Is there such thing as a Lefty fork without a shock?
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  1. #1
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    Question Is there such thing as a Lefty fork without a shock?

    I think it would rock to have a road or cross bike with a Lefty, but I'd want it without a shock. Does that exist? Or maybe is the shock required so that bumps in the road don't over-stress the single connection of the axle?
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  2. #2
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    Interesting idea...

    Does not appear to be any thing on Cannondale's web site, but that would be where to start looking...

    My guess would be that a rigid lefty fork for road or cross would be too heavy to be effective due to the construction necessary to make it rigid enough and durable enough would be counter productive...
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  3. #3
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    Quote Originally Posted by anthrax
    Interesting idea...

    Does not appear to be any thing on Cannondale's web site, but that would be where to start looking...

    My guess would be that a rigid lefty fork for road or cross would be too heavy to be effective due to the construction necessary to make it rigid enough and durable enough would be counter productive...

    I should've mentioned I already checked the Cannondale pages so that's why I'm asking. Good point on the durability vs weight. I just want to freak people out with half a fork flying down the road...
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  4. #4
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    I like the freak out idea!
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  5. #5
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    yes it is called a uniblade and was made by kastan in the 80's-90's

    https://images.google.com/imgres?img...%3Den%26sa%3DX

  6. #6
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    Quote Originally Posted by SuperSlow
    yes it is called a uniblade and was made by kastan in the 80's-90's

    https://images.google.com/imgres?img...%3Den%26sa%3DX

    That's cool! Too bad it looks like they are only for BMX. I want one in a 700c. Although if they can be used for BMX, I'd hope they'd also be sturdy enough for roads and some single track use.

    Edit: Wait, maybe not - check out this quote from the forums on that site: "The ol' Uniblade held up great for me, but I saw a kid in a heat right before me at a national snap his in two. He dropped his front wheel too soon on a set of doubles."

    That would qualify as a bad thing in my book.
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  7. #7
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    yes it is called a uniblade and was made by kastan in the 80's-90's

    https://images.google.com/imgres?img...%3Den%26sa%3DX

  8. #8
    n00bsauce
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    Since all the Lefty Speed forks have lockouts I doubt there would be an issue with rigidity or durability on a rigid lefty. It should also be lighter weight than a double bladed fork. I see no problem but Cannondale must not see a market or they'd probably sell one.
    "Those who can make you believe absurdities can make you commit atrocities." Voltaire

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  9. #9
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    Quote Originally Posted by Mel Erickson
    Since all the Lefty Speed forks have lockouts I doubt there would be an issue with rigidity or durability on a rigid lefty. It should also be lighter weight than a double bladed fork. I see no problem but Cannondale must not see a market or they'd probably sell one.
    I think your right about the market thing. The rigidity is fine too. As for the lockouts they are problematic as they start to devlop play quickly so you'll have several mm's of slop in the fork and it keeps getting worse. Of course, it happens most when people go from road to mtb trail and forget to turn the lockout off. Even if you ride them exclusively on the road they will still eventually develop the slop. To be fair to C-dale many other manufacturers have the same issues with lockouts on their forks.

  10. #10
    n00bsauce
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    I only mentioned the lockout because, when locked out, the fork would essentially act like a rigid fork and put the same stresses on the axle as a fully rigid fork. I had an old DD60 which eventually bit the dust but the lockout worked fine until the day it died.
    "Those who can make you believe absurdities can make you commit atrocities." Voltaire

    There are your fog people & your sun people, he said. I said I wasn't sure which kind I was. He nodded. Fog'll do that to you, he said.

    "We are all ignorant about most things."
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  11. #11

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    Quote Originally Posted by Mel Erickson
    Since all the Lefty Speed forks have lockouts I doubt there would be an issue with rigidity or durability on a rigid lefty. It should also be lighter weight than a double bladed fork. I see no problem but Cannondale must not see a market or they'd probably sell one.
    A single leg rigid fork will most definitely be heavier than a dual leg fork of similar stiffness. Due to the balanced load between legs, the dual bladed leg has less bending and torsion on each leg than the single leg fork, and the extra material needed to be added to the single leg will be more than the weight of the fork leg removed.

    The reason a single leg suspension fork is more viable is because it eliminates not just the extra leg, but all the extra mechanisms in the second suspension leg (bushings and sliders, springs, dampers, rods, the fork brace.

    The only advantage to a single leg fork on a road bike is the reduction in air resistance. This has been used several time for special purpose TT bikes (most often track bikes, but sometimes road bikes). However, when they've tried to adapt the single leg design to a road racing bike, they found the lack of rigidity to cause handling problems, and so reverted to dual leg forks.



    (P.S.: The technical mumbo-jumbo above is just to avoid the real reason no one makes a single leg road fork - the real reason is because everyone knows that road riders are obsessive-compulsives, who would never be able to get over the fact that only something with two or more legs, blades or tynes can be correctly called a "fork".)

  12. #12
    n00bsauce
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    May have been true when most forks were made from steel. Building with carbon fiber can overcome the limitations you describe and be lighter to boot. The real reason is, it's just not needed, at least until someone (like Shimano) can figure out a way to market it to the masses so they can't resist the latest and greatest must have component.
    "Those who can make you believe absurdities can make you commit atrocities." Voltaire

    There are your fog people & your sun people, he said. I said I wasn't sure which kind I was. He nodded. Fog'll do that to you, he said.

    "We are all ignorant about most things."
    Mel Erickson

  13. #13

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    Material properties of carbon don't change the physics/mechanics of fork legs

    Quote Originally Posted by Mel Erickson
    May have been true when most forks were made from steel. Building with carbon fiber can overcome the limitations you describe and be lighter to boot. The real reason is, it's just not needed, at least until someone (like Shimano) can figure out a way to market it to the masses so they can't resist the latest and greatest must have component.
    Why do you believe the same limitations don't apply to carbon? Carbon may (sometimes) have a higher strength/weight ratio and strength/stiffness ratio, but that doesn't change the fact a two leg fork will always be stiffer than a one leg fork (of the same weight). It is a matter of symmetrical legs cancelling the moments in bending and torsion, not material properties.

    Also, the main problem with a single leg fork is one of stiffness. Carbon has typically been used to make forks lighter, not stiffer, than steel forks. Check out Damon Rinard's fork stiffness test, in which the stiffest of the forks
    tested are steel, whereas the flexiest are carbon.

  14. #14
    Roadie with unshaven legs
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    On a mountain bike, where you have two stanchions to deal with (and two sets of seals) weight isn't as big of an issue. Cannondale claims that their Lefty is as heavy as a comparable conventional front suspension fork for the same amount of travel. I do not believe that you can create a rigid front road fork that is stiff and light compared to a conventional carbon fork.

    The big reasons for me to purchase a mountain bike with a Lefty are the relative lack of sticktion and the rigidity. Yes, the Lefty is one of the most rigid front suspension forks (if you can call it that) you can get on a mountain bike because it only has one leg. The engineers at Cannondale really went to town to make this system stiff, stiff, stiff. Also, there is one thing the Lefty does well that a conventional suspension fork doesn't do: side loads while still retaining suspension travel. I know it doesn't happen often on the trail but it does happen and a conventional fork is more likely to cam and lock itself out while a roller-bearing supported Lefty will never have this problem.

    About the Lefty looking unconventional, all I can say is that when I ride mine it doesn't bother me but when I let others ride my Prophet it just looks wrong to me.

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