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64 BCD chainring onto 104 BCD spider?

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64 BCD chainring onto 104 BCD spider?

Old 12-26-19, 07:51 PM
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64 BCD chainring onto 104 BCD spider?

I have a triple crankset. I love wide gearing as i climb a lot. However, i wasn't really happy with my current setup which consists of 28T, 38T and 48T chainrings in combination with an 11 to 32 cassette at the back. So i did something stupid, and without carefully inspecting my crank arms, i purchased three chainrings from China. 22T (64BCD), 32T and 42T (104BCD). They arrived and just as i was gonna install them, i realized that my crankset did not have the inner 64BCD bolt holes. Like i said, it is a triple crankset but the problem is, the medium and small chainrings were "riveted" to each other. Now i can install the 32T and 42T just fine, my crank arm has the 104BCD holes, but it can't really be much of an upgrade without installing the 22T.

So my question to you experienced tinkerers out there: Do i have to buy a new pair of crank arms with 64bcd holes as well, or is there something else that i can do and modify my current crank arm to accommodate the 22T chainring?

Thanks a lot.

PS: My initial idea was to get something like this. I think this is a 64 to 104 adapter. However, i think it will create a larger gap between the two bigger chainrings and the shifting won't work.


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Old 12-27-19, 02:34 AM
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Originally Posted by Newspaper_Nick View Post
I have a triple crankset. I love wide gearing as i climb a lot. However, i wasn't really happy with my current setup which consists of 28T, 38T and 48T chainrings in combination with an 11 to 32 cassette at the back. So i did something stupid, and without carefully inspecting my crank arms, i purchased three chainrings from China. 22T (64BCD), 32T and 42T (104BCD). They arrived and just as i was gonna install them, i realized that my crankset did not have the inner 64BCD bolt holes. Like i said, it is a triple crankset but the problem is, the medium and small chainrings were "riveted" to each other. Now i can install the 32T and 42T just fine, my crank arm has the 104BCD holes, but it can't really be much of an upgrade without installing the 22T.

So my question to you experienced tinkerers out there: Do i have to buy a new pair of crank arms with 64bcd holes as well, or is there something else that i can do and modify my current crank arm to accommodate the 22T chainring?

Thanks a lot.

PS: My initial idea was to get something like this. I think this is a 64 to 104 adapter. However, i think it will create a larger gap between the two bigger chainrings and the shifting won't work.


It would help if you described what model crank you have, and what kind of flange is uses. If it's like this removable spider that's designed to fit your model of crank, that you've pictured, then I don't see why it would not work. What is the reason why you think it wouldn't work?

If your crank does not have a removable spider, then trying to attach a removable spider through the matching bolt holes would most likely not fit.

If you're wanting to get 64mm bcd holes onto your crank, you could think about laser cutting a steel or aluminum plate to be attached flush with the outside of your outer chainring, with both 104 and 64mm bcd holes cut out of it. The 2 circles of holes would have to be arranged some degrees turned from each other so that the 64mm bcd holes clear the flange and the crank arm. Then you'd need something like 16mm of spacers and very long chainring bolts between the 22t chainring and the laser cut plate.

Last edited by tomtomtom123; 12-27-19 at 02:48 AM.
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Old 12-27-19, 04:26 AM
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Originally Posted by tomtomtom123 View Post
It would help if you described what model crank you have, and what kind of flange is uses. If it's like this removable spider that's designed to fit your model of crank, that you've pictured, then I don't see why it would not work. What is the reason why you think it wouldn't work?

If your crank does not have a removable spider, then trying to attach a removable spider through the matching bolt holes would most likely not fit.

If you're wanting to get 64mm bcd holes onto your crank, you could think about laser cutting a steel or aluminum plate to be attached flush with the outside of your outer chainring, with both 104 and 64mm bcd holes cut out of it. The 2 circles of holes would have to be arranged some degrees turned from each other so that the 64mm bcd holes clear the flange and the crank arm. Then you'd need something like 16mm of spacers and very long chainring bolts between the 22t chainring and the laser cut plate.
Sorry for the lack of info. My crankset is a square taper one. It has a fixed spider (non-removable). I couldn't really understand your laser cutting idea. Can you please elaborate it a little bit? Or a photo would be great. What i understand is that you want me to replicate the riveted setup, but use four angled pieces to connect the large and small chainrings together. Is that right?



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Old 12-27-19, 04:44 AM
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The laser cut idea is like having a 104mm bcd bashguard on the outside, but with an extra set of 64mm holes that you can bolt the inner chainring to, with very long bolts and spacers. You have to rotate the holes so that the flange and crank arm doesn't get in the way of the holes. Laser cutting is maybe $30. You have to make a dxf drawing to a laser cutter provider. They supply the metal plates on their Automatic cutting machines
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Old 12-27-19, 06:55 AM
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Originally Posted by Newspaper_Nick View Post
PS: My initial idea was to get something like this. I think this is a 64 to 104 adapter. However, i think it will create a larger gap between the two bigger chainrings and the shifting won't work.



That's a direct mount spider and not going to help you.

