Originally Posted by
gequiroga
Hello! when one converts from flat bars to drop bars, the distance from your saddle to where your hands will be increases, so if the bike feels already big, it will be worse after the conversion, so I wouldn't recommend that bike for the conversion.
When one tries to make this type of conversions you have to consider three main things (this is my personal opinion and only a rough description)
1) Frame Geometry
2) Braking
3) Gear shifting
1) You need to start a conversion with a suitable frame that will accommodate your idea for the bike after. For a gravel bike, you cannot pick a road bike because then you wouldn't have clearance for bigger wheels, and you cannot pick a modern MTB because the top tubes are too long and the bike will end too stretched. I found that hybrid bikes are the most suitable kind to start conversions on because they are generally cheaper, often have some road components, and their initial comfort geometry translates into a nice riding position once you change flat bars for drop bars.
the web 99spokes (can't post links) has a database of geometries that you can check when in doubt, you can go ahead and compare for example, a merida speeder (hybrid) with a canyon grail AL (gravel) and you'll find them to be really similar.
2) Braking: road levers are not compatible with MTB brakes. Mechanical road bike levers pull about half the length of cable than MTB levers, and for this reason you cannot use MTB calipers or V-brakes with road levers, you can use cantilever brakes, mini v-brakes and road calipers like the avid bb5 and bb7 road, tektro spyre and any other specifically designed for road levers. You could also choose to use a pull ratio adjuster to make them compatible.
3) Gear shifting: you have to check if the derailleurs on your bike are compatible with the road lever you intend to put into the bike, because road and MTB groupsets are not always compatible, Shimano, for example, has compatibility between road and MTB up to 9 speeds, from 10 up, they are not compatible. there are also pull ratio adapters and you can look up "mullet drivetrains" for more examples.
Also, road levers are quite expensive, so I think you may want to secure some cheap ones before starting a project like this.
Examples of a possible conversion, out of my mind so you can see more or less the process:
A used trex FX shows up, it's a 3x8, v-brake bike. I check the geometry on 99spokes and a L frame is similar to a M frame on a gravel bike. I buy it.
I get a pair of used Sora levers, 2x9 speeds.
I need a new 9 speed cassette on the back, this is no problem as 8 speed hubs are compatible up to 10 speed cassettes, and 11 if they are MTB hubs.
I need to replace the V-brakes for either cantilevers or mini v-brakes, or buy a pull ratio adapter if the brakes are worth it.
I have to check if I can make the front derailleur work with the 2x lever to shift between the 2 bigger chainrings. I manage to do that and end up with a 48/38 gearing up front
I decide I need a MTB cassette in the back to get a low enough gearing so I buy a 11-40 sunrace cassette and a alivio 9-speed MTB derailleur which is compatible with the 9-speed sora lever because it's less than 10 speeds.
I fit a drop bar on the bike and then find out it's a bit stretched so I replace the 110mm stem with a 80mm one.
I hope that helps a bit.