5

I have been given a Falcon MTB. I've sorted out all its troubles but the front suspension fork is worn. When using the front brake the slack in the tubes make them judder. Is there anyway I can "solidify" the fork as I don't need suspension. Can I drill it back to front and put a bolt through or something like that?

  • Make sure the judder isn’t made worse by a loose headset adjustment. There are no doubt methods searchable online but easy tip is if you can rotate the headset spacers there’s a chance it’s too loose. – Swifty Mar 5 at 20:58
  • I have speculated that you could "lock" some shock designs by obtaining a piece of PVC plastic drain pipe of appropriate dimensions, slicing it in half lengthwise, and strapping it around the strut, perhaps with some bits of rubber at the ends. – Daniel R Hicks Mar 6 at 2:03
5

As others said don't drill the fork, as others said go for a new/used fork they come by cheap in most countries when no suspension is needed. But if you still want to go DIY I will give you a couple approaches.

What you can do instead is to put a spacer inside the fork, that way it will have no travel avaliable. You will need something like Nilon or Lexan, as they have more plasticity than pvc it will only deform under load, so it won't crack and break. You can also use aluminium or steel.

enter image description here

About the "give" between the tubes and the legs that's tricky. You can slide a tappered rubber gromet. You will have to custom fit tho, but it should reduce the jugger.

Tappered grommet

  • My problem is not "suspension, to have or not" it's the irritating judder when using the front brake. I'd just like to stop that without spending too much. Only pedalling 2km to and from my bowling club. I'll pull them apart and see what can be done. Failing that there are some used forks around. – Harry Mar 5 at 15:47
  • Good idea - the only downside is you're still carrying around the weight of the dead suspension, but it does restore rideability to the bike, – Criggie Mar 5 at 18:58
  • “Nilon” should be spelled “Nylon”. Polycarbonate is the generic name for Lexan which is a trademark. Polycarbonate is quite sensitive to organic solvents so keep them away. – Eric Shain Mar 8 at 0:10
  • @EricShain sorry English is not my native language. – dmb Mar 8 at 0:16
  • You can edit the answer. – Eric Shain Mar 8 at 9:19
1

The judder is likely due to slope between the fork stanchion and the bushings in the fork lower. Most solutions to make the fork “rigid” (i.e., no compression or rebound movements) will not address this tolerance issue, so in all likelihood the judder would persist after making the fork “rigid”.

The only real fix is to fix the tolerance issue by replacing the fork bushing, which may not be possible on low-end forks or cost prohibitive.

The best solution therefore may be to replace with an inexpensive rigid fork, as other answers have suggested.

  • Unfortunately suspension compensated rigid forks are hard to find and not cheap. I'll pull them apart early next week, see what can be done. If I can't repair them then one idea is to put spacers in the bottom as per earlier suggestion to stop the suspension. I could then perhaps crush the lower inner end so they are oval to eliminate the slack. – Harry Mar 6 at 18:04
  • @Harry the fork lowers are often made of alloys that will crack and shatter rather than be crush-able like steel. You might be able to shim the bushings with something very thin (e.g., foil wrapper) to take up slack if you fix the suspension travel. – Rider_X Mar 6 at 20:58
  • These forks have a wire circlip at the top part of the slider which retains the bushing in the slider. I've taken it off and rotated the bushing 90 degrees and replaced the circlip. Rotated the other side in the opposite direction. They are very much better than they were and I'm happy with them. Nobody supplies spare bushes, I'm only riding on roads so I think I'll leave it at that. Does anybody know what the plastic bolt head does on the top of each leg? They just seem to rotate with no apparent effect both directions? – Harry Mar 7 at 16:00
  • @Harry brilliant thinking on rotating the bushings, I wish I had thought of that! In regards to the top caps, their function can differ slightly depending on the fork. On many forks they simply hold the spring/internals in place as well as providing preload adjustment. On higher end forks they may may have an additional component to adjust things like compression dampening. – Rider_X Mar 7 at 17:15
  • Thanks Rider. I may have a better idea than the bush rotation. The bushes are around 80mm long, they are split longitudinally so they can be opened and removed. Thinking now to make the gap a little wider so they will close up and tighten on the fixed shaft. I have some good strong self adhesive aluminium tape used for closing the ends of polycarbonate roof sheets. Stick some of this on the outside of the bushing vertically where the most internal wear, back and front, has taken place. Reinserting the bushes should close them up then try the results. Infinitely adjustable. – Harry Mar 7 at 19:21
4

You seem handy with tools. Your best fix is to swap in a different fork from a donor bike.

Things to look for in a replacement fork:

  • Same stem mount format (threadless or threaded)
  • Same steerer outside diameter
  • Enough length in the steerer
  • Same mounts for your existing brakes, whether they be disk or caliper or cantilever.
  • If you need mudguard mounts - they're handy to have too.

Also closely inspect the donor fork for cracks and possible wear in bearing races. You may be able to salvage the lower headset race from the old fork.

You can use a fork from any material, steel or aluminium or carbon, but check its crash history first with the owner.

Where to source a fork? Try your local auction websites like ebay or gumtree or craigslist. Expect to buy the whole bike and pick off the bits that could be useful. You're unlikely to find a new fork with the right fittings for reasonable prices.

Last option is to buy a donor bike with rigid forks, and fix that up as well. Then your N is 2.

  • 1
    Been on a steep learning curve regarding forks etc. Last time I owned/fixed a bike was 40 years ago when everything was fairly standard and interchangeable. – Harry Mar 5 at 15:42
10

DO NOT DRILL HOLES IN YOUR FORKS

That would weaken them substantially and run the risk of them breaking under stress (e.g., when you hit a pothole). A broken fork will probably put you in the emergency room, and potentially the morgue if you're unlucky with vehicles nearby.

Hopefully, other answers will address how to fix your forks; worst case is replacement, which isn't crazy-expensive for rigid forks.

  • 1
    I thought of rigid but they need to be "suspension compensated" by 80-100mm which whacks up the price. Looking for used but not abused now. – Harry Mar 5 at 15:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.