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Thread: Chainring bolts

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    Chainring bolts

    So I'm replacing my chainrings on my Shimano Ultegra FC-6500 crankset and realized that I might need new chainring bolts since mine are a bit old, although they probably work fine but it is nice too have a new set. What size should I buy and how do you measure the size?

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    take 1 out, go to the Bike shop and ask if they have 5 just like that?

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    here's what i know about chainring bolts.

    come in aluminum or steel. there are five of them. pretty standard (one of the few on bikes, it seems) design.

    length is usually determined by crank type. most LBS's will want to know how many chainrings are on your crank. single/track (1), traditional road (2), or MTB (3). i doubt if they know offhand the length of any of them, although they might make a good guess. cost (5), 10-20 bucks?

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    Quote Originally Posted by veganpower View Post
    So I'm replacing my chainrings on my Shimano Ultegra FC-6500 crankset and realized that I might need new chainring bolts since mine are a bit old, although they probably work fine but it is nice too have a new set. What size should I buy and how do you measure the size?
    Unless there's been a change I missed, chainring bolts are highly standardized. You want a pair for double as opposed to track, but those are the most common. Your only choices are details like material, color, and Torx vs. 5mm hex key.
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    I have a couple of FC-6500 cranks on two bikes with thousands and thousand of miles on each and there isn't the slightest thing strange about the chainring bolts I can see. They are steel, standard size and length and take the usual 5 mm Allen key. What is your problem and what possible reason do you have for replacing them?

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    Quote Originally Posted by HillRider View Post
    and what possible reason do you have for replacing them?
    Same as why a dog licks his balls----- because he can.
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    Quote Originally Posted by HillRider View Post
    I have a couple of FC-6500 cranks on two bikes with thousands and thousand of miles on each and there isn't the slightest thing strange about the chainring bolts I can see. They are steel, standard size and length and take the usual 5 mm Allen key. What is your problem and what possible reason do you have for replacing them?
    Well, on a few of them I could see a bit of rust in the threads, although a little grease will probably do the trick. But I'm replacing them just because I'm putting on new front chainrings 52/39 so I can race junior next season. I'm sure they will probably work for another 5 years but it feels best to replace them with some new ones. So there is pretty much only 1 size for double cranks? How do you measure the size? Do you just measure the length of the screw or do you measure the distance from the big ring to the small ring including the spider?

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    Quote Originally Posted by veganpower View Post
    How do you measure the size? Do you just measure the length of the screw or do you measure the distance from the big ring to the small ring including the spider?
    Chainring bolts for double cranks (or triple cranks with a separate bolt circle for the granny) are pretty much standard length and diameter. Any bike shop should be able to provide replacements.

    There are shorter bolts made for single chainring cranks and longer ones for triple cranks where all three chainrings are on the same bolt circle but double cranks are pretty universal. If you are concerned, take one of your old bolts to the bike shop to be sure you get a match.

    Also, there are aluminum bolts which are both weaker and more expensive and some of the newer bolts use a Torx driver (T30 on my new Shimano crank) instead of a 5 mm Allen wrench. Avoid the aluminum bolts and be sure to get the appropriate Torx wrench if that's what your new bolts require.

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