Sidecar Fitting Guide from Simply Sidecars

INTRODUCTION All of our sidecars are designed to be fitted at home by anyone with reasonable mechanical skill. They do not just clip on and go, fitting can be time consuming and will be different for every motorcycle. This page aims to give a good basic guide and cover many of the problems a home fitter may encounter. Ultimately it is the person doing the fitting that must be responsible for the security and safety of the finished motorcycle and sidecar combination. We are more than happy to offer additional advice if needed. Many customers bring their bike to our workshop and discuss fitting before purchasing their sidecar. By doing this we can make suggestions for clamp location, flag up any potential problems and suggest solutions.
CHOOSING THE RIGHT MOTORCYCLE Some motorcycles are easier to fit a sidecar to than others. Our sidecar fitting system is only designed for tubular steel cradle frames. That is a frame made entirely of steel tubes which form a complete cradle round the front and under the engine. Ideally this should have two tubes in front of the engine, although some lighter bikes such as the Royal Enfield 500 may only have one tube. Most twin shock bikes and most custom cruisers would have this type of frame. The frame steering geometry of the original bike should not be at all sporty, so again most retro or classic twin shock bikes as well as most cruisers are correct. A long bike will generally be more stable in a straight line than a short one. A low center of gravity is more stable when cornering, so again cruisers win. It's good to have an under stressed engine with plenty of torque. So for ease of fitment and a very stable easy ride a cruiser would be a good choice. There is however one potential issue to look out for when choosing a cruiser, this is trail. Some cruisers have excessive trail as standard, great for stability but it can make the steering very heavy. Before buying a cruiser quickly check on line and find out the manufacturers rake and trail figures, ignore the rake, but look at the figure for the trail, 100 mm to 120 mm will be stable and light to steer, 121 mm to 140 mm will be very stable but starting to get heavy, 141 mm to 160 mm really will be heavy unless you have very wide bars, above 161 mm and you should probably pick a different bike. Retro and Classic bikes make a good choice, offering straight forward fitment and slightly livelier handling usually having between 100 mm and 115 mm trail
	BEARINGS AND TYRES Adding a sidecar to any motorcycle is going to highlight any existing weaknesses in the suspension, steering head bearings, swing arm bushes, etc. Before fitting a sidecar check the motorcycle carefully. Any slight play in the wheel, swing arm, or steering bearings will cause low speed wobbles and will wear to a dangerous condition very quickly once the additional stress of a sidecar is added. Take a look at the tyres, they do not need to be anything special but ideally they should be flattish on the top to get as much contact area as possible. Ribbed tyres really mess up a heavy fast combo and should never be used, if the front tyre has long lines in the tread going inline with the bike change it before the sidecar is fitted. Think about the suspension as well. If it is adjustable, adjust it to the hardest settings. If it still feels soft even as a solo bike, consider getting aftermarket springs which are stiffer than the originals. Sometimes the non adjustable front forks can be pre-loaded by adding a spacer above the spring inside the forks. Do not rush out and spend a fortune on leading link forks, before even trying the standard set up.
	CLAMP LOCATION Our frame clamps (part # SC/3) are designed to fit steel frame tubes with a diameter between 25mm and 32mm. The clamps should be as far apart as possible to spread the load as evenly as possible across the motorcycle frame. Remember we are very happy to offer advice and suggestions. The unique clamp is both strong and compact.

