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  1. #1
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    KM's with 185+ Rotors and fork flex

    I have a 2011 KM with BB7s and 185mm rotors. Under heavy braking it appears as though the top of the wheel pulls left towards the rotor. The wheel is a Stans No Tubes Flow laced to a ZTR hub. The skewer is tight and intact. I do not notice any play in the bearings, but will confirm tonight. The wheel tension feels consistent all around the wheel and the wheel is true.

    Is it possible that the fork is visibly flexing? Has anyone else experienced similar phenomenon? I am a big guy at 6'4" 230 geared up. Doe you have any simple tests to determine if the fork is, in fact flexing?

  2. #2
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    I'm a similar size as you and have had this problem on another rigid singlespeed (it wasn't a 29'er). It was the spoke tension. I tried many many different things and put some money into fixing the problem. Go around your wheel and tighten each spoke a bit and you'll notice a difference. Your wheel shouldn't do that.

  3. #3
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    I'm pretty sure my KM fork flex under hard braking!
    (also with 160mm rotor!)

  4. #4
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    Surly forks are very flexy, I will give you that, but OP also mentioned seeing his wheel pull to the left under hard braking. That is spoke tension issues, nothing to do with the "wet-noodle"-like forks

  5. #5
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    I will take a look at the tension over the weekend. A quarter turn on each spoke should be a good starting point, right?

  6. #6
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    That's where I would start. That's where I did start, actually, though I can't remember how much mine actually needed. If you know your quick release skewer and hub bearings are not the issue then it is spokes, and you will notice less wheel flex as you tighten the spokes. I tightened mine just enough to where the wheel didn't pull over any more. I'd say to give each spoke a quarter turn (start at the valve so you don't lose your spot) and test it out a few good times...keep going until you are satisfied.

  7. #7
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    Don't rule out the skewer too quickly.

    I am also heavy and I had the same problem when I ran open-cam skewers on my KM with big rotors. Even with Shimano XT skewers, I could still get the front wheel to shift with the 185 rotors if I locked up the front wheel, so I changed to 160s. I have not problems with this set-up, but even with good skewers cranked on tight, I still am redeveloping trust in it.

    jim
    Surly KM half-fat 1x9
    Surly 1x1 half-fat fixed
    A handful of vintage bikes: Klein, GT, Amp Research, Stumpjumper

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