Detailed Advice Please - Converting 3x9 to 1x11 Drive-train

[ForgedMTB]

Morning all,

I have a 2013 GT Tachyon 2.0 that i would like to convert to a 1-by drive-train for a bit of fun. Can someone please provide a detailed guide on what to do, what to look for, whats compatible etc etc. Existing bikes specs below;

Crankset = FSA Omega Triple, 50/39/30t
Bottom Bracket = FSA Mega EXO
Shifters = Shimano SL-R440
Rear Derailleur = Shimano Sora
Rear Cogs = Shiman HG50, 11-25t, 9-speed

What should i be looking at and considering here?

[P!N20]

Mods: please move to The Bike Shed section.

[bychosis]

First thing to consider is what size front ring you need. Base this on the gearing you use on your current setup. No point kitting it out and then finding you set it up so holds are a pain or you spin out on the flat.

I converted my last MTB from 3x9 to 1x9 then to 1x11. 3x9 I use the same sized front ring (32) as the existing middle ring, but got a wider spaced cassette, from 11-28 to 11-34. Worked ok. Then I bought an 11spd mini group set of shifter, chain, derailleur and a 36 tooth narrow wide chainring as I wanted a bit more top end speed and the 11spd cassette had wider gearing. I think it was 11-42, it may be wrong. I calculated the ratios and gained a slightly lower gear and a couple on top.

Anyway. The least you will need is a shifter, compatible cassette, probably Shimano (not all 11spd will fit a 9spd freehub), chain and a front narrow wide ring to fit your current middle position chainring. Running with a 3x middle ring is likely to result in chain drops due to the shift ramps.

[rkelsen]

I think you'll need to change the freehub as well. You can fit a 10 speed cassette on your 9 speed freehub, but an 11 speed cassette is marginally wider and won't fit.

One tip I have: Make sure that you get some proper 1x chainring bolts, or at least shorten yours properly. I was using standard 2x bolts (with nuts that were filed down), and the chain got caught on one of the bolts and scratched my frame. Badly. As in: Took chunks out of the steel.

If you want to do it on the cheap, why not keep it 9 speed? Otherwise you'll need to change the shifter and possibly RD too. You could easily be up for hundreds by the time you factor in freehub, cassette, chain, shifter and possibly derailleur.

[bychosis]

I think you'll need to change the freehub as well. You can fit a 10 speed cassette on your 9 speed freehub, but an 11 speed cassette is marginally wider and won't fit

It depends on what cassette range. Shimano MTB cassettes 11-42 etc have the largest cog offset back over the hub flange so they will fit a 8-10sped freehub and wheel. I did this successfully with my conversion. I’m not sure what size large cog is the smallest that will fit the existing hub.

SRAM started using a special hub with a 10 tooth small ring, but I think have joined Shinano and now go 11-?? And use a standard hub.