Suspension tuning with a sidecar

Some years back I was privileged to attend an highly informative suspension clinic conducted by Dave Sallberg of the Honda Sport Touring Association. What I discovered was that sport bikes and grandpa rigs are entirely different critters. As a service to other three wheel road pilots, I will try to explain some of the fine points of tuning for maximum road handling ability.

Toe-in and lean are two critical issues in sidecar handling, followed by fork suspension travel and rear shock adjustment. All of these contribute to making the sidecar experience one of joy or one of sheer terror. In an effort to alleviate the latter, I offer the reader nearly 35 years of my experience in sidecar tuning.

Having the right tools is essential. Because alignment of the sidecar is so critical it is imperative that precise methods are used to set the toe-in. I have found that a well calibrated set of steel bed rails is the best device for taking initial measurements. If you have a spare set, that would be the best way to go. If you have to remove a set from one of your childrens beds, you will want to try to get them back before the evening which can make this whole process a little rushed. In fact, you probably just want to explain to your son or daughter that they will be sleeping on the floor for a few days.

As for calibrating the bed rails, you will want to make sure that they are straight and true within .001” over their entire length. If you know someone who has a coordinate measuring machine, that would be very helpful. If it is determined that your rails are out of tolerance, place one end in a vice and yank on the other end until you feel some give and then have it re-measured. You may have to do this a few times until you get everything into specification.

Next you will require a good box end wrench or crescent wrench for loosening the attachments between the cycle and sidecar. Be careful if using a crescent wrench so that you do not round over your nuts. Worse still, if the wrench slips completely, you could damage your nuts. Ouch!

It is not necessary that your measuring device has a metric scale if you are more comfortable with inch readings. This is personal preference. A calibrated, digital tape measure is recommended, but there are other alternatives. In a pinch you can tape together two yard sticks making sure that the mating ends are sanded square. Use duct tape if you can to join the two and make sure that you carefully re-mark the tape where you have covered up the scale markings. You may need the markings under the tape. You will want to have paper and pencil at hand to record the measurements you will be taking.

The place to begin this whole process is with some initial measurements. Your rig must be on a flat surface, i.e. the garage floor. Place one of your calibrated bed rails on the floor and against the front and rear wheel of the cycle. Take the other rail and place it against the sidecar wheel. Next, measure the distance between the two rails, first from the rail at the front wheel of the cycle and then between rails at the rear wheel. This is your toe-in dimension. I have found that 3/4”-1” of toe in is a good starting point. All rigs are different and each will be set to what is best on an individual basis.

Assuming that your toe-in measurement needs adjustment, you will have to loosen the struts that connect the sidecar to the bike. In my case, there are two fixed upper mounts and two ball and socket lower mounts. The lower mounts can be moved in or out as necessary and the upper mounts can be lengthened or shortened by screwing them in or out. You will probably find that each mount will have to be adjusted to get the proper setup.

A word of caution is due here. If you disconnect the upper struts in order to adjust the lower ones be careful that you do not lose control of the situation. Should the bike decide to fall inward you will be left looking at something akin to a folded up pita sandwich. Run quickly to the house and look in the mirror, you do not want to miss the expression on your face. This is the voice of experience speaking. If you have dumped your solo bike and had to lift it off of the pavement, you know that it can be a bit of a strain. Try lifting it back up with a sidecar attached and the sidecar wheel dragging against every effort you make. Better still get a ratchet type cargo strap and attach one end to the bike and the other end firmly to one side of the garage or other fixed point and start ratcheting. Do not remove the cargo strap until your upper and lower mounts are once again firmly attached, unless you enjoyed the previous experience.

Assuming that by this time you have set all of your attachments for toe-in, next you must consider lean. Ideally the cycle should lean away from the sidecar by about 1/4’. A carpenters square against the rear wheel is a good way to determine this measurement. Tighten all of your connecting hardware and proceed to a static test of spring compression. You will need a second person to help you here. Place yourself on the saddle while your partner stands behind you. No need for your friend to hang on to anything, you are not going to fall over, Duh! Your friend is there to visually determine whether you need heavier rear shocks or less ass. If it is a good friend, heavier springs will be recommended. You do not want your shocks to bottom out by virtue of your just sitting there. If that happens, I recommend a trip to your favorite cycle supply.

The front suspension may or may not have adjustments. Mine does not. If the front end feels like it wants to dive to the limits when you apply the brake and throw your weight forward, you may need new springs, you may not have any fork oil, or the oil may be of the wrong viscosity. Check the owners manual and head for your favorite cycle supply.

Now the moment of truth has come. After all of your efforts, a road trip is in order as a reward for your hard work. If everything is aligned perfectly your riding will be effortless. Fat chance! Did you really think that you would get it right on the first try? You may be experiencing a tendency for the rig to pull one way or the other. This makes riding very tiring as you constantly fight to keep tracking in a straight line. You will also eat up your rear tires at an alarming rate. You will have to return to the garage and tweak the alignment a bit more until you feel comfortable that the tracking is straight down the road. Ultimately, your tire wear will be a great indication of whether you have things right or not. The wear should be even across the width of the tire. If it is not, you will have to keep on tweaking the alignment. Eventually you will come to a compromise where you find that everything is as good as you can make it or you are just not willing to mess with it anymore.

The sidecar experience can be quite rewarding once these few minor adjustments are made. Just do not expect that once they are made they are permanent. Unfortunately things loosen up and move. You will know when that happens as your arms and shoulders begin to strain at the effort of keeping things on a straight line. Do not despair, by now you have gotten good at aligning your rig and you will certainly be the envy of all of your two wheel friends who constantly risk falling over at stop lights when they forget to put their foot down. Eventually you will make the decision to permanently weld your brackets in place so they cannot move.