Forum home Commuter cycling forum The workshop

Broken spoke

JameyJamey Posts: 2,152
edited October 2008 in The workshop
On the way in to work today I pulled up at a red light and noticed that the rear brakes on my shiny new Tricross were rubbing again (click here to read my thread from last week about the rear wheel going out of true) so I wheeled the bike onto the pavement to take a look-see.

I freed the brakes and sure enough the wheel was out of true again. At first I thought that was it but then I spun it and saw one of the spokes had completely sheared off from the turny bit (technical term there) near the rim.

I was only a few miles down the road from the shop where I bought the bike so I decided to chance it (obviously going very slowly and avoiding any bumps) and fortunately I made it to the store (Evans Wandsworth) in one piece.

I explained what had happened and asked them to have a "good look" at the rear wheel and that's the story so far.

At this point I'm starting to consider my options... I love the bike to pieces and I just want to be able to ride it without worrying. I'm sure Evans will fix it but how long will it last this time? Will the bloke take a proper look or just replace the spoke and do a quick re-truing job. I'm pretty sure they won't rebuild the wheel.

Maybe I should buy a hand-built wheel. I just want something very strong that will take a 700 x 32 tyre and won't go out of true more often than can be reasonably expected.

Or maybe I should do a course and learn to build my own wheels. This one seems to be good value because on the last day you get to build yourself a set of wheels to take away with you.

I just want a quiet life, riding to work every day with the smallest amount of hassle possible. I'd rather not have to resort to doing things myself as I have precious little free time as it is, but if building my own wheels is really the only way to get decent reliability out of them then I suppose I'll do it.

Posts

  • I think you've ust been unlucky. Maybe you've got a "friday afternoon" wheel.

    I'd give Evans one more chance to fix it then demand a new wheel if it goes again. Be v unlucky to get another bad wheel
    <a>road</a>
  • JameyJamey Posts: 2,152
    I did pick the bike up on a Friday, actually. Maybe you're right.

    Anyway, just called Evans. the bike's ready to be picked up so here we go again. Expect another post in a few days, when the wheel buggers itself for a third time.
  • cjcpcjcp Posts: 13,345
    Do Evans receive the wheel factory-built when they receive the box of bits to build the bike up?

    When you say the spoke had sheared off, did it snap or did it unscrew? Just wondering if the spoke was too short,
    FCN 2-4.

    "What happens when the hammer goes down, kids?"
    "It stays down, Daddy."
    "Exactly."
  • JameyJamey Posts: 2,152
    It snapped. I think it might have been overtightened when it was trued last week.

    I'm guessing that yes, they receive the wheel pre-built, probably.
  • robbarkerrobbarker Posts: 1,367
    edited September 2008
    Spokes snapping - usually at the elbow - is a sign of a loose spoke, not an over-tight one.

    Over-tight spokes generally show themselves by pulling the eyelet out of the rim.

    The lack of tension allows the spoke to flex at the elbow so the bend fatigues quickly and fails.

    A properly tensioned wheel will not do this, as the loading on any individual spoke will never overcome the tension of it, and hence it will not go through the loose-tense cycle that results in this fatigue - all spokes will always be held in a healthy tension.

    The secret to achieving this is having a high, even spoke tension. Once one or two get loose the tension starts becoming uneven around the wheel, and the looser spokes start to fail. The solution is to have the whole wheel retensioned by someone who knows what they are doing. Most LBS mechanics are more than capable of it, but are generally not given the time and kit (namely a tensiometer) to do it methodically and properly.

    The other common cause of spoke failure is a lack of stress-relieving during the wheel build. Spokes are made from straight lengths of wire. The elbow is formed by bending the wire, and the metal structure within it contains elements stretched beyond their elastic deformation limit and elements well within it. Stress-relieving temporarily increases the tension across the whole cross-section of the spoke, causing the tensions of different areas of the cross-section to even out considreably. This increases strength in this area and reduces the likelihood of a fracture.

    There's a cracking thread in the mountain bike workshop and tech forum here on bikeradar, entitiled "what makes a wheel strong?".

    As for a solution, find a good wheelbuilder and get them to retension the wheels from scratch, or learn to do it yourself. The later route will need some investment in tools but, if you're going to be a lifelong cyclist, will be well worthwhile.

    If you're tempted, have a look at Roger Mussons e-book, available from www.wheelpro.co.uk.
  • nicklousenicklouse Posts: 81,520 Lives Here
    robbarker
    very nicely said.

    May I add that if you have had one elbow break the chances of more going are high. Even after a fix. as the damage has often already been done.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • BuglyBugly Posts: 520
    On reading the post he said the break was "one of the spokes had completely sheared off from the turny bit (technical term there) near the rim"

    That I would read as broken near the nipple not the elbow.

    So while the comments above are generally valid they dont apply to the break as described.

    to be honest I have never seen a break as described :shock:
  • robbarkerrobbarker Posts: 1,367
    Breakages at the thread are generally brought on by having too-large an angle at the spoke thread / nipple interface, i.e the spoke wants to enter the rim at an angle. This can be due to large flange hubs, deep section rims or an incorrect spoke pattern, i.e building a 28 spoke wheel cross 3. It has been known on big name production bikes!

    I still think the solution is a complete retensioning of the wheel. A censored wheel can be turned into a very good one with the skilled application of a spoke key.
  • JameyJamey Posts: 2,152
    Apologies for my lack of jargon, I'm still learning.

    The spoke broke at the end nearest the rim, just above the silver bit you turn with a spoke key when truing (the nipple, is it?).

    Rob - many thanks, that all makes perfect sense. The guy in Evans said they loosened all the spokes and then went round building up tension again, so hopefully it might be ok.

    If it fails again I may forget Evans (despite it being free) and pay for someone good to rebuild the wheel properly. Does anyone have any recommendations for who I might approach to do such a job? I'm in the South London area but don't mind going anywhere else in London in order to get a truly good job done.
  • st199mlst199ml Posts: 63
    Back to the original post, I've been on the Downland Cycles wheelbuilding course and it is brilliant. I'm now quite happy to build any wheel of any type and actually sell some of what I make on the occasion I get a good deal on parts. If you don't want to spend that money then you can learn a lot from Lord Sheldon (http://www.sheldonbrown.com/wheelbuild.html) or the standard reference work on the subject by Josh Brandt (http://icelord.net/bike/thebicyclewheel.htm).

    Could it be that the spoke didn't actually break, it just wasn't, to use non-wheelbuilding jargon, tight enough? Was there actually a fracture or did it just seem to have popped out from the nipple? As has already been said, uniform spoke tension is everything. One or two loose spokes and the knock-on effect can be disastrous.

    Good luck with it, hope Evans put it right for good. My girlfriend has a bike from Evans and the wheels did need a little fettling after the first few rides, though nothing like as bad as you experienced.
  • JameyJamey Posts: 2,152
    That's something I didn't check at the time (the wheel is fixed now) but I suppose it's possible that the spoke could have popped out instead of snapping, yes.

    I'm doing the normal, two-day maintenance course at Downland tomorrow and Sunday so will see how that goes and may well do the wheelbuilding one at a later date. I presume that when they mention building a wheel to take away with you on the final day there must be some kind of limit on the cost of parts, is there?
Sign In or Register to comment.