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I'm looking to buy a Sora triple crankset. Shimano make two types, one eith 5 arms, and the other with 4 arms1. Which should I get and why would that be a better choice? I'm a slow-ish rider. I'm 50 and speed is not a priority. But I'm planning a long ride in Asia and Africa next year. Which of the two chain-ring types would be a better choice for spare parts and any other considerations? Note: the 5 arm crank has a P.C.D. of 130 compared to 110 for the four arm crank.

Editor's note: The 4-arm R3030 crankset, below, is described as having a 110/74mm BCD.

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The 5-arm R3030-CG, below, is described as having a 130/74mm BCD.

enter image description here

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    5 hole replacement chainrings are widely available and FC-R3030-CG has chainguard. Most of recent Shimano road crankarms use 4-arm design with proprietary chainrings.
    – Klaster_1
    Feb 20 '19 at 14:35
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    For ultimate spare parts availability in poor countries, get a MTB triple instead. Even spaced 4-arm 110mm 28-38-48 is still very common on hybrids and low end bikes.
    – ojs
    Feb 20 '19 at 18:52
  • In road speak (I'm assuming not a triple which is 110/74PCD ~ 74 is the innermost chainring) 130 PCD is known as a standard and can only go to 39t on the smallest chainring. 110 PCD is known as a compact. And can go to 32t (maybe 31t) on the smallest chainring. If you are touring - I'd assume a decent spread of gears would be your preferred option - go with the 110 PCD.
    – OraNob
    Feb 21 '19 at 9:15
  • Thanks for your replies. Since posting this question, I've taken another look at Sugino's XD600T triple crank. It has 48(or 46)-36-26T. It uses a JIS square taper cartridge BB (British thread 68 & 113) which uses a cromoly steel spindle (nice). It's not that cheap but I like simplicity and value, which I think is well represented by this crank. I'm not saying Shimano's 4 arm isn't good, but I would prefer to avoid "proprietory" products. And well established open standards suit my needs much better (I'm thinking about Africa here). But Sugino ship to anywhere in a matter of days so no problem.
    – user41329
    Feb 23 '19 at 4:44
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    Just a quick tech note: I think the Op referred to the R3030-CG Sora crankset as 5 arm. That looks like it’s a 130mm BCD for the outer two rings, and it’s probably 74mm for the innermost chainring. I think some comments/answers may have assumed that the BCD was a uniform 130mm. @TassieViking’s answer correctly points this out. If you all don’t mind, I will edit the links in the post to show the two distinct models of Sora triples.
    – Weiwen Ng
    Dec 26 '20 at 18:54
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With a triple crank it matters more what the inner most PCD is. 110 and 130 both refer to the larger rings only and the length of the crank arms themselves may not suit you and it may not be compatible with your bike immediately either. I have played with bikes for over 40 years and ridden most Shimano PCD types and arm lengths and 4 of the bottom bracket standards too. You may need new bottom bracket bearings installed at the same time, the different standards don't interchange at all. The newer the better from every angle if you need it and the price is right for you. Sometimes the bike is better to be replaced if you know enough to understand what you need and more than a few things need to be replaced at once on a mediocre older bike.

Your described style of riding tells me you need the model that comes with the smallest number of teeth on the smallest ring of the crankset. This selection will provide the easiest effort to you regardless of most other things. The other gears are almost always properly spaced to provide 3 separate ranges of gears you can use for riding comfortably uphill, downhill and more level ground. Practice using all you gears to learn when you may wish for just that particular effect on your comfort and your efforts.

Just like your brakes it is important that your gears work just as you need them to when you need then to.

I have used middle and inner ring minimums on 48/34/20T with 94/58PCD and 54/39/24T with 130/74PCD and others in between. Your tyre size, terrain you ride and what you will carry on it really sets your gearing needs the most. If you learn to enjoy using more effort and sweating when you ride your gear needs may also evolve.

