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  1. #1
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    Are full suspension rear swing arm frames flawed?

    Frames such as these. Name:  fframe.jpg
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    I have not seen modern mountain bikes with this design, but I have seen these designs being used on Walmart bikes with heavy marketing making them appear as mountain bikes.

    Is there any advantage to this design?

  2. #2
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    That design is known as a Unified Rear Triangle (URT) and yes it's pretty bad.

    The biggest problem is that the suspension behaves differently whether you are sat down or stood up. If you sit most of your weight goes through the suspension, if you stand your weight goes through the swingarm and isolates the suspension. The result is that you can only set the bike up to ride nicely when you sit, which is rubbish when you spend sixty percent of your time off road standing.

    They are cheap to fabricate though, which is why so many Walmart bikes use the design.

  3. #3
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    Quote Originally Posted by LewisDoes View Post
    Is there any advantage to this design?
    Do you own one?

    In the early days there were so many weird, wonderful and woeful suspension designs and you are right, many of them we no longer see being used. The answer is simple. We figured out which ones worked the best and kept using those while poorer performing ones died. Why would you make a bike using a poor suspension design if it cost the same to use a good one?

    Most box-bikes are built in China, very cheaply. No one is trying to make a bike that is as good as it can be, the name of the game is making a bike as cheaply as possible so they'll use parts and designs they already have, build frames that are cheap to make or they already have the tooling for etc. For example that shiny rear end in your picture is made of cheap steel.

    Do the have any advantages? They are cheap, that's an advantage. In performance terms, no. I think it's hard to go into a shop today and buy a bad suspension bike, if you spend proper money, but the exceptions are the box-bikes you're talking about. They have suspension and it kinda works, sort of, but it's not a patch on the designs used on higher quality bikes.

  4. #4
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    I do, I have a cheap mongoose xr-75. Many tenants abandon these department store bikes and I'm not surprised why. This one so far was the strangest design I have seen.

  5. #5
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    My buddy had a Klein Mantra which was expensive for the day. Pretty sure simply putting a suspension seatpost on a hardtail would have made for a better bike.
    It is no measure of health to be well adjusted to a profoundly sick society.

  6. #6
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    URT's were pretty cool in about 1996. Fisher, Trek, Klein, Barracuda and several other big names had their take on the design. Some had the pivot point halfway up the downtube like Klein or Barracuda. Some had a low pivot and bobbed along like a caterpillar - Trek and Fisher.
    Less isn't MOAR

  7. #7
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    Single speed fodder.

  8. #8
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    I'm pretty sure that would handle like shit no matter how you set it up.
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  9. #9
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    Quote Originally Posted by LewisDoes View Post
    I do, I have a cheap mongoose xr-75. Many tenants abandon these department store bikes and I'm not surprised why. This one so far was the strangest design I have seen.
    any department store bike is pretty much disposable. doesn't matter what it is.

  10. #10
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    Quote Originally Posted by life behind bars View Post
    Single speed fodder.
    Yeah, they're daft enough to ride anything.

  11. #11
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    Quote Originally Posted by Fix the Spade View Post
    That design is known as a Unified Rear Triangle (URT) and yes it's pretty bad.
    This is mostly correct. Correct: that design was the worst suspension design, ever.

  12. #12
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    URT was adequate in the early days of biking but it's the equivalent to having a cassette player in your car now. By modern standards, modified single pivots have replaced URT for simple, inexpensive full suspension design.
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  13. #13
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    URTs date back to the early 90, before the bike industry as a whole understood what suspension was or what it was supposed to do. If you're looking for a bike that's mushy when you pedal, then firms up when you're standing and most want suspension, they're great.

    Since you aren't looking for that in a bike; no one is, they're not so great.

  14. #14
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    Quote Originally Posted by LewisDoes View Post

    Is there any advantage to this design?
    There's a line of argument that goes like this:

    A mid-pivot URT (Castellano's "sweet spot", like the Schwinn Homegrown or Ibis Szazbo) lets you make a bike that pedals efficiently despite having a couple inches of rear suspension. In the saddle, it's enough to take the edge off and make a more comfortable XC endurance bike. Out of the saddle, the suspension stiffens up enough to make a firm platform for sprinting. There's no pedal kickback or chain growth, no difference in characteristics in different chainrings, and the pivot location gets you decent non-chain-induced anti-squat (acceleration vector through pivot). In short, it's supposedly an efficient design that can be optimized for minimizing fatigue, not DH performance.

    I'm not sure I buy that - I've never ridden a SweetSpot URT - but I can see where that would make a lot of sense. Imagine a market where full suspension is new, most other designs are actually awful, and the alternative is a hardtail.

    Of course, pivot location means everything in the suspension world. Trek/Klein went to both extremes, raising the Mantra's pivot way up high to maximize the stiffening effect (practically a lock-out), and lowering the pivot on the Y-bikes nearly to the BB and drastically increasing pedal bob. Both bikes are disasters by today's standards.

    So today, with a better understanding of suspension design, modern compression dampers, and two decades of trial-and-error, there's no reason to make a (high-end) bike with URT, Sweet Spot or any other type.

  15. #15
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    That design is popular with lower cost makes. It was a good design back in the day when there really wasn't much else to chose from at a certain price point. But there are better designs available now.

  16. #16
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    Quote Originally Posted by OliverMoore27 View Post
    It was a good design back in the day
    No, it wasn't, there were still way better bikes available back then.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  17. #17
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    Quote Originally Posted by Jayem View Post
    No, it wasn't, there were still way better bikes available back then.
    Yup, it was a design that they didn't have to pay liscensing fees to four bar designs for.

  18. #18
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    Quote Originally Posted by root View Post
    Yup, it was a design that they didn't have to pay liscensing fees to four bar designs for.
    4-bar was a marking term that specialized decided to use, very effectively, to try and claim that other 4-bar (linkage) bikes were not "true", but even the stuff like the diamondback V-links and others of the era were vastly better than the trek, gary fischer, ibis, klein and other URT bikes.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  19. #19
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    Walmart has everything..

    No cranks needed... sling walmark horsey stirrups thru front triangle +gheymax ekit. Yeehaw

    https://www.walmart.com/ip/Gymax-26-...&wl13=&veh=sem

    https://www.walmart.com/ip/Western-S...&wl13=&veh=sem
    video=youtube;][/video]...

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