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I have 2012/2013 (alleged) Kona Ute. I need to replace a the crank arm due to stripped pedal thread.

It currently has an FSA Powerdrive 118mm/68mm Bottom Bracket. I am not 100% certain but I believe the current Q-Factor is "Q-Factor - 170mm(C.L.48mm)" from this source

Due to availability, it is easiest for me to replace it with a square tapered bottom bracket and crankset.

Due to the relatively unusual size and shape of the Kona Ute frame (long tail cargo bike), I'd like to try and achieve a similar Q Factor and Chainline with the new crankset.

Can I use 118mm as my size for purchasing a square taper bb for a 3x9 or 2x9 crankset.

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    You have to specify your crankset and your desired Q-factor. Different cranksets require different spindle lengths. Be careful about the chainline. But just 118 mm without specifying the crankset does not mean anything. Commented Apr 6, 2022 at 14:19
  • thanks @VladimirFГероямслава i've updated the post.
    – J Mac
    Commented Apr 6, 2022 at 14:47
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    OK, but which crankset do you want to use? Commented Apr 6, 2022 at 14:49
  • We are currently looking at 3x9 and 2x9. Also, I am a bit confused. I am under the impression that the primary driver of Q factor is Spindle Length. Is there another factor?
    – J Mac
    Commented Apr 6, 2022 at 14:55
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    You must always consider the specific crankset model. Only then we can speak about choosing the spindle length. Cranksets normally come with a spindle length specification they are supposed to be used with and the Q factor that results from that is also specified. Commented Apr 6, 2022 at 15:42

2 Answers 2

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If I understand your current situation you now have a broken crankset and a Power Spline (Truvativ compatible) bottom bracket with a 118 mm spindle, but there is a lack of Truvative compatible cranksets now.

Three piece cranksets general do not all use the same spindle length. It depends on the specific model you choose. Generally, cranksets come with an indication which bottom bracket standard and which spindle length you need to get the default chainline and the default crankset.

The normal recommendation is therefore to follow the specifications of that specific crankset model unless you need to somehow modify the chainline and the Q-factor. The Q-factor and the chainline achieved with the specified spindle length is also normally indicated in the crankset specifications.

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  • The last truvativ BB I got took 3 months to arrive and came from Singapore. Seems a good opportunity to get off a dead/rare standard.
    – Criggie
    Commented Apr 6, 2022 at 21:53
  • Thanks for the advice!
    – J Mac
    Commented Apr 7, 2022 at 5:04
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While you have accepted an answer, I would like to add more detail.

The chainline you have specified, 48mm, is quite normal for a standard mountain bike chainset, which are usually specified at 47/48mm and 50mm.

While the UTE is quite a special bike, you can determine if a reduction in q-factor is possible or maybe even desirable by checking how much clearance you have between the current crank arms and the chainstay. A few mm is sufficient and your current cranks probably give a very wide clearance. Many people find a narrower Q-factor desirable.

Most Shimano cranksets that use sqare-taper have a wide q as they are fairly lowly nowadays. The required bottom bracket is specified in the informationsheet to give a specific chainline.

Other manufacturers also list these figures. Examples:

Middleburn specify a 113mm square taper bottom bracket to give a 50mm chainline with the RS7 crankset using a triple spider. You could reduce this chainline to 48.5mm by using a 110mm bottom bracket.

SunRace specify a 122mm bottom bracket spindle for a 50mm chainline with the FCM914 crankset. This could be reduced to a 48mm chainline by using a 118mm bottom bracket.

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