Adjusting and Aligning a Motorcycle Sidecar


There are three adjustments to consider when setting up a sidecar.
Sidecar Lead

In addition the sidecar should be set level.

This page shows a suggested method for adjusting each parameter.

Sidecar alignment
In the interests of predicable handling and minimum tyre wear,the sidecar should be adjusted to have as little toe-in as possible and the motorcycle should lean out slightly.
Sidecar lead.

This dimension is the distance between the centreline of the rear wheel and the centreline of the sidecar wheel (the dimension shown by the Arrow on the right).

This can be as much as 450mm or as little as 0mm; but typically it is 250mm to 350mm.

The dimension is not critical but the more lead the sidecar has the less likely it is to tip when turning away from the chair. However this is at the expense of greater tyre wear because as the sidecar wheel moves forward it will tend to scrub more on the corners.

Sidecar Lead

Toe- In

Some toe-in is usually need to help the sidecar track straight under normal conditions. The off-set weight of the sidecar means it is always dragging the bike towards it. This can be countered by steering the sidecar towards the bike slightly.

Larger sidecars often require more toe-in to counter the increased wind resistance they encounter and their larger weight.

Toe in is adjusted by altering the length of the front or rear lower mountings (shown here with the black arrows). Shortening the front mounting increases toe-in.

Adjusting Toe-in
The image below shows one method of checking wheel alignment using two straight wooden batons.
Both straight edges were mounted on wooden blocks so that they could more easily pick up the tyre edges and establish the angle of the wheels.
The baton for the bike was further spaced from the rear wheel so that it was clear of the front wheel - important as it is the back wheel which is the datum for measuring toe-in.

Taking sidecar wheel angle

 Taking bike rear wheel angle
As a starting point toe-in should be set to about 15mm or 20mm.

This dimension is the difference between the two measurements shown on the right.
Two straight edges are used to find the angle of the sidecar wheel and the rear motorcycle wheel. The difference between the distances shown should be 15mm or 20mm less at the front.

As a general guide, at 30mph on a road without excessive camber the combination should track straight with little input needed on the bars.

Toe-in Initial Settings

Checking toe-in dimension at the front

Once toe-in is set  to an acceptable amount then the bike lean can be adjusted.
Bike lean is to help the bike run straight when a road is cambered.

This is adjusted by lengthening or shortening the top connecting links.

Drawing showing lean out of Bike
One way to set lean is to use a piece of string with a weight on it, hung on one side of the rear tyre. However this process only works if the combination is stood on a level surface. Take some time to find a patch of ground that is at least level across the bike.

With the string taped in place the gap at the bottom between tyre and string should be between 4mm and 6mm.

As shown here the string needs to be hung behind any hub, chain or final drive components to pick up the angle of the wheel.

Measuring bike lean

A road test is needed to verify these starting settings.
If constant pressure is needed on the handlebars to keep the bike running straight then a toe-in adjustment should be made. If a left side mounted sidecar pulls towards the curb when driving on the left, then more toe-in should be added. Always aim to get the combination tracking straight on a typical road at 30mph constant speed.