[brentos]

Hey all, I'm looking for cranks shorter than 165mm that are comparable with a PF121 BB, will accommodate a 75ish mm chainline , and have 1x chainrings available down to 26 or 28 tooth?

I have a 165 GX crank on the way, I purchased because it's rarely available and I couldn't find any shorter options, but I'm concerned it might not be short enough for my son.

TIA

 

[htrdoug]

Man,I would consider frame swapping to get a threaded bottom bracket, then you can run the short suntour XCT jr cranks that are under 40 bucks with removable triple rings,you can then switch to whatever you need as far as chainrings. Square taper bottom brackets are disposable cheap too. Running a 160 Suntour on my Kona Wo. Made a massive difference for my old legs. XCT jr. cranks come in 152 also.
I know switching frames is a big deal but getting crank length correct means more to me than even frame size.

 

[bme107]

You don’t mention you son’s height but if somewhere between 4’-6 and 5’-6 I bet he’ll do just fine. Kids are much more adaptable. A thicker body flat pedal and winter boots can take up some of the length as well.

My kids jumped from 135s to 165s at age 12 when they were +/- 5ft

Check out the riding with kids sub-forum and ask there too if there are short cranks with removable spindles. Trailcraft Cycles used to make some but don’t see them on their site anymore.

 

[Jayem]

With a 30mm or 28.99 SRAM or RF (but they don't do the 28.99) spindle you can swap crank-arms that are of the same spindle-size. I just did this two days ago on my fat-bike, pressed-off the mountain spindle on my 30mm X01 cranks and then pressed them onto a RF 189mm spindle.

So if you had the 30 or 28.99 spindle and shorter arms, you could "make your own crankset", like I did. 30mm is probably out of the question though, since PF121 is a wider BB92 and they didn't leave enough space for big-enough bearings with the standard (why SRAM was somewhat forced to come out with 28.99).

 

[brentos]

With a 30mm or 28.99 SRAM or RF (but they don't do the 28.99) spindle you can swap crank-arms that are of the same spindle-size. I just did this two days ago on my fat-bike, pressed-off the mountain spindle on my 30mm X01 cranks and then pressed them onto a RF 189mm spindle.

So if you had the 30 or 28.99 spindle and shorter arms, you could "make your own crankset", like I did. 30mm is probably out of the question though, since PF121 is a wider BB92 and they didn't leave enough space for big-enough bearings with the standard (why SRAM was somewhat forced to come out with 28.99).

Thanks Jayem,

I knew BB30 and Cinch were of the same spline specification. Is DUB also the same spline? Also, are the SRAM DUB & BB30 Non-Drive arms able to be separated from the BB spindle? Looking at my XX1 DUB set, I don't see a way.

I appreciate the help everyone, it got some ideas going. My son is 4'8" and other wise is actually a pretty good fit on the bike. I'll see how the 165's work for him over longer distances, if I end up needing and finding a solution to go shorter, I'll post back on here.

 

[Jayem]

Thanks Jayem,

I knew BB30 and Cinch were of the same spline specification. Is DUB also the same spline? Also, are the SRAM DUB & BB30 Non-Drive arms able to be separated from the BB spindle? Looking at the XX1 DUB set, I didn't see a way.

I appreciate the help everyone, it got some ideas going. My son is 5'8" and other wise is actually a pretty good fit on the bike. I'll see how the 165's work for him over longer distances, if I end up needing and finding a solution to go shorter, I'll post back on here.

I looked into doing the same thing with Dub. This seems to indicate that they aren't interchangeable:

I'd like to know for sure too. I just keep my 30mm spindles going since the bearings are much easier to source (PF30, not the BB92/141). Some day I'll have to move away from that if supplies dry up.

 

[Jayem]

I found a much better way to remove the spindle was to cut a piece of PVC pipe, get some 3/4 or 5/8 washers, put the PVC over the spindle, put the washer(s) and bolt on the opposite side of the spindle, having about 1cm extra length over the spindle with the PVC is what makes it work, tighten down the bolt and it pushes the crank arm off the spindle.