Condensed Answer: It’s possible to install drop bars on a flat bar road bike. However, the conversion requires a multitude of new parts that could greatly increase the final bill.
It’s also necessary to obtain basic mechanic skills or pay a professional to perform the conversion.
In some cases, the top tube of the bike could be too long and cause an uncomfortable riding position.
The Needed Parts
Part 1: This section contains components that will be needed in all cases.
- Drop bars + Bar Tape
Most flat bar road bikes use shifters mounted near the brakes. Those shifters cannot be re-installed on drop bars because:
- The grip areа of flat handlebars where the shifter goes has a diameter of 22.2mm. The clamps of flat bar shifters reflect that. Meanwhile, the diameter of average drop bars is 23.8mm. Consequently, standard flat bar shifters can’t slide onto drop bars.
That said, some people have modified flat bar shifters (e.g., grinding the inner part of the clamp) to make them fit on drop bars.
2. The flat part of some carbon bar drop bars is not round and thus cannot accept standard flat bar shifters.
But even if flat bar shifters were fully compatible with drop bars, installing them makes ergonomic sense only when they’re mounted on the flat part (tops) of the bars.
If the flat bar shifters go there, the rider will have to move their hands away from the hoods (brakes) to shift. Some people dislike that mechanic.
Consequently, the standard conversion requires the user to purchase a set of brake-shifters such as STI.
(Brake-shifters are a unit that combines a shifter and a brake designed specifically for drop bars.)
Brake-shifters are not cheap. In some cases, they could make up 50% of a road bike’s price.
If you’re looking for a cheaper solution, you may consider using downtube shifters. If you’re converting an old road bike, chances are that it already has them. In that case, you don’t need brake-shifters. You can just buy drop bar brake levers which are much cheaper since they don’t have an integrated shifting mechanism.
The other options are:
a/ Bar-end shifters – bar-end shifters can be combined with drop bars too. Their downside is that the user has to move their hands away from the brakes to shift.
b/Alternative flat bar shifters – there are shifters such as SHIMANO A050 which are compatible with the flat part of drop handlebars. (The model isn’t always easy to find, though.)
- Cables and Housing
The conversion will require new cables and housing because the old ones are very likely to be of the wrong size.
Part 2: Potentially Needed Parts
The next section contains parts that could be necessary in some situations:
- A Shorter Stem
Standard road bikes with drop bars have shorter top tubes than bicycles of the same size designed specifically for flat bars.
The shortening of the top tube is a necessary geometry modification caused by drop bars. The primary position on a set of drop bars are the hoods which are positioned at the front of the drop bars.
Thus, the rider is stretched significantly to reach them. For that reason, the effective top tube of road bikes has to be shorter than that of MTBs and hybrids.
Therefore, if the flat bar road bike that you have is originally designed for flat bars, chances are that it has a long top tube that will result in a very stretched position when you convert to drop bars.
The straightforward way to mitigate that issue would be to get a shorter stem. That said, installing a shorter stem on a road bike has a downside – shorter stems make steering less stable when moving at high speeds. For that reason, road bikes use fairly long stems.
- New Brakes
If the bike in question operates with long pull brakes (e.g., V-brakes), then road brake levers won’t be compatible with the brakes as they’re designed for short pull brakes (e.g., cantilever brakes, caliper brakes).
If you want to use brake-shifters, you will have to switch to short pull brakes (if the bike doesn’t have them already).
If you’re going to rely on an independent shifting system (e.g., downtube shifters), you can keep the brakes, but you have to make sure that the new levers are long pull and therefore compatible with your existing brakes.
- New Mech
The gearing/transmission of the bike can also create incompatibility issues when going from flat bars to drop bars.
Some owners of flat bar road bikes often use MTB/hybrid drivetrain parts because those are cheaper and easier to find.
However, when you switch to road parts (e.g., brake-shifters), you may encounter problems due to the different rear shift ratios of road and MTB derailleurs.
The rear shift ratio of a derailleur describes how much the derailleur moves per 1mm of gear cable pulled or released by the shifter.
When we use index shifting (modern shifters), each click of the shifter moves a pre-determined amount of cable that’s not subject to change. Since both the cable pull or release by the shifter and the rear shift ratio of the derailleur are pre-determined numbers, one cannot always mismatch road and MTB derailleurs.
For example, the rear shift ratio of 10-speed MTB derailleurs is 1.2 whereas that of 10-speed road derailleurs is 1.7.
If you’re converting a drop bar road bike equipped with a 10-speed MTB mech, you won’t be able to use 10-speed brake-shifters due to the different rear shift ratios of the derailleurs. Thus, you will also have to replace the derailleur.
Luckily, 6 to 9-speed Shimano MTB derailleurs and 6 to 10-speed road derailleurs use the same rear shift ratio (1.7). Thus, you will be able to combine a 9-speed MTB derailleur with a 10-speed road shifter as long as the derailleur can cover the entire cassette.
A Note on Friction Shifting
Rear shift ratios create compatibility issues only when the user relies on index/pre-determined shifting. If the user has old-school friction shifters, he can manipulate how much the derailleur moves via the friction shifters.
This property of friction shifters makes rear shift ratios irrelevant and allows the combination of MTB and road parts.
The downside of friction shifters is that they’re slow and old-school. Thus, they’re only available in the form of bar-end, downtube, and thumb shifters.
When Is The Conversion Most Likely To Succeed
Conversion from flat to drop bars is most likely to succeed when:
- You’re converting a road bike that has been originally assembled with drop bars and later on converted to flat bars. In that case, the geometry of the bicycle is unlikely to be a problem.
2. The bike that you’re converting has a frame that’s slightly smaller than what’s recommended. In this particular situation, this is beneficial because smaller frames have a shorter top tube and are therefore better suited for flat to drop bar conversions.
3. You can find the necessary parts for a good price.
The Advantages of Converting From Flat Bars to Drops
1. More hand positions
Drop bars are among the handlebars that offer the highest number of hand positions. Hence why drop bars are often used on touring bicycles as a way to prevent wrist and finger numbness.
2. Aero position
Drop bars offer an aero position which greatly reduces drag. Thus, drop bars are notably faster than flat bars.
Some people consider drop bars highly aesthetic.
5. Slim profile
Drop bars are about 40-44cm wide and thus much narrower than the average flat bar. This makes them better for riding through traffic.
The Disadvantages of Converting From Flat Bars to Drops
1. Expensive conversion
As already mentioned, the conversion could be very expensive, especially if it’s necessary to pay for labor too.
2. Questionable benefit
Drop bars are nice but they aren’t for everyone. If you can, try riding a drop bar bike before converting to see if you like the positions.
3. Uncomfortable geometry
The final result may cause discomfort due to the narrowness of the bars and the stretched position.
Summary: What You Need To Know
- It’s possible to convert a bike from flat bars to drop bars.
2. The conversion will require new shifters and brake levers.
3. If the brakes of the bike are long pull, new brakes will be needed too.
4. The cons of the conversion are the price and the negative changes to the geometry, namely the potentially overstretched position. This happens because the top tubes of bikes originally designed for flat bars are longer than those of drop bar bikes.
5. The pros of the conversion are the extra hand positions and the option to assume an aerodynamic stance by grabbing the drops.