AXLE LEAD AND TOE IN Sit on your motorcycle to see how much the suspension drops with your weight. Use ratchet straps to slightly compress the suspension so the motorcycle remains at this level when you get off. If possible support the motorcycle securely with blocks of wood so it is on its wheels and upright. The first measurement to look at is how much the sidecar axle is in front of the rear wheel axle of the motorcycle as shown at C and D on this picture. This needs to be between 20 and 30 cm, less axle lead (20 cm) will produce a sidecar outfit which turns quickly but is less stable at speed. It will also require slightly more toe in. More axle lead will produce a sidecar outfit that is slightly heavier to turn but it will be more stable at speed. It will also require less toe in. Arrange the sidecar chassis on blocks of wood next to the motorcycle so it is level and the axle lead is correct. Loosely attach the two lower mounts. The front lower mount should be as low as possible and as far forward as possible, This can usually be attached to the main horizontal frame tube just before it turns to go up towards the headstock. The rear lower mount should be as far back as possible. This one often needs an additional subframe making to take the mounting point as far back on the motorcycle as possible. You will need four bricks and two straight lengths of steel. Place the two straight edges on the bricks either side of the bike and sidecar. On the bike side measure accurately and adjust the straight edge so it is 25 mm away from the wheels rims. You should be able to measure this at four points. Rear of rear wheel, front of rear wheel, rear of front wheel and front of front wheel. Then do the same on the sidecar wheel but as you only have one wheel you will have to rely on two measurements. Finally measure the distance at right angles to the bike just behind the rear wheel (marked A) and again just in front of the front wheel (marked B). This is the amount the vehicle toes in over the whole length. There are no hard and fast rules for this but a good starting point is 15 to 25 mm. So to be clear the distance between your two straight edges should be 15 to 25 mm greater at the back than it is at the front. (These measurements do assume that the wheel rim is the same width front and back even if the tyres are not the same size). If you had near 30 cm axle lead set the toe in close to 15mm and if you had near 20 cm axle lead set the toe in close to 25 mm.
	LEAN OUT Once the toe in is set and the lower mounts reasonably tight the lean out can be set. Loosely attach the two upper mounts. The front upper mount should be as high as possible. This is usually clamped round the frame near the head stock. The rear upper mount should be high up and as far back as possible. It is usually possible to clamp very close to the rear shock absorber top mount. The motorcycle must lean very slightly away from the sidecar. This must be measured with the steering straight ahead but the measurements are usually carried out on the rear wheel. Tie a washer to some cotton and hold the free end of the cotton near the top of the wheel so the weighted end hangs down on the outside of the wheel. Note where the cotton touches at the top and measure the gap between the cotton and the similar spot at the bottom of the wheel. Over the height of the wheel the lean out should be 4 to 6 mm. If the sidecar will be used most of the time with a heavy load this lean out should be increased to 8 to 10 mm. Once the toe in and lean out are set. Tighten everything and remove the supports from the motorcycle. Release the ratchets used to compress the suspension.
	CAMBER This is less important than axle lead, toe in or lean out but still worth considering. As the bike turns right the suspension on the sidecar will compress and the suspension on the bike will lengthen causing some body roll. In turn this will mean in hard right turns the top of the sidecar wheel will move away from the sidecar as the bottom moves towards it. At rest the sidecar wheel should be set to either upright or slightly leaning in towards the sidecar. It should not be set leaning away at the top as this will increase when cornering. When set slightly leaning in at the top the outfit will be more stable in corners and the forces will go through the wheel and bearings in a straighter line putting less stress on the spokes and bearings.
SUBFRAMES AND OTHER SOLUTIONS Our universal fitting kit is incredibly adaptable, but sometimes the chosen motorcycle will not have a good strong mounting point just where it's needed. Small, but strong subframe's can be easily made by anyone with the ability to cut and drill steel. It is very important that the sub frame is supported by triangulation both up and down and side to side. We are happy to offer advice and suggestions if you get stuck. The example shown to the right fitted to this Triumph Scrambler uses three lengths of 6mm thick steel. Part 1 is simply drilled and bolted to and existing strong mounting bolt. Part 2 is almost the same but has a arc removed to clear the main motorcycle frame. Part 3 bolts to the other side of the motorcycle to give side to side support. Part 3 is bent in two places close to each end. All three join at the eye bolt which holds all three together. There is no welding needed and no modification to the original motorcycle. Another solution to tricky mounting locations can be seen on the Kawasaki cruiser shown below left. The front lower mount has to go just below the frame to keep the front of the sidecar low enough. The original motorcycle is fitted with foot boards on substantial mountings. The block from the our standard clamp (part # SC/3) is welded to the 6mm plate steel foot board support. It is welded both front and back to ensure strength. A lock nut is then added to the back of the block (part # SC/NUT27) Occasionally a mounting prop (part # SC/5) will cut across the controls of the bike. The forward controls on the Honda, shown below right, interfere with the location of the front prop. The prop has been bent in a professional pipe bender and a fillet cut from 4mm steel plate and welded in to support and hold the curve of the prop.

ELECTRICAL CONNECTION Lights usually fitted are front white marker, front amber direction indicator, rear red marker, rear red brake light and rear amber direction indicator. If your bike does not have indicators there is no requirement to have indicators on the sidecar. Most motorcycles have a main wiring loom going to the rear lights and indicators located under the seat. This is the best place to connect the wiring. If you are using our cable kit (part # SC/WIRE) a waterproof connector is supplied with enough wire each side to go to the sidecar in one direction and the bike in the other. The original left hand direction indicators should be removed from the motorcycle if possible. If it is not possible to remove them completely the bulbs should be removed so they no longer flash.
	WARNING AND THE SMALL PRINT Our sidecars are designed to be fitted by competent home mechanic. We are happy to offer advice. BUT ultimately it is your responsibility to ensure all work is carried out to a safe standard. We strongly advise that any welding, or specialist bending is carried out by a professional fabricator.