Tiller effect…

SteeringAlignmentOpt

Before mountain bikes appeared, I had never thought of positioning my handlebar other than in alignment with the steering axis; it was what I was used to from my motorcycling background.

However, there they were, these off-road bikes from the yew-ess-ov-aye, with handlebars extended out over the front wheel. Everyone raved about them, who was I to contradict the experts?

Try as I may, I simply could not get used to handlebars with a forward extension, nor could I figure out why such a relatively small aspect of a bicycle’s design should make riding it so very unwieldy and uncomfortable.

Anyway, it took me years to eventually analyse the mechanical dynamics of the tiller effect and consider why this design practice had come about in the first place. The experts are clear in their view; you cannot control steering unless your weight is over your front wheel. If this is true, then logically it should be impossible to pull a wheelie and ride on your rear wheel only, or successfully ride a unicycle. Since steering and balancing are basically the same action; you must be able to steer in order to balance, if you can’t control steering, logically you can’t balance.

Extended

This illustration shows a handlebar that is not as wide as the typical with a 100mm forward extension. When the handlebar is turned, notice how the centreline of your hands is shifted away from the centreline of the bicycle. The positions of these centrelines give an overall indication of the position of the centre-of-gravity of you and your bicycle; as you may well understand by now, controlling your centre-of-gravity is key to controlling your balance and steering.

Every time you turn a forward-extended handlebar, the tiller effect results in an unavoidable shift of your upper body, exacerbated by the typical mountain bike stretched-out posture, where both arms are fully extended.

Steering left, your left arm can bend as the handlebar moves towards you. However, your right arm, already fully extended, has to stretch further forward, pulling your shoulder and upper body with it, thus forcing both an unwanted centreline sideways shift and forward weight shift.

This handlebar forward extension idea comes from cycle racing on a smooth race track or road; it was what mountain bike innovators were used to with their roadie backgrounds. In that context a ‘fixed’ rider position is most efficient and speed the imperative. This centreline sideways shift is advantageous; the rider can initiate a turn without altering their body position very much, allowing them to maintain power input and speed output.

Riding relatively slowly on uneven terrain is a different matter altogether. For instance, you may wish to wiggle around a rock, but continue in the same direction. If, when doing this, you also shift your centre-of-gravity, you’re initiating an unwanted turn, which you have to fight to correct. Could it be that many riders prefer a bit of a battle with steering? Certainly their excessively wide handlebars which exacerbate the problem whilst giving the illusion of greater control, will make their rides seem more dramatic.

The Landseer’s handlebar is aligned with the steering axis, so there is little, or no, sideways centreline shift when steering, with the minimum of effort your centre-of-gravity remains where you want it.

Aligned

Additionally, the Landseer’s hand position is fairly close to the saddle; there’s plenty of flexibility in your arms. Whether you’re just keeping balanced when almost stationary, avoiding a small hazard or riding a corner at speed, you always have that same flexibility and centre-of-gravity control; you don’t have to fight for balance.

What about steering geometry?

Click here to go to the beginning of the whole story.

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About gmacleland

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7 Responses to Tiller effect…

  1. gmacleland says:

    Yep, Ian, to you, me and a very few others, it all makes perfect sense.

    It’s worth noting that no off-road motorcycles have a handlebar forward extension ~ they’ve been around a lot longer than mountain bikes, and a motorbike would be far less affected by the tiller effect.

    Curiously, most bicycle design is a belief system based on empirical evidence. When any evidence is derived from ‘scientific’ experiments, assumptions are always made:

    – the rider is young and fit
    – the aim is as high a speed as can be achieved
    – the bicycle is very lightweight
    – the terrain is predictable

    Have you ever seen a scientific cycling experiment featuring a smoking pensioner with arthritic knees riding a heavy machine with flat tyres over the ornamental rockery outside the laboratory window?

    I know what I’m doing makes sense ~ it’s trying to share that information that seems pointless, and probably is pointless. Life is too short.

    • Ian... says:

      It’s a bit like people buying a computer – for a massive chunk of users a web browser is all they’ll use, but how many of them are sold a Chromebook?

      We’ve discussed Dutchbikes many times…here’s a pic taken riding one a few years ago…am sure you’ll see it straight away!

  2. Rich Jewell says:

    Keep on sharing Geoff. You’ve got a small but hardcore group (a confusion?) of fans to whom this makes perfect sense.

  3. Rich Jewell says:

    Your fans are always waiting keenly for your next post! Many of us are builders and experimenters ourselves. For my own part I’m not in your league with ideas and engineering solutions, but I’ve built up one bike in the Cleland style and I’m now working on a more hardcore version, truer to the Cleland ideals. Keep at it, you’re inspiration for the rest of us!

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