I've not seen or heard of less than 20T on a crankset. If both cranksets have the same lower number, then, the wider of the other 2 gears would be my recommendation. You can usually change just the inner ring very cheaply if you need a change but it can only go so small with each PCD.

Bike parts are usually so reliable as metallurgy has improved greatly in our lifetimes, thinking about ongoing costs is not very relevant apart from maintenance of the chain. Keep it clean and dry lubed following the directions is the biggest money saver you can make. It is possible to have a chain last many 1,000s of kilometres with regular care.

Edit: Only now that I've returned have I actually seen these 2 crank set images you referred to. I'd select the 5 arm Shimano with a new BB, the 2 piece design was introduced 20years ago and lots of spares and a 24T is possible in place of the 26T if needed. Bending any axle or crank arm is likely with enough force regardless of the system.

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  • Good observation about the innermost chainring having a different BCD than the big two.
    – Weiwen Ng
    Dec 26 '20 at 18:57
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Seems to me the main difference is that the 5 arm version has a chain guard. The larger PCD is different but both come with a 50t large chainring per default, so that in itself doesn’t make a functional difference. I can't find a weight for the 5-arm chainring version, but I suspect it to be heavier.

Chain rings generally last >10Mm, so I don’t think spare part availability matters much. An unexpected failure is unlikely, with a broken tooth on the big chainring being the most likely. But then you can still continue on the smaller chain rings without much of a problem.

If you don’t need the chain guard, I’d just go for the 4 arm version.

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    Usually, you can continue on the big chainring with one tooth less. I broke off a tooth from the biggest chainring on a Deore triple many years ago and there wasn't any need to buy a new one whatsoever. I am still using it and will only change it due to the general wear. The missing tooth is a non-issue.
    – Vladimir F
    Dec 26 '20 at 19:06
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I'm looking to buy a Sora triple crankset. Shimano make two types one has 5 arms and the other only has 4 arms. Which should I get and why would that be a better choice?

The one where you can reasonably rotate the chainrings in the best possible manner.

Normally, that would mean 4 arm. However, the Sora 4 arm crankset has an asymmetric bolt circle. It means you cannot rotate the chainrings to get maximum life out of them. Not only that, but sourcing these asymmetric chainrings is a major burden.

So the 5 arm is better in your case. The rotation to even out wear life is not perfect (a 4 arm crankset allows you to rotate the chainring exactly 90 degrees, the maximum possible rotation, whereas with 5 arms you get 72 degree rotation).

However, the 130 BCD doesn't allow a compact gearing. I looked at the cranksets and today it lists 110 BCD double and 130 BCD triple for the 5-arm designs. The 110 BCD double is the best bet for slow riders as you won't want a triple due to its unoptimal chainline on the big ring.

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    As far as I know, rotating chainrings is not a standard practice. The wear stems from the chain's rollers pulling on the chainring teeth. Every tooth is in the proverbial firing line at some point during a crank revolution. If this practice were valid, then provided the arms were symmetrical, why should 4- versus 5-arm cranks be any different? (And by the way, isn't sourcing any 4 arm chainrings a bit of a burden, since there are the 3 major manufacturers with different designs and BCDs?)
    – Weiwen Ng
    Dec 26 '20 at 22:09
  • @Weiwen Ng More wear occurs during the power zone of your pedal stroke. Rotating chainrings is indeed a practice I’ve never heard of before, but it does not seem unreasonable. I believe Shimano 4 bolt chainrings have an asymmetric bolt pattern, so you can’t rotate the chainrings on one of those cranks.
    – MaplePanda
    Dec 28 '20 at 1:39
  • I can’t see how rotating a chainring 90 or 180 degrees will make any difference to wear ? Anything that revolves around 360 degrees is subject to the same pattern regardless to starting position.
    – Dan K
    Dec 28 '20 at 17:06
  • @Dan K Humans don’t produce power equally throughout the pedal stroke. The tension and thus wear differs. How much of an effect this has, I don’t know.
    – MaplePanda
    Jan 4 at 4:33

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