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74mm chainring position between these two cranks

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74mm chainring position between these two cranks

Old 09-20-23, 05:48 AM
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74mm chainring position between these two cranks

These are the two cranks in question:

1) https://dimensionbikeproducts.com/products/110-crankset

2) https://www.somafabshop.com/shop/new...attr=1279,3685

I have the first one, and the position of the 74mm chainring is such that I would need to use a rather wide spindle bottom bracket (say 127.5mm) if I wanted to run it as a 1x. I'm curious if I could get better results with crank #2 (recommended to me by a forum member in another thread) since it seems to be designed as a double/compact, and maybe crank #1 was designed with triple chainrings in mind? Physically they can both take a pair of 110 chainrings and a 74, but was thinking if #2 is designed as a double, maybe the positioning of the 74 is different? I have no real way to know besides just buying the thing and trying it, which I may just do. But thought I'd ask here first in case anyone has any knowledge.
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Old 09-20-23, 08:07 AM
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2) gives you the expected chain line for running a double with 2 different size spindles.

  • JIS square taper (110mm BB spindle recommended for a 45mm chainline, 113mm for 47.5mm chainline)
Since you have the first, you should be able to figure it out and be close enough. The second is made for 10/11 speed bikes. The first doesn't say, So there might be a tad bit of difference in the ring spacing that might throw off your exact calculations. But still you chain line shouldn't be that finicky that it can't be off a little. And if it happens to be in favor of the side of the cassette you use the most, then maybe all the better.

Isn't there a affordable crankarm set with a spider for a single ring?
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Old 09-20-23, 08:51 AM
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Originally Posted by Iride01
Isn't there a affordable crankarm set with a spider for a single ring?
Not for 74mm. Turns out 1x square taper 170mm cranks for chainrings 30T and smaller are quite hard to find.

Tempted to give that Soma a try.
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Old 09-20-23, 09:09 AM
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Originally Posted by brokewheelspoke
Not for 74mm. Turns out 1x square taper 170mm cranks for chainrings 30T and smaller are quite hard to find.

Tempted to give that Soma a try.
BB's are inexpensive. Why not add another 18 USD to your budget and get a crank with a ISIS or Octalink spindle interface? Then you won't get odd looks for missing the big ring. And you'll probably find them less hassle to remove the crank arms if you ever have too again, as many have self extracting crank arms.
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Old 09-20-23, 09:17 AM
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Originally Posted by Iride01
BB's are inexpensive. Why not add another 18 USD to your budget and get a crank with a ISIS or Octalink spindle interface? Then you won't get odd looks for missing the big ring. And you'll probably find them less hassle to remove the crank arms if you ever have too again, as many have self extracting crank arms.
No no no, I've only ever worked with square taper. I only have square taper tools: Park BBT-22 and the Phil Wood tool. Don't want to open the Hellraiser box getting into other configurations. I don't mind buying a different square taper BB if I need a different spindle length, but I don't want to get lost in the world of new age cranks.
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Old 09-20-23, 09:42 AM
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These new age things you fear are from the previous century.
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Old 09-20-23, 10:17 AM
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Don't listen to those guys that are trying to sell you oddball BB spindles. Next thing they'll be trying to convince you the bearings should be outside of the shell or other flapdoodlery.

Both of the cranks listed seem to be of the "newer" (post-1993 - stop laughing) type designed for a narrower spindle. The Soma even helpfully lists recommended spindle widths. In fact, the Soma closely resembles the current setup on my commuting bike (chainguard / 40 / 24).



Using a 127 spindle just might get that 74 inner ring out far enough to be close to centered for a 1x setup. The side effect will be a widened pedal tread & "Q factor", but this typically doesn't bother some people. But the only way to be sure would be to test it, given the uncertainties of spindle tapers, crank draw, etc. I would not recommend using aluminum spacers between the fixed cup and the shell, as these can deform from stress and allow the fixed cup to loosen. Steel spacers (same as freewheel spacers) should be OK. In either case, using spacers can cause the left crankarm to be close to the frame if the frame has widely-spaced chainstays.

Both the Dimension and Soma cranks are mighty pretty, but if I was to attempt such a setup I'd get a used 110/74 crank from a co-op and clean it up a bit. But it's your bike and if it deserves shiny new cranks who are we to deprive it from such a destiny?
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Old 09-20-23, 05:40 PM
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Originally Posted by brokewheelspoke
Not for 74mm. Turns out 1x square taper 170mm cranks for chainrings 30T and smaller are quite hard to find.
https://www.ebay.co.uk/itm/186028603850
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