My son wants to go 1x10


Active Member
Hey guys still getting up to speed on all of the changes over the last 15-20 years. My 12yr old son is currently riding a 06 fuel ex8 on 26's with a 2x9 gearset (we pulled the large and put a guard in its place) He is asking me to change him over to a 1x10 setup. Thing is we mostly ride in the Tourne and Dickerson mines and he does go into the granny gear currently. What should i be looking at for gearing if we go this route. The shifters and rear derailer are the easy part. pull of the old replace with newer clutch style. The gearing I do not know and most of what I have found is based on 29ers and 27.5 gearing not even counting we are taking someone without the leg strength of and adult. Any advice would be appreciated.


Well-Known Member
are you on Shimano or SRAM?
both will go up to 40T (get the Sunrace stuff, cheaper than SRAM or Shimano)

but probably want to go with 42T, SRAM will need a longer B-screw and Shimano an extender from the dropouts

Also get a 26 or 28T front, which is between the typical two smaller rings. Though you'll need to find one that is offset and mounts on the smallest ring to get a decent chain line. Measure to make sure you have the right BCD

at today's prices, you might just want to go 11spd, it's designed for the bigger gearing and 1X


Well-Known Member
The bike I built for my 12-tear old son for NICA last fall uses 1x10 (includes a 40-tooth cog) with a 30-tooth chainring on 26-in tires. (he moved from a 1x9 24-in fat bike)
Definitely a good starting place as he does not need to learn/remember FR.
What I am seeing is
* he still needs the low end to get up hills (although he uses the 40 less and less)
* but runs out of gears trying to go fast (long flats or when we do training rides on gravel). I see him spinning on his fastest gear and not keeping up. The 26-in tires definitely play a role and you'll be in the same boat.

Since we are not worried about top speed in 6th grade, this works out fine.
At this rate his next bike will have to have more then 10 (or maybe even 11) gears. By the time we get there (I am assuming next spring) who knows what the sweet spot performance/cost will be.


Well-Known Member
Team MTBNJ Halter's
Tell him to stick with the 2x9 and the next bike he grows into may have 1X

If he was able to push a 30 or 32 in the front, it's an inexpensive upgrade. It sounds like you'd have to dump tons of $$ into this with the benefit of maybe some less weight due to the loss of a front derailleur.


aka Fidodie
Staff member
what is the goal?

More low end?
there are 9 speed clusters with a larger big cog (11-42 or 11-40) - might not even need to change anything but the b-screw setting.
this is a very economical solution. Link:

More high end?
without changing the freehub to accept a 10-XX cluster, that means a larger chainring, which means wider cluster to compensate (11-42 or 11-46)
Again, this can be done as a 9-speed economically. the gear ratio spacing gets wider

More gear choices?
the 10 speed (or 11 speed) cluster will give closer ratios between shifts, Is that important? will a kid notice if you don't bring it up?
although it makes a good math problem, which should be right in a 12yo's wheelhouse
(see @UtahJoe's Take Kid to Work Day display on here somewhere- which i can't find right now)
and probably more choices in cluster range.

Wrenching with the kid?
OK - this might just be the answer - learning about pull ratios, and why things need to be changed to make it work.
creative cable routing. if it doesn't get trashed, then it can always move to another bike.

my kid grew 5-6 inches when he was 12-13, you are going to need another bike soon. cause puberty. :eek:

picture of kid riding some single track now required.
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2018 Fantasy Football Toilet Bowl Lead Technician
Team MTBNJ Halter's
You can make the upgrade for so cheap (assuming the freehub can take an 11sp cassette)


Well-Known Member
Team MTBNJ Halter's
I would definitely go 1x9 but wouldn’t I need a clutch derailer as well as a cassette?
Maybe, maybe not. I found I never dropped the chain with my 1x9 conversion on my 9 speed bike, and I am pretty sure I had the long cage derailleur. It maybe happened a handleful of times, but I can't remember if it actually ever happened. On my 1x10 I never dropped it, although I have a short-cage on that bike.

Narrow-wide on the front ring on both bikes.


Active Member
I guess at this point one of the other reasons I wanted to change him over is I would like to move him down to a shorter cranks as well. right now that came has 175mm cranks on it. I think I would prefer to put some shorter 165 cranks on it so his knees don't bend as much. Shimano only offers 165 cranks on there Zee downhill cranks were I can get my hand on the Sram NX 165 crankset.


Active Member
Ahhh I never updated this post... Thanks to an Ebay coupon a few weeks ago and one of the members here. I swapped him over to a 1x10 with 165mm cranks. Sunrace CSMX 11-40 cassette and Sram X9 derailleur and shifter. My son absolutely loves the new setup and with the shorter cranks he is actually sitting more to climb instead of mashing out of the saddle.. All said and done the complete swap was under $200 and well worth the money in my opinion.. I did keep everything that I took off the bike so next year depending on what we do bike wise we may move this stuff over or sell it off.