Condensed Answer: It’s possible to install road cranks on a track bike. The conversion will not allow you to use track chainrings (unless the cranks are old) and may require a new bottom bracket.
It may also be necessary to perform a few modifications to acquire a decent chain line.
The Differences Between Road and MTB Cranks
- Different BCD
Road and track cranks have different BCD values.
BCD stands for Bolt Circle Diameter (BCD) and represents the diameter of the circle that goes through the center of the bolts supporting the chainring.
The BCD of a crankset determines the type of chainrings that it can accept.
The BCD of modern road cranks is 130mm. Track cranks are designed for 144mm BCD.
As a result, it’s not possible to install a track chainring on a modern road crankset.
If you want to use a modern road crank on a track bike, it will be necessary to stick with a road chainring due to the dissimilar BCDs.
However, it’s also worth mentioning that many vintage road cranks from the 70s, 80s, and even 90s are designed for 144mm BCD and thus meet the criteria. The most common example would be Campagnolo’s models from those eras.
FAQ: Why did road bikes start using smaller BCDs?
One of the reasons would be to fit smaller chainrings. A crank designed for 144mm BCD cannot operate with a chainring under 42 teeth. Meanwhile, modern road bikes use an inner ring that’s often under 40 teeth. Hence the need for a smaller BCD value.
FAQ: Is it detrimental if I can’t install a track chainring on my road cranks?
Not really. The main point of knowing that road and track cranks use different BCDs is to get the appropriate chainring size and avoid unneeded purchases.
A 12-speed road chain has a 5.3mm outer width and a 2.18mm inner width.
Meanwhile, a standard single-speed chain has a 1/8″ (3.3mm) inner width and about 9mm outer width.
Single-speed chainrings are therefore thicker to fill up the extra space. The additional thickness makes the chainrings more durable. That said, road chainrings are still durable enough.
- Crank Arm Length
Crank arm lengths vary a lot, but in general track bikes often use 165mm cranks whereas road cranks are 170-175mm.
The purpose of shorter track cranks is to make it easier to reach and maintain a higher cadence. (Cadence = Rotations of the Cranks Per Minute). Since track bikes have one single gear that is fairly high, the shorter cranks facilitate spinning in that gear.
In different, road bikes have rear cassettes. The rider can simply shift to a lower gear if a high cadence cannot be maintained in the current one. For that reason, crank length doesn’t have a notable impact on the RPM when it comes to road bikes.
Ultimately, the length difference is not super important and doesn’t create an incompatibility. It’s possible to find shorter road cranks and longer track cranks. It often comes down to personal preference.
Expensive track cranks and chainrings are known to be perfectly round. Their roundness makes pedaling more efficient and eliminates the spots where a non-round ring would alter the chain tension.
Constant chain tension is more important for single-speed bikes, and especially track/fixie models because there isn’t a derailleur that can make up for the alterations. The result is smooth pedaling.
That said, recreational cyclists are unlikely to notice the difference.
Chain Line Issues
Road cranks make it more difficult to get a straight chain line. It’s often necessary to install the chainring in the second position to get a straighter chain line. Some will consider this setup non-aesthetically pleasing. One way to “camouflage” it is to install a chain guard at the big ring position.
The other two methods to adjust the chain line are:
- Install a longer or shorter bottom bracket spindle to put the cranks closer or further away from the frame.
- Play with the position of the rear cog and the spacers around it if you’re using a standard road cassette hub.
The Advantages of Using Road Cranks On a Track Bike
- Money savings
The main incentive to use road cranks instead of purchasing a dedicated track crankset is to save money.
Road cranks are a lot more common than track models thanks to the popularity of road cycling. As a result, you will have more options.
- Properties Transfer
If you have road cranks with a power meter, for example, you will be able to take advantage of that function on your track or fixie.
If you go for a vintage 144mm BCD crankset, you will give a retro appearance to your bicycle.
- Multiple Bottom Brackets
The vast majority of track cranks rely on square taper bottom brackets. Meanwhile, road cranks come in greater variety and thus allow you to use whatever bottom bracket you want or already have.
The Disadvantages of Installing Road Cranks On a Track Bike
- Inability to use 144mm BCD chainrings unless the crankset is old.
- Chain line issues require you to use the second (lower) position of the cranks resulting in a less-than-ideal appearance.
- Faster chainring wear (road chainrings are thinner)
- Non-round cranks and chainring (non-perceivable by amateur riders)