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I’m building a split-frame touring bike from scratch and want to use a belt-driven internal gear hub (no engine) using one of these front sprockets from Gates.

Main question: What crankset still exists - either as a complete set or individual parts - could fit a 5-bolt 130mm BCD or a 4-bolt 104mm BCD sprocket? I'll worry about belt length and tooth count later.

These dimensions seemed to be a standard size at one time, but everything I find in 2021 is either out-of-stock, an off-brand, or for kids. This post suggests that cross-compatibility is a thing of the past. The reps at Gates assure me it’s the standard.

I could only find the Sugino RD2 Single Speed Cranksets and Brompton cranks but these don’t look like they can take a beating. The SRAM S300 1.1 GXP Track Crankset and Gate cranksets require a GXP BB, which limits me in the future.

Side quest-ions (optional)

  • Is there a brand that isn’t a hegemony (Shimano), off-brand, or $400?
  • Is there a setup where components could be replaced in a developing country were something to break? (i.e., not specific to a series)
  • Sheldon Brown suggests that having the spiders+crank arms as one piece is preferred
  • Any tips on knowing if the chainring is detachable from a given
  • If going with a spider, what should I look for in crank arm compatibility?
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  • Shimano Alfine maybe? (5-bolt, 130mm BCD), if you can remove the chainring and replace it by the Gates one — a quick search on internet shows that it seems possible to use such crank with a Gates chainring, if your tourer has a 68mm bottom bracket shell.
    – Renaud
    Oct 28 '21 at 16:20
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    If you're saying that you don't think the Sugino RD2s can take a beating, I'd disagree; they should be more than durable enough. It is very hard to break a crank. I'd probably prefer something with a square taper BB for ease of replacement if you're touring in a non-OECD country, but that's not guaranteed - they might not have the correct length taper in stock, although you could probably accept a few mm mismatch (I think; this is based on experience with chain drive only).
    – Weiwen Ng
    Oct 28 '21 at 17:44
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    @WeiwenNg the belt wants to be straight very much and trying to make it deviate by even a couple of mm is working against all that makes it a good choice. Hollowtech2 cups might be a good choice as it's a common system and the bearings/cups are light and compact for postage where necessary
    – JoeK
    Oct 28 '21 at 18:48
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    I second the vouching for the Sugino cranks. If you want maximum durability and longevity then forged square taper Japanese cranks are exactly what you should be looking for, and Sugino is one of not that many left. All touring bikes should have cold forged cranks. Oct 29 '21 at 2:37
  • @JoeK Good to know. To be clear, I have no experience with belt drive, so I didn't appreciate this.
    – Weiwen Ng
    Oct 29 '21 at 15:57
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Gates make some cranks that mate with a square taper bottom bracket. These come with a nylon ring.

You could buy something like a Middleburn crank and spider setup, where you can choose the spider that meets your needs and either a hollowtech2 or square taper bottom bracket. The arms always used to have a lifetime warranty even for downhill riding so I wouldn't worry about breakage for your use. they are now available from BETD in the UK. The spider system means that you can choose 4-arm or 5-arm and don't have to replace the whole crankset if you want to use a different style ring in the future.

Praxis may offer something that is spider based too.

You could find a Sugino RD2 or clone, but you are back on the square taper bb that way, and some of the clones may not have the accuracy of production you'd like.

You could buy something used or reach out to a cycle shop to see if any of the old 5-arm shimano cranks are sitting around new or used. You can probably make the chainline work with a 5-arm road triple or 130bcd double.

That's about the limit of what I would try. Shimano, SRAM and Campagnolo aren't producing new 130bcd cranks but there may be a 4-arm in the mountain range that you can strip the rings off and replace with your belt ring.

Replaceable-spider cranks don't create problems when well designed. Most of the new SRAM cranks have removable spiders and have for years. They don't cause a problem in road or mtb. Middleburn have been using their system for maybe even longer and it's a well proven design.

Hope that helps you.

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  • For the Gates crankset, the nylon sprocket is from their budget CDN series. Wouldn't make it very far on that. Haven't been able to locate CDX cranksets for sale. Great point about the versatility of a spider set-up. I was about to write them off altogether.
    – Laoshi
    Nov 2 '21 at 13:06
  • Is there a way to determine if the chainring is detachable?
    – Laoshi
    Nov 2 '21 at 13:11
  • @Laoshi I don't think the nylon sprocket is that bad. Because it's so big, the wear is not so much a problem. Anyway, the ring is detachable from both the 150 and 250 cranks, both are 130bcd. Though they are not very exciting cranksets. If you are buying another ring anyway, you would may as well spend a bit more and get the middleburn (even in square taper) or something else similar.
    – JoeK
    Nov 2 '21 at 13:59

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