# Am häufigsten gestellten

## Am häufigsten gestellten

### 01. Why use 24 spokes for the rear wheel?

The front wheel only has lateral (direction of axle) and radial/frontal (perpendicular to the axle) forces to handle. The rear wheel however also has to deal with the rider's power transfer [1]. This creates higher forces in the trailing spokes, because only the trailing spokes can transfer the power of the rider to the rim. The leading spokes will slacken when there is a momentum [2].

Let's say a rider is on a hill and pushes the pedal with a force equal to 150kg [3]. When the gearing is on its lowest (for instance 39x27), the momentum in the hub is the highest. The initial load in our spokes is 110/120kgF in the rear and 90/100kgF in the front. The extra load (due to the drive momentum) that the rider puts on these spokes will be: 150*(175/78)*(55/23) = 800kgF [4]. This force has to be spread out over all trailing spokes. Less spokes means there will be higher peak forces in the rear wheel.

24 spokes -> 120+(800/12) = 187kg peak
20 spokes -> 120+(800/10) = 200kg peak

That could be a reason why other manufacturers sometimes use a lower initial load on their spokes when using 18h or 20h. To keep the peak forces under control. This lower initial load, however, will decrease the lateral stiffness of the wheel (in other words: less force is needed to displace the rim sideways -> not a good thing).

So, therefore FFWD decided to put in an extra 20g, but in exchange we can build wheels with a higher durability, stiffness and more responsiveness. For those who feel that they need more rigidity than our standard 20/24h lacing (cyclocross for instance), we propose the ControlTM version with 24/28h lacing. ControlTM is available on most models.

### 02. Why use 3K carbon for the rims?

We actually use multiple layers of different types of carbon. Only the outer layer is made from a 3K weave. Underneath this layer are layers of UDF (Uni-Directional Fiber) sheets. A mixture of different angles to resemble a uniform material. Because carbon fiber can handle tension very well, we have to mix up the layers to make the rim stiff and strong enough. Pressure is not a great feature of a fiber. Just think of a string being pushed [1]).  But when mixed correctly, the different angles interconnect through the resin to make it resistant to all kinds of forces [2].

The 3K has a slightly lower stiffness/weight ratio than UDF (Uni-Directional Fiber) sheets of equal fibers, but it makes up by giving the rims a bombproof feature. Why? Because when a strand (or multiple) gets cut in UDF, by crashing for instance, the sheet is compromised and the tear will expand through a larger part of the sheet at continuous workload. A weave will stop the tear because it is intervened by the crossing layer of strands [3].

Although it is not advised to ride with a 'hole' in your rims, situations can occur where you might not know of a damaged rim or it is not an option to stop right away. Then you have the extra safety of the 3K weave to get you home.

### 03. The FFWD wheels aren't the lightest on the market. Why is that?

Durability is one of the goals set by FFWD from the get-go. Therefore we demand more of our rims than we would if we had lower spoke tensions in our wheels or if we had weight limits* for our wheels.

For instance, our rims have reinforced strips [1] where the spoke holes are placed, to ensure that high tensions are not an issue. In a regular rim [2], you can't control the specific stresses by layup only. The spoke force is concentrated around the nipple hole. With a pre-defined reinforcement strip [3], we can put the right fibers at the right place. The spoke force is spread out through the reinforced strip and distributes the stresses over a larger part of the rim. The rims are now capable of withstanding a spoke force of 300kgf. This force is around the same as the ultimate strength of the spoke itself. And we only use the best and the lightest spokes available on the market today, so you can imagine how durable the wheels are when the rims are laced up by professional wheel builders.

The fact that we use a clear coat [4] on our rims (except for the Discs) is also done with the focus on durability. It adds a little bit of weight (think of 20g for a F5 rim), but we are pretty proud of our decals and we therefore want to keep them on the rim as long as possible. If the decals weren't protected by the clear coat, they would very likely get damaged by cleaning, weather, etc. Plus it gives you that smooth overall look. Carbon shine all the way!

Furthermore, we feel that the weight factor is much less important than the aerodynamics factor. See up ahead in the FAQs section.

Another factor, although small, is the use of 3K carbon as the outer shell. This material has a slightly lower stiffness/weight ratio than UDF sheets of equal fibers, but it makes up by giving the rims a bombproof feature.

* The F2R does have a weight limit, see FAQ for further information.

### 04. Perchè esiste un limite di peso sulle ruote F2R?

Il limite di peso è necessario per garantire la sicurezza del ciclista nei percorsi collinosi . Abbiamo eseguito dei tests con più di 90 corridori , ma abbiamo deciso di creare un più ampio spazio verso i limiti di sicurezza per questo specifico tipo di ruote . La costruzione della ruota/cerchio noè assolutamente un problema. La rigidità e la forza sono li con in migliori se si considera il set di ruote per la salita. Il problema è la discesa nella quale si potrebbe generare un problema la dove corridori più pesanti possono creare più calore durante la frenata. Il cerchio è troppo leggero (basso volume) per mantenere il calore entro limiti ragionevoli . L’eccesso di calore influenza in modo negativo la qualità della frenata e potrebbe , quindi , scendere sotto lo standard che noi abbiamo fissato come minimo valore

### 05. What is FFWD's view on weight vs. aerodynamics?

FFWD's focus is on fast, durable wheels. We don't consider weight to be of equal importance although we of course try to make the wheels as light as possible within the standards we have set.

