Chainrings bolts - how small is too small?

silentphoenix
silentphoenix Posts: 6
edited September 2012 in MTB buying advice
Heya all,

I've just started to use my newly self made commuter bike and have not paid enough attention to loose bolts and I've lost 2 chainring bolts!

The crankset is a Shimano XT M750, which has M8 x 9.2mm boltsets. Unfortunately they are not so easy to find in Heidelberg (Germany) and was wondering how much of a difference using slightly short bolts would make. I was planning to buy some M8 x 8.5 from my LBS which I guess would leave the last 1.5 threads open.

Does this sound OK?

Cheers,

Nav

Comments

  • nicklouse
    nicklouse Posts: 50,675
    what is your crank ring/bash set up?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • benpinnick
    benpinnick Posts: 4,148
    It will be fine if you are running the standard set up. Oddly Ive just had the exact same problem. Lost 2 bolts on my XT cranks. They've been going 2 years no issues, then boom. No bolts.
    A Flock of Birds
    + some other bikes.
  • silentphoenix
    silentphoenix Posts: 6
    nicklouse wrote:
    what is your crank ring/bash set up?

    Ring setup is 48-36-26 (all XT rings) on FC-M750 (4 bolt).
    benpinnick wrote:
    It will be fine if you are running the standard set up. Oddly Ive just had the exact same problem. Lost 2 bolts on my XT cranks. They've been going 2 years no issues, then boom. No bolts.

    Cool - I've found a guy selling Ti bolts (5 pairs of M8 x 8.5) for 15€ which I might try out.

    :D. I just find it so strange that up until yesterday everything was fine and then I don't have 2 chainring bolts! Although loosing 4 at the same time is even more bizarre. Almost sounds like a theft, but why the chainring bolts of all things!
  • benpinnick
    benpinnick Posts: 4,148
    I cant explain it either. They weren't running loose or anything like that until a ride the other day, and I lost two in the space of 1 hour, and nearly lost the other two. Annoyingly I had no Torx drive to hand, so I had to ride home in granny. I faced the same issue, all I had to hand was some slightly shorter bolts in my tool box, so thats what I have used. No issues so far.
    A Flock of Birds
    + some other bikes.
  • thelonegroover
    thelonegroover Posts: 1,073
    I don’t think this is a function of the length, more likely they’ve just come loose. Another 0.6 or 0.7 mm is going to stop them coming loose. Put a drop of Loctite on.
    Planet X Kaffenback 2
    Giant Trance X2
    Genesis High Latitude 2x10
    Planet X n2a
    Genesis Core 20
  • silentphoenix
    silentphoenix Posts: 6
    Thelonegroover wrote:
    ... Put a drop of Loctite on.

    So obvious, yet I didn't think of it! Thanks! Very sound advice as I don't want to lose my shiny new Ti bolts... let see what the German equivalent of loctite is...
  • thelonegroover
    thelonegroover Posts: 1,073
    I think it may be German (Henkel)?
    Planet X Kaffenback 2
    Giant Trance X2
    Genesis High Latitude 2x10
    Planet X n2a
    Genesis Core 20

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