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Rear rim cracked - rebuild ?

EdwardKEdwardK Posts: 15
edited June 2009 in MTB workshop & tech
Right back in the workshop again...
Noticed my back wheel had a slight buckle in it the other day (two weeks ago) - not much, maybe 5mm or so.
Was stopped at a junction waiting to turn left and felt a bump... turned round and a woman in a 4by4 had wedged her vehicle onto my back wheel. Had to get off and physically wrench the bike from under her bumper. Sort of a long day for me and I tend to try and avoid grief these days, no harm done I thought so pedalled off.

Just went to true my back wheel and noticed it is waaay off now. Started loosening/tightening spokes but gave up immediately as I have noticed that about 4 areas are cracked where the spoke goes into the rim. THey are pulling the metal of the rim out and have cracked/ripped the rim....

Would a car bumper landing on the back wheel cause this ? If so I will have to track her down at the supermarket (where it happened). If this is the case should I ask for payment for a brand new wheel (bearing in mind the wheel had a buckle before (but no cracking).

Right next question...
It's a Hope Pro II hub with Mavic 717's. It is my only transport for work and everything else, should I order a new rim and spokes and have a go at rebuilding a rear wheel based on the Hope hub or should I order a brand new wheel with Hope hub all made up and then try to rebuild this as a spare ?

Last question,
is it safe to ride like this ? ! I feel it isn't but it's going to be a long walk to work tomorrow (45 mins) or I guess I could pedal slowly (cycle track / not much traffic). Will it fail suddenly or gradually ?!
Thanks
Ed

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Probably caused it.

    New rim is about 35 quid - if old spokes have never broke, reuse them (for the same rim)
  • EdwardKEdwardK Posts: 15
    Thanks - is the Mavic XC717 still a good rim to go for ? Or should I be looking for something a bit less lightweight and more robust ? If so what is a good Mavic rim to go for ?

    Just been looking around and might get a quick spare rear built up to basic standards for £40/£50 from Merlin or CRC. (Mavic XM317 / Deore hub / DT plain gauge).

    Good as a standby ?

    What is the likelihood of me being able to rebuild a rear wheel from hub up ? How hard is it ?
    Am I likely to get a decent wheel out of it ?
    Would I be better off sending my hub back to Merlin (once I have the spare Deore set up) and asking them to rebuild it onto a Mavic 717 or stronger ?

    Or is wheel building easy ? (Another good skill to learn ?)

    Thanks Ed
  • supersonicsupersonic Posts: 82,708 Lives Here
    It is a good skill to learn - with old cheap stuff!

    How much do you weigh, and how hard do you ride? And what bike?

    Ignore plain guage spokes, butted are much better.
  • EdwardKEdwardK Posts: 15
    It's a year 2000 Cannondale SL2000 or something like that (about a grand new back then). I use it mostly for commuting to work now and so put on skinny slicks.
    Maybe that has something to do with the cracking ? High pressure slicks ?

    I'm about 13 stone I guess and don't ride hard - no drops etc but say twice a week I carry about 5 to 8kg of shopping. Prob no good for the back wheel either...

    Read a review on CRC of XC717's and someone else mentioned rim cracking around spokes - how common is this ?

    Am thinking of going for a chunkier back rim to avoid this in the future and maybe get a new set of light wheels in addition for weekend XC - seems pointless to commute with XC wheels...

    Guess I could buy something for commuting and tehn set up the MTB for XC like it was originally ...
    Thanks
    Ed
  • tmgtmg Posts: 651
    I had 717 on front and back, the back one blew whilst riding, completely shattered along the rim. Weigh about same as you.

    So I had a new wheel built around my existing hub, 719 with double butted DT spokes.

    I'd never ride on a wheel thats got a crack, even to the shops.
  • Matt 24kMatt 24k Posts: 186
    I run XM719's with skinny city tyres pumped to the max during the week and 2.3 Nevegals off road. Never had to true them unlike mates that run XC717's. The skinny tyres at high pressure possibly put a greater load of a smaller area than the off road tyres at lower pressures. The 717's are lighter but need more TLC. The upside of this is that you will get better at trueing wheels :D
  • EdwardKEdwardK Posts: 15
    Just had a check on CRC :
    XC 717 - 420g - 1.0 to 2.1 (tires)
    XM 719 - 475g - 1.5 to 2.3

    Also:
    EX 721 - 590g - 2.3 to 3.0
    XM 317 - 440g - 1.5 to 2.3

    Am leaning towards keeping the existing 717 for the front wheel and getting a 719 for the rear - sounds like they are a bit tougher...

    Still riding slowly on my death trap... will order a spare 317/Deore 40 quid rear wheel from either CRC or Merlin today I think.

    Thanks Ed
  • EdwardKEdwardK Posts: 15
    Bought a pair of spare wheels to use for when the good ones are trashed (Shimano Deore XM317- £75 a pair) and a XM 719 rim to build back up with the existing spokes and hub.

    Any good resources for wheel building ?

    Do you need a wheel jig or can you knock something up with wood ? :)

    Thanks for the advice - Ed
  • supersonicsupersonic Posts: 82,708 Lives Here
    Try Sheldon Brown's site for wheel building.
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