Why does the steering on my trike shake so much?
Here at Rhino trikes, I get such a number of phone calls from people who’ve bought or had trikes built, then when they take delivery of them, are afraid to ride them because of the front wheel/steering shake.
A first thing first; is your trike shaking its head or is it more of an oscillation or weave, what bikers call a "tank slapper."
If it’s more of a tank slapper you are experiencing, your problems are more serious than this article covers and you need to go back to basics, check that nothing is loose or worn. A tank slapper can be very dangerous therefore we recommend you get the trike examined as soon as possible.
Ok, so we have established that it’s more of a shake than a weave. They want to know what they can do, fit a steering damper, softer suspension, heavier fork oil?
The reason for the wibble wobbles is simple and almost fundamental to bike/trike conversions: Motorcycle steering is designed to self steer when the forks leave the vertical plane or when the bike begins to lean over, the rider then subconsciously counter steers which keeps the bike in the corner until the rider straightens up.
Of course, with a telescopic fork equipped trike, the rider cannot lean the rig but unless the trike is being ridden on a frozen pond, road surface irregularities will still be sending signals to the fork geometry, telling them to start the front tyre deflecting, thus causing the front to steer away from the bump before springing back as the outfit returns to level. Multiply this many hundreds of times and you can understand why you get the wobbles. The cure is to increase the contact patch between tyre and road, thereby increasing road/tyre friction and damping down the reaction of the tyre preventing it from having time to transfer the information to the forks.
You could fit a heavy steering damper but to be honest, this would be treating the symptoms and not the disease; besides, a steering damper would make the steering impossibly heavy at low speeds.
Not all steering anomalies fall into this same category, however there is a self-help test I suggest to everyone; let the front tyre pressure down to around 10 psi then give it a go. If the problem is significantly reduced, the solution is to fit a square tread tyre. My own recommendation is the trusty old Avon Speedmaster MKII, which is available in 18" and 19". You can use an Avon Sidecar triple duty for 19" rims but they are not my favourite choice. Another alternative for smaller trikes is the Avon supreme, an H speed rated tyre which comes in an 18" size only but has a slightly more bike style profile and more up to date tread pattern. I am not on the payroll of Avon tyres and there may be other brands, which offer flat tread bike tyres but so far, I am yet to encounter any, at least not on sale in the UK.
Increasing the headstock rake on a trike will also help to address the problem by slowing the steering; again, the trade off would be heavy steering.
At Rhino trikes, we have used a combination of front rake/trail and rear suspension design coupled with the choice of donor bikes we use to give what we consider to be the best compromise between road manners and ease of control without the need for special tyres.
Visit our site at: http://www.rhino-trikes.co.uk