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I am riding a Dawes made sometime before 1974 and have read in a Swedish report (http://vti.diva-portal.org/smash/get/diva2:694821/FULLTEXT01.pdf) that front fork failure is a not uncommon cause of sometimes serious injury. However, I cannot find any tips on how to know when to change my fork? All tips and advice would be much appreciated!

  • I've never heard of a fork failing, when it had not been damaged somehow first. I would imagine, though, that some cheap shock forks are subject to falling apart. And, of course, aluminum and fiber forks are subject to fatigue failures. – Daniel R Hicks May 10 '18 at 11:45
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My experience is: Any bike part can, and will fail under heavy use. This includes frames, forks, stems, seat-posts, handle bars, cranks, you name it. I have broken at least one of all these in my life already.

Obviously, the risk of breaking things depends on some variables:

  • Your weight.

  • Your power.

  • The distance that you've ridden.

  • The street conditions and tire pressure
    (how much/strong vibrations does your bike have to endure).

If your usage is particularly heavy for some reasons, it might be worth routinely replacing crucial parts like fork, stem, and handlebar. I have decided not to trust these parts for more than 10000km, simply because each of these has already failed me at least once.

The 10000km that I use are just a round number that fits with my experience of my failures, and it's heavily dependent on my bike usage, which is rather rough. Your usage is likely less stressful on your material, and may thus warrant a longer replacement interval. Also, the 10000km take into account, that a handle bar failure is always catastrophic. I do not want to experience any more of these failures. Thus, I try to err more on the safe side. YMMV.

  • There's no reason to periodically replace fork or stem, since cracks can be investigated easily. The non-carbon-fiber parts don't fail suddenly; they fail by developing cracks. Handlebar replacement periodically is sane if it's one of these modern lightweight handlebars. You cannot investigate a handlebar for cracks on a road bike, as it's covered by handlebar tape. – juhist May 10 '18 at 10:55
  • @juhist I'm talking about steel parts only, and I have never managed to find a crack before the part failed. Of course, if you are content with giving your fork a close inspection after every few hundred kilometers, you may get lucky and spot a developing crack. But I wouldn't trust myself to do it. Some new parts at an interval of 10000km seems to be the less costly variant to me. – cmaster May 10 '18 at 14:52
  • I see your point about replacement, but rather than simple unilateral replacement at a mileage, consider doing the monthly M check for safety and keep an eye on anything suspect. IE, I have a dented seat stay on a steel road bike, so I check it for change. No change and its fine to keep riding - if it started bending more I'd make a decision then. – Criggie May 10 '18 at 22:55
  • Yea some people would be changing forks every 9 months this way – gaurwraith May 11 '18 at 10:26
  • I feel like you may be a bit of an outlier. Most modern mainstream bikes have a weight limit of about 250-300 lbs. If the load on the bike is high (e.g., 300 lbs rider and luggage) then I could see this happening, otherwise this advice is largely anecdotal. – Rider_X May 11 '18 at 19:19
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Forks are not a 'wear component' that need to be replaced periodically. Bicycle frame makes are clever enough to make their products sufficiently durable and it's not something riders generally need to worry about. That said there obviously are instances of frames and forks cracking and failing, but this is not the norm.

However, in your particular case, with an old steel frame, it's a good idea to periodically inspect it for any cracks that might be developing in any of the welded or brazed joints. On the fork you should look for cracks near the fork crown as that is where forces are highest.

As as aside, I haven't tried to put the document through Google translate yet, but there may be a slight misunderstanding. I think perhaps you are interpreting it as: bicycle forks commonly fail, leading to injury, when perhaps that should be if a bicycle's fork fails, injury is common.

Personally, I've never seen or heard of a modern bicycle fork catastrophically failing in regular use (crashes and extreme mountain bike riding are another matter).

  • One tandem manufacturer says to replace their older front forks because they were underengineered for the stress on them. But that’s about it. – RoboKaren May 9 '18 at 14:24
  • "Bicycle frame makes are clever enough to make their products sufficiently durable" No. Just no. They make their products durable enough to not fail the average rider, but they fail to make their products durable enough for riders with more weight/force/milage than average. I have already broken several forks in my life (along with pretty much every single other part on my bike), and for the forks, stem, and handlebar, I do routinely replace all of these every 10000km now. Simply out of experience that these parts failed me too often. – cmaster May 10 '18 at 10:30
  • @cmaster by the time you've replaced those and all the components that wear regularly, wouldn't you be better replacing the bike? If your forks are really suffering that much, your frame probably is too – Chris H May 10 '18 at 11:42
  • @ChrisH Since I'm riding diamond frame bikes which have enough redundancy built in to avoid catastrophic failure (if one tube breaks, the other will keep your bike in one piece, allowing you to stop safely), I don't fear frame failures. And my bike has enough peculiarities which make me slow to just replace the entire thing. Obviously, other people may have other priorities, and just opt for buying a new bike every 10000km, bikes can be cheap after all. How you replace these parts (by replacing the parts or the bike), is pretty much irrelevant to the safety. – cmaster May 10 '18 at 15:10
  • @cmaster fair enough, but I've got 25000km on my Al hybrid (since I started counting, so actually considerably more) and the parts you mention are still going strong (though I broke a back wheel). When it comes to steel I've only had my tourer just under a year (5000km). I don't expect to replace major structural parts every couple of years. – Chris H May 10 '18 at 15:46

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