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Bicycle Helmet Safety Institute



Bicycle Sidecars


Summary: Responses to our comment on sidecars on our page on child carriers.





I was interested to note that your section on children riding in bicycle sidecars basically said "Heck, we don't know".

As an avid bicyclist, veteran motorcycle (and sidecar) tester, and neighborhood safety Nazi, I'd be glad to write a quick blurb on the handling peculiarities of sidecars.

In short, they are diabolical. They don't just handle like a tricycle; they cycle back and forth between bicycle and tricycle without much in the way of warning. And since bicycles (and motorcycles) steer by countersteering (ie, turn the handlebar left to go right), and a tricycle does not, you can wind up with a vehicle lurching all over the road.

If the sidecar is mounted on the right, turning right tends to make the sidecar wheel come up off the ground, instantly turning the thing into a bicycle. So you're turning right, or so you think, and now, suddenly, that same steering input is causing you to turn left. Whoa!

Accelerating and braking are also problematic. The sidecar tends to hang back, due to inertia, under acceleration, forcing the operator to compensate with steering. Under braking, the opposite is true; the sidecar tends to keep on going (unless it has its own brake) as the bicycle slows, forcing the rider to compensate yet again. So you wind up making constant steering corrections every time you pedal harder, shift, brake, etc.

A well-trained rider learns to compensate for these quirks, most of the time. But all bets are off in a panic situation. And it's also problematic that a sidecar, with its extra width, has already sacrificed much of a bicycle's inherent advantages of maneuverability, and the ability to go through narrow gaps, as in between cars, to escape a touchy situation.

Would I ride with a child in a sidecar, in traffic? Not if I liked the child.

Dexter Ford
Editor At Large
Motorcyclist Magazine
res0ftic@verizon.net

And another point of view from Andrew Roddham

I have to reply to Dexter Ford's comments about bicycle sidecars.

He is totally, totally wrong. His opinions are valid for most motorcycle sidecars in the UK but the majority of bicycle sidecars are not fixed rigidly to the bicycle frame but pivot to allow the bicycle to lean in the normal manner. This changes their characteristics enormously.

I am an experienced pilot of both bicycle & motorcycle sidecar combinations and would have no qualms about taking my children in them at all. In the UK, the motorcycle-sidecar combination is statistically the safest vehicle type on our roads !

With most bicycle sidecars, the sidecar frame is hinged low down on the bicycle frame & when riding, the rider steers & leans in the normal way. The sidecar wheel simply skids sideways to allow for the lateral movement. This gives a heavy feel to the steering but does not affect the directional stability. I cannot say that I have particularly noticed any significant mass-steer effect, that you would expect to encounter with a motorcycle-sidecar combination, at cycling speeds.

However, there are some design aspects that need to be considered when fitting a hinging sidecar. The mountings to the bicycle need to be rigidly fixed to the bicycle and to be as far apart as possible, otherwise the forces involved can twist the frame and/or set the sidecar into a forward/back resonance in time with the pedalling frequency. The pivot point needs to be as low as practicable as, the higher the pivot point, the worse the sidecar tyre scrub and wear (extra sideways movement you see...). Otherwise, the design & physics of it are fairly simple.

I have built & ridden a rigid bicycle sidecar but I cannot say that I recommend it. The acrobatics needed to keep all wheels on the ground are not for the faint hearted as, unlike a motorcycle combination, the rider is the most significant part of the mass involved and therefore has to provide pretty much all the balance force by moving over the sidecar on (in the UK) left hand bends (right hand bends for a right hand side fitted sidecar, as in the US).

The advantages of bicycle sidecars are, in my opinion, that the rider is in easy contact with the passenger and rather than being behind the rider in the direct path of overtaking vehicles & flying debris from the wheels, is on the inside of the bicycle, low down next to the pavement - surely the safest place.

Andrew Roddham


This page was last revised on: August 28, 2006.

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