At FLO we have two construction methods for our rims. The first is a Carbon Clincher rim and the second is an Aluminum + Carbon rim. You may wonder what this differences between the two rims are and why you would want one vs. the other. This article will answer those questions by discussing rims, the differences between the two construction methods, and what is best for you. Let’s get started.
The Difference Between A Wheel & Rim
A cycling rim is the outer part of the wheel that is connected to the spokes and holds the tire. Historically, rims have been made from iron, wood, steel and thermoplastic, but these days they are typically composed of two different materials, aluminum and carbon fiber.
You may also hear the term “clincher” when talking about rims. This refers to rims that use clincher tires, which is a good majority of cycling wheels. For more info on tires, take a look at the article here.
Pictures always help. The image below shows a wheel on the left and rim on the right. The rim is a component of the whole wheel.
Wheel vs. Rim
Carbon Clincher vs. Aluminum + Carbon Rims
There are three main differences between these two types of rims.
- The materials used to make them.
- How they are made.
- Where the structure comes from.
Carbon Clinchers: Carbon Clinchers are made from 100% carbon fiber.
Aluminum + Carbon: Aluminum + Carbon Wheels use both carbon fiber and aluminum.
The image below shows a section of a cut rim. A Carbon Clincher rim is on the left and an Aluminum + Carbon rim is on the right.
Carbon Clincher vs. Aluminum + Carbon Rim
How They Are Made
Carbon Clincher Rims
Carbon Clincher rims are made from Prepreg carbon fiber. PrePreg is a mixture of carbon fiber and expoxy resin laid out in sheets. The steps taken when making a Carbon Clincher rim are:
- PrePreg is cut into pieces and placed in a mold. The specific type of mold is called a bladder mold.
- To create the hollow space inside the wheel, a silicon bladder is inserted into the hollow space and inflated with air during the curing process. This also creates the required pressure.
- The rim is cured by placing it into an oven and then it goes through a ramp cycle. A ramp cycle is when you start a low temperature, ramp to a higher temperature, and then to a lower temperature, all at specific times intervals.
- Once the curing cycle is complete, the rim is removed from the mold and finished. This includes surface work and drilling spoke and valve holes.
Aluminum + Carbon Rims
Aluminum + Carbon rims are made in a multi-step process. Let’s look at these steps.
- The Aluminum rim is molded through an extrusion mold. An extrusion mold is much like a pasta maker. Under pressure and heat, aluminum is forced through a mold to create the desired shape.
- After extrusion, you have long sticks of rims. Rims are then cut and rolled into circles. This gives the correct size for the rim.
- The ends of the rim are welded together and spoke holes are drilled.
- Rims are anodized to produce a black color.
The carbon is made the same way a Carbon Clincher is made. The only difference is that the carbon used in an Aluminum + Carbon wheel is shaped like a U compared to a fully enclosed structure.
Bonding Carbon To Aluminum
Once both parts are made, the carbon fiber is bonded to the aluminum rim with an adhesive to hold the carbon fiber securely in place. Final spoke holes are drilled in the carbon and then the rim is complete. The picture below shows side profiles of cut Carbon Clincher and Aluminum + Carbon rims.
Carbon Clincher vs. Aluminum + Carbon Rim
Where The Structure Comes From
A rim has to be strong enough to support your weight. Your weight is transferred from the spokes to the rim, so this interface where the spokes and rim connect is important. In a Carbon Clincher, the carbon fiber provides the structure so it has to be designed in a way to accomplish this task. At FLO we use double walled rims. The double walled rim provides the required structure for the rim to support your weight.
Carbon Clincher Rim Detail
Aluminum + Carbon
In an Aluminum + Carbon rim, the aluminum provides the structure. The carbon fiber component is there for aerodynamic improvement only. This means the carbon fiber is non-structural.
Aluminum + Carbon Rim Detail
This also affects where the spokes are attached. In both rim types, the spokes are connected to Wall 2. The picture below shows this. In the case of the Aluminum + Carbon rim, a hole is drilled in the carbon fiber and the spoke simply passes through without touching it.
Spoke Nipple Rim Interface
What Rims Are Best For You?
There are two main reasons you would pick an Aluminum + Carbon rim.
- Cost - Aluminum + Carbon Wheels are about $100 cheaper per wheel.
- Rim Brakes & Wet, Sandy Roads - If you have a rim brake bike, live in an area like the pacific northwest where it is very wet and sand is used for snow control, then you may prematurely wear your brake tracks. When you brake, the sand from the road sticks to your rim and brake pads which causes you to essentially “sand” the surface of your rim. Aluminum handles this better than carbon fiber.
If you are not concerned with these two issues or you have a disc brake bike, then Carbon Clinchers are your best bet. Here are the pros of Carbon Clinchers.
- Weight- They are about 1lbs lighter per set.
- Aerodynamics- They are more aerodynamic. Carbon Fiber is able to be shaped more precisely.
- Ride- They produce a more compliant and comfortable ride since the carbon side wall acts as a leaf spring.
- Rain- You do not worry about water entering the fairing and rim in heavy rain.
- Braking- Braking performance now matches aluminum braking performance with specially designed brake pads.
Our sales consist of about 70% Carbon Clinchers. Unless you have a good reason for an Aluminum + Carbon wheel, we recommend our Carbon Clinchers.
1. From time to time I get a squeek from the carbon brakes (going downhill). Is this something to be concerned about?
Not at all. Small squeaks are ok.
2. Is there any braking techniques that I should be aware of when going from alum to carbon wheels?
We wouldn’t have you modify your braking because the of the carbon rim.
Neat, I have your first gen 60’s alum rims and last year got 45 carbons.
From time to time I get a squeek from the carbon brakes (going downhill). Is this something to be concerned about?
Is there any braking techniques that I should be aware of when going from alum to carbon wheels?
Also it would be nice to touch on maintenance, right now I do nothing on either wheel type but make sure that the brake pads are aligned.