Honestly I'd just bite the bullet and spend the money on a different $30 crank W/22/32/42 installed and chalk it up to a life lesson. Worst case you also need to buy a $10 UN 26 or $15 UN 55 bottom bracket of the correct 122.5mm spindle length, but I'd guess your existing BB spindle will be close. Before you buy a BB you need to do some measurements to avoid a similiar issue of compatibility.
https://www.jensonusa.com/Shimano-Ac...quare-Crankset

https://www.jensonusa.com/Shimano-UN-26-Bottom-Bracket

Last edited by dedhed; 12-27-19 at 07:01 AM.
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Old 12-27-19, 05:52 PM
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Yeah thanks for the replies. I will get new cranks arms. It was about time anyway.
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Old 12-27-19, 07:34 PM
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Originally Posted by Newspaper_Nick View Post
Yeah thanks for the replies. I will get new cranks arms. It was about time anyway.
Be aware, the crankset chosen determines what bottom bracket (BB) type or spindle length you will need for it to install for intended chainline. First measure your BB shell width.It'll most likely be 68mm or 73mm, most likely English threaded given the crank on it now. If you get another sq taper crank see what spindle length the new crank requires. Measure your old spindle length and maybe you won't need a new BB. Really though if you have some miles on the bike you might just replace it anyway and keep the old one for a spare. If you have a coop, nearby you may be able to pick up a used crank cheap that will use the chain rings you already bought or have good rings you prefer already on it.
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Old 12-31-19, 08:20 AM
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Originally Posted by dedhed View Post
Be aware, the crankset chosen determines what bottom bracket (BB) type or spindle length you will need for it to install for intended chainline. First measure your BB shell width.It'll most likely be 68mm or 73mm, most likely English threaded given the crank on it now. If you get another sq taper crank see what spindle length the new crank requires. Measure your old spindle length and maybe you won't need a new BB. Really though if you have some miles on the bike you might just replace it anyway and keep the old one for a spare. If you have a coop, nearby you may be able to pick up a used crank cheap that will use the chain rings you already bought or have good rings you prefer already on it.
Thanks for the heads up. My bottom bracket shell is 68mm. And my spindle length is 122.5mm. I purchased the following crankset for a good price (hopefully it will arrive in a month). It already has the chainring sizes that i wanted. The chainrings i purchased previously will also fit this so i will keep them as spares. I like having spares

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Old 12-31-19, 08:33 AM
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Originally Posted by Newspaper_Nick View Post
Thanks for the heads up. My bottom bracket shell is 68mm. And my spindle length is 122.5mm. I purchased the following crankset for a good price (hopefully it will arrive in a month). It already has the chainring sizes that i wanted. The chainrings i purchased previously will also fit this so i will keep them as spares. I like having spares
Dollars to donuts you're going to need a new, shorter BB.
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Old 12-31-19, 08:42 AM
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Originally Posted by Retro Grouch View Post
Dollars to donuts you're going to need a new, shorter BB.
Why? I am currently using a square taper triple crankset. These are almost identical. Why will i need a shorter BB?
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Old 12-31-19, 08:59 AM
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Originally Posted by Newspaper_Nick View Post
Why? I am currently using a square taper triple crankset. These are almost identical. Why will i need a shorter BB?
122.5 is a pretty old but common spec. Newer cranksets tend to have more offset and consequently require shorter BB spindles.

If it was my bike and you're not in too much of a hurry, I'd wait for the crankset to come in and test fit the new crankset to your existing spindle. That way you can see if your front derailleur will reach the biggest chainring or not (my bet}.

If you are a chainline purist you can hold a straight edge against the middle chainring and see how closely it comes to bisecting your cassette. If you're more like me, you'll just eyeball how far you think you need to move the chainrings inward and buy a BB with a spindle short enough to do that. It doesn't have to be perfect. If you're a risk taker you'll probably need something in the 112mm to 116mm range. The lowest cost solution is to find a donor bike so you can hunt around while you're waiting for the crankset.

Don't forget that BB spindles have two ends. In most (but not all) cases, if you want to move your chainrings inward 5mm you'll need a BB spindle that's 10mm shorter.
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Old 12-31-19, 09:18 AM
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Originally Posted by Retro Grouch View Post
122.5 is a pretty old but common spec. Newer cranksets tend to have more offset and consequently require shorter BB spindles.

If it was my bike and you're not in too much of a hurry, I'd wait for the crankset to come in and test fit the new crankset to your existing spindle. That way you can see if your front derailleur will reach the biggest chainring or not (my bet}.

If you are a chainline purist you can hold a straight edge against the middle chainring and see how closely it comes to bisecting your cassette. If you're more like me, you'll just eyeball how far you think you need to move the chainrings inward and buy a BB with a spindle short enough to do that. It doesn't have to be perfect. If you're a risk taker you'll probably need something in the 112mm to 116mm range. The lowest cost solution is to find a donor bike so you can hunt around while you're waiting for the crankset.

Don't forget that BB spindles have two ends. In most (but not all) cases, if you want to move your chainrings inward 5mm you'll need a BB spindle that's 10mm shorter.
I think i will be fine with my current bottom bracket. One of the buyers commented that the smallest chainring is flush with the square taper hole of the crankset. So i am assuming this crankset is one of the older types that you mention, which will need a longer spindle. Of course i know that there also is the issue of the spindle types (JIS or ISO). They are somewhat interchangeable as far as i know. I have swapped my BB before and realized that my cranks almost bottomed out with this new BB. But they still work. If i am not mistaken, 1x systems have much worse chainlines than i can ever have with my triple setup. So i assume i will be fine.
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Old 12-31-19, 09:26 AM
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Originally Posted by Newspaper_Nick View Post
Why? I am currently using a square taper triple crankset. These are almost identical. Why will i need a shorter BB?
"Almost identical" doesn't mean anything. You need to look up the model of the new crank and see what spindle length it requires.
I wouldn't be surprised if it takes a 113mm
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Old 01-02-20, 01:15 PM
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Originally Posted by dedhed View Post
"Almost identical" doesn't mean anything. You need to look up the model of the new crank and see what spindle length it requires.
I wouldn't be surprised if it takes a 113mm
All right i changed my order to this. I checked the BB spindle length requirement this time and it is correct. There also was an octalink variant but i have spare square taper bottom brackets and i would like to use them. I will also be able to use the previously bought chainrings with this crank. I hate wasting stuff. I also have a spare cassette

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