Let's take a look at the forces that effect a system like a bicycle plus rider. If the conditions are; flat road, no wind, sea level and frictionless bearings, then the forces are rolling resistance, air resistance (frontal area) and wheels drag [1].

Some conclusions can be drawn from this graph:

* 1. The rolling resistance is constant. It depends on weight, tire and type of surface.
* 2. Both air resistance and wheel drag increase non-linear.

If you look at the formula [2] that calculates Drag Force, you can see that the speed v is squared. This means that when the speed of the system doubles, the Fd quadruples:
(1*v)^2 = v^2
vs.
(2*v)^2 = 4*v^2

And since Power (Pd) is Force x Velocity (Fd*v), the Power required to overcome the aerodynamic drag increases as the cube (^3) of the velocity. So, if you double the speed, you need eight times the Power, because you do four times the Work in half the Time.
Okay, now you should 'feel' the importance of lowering air resistance as much as possible if you want to go fast...forward.

But what about weight vs. aero?

Well, when you decrease weight (-10%), the rolling resistance decreases as well. But the lighter wheels usually also create more drag (let's say, +10% Cd, but this could easily be more), so that when you add the extra drag to the F4 and put the results in a graph [3] you can see that there is a certain point (break-even) where the weight becomes a less important factor than drag for higher speeds. In this example it is around 4.5 m/s (16.2 km/h).

When the drag is more than the assumed +10%, then obviously the break-even point will be at a lower speed -> the advantage of the lower weight will turn into a disadvantage even sooner.

Remember that in the beginning of the text I assumed some conditions to be constant or absent. For instance, no wind means that the air resistance acts directly from the front. It becomes a different story when there is a wind coming from a certain angle. This will influence the speed-power comparison very much and the aero characteristics of the wheels play an even bigger role in this case.

Same goes for the 'flat road' condition. If you are on a climb, the gravity plays a big part in the equation. As with the air resistance vs. weight, you also reach a break-even point (certain angle of the road) when the advantage of the lesser air resistance is gone because the climb becomes too steep (gravity pulls too hard on the weight of the wheels).

### 06. Can I use the supplied FFWD carbon specific brake pads for my alloy rims as well?

No, you can't!
There are two very important reasons for this.

1) The brake pads we supply with our wheels are for carbon rims only, because of the special compound of which the pads are made. This compound mix is not suitable for optimum brake performance on alloy surfaces.

2) It is also very important to keep the brake pads that are used for alloy rims separate from the ones you use on carbon rims. It is very possible that alloy splinters can accumulate on the pad when braking.  And when you would use these pads on carbon rims, the splinters will scratch the carbon and possibly damage the fibers. This is an important safety issue which must be avoided. So, please think of your pads when you have different wheel sets.

### 07. What does 'hand built' mean in practice?

It means quality, durability and longevity!

FFWD laced wheels are built in such a manner, that they stay true throughout their lifetime when used in normal conditions.

* Laced up by hand
* Stress relieving and spoke bending for correct alignment from hub to rim
* Trued by hand
* Spoke tension is measured in every spoke to ensure equal tension

We have master wheel builders who have years of experience in lacing and truing wheels. These people are passionate about cycling, but crazy about wheels. You could say that it's their oxygen. So, you can imagine that they would do anything to prevent a wheel being released to the market of which they are not proud.

### 08. How do I mount the valve extensions?

Please see the pictures for mounting instructions.

### 09. How do I select the right wheel set for me?

If the information on this website is not sufficient to make a confident choice, it is always possible to contact FFWD by mail or phone.

Factors you have to consider are:
* Type of terrain.
* Intended use (racing and/or training, hills and/or flat courses).
* Weather conditions (wind, sea side)
* Rider factors (weight, power, riding style)

### 10. How do I mount the tire on my tubular wheels?

You can find a comprehensive  instruction on the Vittoria site or on the Schwalbe site.

FFWD Wheels does not recommend the use of adhesive rim tape for mounting tubular tires. Tubular tires are best fitted to the rim when glued with specific glue for carbon rims.

NEVER sand a carbon rim!! This instruction only applies to alloy rims.
NEVER use a metal tool to mount the tire!!

### 11. When choose a Control version?

The Control wheels come with four additional spokes in the front and rear wheel compared to the standard wheels.
Our recommendation to choose a Control version is when the rider weight is around 90 to 95kg or more.
The extra power that heavier riders are able to put onto the wheels is split over the additional spokes resulting in a stiff and rigid wheel set.

The Control wheels can be recognized by the 'C' in the model name where the standard wheels are indicated with an 'R' like F6R and F6C for example.
The standard wheels are build with 20 spokes in the front and 24 spokes in the rear. Control wheel sets are build with 24 spokes in the front and 28 spokes in the rear.

Our Control models are:

* F4C (tubular)
* F4C-c (clincher)
* F6C (tubular)
* F6C-c (clincher)

### Can I get FFWD wheels in different color options?

FFWD offers only wheels with the red/white decals which are under the clear coat for durability. The F4R, F6R and F9R models are also offered with white decals which enables you to combine wheels with any frame color. The white decal option is not available for the Control versions.

There are also special editions of the F6R in matt black or Celeste.

Color options you might have seen have been produced especially for a bike brand or have been a limited special.

We are also aware of some sticker companies that produce decals in different color options. These decals are however applied on top of the clear coat.