This post compares the advantages and disadvantages of cottered and cotterless cranks.
Definitions
Cottered Cranks
Cottered cranks are attached to the bottom bracket spindle via a wedge inserted into the crank arm. This style of cranks is common for older bicycles produced in the 70s or prior.
Cottered cranks can be easily identified by looking at the attachment points. If there’s a small wedge perpendicular to the crank arm, the cranks are cottered.
Cotterless Cranks
The term cotterless cranks refers to all crank models that do not attach to the bottom bracket spindle via a wedge.
The attachment mechanism of cotterless cranks depends on the bottom bracket. For example, square taper bottom brackets connect to the cranks via a set of bolts threaded into the bottom bracket axle.
The Advantages Of Cottered Cranks
- Retro Aesthetics
Cottered cranks have no technical advantages over cotterless cranks. Their main value is found in the retro aesthetics that they offer.
Some cottered cranks have a shape/style absent among modern cotterless cranks.
Thus, if the user is looking to achieve a certain retro look, cottered cranks can potentially help with that task.
The Disadvantages of Cottered Cranks
Cottered cranks have a great number of disadvantages. This is the main reason why they have been out of production for decades.
The cons of cottered cranks are:
- Heavy Crank Arms
Cottered cranks have steel arms because aluminum is a soft material that will be deformed by the wedges (cotters).
Consequently, cottered cranks have heavier arms than their aluminum cotterless rivals.
- Limited Supply
Cottered cranks are available only on the second-hand market. In many cases, they’re overpriced for what they are due to the shortage of available models.
To find a good set, you will have to browse a website for used parts, a forum, or a Facebook group.
- Limited Number of Service Tools
Since cottered cranks are a rarity, the companies making bike repair instruments have lost the incentive to produce cotter cranks related tools. Consequently, many people improvise when working on cottered cranks.
Ideally, you will have a cotter puller/press. Some people machine them and sell them online. Since the item is highly specialized, the price is often high for mechanics who want to use the unit a single time and be done with cottered cranks.
Alternatively, you can make your own cotter press out of a top beam clamp as shown in the video below:
Note: Without a cotter press, working on cottered cranks can be a nightmare. Thus, if you often find yourself servicing vintage bikes with cottered cranks, you will benefit greatly from one.
But if you want to remove a single set, the investment is of dubious value. In that case, you can use a more savage method such as hammering out the pin as shown in the next video:
An even more brutal strategy would be to secure the cranks and cut them out with a rotary tool of some sort.
The downside of this approach is that the cranks will be destroyed, and you won’t be able to sell them on the second-hand market. Thus, it’s recommended to avoid this method.
- Cheap Quality
As cotterless cranks gained momentum, bike manufacturers lowered the quality of cottered cranks due to the low demand.
Consequently, many of the cottered models available online are average at best. For example, most cottered cranks come with riveted chainrings which cannot be removed without replacing the cranks too.
- Limited Bottom Bracket Choice
Cottered cranks cannot operate with modern bottom brackets. To use cottered cranks, you will need a bottom bracket spindle designed specifically for cottered cranks. Cottered spindles have beds cut out for the cotters holding the cranks.
- Limited Crank Length
Since cottered cranks aren’t popular, they do not come in a variety of lengths. Most cottered cranks are 170mm. This will prevent you from using shorter cranks if you so desire.
- Limited Chainring Choice
Cottered cranks will limit the chainrings that you can use for two reasons:
- Many cottered cranks come with riveted (non-removable) chainrings.
- Some cottered cranks have three rather than five attachment points for their chainrings. Thus, you won’t be able to use modern chainrings with those models even when the chainrings aren’t riveted.
The Advantages Of Cotterless Cranks
- Up to date
By upgrading to cotterless cranks, you will gain access to a large variety of modern cranks, chainrings, and bottom brackets. If you want your bike to be up-to-date and use the latest components, cotterless cranks are the way to go.
- Friendlier Installation and Removal
Modern cranks are fairly easy to install and remove as long as you have the right tools. For example, if you have square tapered cranks, you will need a crank extractor. That said, some of the latest models attach to the bottom brocket solely via Allen bolts. Thus, you can remove them by using even the simplest multi-tool.
- Lighter
Modern cotterless cranks could be noticeably lighter than old-school cottered cranks.
- Cranks of Different Lengths
Cotterless cranks are available in a variety of lengths. If you want to experiment with shorter or longer cranks, cotterless cranks will allow you to do that.
- Stronger
Cottered cranks pre-date MTBs and BMXs and were designed primarily for road bikes and commuters.
Subsequently, a set of cottered cranks won’t offer top-level strength simply because it wasn’t needed at the time.
The Disadvantages of Cotterless Cranks
Cotterless cranks have no technical disadvantages when compared to cottered cranks.
One can argue that cotterless cranks aren’t nearly as aesthetic when installed on retro models. That may be true if one is referring to modern cotterless cranks. However, there are many cotterless cranks from the 70s and 80s that look just fine on a retro bicycle that’s even older.
FAQ: How can I convert from cottered to cotterless cranks?
It’s possible to convert from cottered to cotterless cranks. The procedure is as follows:
Step 1: Remove the cranks from the bottom bracket spindle via one of the methods described above.
Step 2: Remove the bottom bracket.
Since cottered bottom brackets are fairly old, you will need a specialized tool for the lockring and the cups.
Step 3: Measure the bottom bracket shell to determine how wide the new bottom bracket body should be.
Measure the length of the old cottered spindle and make sure that the new bottom bracket has the same total width.
Those steps are necessary to ensure that the new chainline is as close as possible to the old one.
Usually, bottom brackets have a size indicator consisting of two numbers e.g., 68×113.
The first number (68 in this case) indicates the width of the bottom bracket body whereas the second (113) shows the length of the spindle (total bottom bracket width).
Step 4: Install the new bottom bracket and cranks.
