Converting drop bar bike to flat bars

[yoav]

I'm thinking of converting my town frankenbike from drops to flats without having to replace too many bits or do too much rebuilding. My issues are:
1. Gears - currently I have 10 speed indexed Shimano bar end shifters - rear is a 9 speed Shimano XT MTB mech with a 10 speed 12-34 10 speed road cassette. The indexing works remarkably well. Front mech is an old Campag triple controlled by friction shift. I think that a set of Paul's Thumbies would work on flat bars and enable me to retain the current gear setup. Is that the best option or is one of Shimano's trigger shifters better and if so which one?
2. Brakes - currently have TRP brake levers operating calliper brakes, the cables run under the bar tape. Would these levers work on flat bars?
3. Stem - I assume a shorter stem is needed. Any formulae to work out how much shorter or is it trial and error?

I'm not really experienced with flat bar bikes, the only one I have is a Brompton, so thanks for any help.

[LittleWheelsandBig]

Yes, thumbshifter converters is the way to go. https://www.sjscycles.co.uk/gear-spares/jtek-special-thumb-shifter-brackets-for-222-mm-bars-black/ is cheaper than Paul’s.

You will need flat bar levers (cantilever-compatible, not V-brake).

Generally you need a longer stem because a drop bar bends forward. The same length may work if you also fit bar ends. Check the handlebar diameter as drop bars may be larger diameter than flat bars.

[ACyclingRooster]

I'm thinking of converting my town frankenbike from drops to flats without having to replace too many bits or do too much rebuilding. My issues are:
1. Gears - currently I have 10 speed indexed Shimano bar end shifters - rear is a 9 speed Shimano XT MTB mech with a 10 speed 12-34 10 speed road cassette. The indexing works remarkably well. Front mech is an old Campag triple controlled by friction shift. I think that a set of Paul's Thumbies would work on flat bars and enable me to retain the current gear setup. Is that the best option or is one of Shimano's trigger shifters better and if so which one?
2. Brakes - currently have TRP brake levers operating calliper brakes, the cables run under the bar tape. Would these levers work on flat bars?
3. Stem - I assume a shorter stem is needed. Any formulae to work out how much shorter or is it trial and error?

I'm not really experienced with flat bar bikes, the only one I have is a Brompton, so thanks for any help.

Hi yoav. I built a 50cm  Bianchi Via Nirone 7 Alu Carbon as a Flat-bar Hybrid from the naked frame but very very reluctantly sold it on E'bay recently  https://www.ebay.co.uk/itm/303563170370

There is a full description of the bike on E'bay,the bike was built using 10spd Campagnolo Veloce Flat-bar levers that were purchased from Chain Reaction in Belfast and using Veloce components with Stronglight 140mm cranks and Marcel Berthet Lyotard Platform Pedals.

[Rod Marton]

You will definitely need a longer stem. When I converted a bike a few years ago I found that I needed to use a 130mm stem to get a comfortable position. I don't know of any formula to do the conversion, but if you find you are comfortable riding on the hoods, think what distance your hands are at and this is the sort of distance you want your bar to be. I found bar extensions a good idea as well, but treat these like going onto the drops - you get a longer lower position but probably not your default.

[nikki]

There's a bit of discussion around my cantis, drop bars and bar end shifters to flat butterfly bars conversion here, just in case there's anything useful in that for yoav or any others who come through in the future...

https://yacf.co.uk/forum/index.php?topic=87518.msg2161725#msg2161725

[Asterix, the former Gaul.]

My town bike is straight bar one off the peg.

It's a good machine for short trips into town but I'd say the straight bars are its worst feature for me.  They were too wide for starters so I cut bits off the ends. Then I find it uncomfortable riding for long with my hands at the angle they demand.  The upright position they require is uncomfortable on our potholed roads - I had to buy a sprung saddle.

It would look silly with curly bars but I would like those bar extensions letting me turn my hands 90 degrees.