular, when the forks have been damaged, the mechanic must check the wheel, the headstock bearings and the frame at the headstock.