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Wtf?! Bmw r1150r

Discussion in 'Adventure/Enduro' at netrider.net.au started by NiteKreeper, May 3, 2011.

  1. I was on-site for work today, and happened to park next to one of the above beemers.
    Now, maybe I've been living under a rock, and maybe I'm just not a BMW fan, but WTF is going on with the front-end on those things?!!
    Not so much a triple-clamp as a single-clamp, but with the addition of another swingarm and monoshock on the front! WHY??!!
    To squeeze the assembly in there, the radiator has been cut in half and both pieces mounted in the "ram air" intakes next to the tank - not very simple...
    There's gotta be a good reason for all that trouble, so can anyone enlighten me?


     
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  2. That's BMW's Telelever suspension.

    The advantages are somewhat to do with the flaws of telescopic-fork suspension.
    On a telescopic fork (ie: "normal" bike suspension) bending forces due to braking and so on try to bend the moving parts of the fork, which can result in binding, increased 'stiction' and generally poor suspension performance. Sliding parts behave unpredictably (if at all) when put under large bending moments and this makes suspension designers very very angry. Macpherson/Chapman struts on a car have the same problem in fact, when subjected to large lateral cornering forces.

    On a telescopic fork, suspension dive occurs due to braking, which eats into the amount of fork travel left to absorb bumps. It's not uncommon to be braking hard on a softly-suspended bike and hit a minor bump which then bottoms the fork out completely, which is a Really Bad Thing in terms of front wheel grip and could damage the suspension, result in a crash, etc.


    Telelever fixes that:
    The bending forces are all carried by the swingarm, leaving the staunchions and shock absorber to travel freely without any stiction induced.

    The 'roll centre', for want of a term, is different to traditional forks and can be moved around by the designer. That means the bike can be designed to have very little, if any, dive under braking, which means even under maximum braking effort 100% of the suspension travel is available to absorb bumps. No brake dive or very little brake dive also means that the spring and damping rates can be set up for optimal grip on "real life" road surfaces rather than trying to 'fix' the brake-dive issue with stiff springs that aren't optimal for bumpy real-life roads.


    Telelever has its own flaws, of course. It's impossible to set up very-long-travel suspension in Telelever configuration, for the same reasons a Mazda MX5 will never be a rock-crawling monster 4x4. More realistically, and I say this having never rode a Telelever-equipped bike before, most reviews of Telelever-equipped bikes say the front end feels a little "vague" compared to competitors' traditionally-sprung bikes. Maybe due to the lack of brake-dive and lack of disruption caused by bumps compared to a 'normal' bike.
     
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  3. Awesome Spots, thanks for that - I've heard of telelever before but never seen it.
    And it made sense as soon as you mentioned the "bending forces" too...
    It would have to work perfectly for me I reckon, since it makes the bike look damn ugly up front - kinda like someone has mounted a 4Kg gas cylinder behind the front wheel...
    (But then again when your footrests are also cylinders, what's a bit of ugliness you can't see from the saddle?!)
     
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