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    • CommentAuthorbettermade
    • CommentTimeJun 27th 2011 edited
     
    So i recently came across a dent and a big scratch in my chainstay, right where the end of the driveside crank would touch, i took a fall some time ago so i figured it would be from that. Funny thing is a friend has the exact same dent, were both running omniums. So i decided to push the crank sideways and i noticed ALOT of side flex in the omniums, about twice as much as on my sugino 75. There is a 5mm gap between the crank and the chainstay and i could easily push it to a 1mm gap.

    What are the odds that both me and my friend take a fall with our cranks EXACTLY alligned with our chainstay? im starting to think it might be from skidding (sideways), only thing i can think of where we both would have our cranks horizontal and alligned with our chainstays.

    Are there any more people on here that notice a dent/scratch in their chainstay and are running omniums?
  1.  
    I'm running omniums and have had no issues. I also skid (maybe not as often as you because I also run a front brake. But I haven't noticed any side play. faulty installation?
    • CommentAuthorbettermade
    • CommentTimeJun 27th 2011 edited
     
    nope, installation was done proper.. theres no play from not enough grease, not tightening it enough etc, the arms itself just flex (bend) :o

    they are clearly one of the, if not the stiffest crankset on the market when putting the power down, but definately not to the side, we both bought them at the same shop around the same time, could be a bad production line or something, pff im lost.
  2.  
    I just checked, at 12:30am, and I have maybe, maybe 1mm of play in my drive side Omnium arm with all the force I could apply with both hands. If you're getting 4mm of play with just your hands, either you have a very flexy frame, or you've done something wrong. I'd tend to doubt that it is frame flex.
  3.  
    Posted By: bettermadethe arms itself just flex (bend)

    ... Show us.
  4.  
    I have no issues with mine on my Concept with minimal flex.
    • CommentAuthorbryyando
    • CommentTimeJun 27th 2011
     
    You sure it isn't a crimp?
    • CommentAuthorstalag13
    • CommentTimeJun 27th 2011
     
    Posted By: bryyandoYou sure it isn't a crimp?


    this is what I was thinking. some frames have a second crimp to clear really long crank arms.
    • CommentAuthorGloomy
    • CommentTimeJun 27th 2011
     
    I can do the same with both of my Sugino 75 on two different bikes. I think I just realise why I have that new scratch on my chain stay! I guess it's normal...
    • CommentAuthorbettermade
    • CommentTimeJun 28th 2011
     
    nah its no crimp, has a scratch in it too, just a really small ding, wasnt in there before.. am just curious to see if it can happen by skidding or when pulling up real hard while accelerating.
    • CommentAuthor2011
    • CommentTimeJun 28th 2011
     
    Do you do whip skids where you skid the back wheel out to the side? Skidding is really bad for bikes (frame, hubs, rims, tires, etc). Chances are the chainstays are flexing slightly and hitting your cranks. What length cranks do you have? You may want 165mm if you're going to keep up the skidding crap.

    Some people have been known to use an angle grinder and grind off abit of the back of the crank arm on the Omniums so they have more frame clearance.
  5.  
    Posted By: 2011Do you do whip skids where you skid the back wheel out to the side? Skidding is really bad for bikes (frame, hubs, rims, tires, etc). Chances are the chainstays are flexing slightly and hitting your cranks.


    really?? i do whip skids and I've never ever had any instances where the chainstay hit my crank arm. it must be something else.

    Posted By: 2011Skidding is really bad for bikes (frame, hubs, rims, tires, etc)


    I always wonder if skidding really puts that much stress on a frame
  6.  
    If you are throwing your skids out to the sides like fish tailing yes it will flex that rear triangle unless you have a really really stiff frame it will flex when you skid.

    Posted By: 2011Skidding is really bad for bikes (frame, hubs, rims, tires, etc).

    True
    • CommentAuthorbettermade
    • CommentTimeJun 28th 2011 edited
     
    Posted By: 2011Do you do whip skids where you skid the back wheel out to the side? Skidding is really bad for bikes (frame, hubs, rims, tires, etc). Chances are the chainstays are flexing slightly and hitting your cranks. What length cranks do you have? You may want 165mm if you're going to keep up the skidding crap.

    Some people have been known to use an angle grinder and grind off abit of the back of the crank arm on the Omniums so they have more frame clearance.


    im running 170mm, ya i was thinking it would hit my chainstays, would be too much of a coincidence both me and a friend took a fall with our cranks aligned to our chainstays. ill try to grind it a bit, for the skidding, its bad yeah, but for me half the fun of riding a trackbike on the street is fooling around whip skidding down hills like a kid haha.
  7.  
    Posted By: bettermadefun of riding a trackbike on the street is fooling around whip skidding down hills like a kid A BOSS haha.
    • CommentAuthorbettermade
    • CommentTimeJun 28th 2011
     
    ^^ hahaha

    Im checking the inside of the crank now, and the sram omniums have real sharp thin edges whereas other cranks i have all have rounded edges, sg75 for example, think that explains it.
    • CommentAuthor2011
    • CommentTimeJun 28th 2011
     
    Posted By: whitekimchee
    Posted By: 2011Do you do whip skids where you skid the back wheel out to the side? Skidding is really bad for bikes (frame, hubs, rims, tires, etc). Chances are the chainstays are flexing slightly and hitting your cranks.


    really?? i do whip skids and I've never ever had any instances where the chainstay hit my crank arm. it must be something else.

    Posted By: 2011Skidding is really bad for bikes (frame, hubs, rims, tires, etc)


    I always wonder if skidding really puts that much stress on a frame


    It really depends on what type of frame you're riding and also how heavy you are.
  8.  
    Posted By: 2011type of frame you're riding


    I didn't see it mentioned that omniums have clearance problems on some frames. Maybe this is the problem?
    • CommentAuthor2011
    • CommentTimeJun 28th 2011
     
    Omniums DO have clearance problems on quite a few frames. However, I was referring also to the stiffness of different frames and materials. A steel Kilo TT is going to have much more flex than a Mash or something.
    • CommentAuthorcampystamp
    • CommentTimeJun 28th 2011 edited
     
    Judging from the size of your bikes, you are a fairly big rider. You probaby need stiffer cranks, possibly frame.
 
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