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Thread: Flutter with Frog Legs Carbon Forks

  1. #1

    Flutter with Frog Legs Carbon Forks

    I have some sort of bad karma with things not working right, I swear. My Ki Rogue had the uni-tine forks changed, because they were grinding on one side, and continued to be a problem. So they got me these FrogLegs carbon forks. Major flutter. I was told to take to a bike shop, where they could'nt figure out how to tighten them down, and then lost a little part. Got sent a replacement, and then finally my DME sends out a tech guy, who's an engineer even, and puts in the part that was missing, but explains these don't tighten down. Flutter is now much worse. He comes back out, and says Ki Mobility said to make the forks pushed forward 3 degrees. This is AWFUL, and I can't even turn without it feeling like it was going over a hump. He makes it down to like 1 degree. Tells me there has to be a compromise, these are not designed for a dog pulling me (I get that a lot, and I guess it's a fair thing, since we CAN go fast, but not usually). This is so so bad. It's like having two little freewheels on, where I can't sit in place without the forks rolling around to facing away because of the angle. Now they can't come work on it til Friday. I'm stuck with this, and it's making me crazy. I wonder if I can fix it myself, or have another bike shop do it. I have no idea why the DME won't have me come into the shop. They're probably done with me, and just want to get rid of me about now.
    I can't seem to catch a break in getting this chair right. These forks are so new, I guess nobody really knows how to deal with them? Anyone adjust their caster forks on a Rogue?
    Last edited by heartdog; 12-20-2018 at 01:59 AM.

  2. #2
    Senior Member
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    In my experience, flutter happens when the casters aren't at the same height (even off by just a millimeter will cause flutter) and/or things aren't tightened properly. If the forks are at 90 degrees to the ground on a perfectly flat surface and reasonably tight there shouldn't be any issues. I've seen the footplate left and right tubes be tightened at different heights that caused some tweaking especially on open frames. You could loosen the vertical adjustment of the footplate to see if that helps. ...Or it could be that your chair frame is tweaked slightly. It's hard to say. You need to keep troubleshooting until you find a solution. If nothing works, I would say it's a bad frame.

  3. #3
    Just for clarification, are your casters fluttering under normal pushing speeds or only when you are going fast (downhill or being pulled by dog)? I have flutter issues with my Frog Legs if I go too fast downhill, but have not had issues under normal conditions. I'm sure you or the DME have checked, but the casters need to be perfectly vertical when pointed forward. If there is any play in the left/right tightness of the wheel, it will flutter. Since yo said they came out and tightened it down, you've probably already addressed this, but and issue I had at one point was the axle screw was coming loose and it allowed my wheel to shift right and left and caused flutter. I ended up using lock-tite to make sure it didn't come loose again and haven't had issues since.

  4. #4
    So they came out but Ki told them to make it at 3 degrees angled forward. This is so bad I can't transfer well at all, and I fell out of my car just earlier cuz it rolled. I'm betting it's frame related, as the frame has creaked and cracked constantly, and there was a bent shaft for the original forks when they brought it to me. I mean really bent. They supposedly replaced it when the carbon forks were put on, and 'machined' it. But very well could be that one was slightly different height. My COG was moved too far forward, too. I like where the wheels are for pushing, but it's harder to push up any incline, and almost impossible on a ramp. So I imagine that contributes. They keep saying these Frog Legs cannot be tightened down. There's not much too them, and there's a bearing in there, but nothing really to tighten down on it, unless you put a washer in there or something.

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