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On a 16" folding bike, the front fender slider tends to release over time and increase the distance between the tire and the fender. This is a problem because, as the fender angle changes, the end of the fender (which terminates before the brake) rubs against the tire.

I could get new sliders and stays (they're inexpensive plastic parts) but this has been a problem with this bike since it was new and same problem will recur fairly quickly. How can I solve this problem?

The bike: Bike

Front fender when it's tight and all is well: Fender tight

Front fender when it loosens and rubs against the top of the tire: Fender loose

The fender end: End of fender

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  • Nice bike! I especially like your handle. :-)
    – RoboKaren
    Commented Jul 4, 2017 at 18:59
  • p.s. If that's your garage, I'd do a better job of securing it than that cable lock (which can get cut with a pair of pliers in less than 10 seconds). We have tons of members who've had bikes stolen from garages.... I would find the largest eyelet bolt, U-shaped pipe hold-down, or truck bed hold down that you can find in the hardware store, bolt that to one of your framing members with a security bolt/nut and pass a U-lock has through it. Something like these motorcycle security anchors: pjbsecurity.co.uk/…
    – RoboKaren
    Commented Jul 4, 2017 at 19:04
  • As suggested by Sheldon Brown, you can glue the fenders with hot glue / epoxy.
    – Batman
    Commented Jul 4, 2017 at 19:52
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    @RoboKaren Thanks! Thinking about getting red brake cable housings when it comes time to replace those. Commented Jul 5, 2017 at 1:41
  • @RoboKaren - Agreed, this isn't my usual locking method. Commented Jul 5, 2017 at 1:41

3 Answers 3

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The problem is that the metal fender (or fender bracket) has some spring in it and wants to spring back placing constant tension on the plastic retaining bits that hold the slider. Ideally, the sliders should not be under any tension or compression - they just should keep the fender from some side to side and a little of fore and aft movement.

If you have a metal fender: I would bend the fender so that it's closer to the wheel even when under no tension:

  • Take off the sliders
  • Push the rear of the fender against the wheel with enough pressure that you feel the metal bending
  • Release and repeat until the fender springs back to about the position you want it to stay in.
  • If it keeps springing back even though you've pushed it against the wheel, you might need to take the wheel off to get some additional space to push
  • Once the fender is about where you want it, then (put the wheel back on and) the sliders back on

Plastic fenders: If the fender is made of plastic or wood, then there is a metal L-bracket underneath the brake calipers bolt that holds the fender on. This bracket needs to be bent just a tad so that the fender is at a better angle viz a viz the wheel. It's easier to bend this with the fender removed as you can crack a plastic or wood fender.

Finishing Touches: After you've done all that, you can put some polyurethane or hot glue on the sliders to help them grip a bit more. I like to use glues that I can easily take off again. One brand I like is ShoeGoo. It is incredibly tough and tacky but you can also get it off hard plastics and metals if you need to readjust the fenders again.

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    I think Im going to try bending the bracket first; will report back. (It's a plastic fender with an L-bracket behind the brakes.) Commented Jul 5, 2017 at 14:53
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    To update this - the fender brace bent quite easily and it seems to be holding well. Commented Aug 4, 2017 at 0:43
  • Further update - the problem is back, clearly bending the brace helped but not enough. Will bend the brace a bit more and report back. Commented Dec 12, 2017 at 15:07
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    The fender stayed away from the tire for longer, but it did eventually come back. Have removed the fenders from this bike for now. Commented Jun 14, 2018 at 20:28
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If the fender is sliding in the mount, I suggest hot glue. You can get it in black online if you're worried about it matching. Just a little adds friction, or you can apply a bead along a joint when everything is set up just right. It sticks quite well to most plastics but can be removed if required, and I've found it very useful for plastic bike bits, for adding grip and locking down rattling parts.

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  • To add, this is a safety feature -- if something is caught in the fender, the fender is supposed to slide through this. Hot glue should hold it into place, but still allow the fender to come off.
    – Batman
    Commented Jul 5, 2017 at 0:31
  • Good point @Batman. In that case I wouldn't clean the surface too well before gluing, and would try a minimal dab of glue to start with. I'm used to more solid mudguards.
    – Chris H
    Commented Jul 5, 2017 at 7:27
  • The Sheldon Brown link I put in the comments has a picture on roughly how to glue it.
    – Batman
    Commented Jul 5, 2017 at 16:49
  • @Batman coincidence or bad design that the ones pictured on Sheldon's site are the same as the ones here. Didn't see your comment as I'm on a patchy signal and wrote my answer offline.
    – Chris H
    Commented Jul 6, 2017 at 7:07
  • Well, they're the planet bike ones. In the US, they're probably the best reasonably priced option you can get.
    – Batman
    Commented Jul 6, 2017 at 11:38
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Thread or knurl the stays so there's more friction with the black plastic clamps.

If that's not enough, do you ever remove the fenders/mudguards? Two small metal jubilee clips should provide more compression around the stays. An extreme solution would be to apply threadlocker or superglue inside the clamp.

You seem to have enough room between the mudguard and the tyre. What if you bent the stays upward to 90degrees, so the plastic clamps rotated on their screws and pointed almost straight down?

Another option is that guard extension looks like rigid plastic - Some bikes have a 100-150mm (4-6 inch) piece of leather as a mudflap right at the bottom. The added damping might help, and will help protect the drivechain and BB.

Last resort is to replace the two sliders and clamps with a single straightened coathanger. This would be a two-leg U shape such that the stay passes around the outside of the guard, with a retaining saddle clamp, and then back to the fork on both sides. That way it can't possibly slip back. In fact I'd probably just do this and not bother with the other solutions.

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    I thought about the plastic coathanger in a U idea, but the fender being able to release is a safety feature in the event debris gets caught in the fender. Commented Jul 5, 2017 at 14:54

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