Full Suspension Frame Build Gone Wrong- Mtbr.com
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  1. #1
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    Full Suspension Frame Build Gone Wrong

    Built my first full suspension frame last month and the results were not great. Plan was a simple single pivot, 140mm rear, 160mm front, two bottle cages, kind of do anything bike. The rear triangle ended up being way too flexy and the geometry was off from my intended design. I was able to get some rides on the bike including a day at Northstar. At least it held together! Heres were thing went wrong:
    1. Wrong seat tube length (2 too long as I had forgot to subtract the top seat post collar portion. I cut out the top tube, shortened the seat tube and welded another TT in. My 80/20 fixture did not hold the geometry correctly and the head angle became steeper, ~68 and the seat tube as well ~78. This did make the bike climb steep rocky stuff pretty well though!
    2. I think the diameter is too small on rear triangle tubes, was planning on 7/8 and ended up going with 5/8 for better clearance and weight savings. The overall design of rear triangle was not very triangular, kind of let aesthetics get in the way of a sound design.
    3. The main pivot does not seem stiff enough. I used 2 headset but went with a low stack height head set which put the bearings kind of close to together.

    I have since purchased a Commencal Meta TR which I love! Comparing it with my frame I think 1/3 of the flex was suspension and just not being used to it after riding a hard tail the last 3 years, another 1/3 the 27.5x2.8 tires and the remaining 1/3 in the frame.

    I will probably give it another go at some point after I get some other projects completed. Comments/recommendation for future builds are totally welcome. Thanks!

    Here are some pictures:
    Attached Thumbnails Attached Thumbnails Full Suspension Frame Build Gone Wrong-bike_2.jpg  

    Full Suspension Frame Build Gone Wrong-bike_1.jpg  

    Full Suspension Frame Build Gone Wrong-bike_3.jpg  


  2. #2
    will rant for food
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    Gone "wrong" is maybe an overstatement, clearly it is a bike. However, knowing your partial failings is tough, and talking about them is part of getting over your past mistakes. Kudos to you, I say.
    Disclaimer: I run Regular Cycles (officialy in 2016, functionally in 2020).

  3. #3
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    I agree, very worthy looking first time project like that.
    It seems like you can dial everything in on the next version or some mods and changes. It looks "modern".
    "Before you criticize, you should walk a mile in their shoes. You'll be a mile away from them and you have their shoes"

  4. #4
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    Is there a bridge on the seatstays or is the only contact between stays the shock yoke? Having a bridge will help eliminate a lot of twist in the rear triangle.

  5. #5
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    Full Suspension Frame Build Gone Wrong-rear_triangle.jpg

    Yeah, there's a little bridge in there! Looking at the seat and chain stays they seem way too parallel. Im also looking into some angular contact bearing for the next attempt. I might even do some FEA if just to compare relative deflection between this and a new design.

  6. #6
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    I'm curious which shock yoke you used? And why you chose it?
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  7. #7
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    The yoke is a BikeYoke #6 for a Specialized Enduro. I liked the fact it came with the bearings already pressed in. The yoke made the shock movement very linear which I hoped would make tuning fairly simple. Seems like yokes are mostly used with a linkage to support it. Might try to go that direction next time.

  8. #8
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    Very cool, even if it didn't come out quite as well as you wanted! I've been working on a design for my first full suspension, and man, are there a lot of details that just don't come up with a hardtail! One area that I keep having trouble is just figuring out how to do the pivots, and I'd say it looks like you did them sort of similarly to how I've thought I'll probably do at least the main one (I'm hoping to pull off a linkage driven single pivot), but I might not be seeing yours right. You said you used a headset, so I'm assuming you put something like a piece of headtube horizontally, and pressed cups into it and them used the clamps on the swingarm to clamp what is essentially a piece of steerer? It seems like that main pivot has so much torsion on it that putting the bearings wider would be good, but I don't have a mill, so keeping the bearing bores round after welding seems like it's going to be tough. Anyway, I'd love to hear your thoughts, and again: good job!

  9. #9
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    I build two frames using the horizontal head tube as main pivot tube and it works well.

    Use a 44mm headtube and two top bearings sets.





    That bike was built with no jig or mill or machine tooling. Hacksaw, files, vise, and some straight lengths of L channel.

  10. #10
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    Very cool! Thanks for the photos! Now I just need to buy a reamer for a 44mm headtube, but I guess I'll need to get that anyway. My only issue with this is that if I want to do a rocker I'll still need to figure out how to do some other smaller pivots, but I guess I'll cross that bridge when I get there. How have headset bearings held up? I would ideally use some enduro max bearings to make things more durable, but maybe the headset bearings are large enough to make them tough. What's your experience been, Shirk?

  11. #11
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    The headset bearings do just fine, same as they do in a headset.

    For your rocker incorporate the other bearings into your rocker.

    On fully #2 this is what I did.





    The links shown in the built picture were trimmed down, I was impatient to get a ride in on it and they were just rectangle slabs at that point.

  12. #12
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    On fully #3 again the links themselves hold the bearings.

    The main pivot uses bearing hearwear from a Devinci Wilson.





    If you don't have access to a mill I suggest you re-purpose the links from an existing frame. Buy a junker frame that you want the same layout and steal it's links, or some brands have the linkages / rockers available as spares that are easy to purchase.

    The main thing I've learned in building my three full suspension frames is keep it simple. Well unless you have a mill and boat loads of time, then do what you want. It's going to take 2-3x more time than you think it will.

  13. #13
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    Shirk: Wow, those are rad, and I love those very raw looking linkages. I dig the caution that it's going to take longer than you think. I've thought of using linkage parts from other companies, but I haven't quite found what I want. Maybe I'll change a bit, since I know Rocky mountain offers some that could work with a design similar to what I want. ...and then maybe I should just go with a simple single pivot design. Did you have a mill on either of those second and third ones? I've thought of trying to get an end mill that would fit in my drill press just to make a good shoulder on bearing holes in a rocker, because I thought that I could simple drill big holes, and use an end mill to clean and square up the inside for the bearings. I like how you made them into clamps though, and that's something I think I'll try. Anyway RAD frames. Dig those linkages too! I'd be stoked to get to see how they ride

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