Retro Shifter Compatibility Question 2x 3x

The question feels retro – not the shifters sorry.

I’m toying with bodging a gravel bike out of the hybrid I have in the shed, as cheaply as possible.

Base bike is a Voodoo Marasa that’s done a couple of hundred miles, not sure what year 2018 maybe, the orange and grey one.

It’s got a 3×9 Altus groupset on it and hydraulic brakes.

I’ve got some single piston disc brakes in a box somewhere taken off an old commuter so I could recommission them meaning I can could just get some Sora brifters on the cheap. But 2×9 are much easier to come by than 3×9. Is it possible to index the front shifter to just use the outer or inner 2 rings of a 3x chainset in the short term?

If that works I think all I’ll need is bars a shorter stem and bar tape, I think I could convert it for about £60 with some used shifters, if I have to go 3x price shoots up and I’m not sure if I should just get something like a used Voodoo Lima off FB market place.

I’ve tried riding the hybrid as it is, but the flatbar isn’t working for me, I’ve tried ergon grips with the stubbie bar ends but I don’t like having my hands so far apart unless I’m mtbing.

Any thoughts? Have I missed anything from my shopping list?

Do you mean you have a pair of mechanical disc callipers?
If so what specific sort because some are designed for road bike lever cable pull and some for MTB (v-brake) lever cable pull and they don’t work very well with the wrong lever/calliper combination.

WRT to your front mech Question, yeah you can set the mech to just use the inner/middle rings and a 2x road shifter should pull it across OK, don’t know how different 9 speed Road and MTB chainrings are spaced though, shouldn’t be wildly different though should it.

Edit:

I’ve tried riding the hybrid as it is, but the flatbar isn’t working for me, I’ve tried ergon grips with the stubbie bar ends but I don’t like having my hands so far apart unless I’m mtbing.

Stupid question, could you not just move the controls inboard and trim some flat bars if it’s just about how wide apart your hands are?

Brakes are from a tiagra equipped road bike so all good there.

Think I’m going to give it a go and see how it goes, tbh from experience I’d rather buy a new chainset than spend the extra and then deal with the extra faff of a triple set up so I’ll got for the 2x9s.

Watch your cable pull ratios on teh brakes – Road Brakes don’t pull enough cable for MTB calipers.  You may need road calipers or a cable pull adaptor.

Look at AliExpress for shifters.  I’ve got LTwoo 3×8 ones and while clunky are completely functionally fine and seem robusts.  I’ve also got some Sensah 2×8 ones I’m yet to fit, so cannot comment on those really, but they feel nice out of the box (nicer than the LTwoo tones)..  Completely different shifting action though.  I beleive both of these are availabe with 8, 9 10 or 11 speed mechanisms within them, so give the same ergonomics.

And yes, just set teh cable to only operate the big/middle rigns on teh front mech.  But front mech cable pulls are slightly different between road and MTB I think, so you may not get perfect shifting.  Not sure about 9 speed there though….

Or get some Surly (or ali-express knock-off) “Corner Bars”.  these are kind-of drop bars that are sized to take MTB shifters/brake levers. Easy swap over, minimal equipment change, may need some nre cables….Keep the hydraulic brakes into the bargain too….

And if those (genuine?) ergon grips you tried are going spare, I might be interested in taking them off your hands….   Though they would fit on a “Corner Bar” or similar, and I’m be intrersted to see the results/feedback if you try it!

Carbon version (not sure if they post to UK) https://www.aliexpress.com/item/1005005991084426.html?spm=a2g0o.tm1000009216.d0.1.46226f3dhkLcIR&sourceType=561&pvid=83926a15-6fa6-4800-8f81-2e611098df88&pdp_ext_f=%7B%22ship_from%22:%22CN%22,%22sku_id%22:%2212000035206672959%22%7D&scm=1007.28480.379202.0&scm-url=1007.28480.379202.0&scm_id=1007.28480.379202.0&pdp_npi=4%40dis%21GBP%21%EF%BF%A181.17%21%EF%BF%A130.03%21%21%21726.69%21268.86%21%402103835e17341065204895472ec949%2112000035206672959%21gsd%21UK%214806665651%21X&channel=sd&aecmd=true

I’ve just taken some rough and ready measurements from my 18″ frame Marasa from ’20 (black with reflective gold decals)…

Reach ~425mm

Stack ~560mm

bars (end to end of default grips) ~680mm

Stem 50mm -/+6

My Cube Attain GTC Disc ’16 road bike is 388mm reach, 610mm stack, came with 110mm -/+6 stem but I swapped it out for a Deda adjustable 120mm -30/+40 so I could have close to a “normal” road bike when my lower back was ok.

I thought about putting the old 110mm stem on the Marasa with a 620mm Ritchey flat bar I have in the spares box, but not got around to it, because of priorities and long covid. Would put bar at similar reach to back of hoods on my Cube.

But combining drops (which will have ~75mm reach) and at least an 80mm+ stem is going to a compromise of a comfortable hoods position and twitchy handing on the road?

I’m going the other way with the stem, thinking 35mm to counteract the extra reach of the drops. I wish I’d dry fitted the bars from my road bike before I sold it. It definitely feels too short as it is currently, so could afford a bit of extra reach but 75mm will be too much. I think mine has a 70mm stem from memory, I’ve got a feeling its shorter than the black paint model.