Find answers, ask questions, and connect with others in our UK cycling & mountain bike forum.

  • Structural Integrity.

     Robmet updated 3 years, 8 months ago 5 Members · 17 Posts
    This page may contain affiliate links which means that Cycling Addicts earns from qualifying purchases. See our full disclosure.
  • Mustard

    Member
    24 November 2016 at 9:08 am

    Yet again the structural integrity of modern lightweight bikes is brought into question. A 50 year old Australian man was killed when the alloy steering tube on his carbon fork catastrophically failed as he was pounding up a slight hill. His bike was several years old and had done a lot of miles.

    The coroner questioned whether modern lightweight bikes should have a certified life span of safe usage? (Miles/age.)

    The latest alloy bikes are lighter than ever, but despite the claims of superior alloy and all that, alloy has limitations with regard to flex, and fatigue failure. (As in aircraft, which use ‘superior’ alloy as a matter of course.)

    Is there not a weight/strength limit below which it seems unsafe to venture, IF the bike is expected to last for a reasonable length of time, and/or miles?

  • Robmet

    Member
    24 November 2016 at 5:02 pm

    Interesting stuff.

    Difficult to know where or how to draw a line, its also hard to predict what sort of life a bike will lead when it leaves the shop.

  • Gunner

    Member
    24 November 2016 at 7:53 pm

    Interesting stuff.

    Difficult to know where or how to draw a line, its also hard to predict what sort of life a bike will lead when it leaves the shop.

    Totally agree.

  • Roberto

    Member
    24 November 2016 at 8:44 pm

    When I built my CR1 up the frame felt like it was made from toilet roll tubes, really scarily light.

    Took a while before I stopped butt clenching when hitting pot holes 😀

    Also, when torqueing up the stem on the carbon steerer I had to go well past the max torque otherwise the headset would come loose.

    We have a local climb/descent with a cattlegrid half way down, hitting that at 30mph plus is so scary.

    BUT ive also heard it said that the UCI lower weight limit of 6.8kg or 15lbs is outdated and bikes could be safe at much lower weight.

  • Mustard

    Member
    25 November 2016 at 8:06 am

    Obviously, that coroner would have been aware that how a lightweight machine is used (or abused) introduces an uncertain element in how it must react, BUT!

    As Roberto said,how many ‘hits’ (potholes-cattle grids- cobbles- rough roads- all taken at speed) can a lightweight aluminium structure with all different weights of rider take before suffering fatigue failure? THAT could obviously be tested to destruction by the manufacturers. (Including lightweight carbon structures.) I believe some (Specialized for one) do their own internal tests, but surely there should be some independent agency to lay down riules.

    It’s also misleading for manufacturers to set arbitrary weight limits on riders, as though any weight which doesn’t exceed that limit is safe, but any weight above it is unsafe. (Again, all depends on how hard the bike is ridden.)

    What seems to be happening is that lightweight bikes are now seen as consumer discardables -i.e. constantly being replaced almost year on year by the latest and greatest and even lighter still must have! So what’s to stop them pushing the boundaries?

    Perhaps some independant authority needs to be involved with destruction testing as in other industries, setting out reasonable standards of safety. I believe some manufacturers (Specialized for example) test their own products so.

    With the ever growing danger of more and more traffic, and often aggressive car drivers on the roads, any sudden bike failure could easily prove fatal. I find it odd that many renew crash helmets on a regular basis, whether they have been damaged or not, yet never give a thought to their thin tubed (skinny) bike failure!

  • Richard A Thackeray

    Member
    25 November 2016 at 11:13 am

    Was it Kinesis, who recently issued a recall on certain forks, due to similar fears

  • Robmet

    Member
    25 November 2016 at 1:59 pm

    I think most of the bigger brands will have their own in house testing facilities, there are also the CE marks and associated tests and I think Germany has its own higher level tests for bicycles to be sold in Germany.

    The problem is with structures that are designed to be as lightweight as possible then you are always going to reduce their overall capacity compared to more robust (heavier) structures. Is it a risk the consumer should be informed about and left to their own decisions? I know that personally I wouldnt buy a 2nd hand light weight bike, it would just play on my mind about its history.

    Now my Supersix is coming up 4 years old i’ve started thinking about whether it should be replaced for basically similar reasons? 😕

  • Richard A Thackeray

    Member
    25 November 2016 at 11:50 pm

    Robmet

    I have a 1994 Dyna-Tech; one of the bonded titanium frames (the rest is 653)

    After a Ridley superceded it, I used it as a commuter for several years, whilst it was retired/replaced by a Ribble (mainly because I wanted proper mudguards, & bigger tyres than ’20’ section) it was still going strong

    It’s still hanging in the garage, & barring a sticky right STI lever, it’s a comfortable superbly handling bike

  • Robmet

    Member
    26 November 2016 at 3:47 pm

    Richard, I know the ones. My mate used to ride his until without warning one ride:

    The downtube let go.

    😯

  • Gunner

    Member
    26 November 2016 at 6:36 pm

    😯 😯 😯 😯

  • Richard A Thackeray

    Member
    26 November 2016 at 7:20 pm

    Richard, I know the ones. My mate used to ride his until without warning one ride:

    The downtube let go.

    😯

    Mine’s the road-bike

    I was thinking more in terms of the life-expectancy of the adhesives used for the lug-to-tube joints

    Then again, it was meant to be aerospace standard

  • Roberto

    Member
    26 November 2016 at 10:14 pm

    Richard, I know the ones. My mate used to ride his until without warning one ride:

    The downtube let go.

    😯

    That frame could easily be repaired with gaffa tape, the bigger problem is how did he stop the USE seatpost from sliding down its shim 😆

  • Mustard

    Member
    27 November 2016 at 7:51 am

    Drill a series of small holes through the seat tube (as with alloy or carbon windsurfing extensions) and insert pin at required height. Doubt it would weaken it unduly.

    Or, just wrap a few turns of Gorilla ‘Gaffa tape’ around it! 😉

  • Robmet

    Member
    28 November 2016 at 10:25 am

    Drill a series of small holes through the seat tube (as with alloy or carbon windsurfing extensions) and insert pin at required height. Doubt it would weaken it unduly.

    Or, just wrap a few turns of Gorilla ‘Gaffa tape’ around it! 😉

    Not as much as the 1″ gap in the downtube?

  • Mustard

    Member
    28 November 2016 at 4:01 pm

    I was joking about your ‘bigger’ seat post problem Rob. I had similar with a carbon one, but a couple of winds of tape around where it entered the seat tube did actually stop it slipping down.

    As for the frame, well… I once bodged up an old bike frame snap by cutting a gap between the two parts to leave room to insert a couple of distance pieces (tube, for bolts, to stop crushing the frame tube) and drilled and bolted two strongish alloy shaped half tube plates, one either side, bolted hard up against the distance pieces with no free play between the holes and bolt sizes. (The tricky part.)

    It actually held together for a try, but It wasn’t really worth the effort (An old heavy bike.) But it filled a few hours of faffing and fiddling time, much preferable to sitting watching bleeding television!! 🙄

Viewing 1 - 15 of 17 posts
Original Post
0 of 0 posts June 2018
Now

New Report

Close