Condensed answer: It’s possible to install cruiser handlebars on a road bike. However, the conversion changes the bike’s geometry and requires some gear and brake re-arrangements.
The Stem and Bar Diameter
The first part of the conversion requires an examination of the stem and handlebars. Old-school road bikes rely on a quill stem whereas modern models use a threadless stem with a faceplate.
If you have a quill stem you will need a cruiser bar with a 25.4 or 26mm diameter in the center.
If you have a modern stem, you will need a cruiser bar with а 25.4 or 31.8mm (more common) diameter.
If the diameter of the stem is too large for the cruiser bars that you have in mind, you can use a shim. The role of the shim is to artificially increase the diameter of the bars and make them compatible with larger stems. The solution is not aesthetic and optimal but it does work especially on bikes that aren’t used for off-roading.
Conclusion 1: The stem and the bars should be of compatible sizes.
Road bikes use three main types of shifters:
Brake-shifters (e.g., STI) are found on most modern road bikes. They are indexed and allow you to shift without moving your hands away from the hoods.
Brake-shifters are designed specifically for drop bars. When installed on a cruiser bar they create uncomfortable ergonomics and are therefore unusable.
For that reason, you will have to replace the brake-shifters with a model designed for flat bars.
The straightforward solution would be to go for flat bar road shifters matching the number of speeds of your current drivetrain.
If you’re using fewer than 10 speeds, you can also install an MTB shifter for the cassette. Up to 9 speeds, road and MTB derailleurs have the same rear shift ratio.
The term rear shift ratio describes how much a derailleur moves per 1mm of cable pulled or released by the shifter. The rear shift ratio of 7-9-speed MTB and road derailleurs is 1:1.7.
Or in other words, the derailleur moves 1.7mm per 1mm of cable movement. This makes the shifters in that speed range interchangeable.
For the chainrings, you will have to use road-specific shifters as the shifting ratio of front MTB derailleurs is different.
Conclusion 2: If you have brake-shifters, you will need to replace them with flat bar shifters compatible with your current drivetrain.
- Downtube or Stem Shifters
If you have an old-school bike with downtube or stem shifters, you don’t have to do anything because the shifters are not connected to the handlebars.
You can still switch to flat bar shifters as they offer more comfort, but it’s not mandatory because the existing shifters will still be operational.
- Bar-end Shifters
If you’re converting a road bike with bar-end shifters, you will have to reinstall them on the new bars.
Unless you have a road bike with flat bars, the brake levers will have to be replaced too because brake-shifters are not in ergonomic accordance with cruiser bars.
The vast majority of road bikes still use caliper rim brakes. For that reason, you will need short pull brake levers for flat bars to complete the conversion.
Caliper brakes have a smaller mechanical advantage than other rim brakes such as V-brakes and require short pull levers.
If you combine calipers with long pull levers, you will get poor brake actuation (control over the braking power) because the brake arms will bottom out against the rim before the lever has finished its full movement. For a more detailed explanation of this principle, consider reading this article.
Cables and Housing
It’s also recommended to replace the brake and shifters’ cables along with the housing.
This doesn’t apply to the shifters if you decided to keep using your downtube or stem shifters.
Normally, cruiser handlebars operate with handgrips rather than bar tape.
Changes to the Geometry
Cruiser handlebars have a rise and put the rider in a more upright position. This results in less stress on the back since the rider does not have to lean forward.
There are two downsides, however:
Increased drag. The more upright you are, the more drag your body creates which is why road bikes have drops allowing the rider to “hide from the wind”. Since most people looking into cruiser bars are unlikely to care about speed, this isn’t a big issue.
That said, the poor aerodynamics make pedaling hard, especially on hills. Thus, it’s often wise to upgrade the transmission by adding lower gears.
Stress on the Sit Bones. The upright position will shift more weight on the back wheel and the rider’s sit bones. For that reason, it’s recommended to replace the original saddle with one designed for upright riding. Otherwise, the chances of getting “saddle sores” are high because road saddles aren’t designed for upright cycling.
Poor Leverage For Climbing. Cruiser bars don’t work nearly as well as flat bars and drop bars for out of the saddle climbing – one more reason to get a lower gearing and reduce the need to get out of the saddle.
Summary: What You Need To Know
A road bike with drop bars can be converted to cruiser bars when the following conditions are met:
- The stem and the bars should be of compatible sizes. Most quill stems require 26mm bars whereas modern threadless stems work with 31.8mm bars.
2. If you have brake-shifters (e.g., STI), you will have to replace them with flat bar shifters.
3. If you have downtube, stem or bar-end shifters, you can keep using them.
4. You will need short pull flat bar brake levers for the caliper brakes.
5. The conversion will also require new grips, cables, housing and a saddle for upright riding.
6. If you have a road bike with race-oriented gearing (e.g., 52-42 chainrings), you will benefit from adding lower gears to the transmission.
The benefits of converting to cruiser bars are:
- Relaxed riding
- Less back stress
The downsides are:
- Extra drag (slow speed)
- Poor out of the saddle climbing experience
- Extra stress on the sit bones
- Fewer hand positions