July 31, 2011
FLO Cycling - Component Series Part 3 - Sapim Spokes
This is Part 3 of our FLO Cycling Component Series. In Part 1 we discussed the EZO Bearings we use in our FLO VORTEX Hubs and in Part 2 we discussed our FLO VORTEX Hubs. If you would like to read those articles you can find them in the links below.
FLO Cycling - Component Series Part 1 - EZO Bearings
FLO Cycling - Component Series Part 2 - FLO VORTEX Hubs
FLO Cycling - Component Series Part 2 - FLO VORTEX Hubs
FLO Cycling - Component Series Part 4 - FLO WIDE RIDE Rims
They say a chain is only as strong as it's weakest link. What good would our high quality hubs and rims be if we connected them with a low quality spoke? The answer to that question is obvious and the reason why we at FLO Cycling chose to not cut any corners when selecting our spokes. Here is a list of some of the things a spoke is responsible for:
- Supporting the riders weight
- Withstanding the fatigue experienced by a rotating wheel
- Transferring power from the hub to the rim
- Keeping the wheel true
The above points tell us that a spoke should be strong/resistant to fatigue, and manufactured in a way that all spokes are nearly identical. At FLO Cycling we decided to select Sapim spokes. Sapim spokes are manufactured in Belgium and are known the world over for being an industry leader.
We chose to use two types of Sapim spokes at FLO. Our FLO 60, FLO 90 and FLO CLIMBER race wheels will use Sapim CX-Ray spokes and our FLO DISC will use Sapim Laser spokes.
Let's start with Sapim's description and a picture of each spoke.
Sapim Aero spokes not only give an aerodynamic edge, they also make wheels lighter and stronger. As light as titanium spokes, CX-Ray spokes still receive the best results in fatigue testing of any spoke. No doubt why CX-Ray are used by top bike racers and triathletes around the world. Even downhillers use them, recognizing their strength and flexibility. Special alloy treatment and sophisticated production make this all possible. Aero spokes are produced from the best suited stainless steel for spokes: high-tensile, fatigue-resistant 18/8 stainless steel conforming to SAPIM quality standard specifications. The CX-Ray fits easily into all standard hubs.
|Sapim's super light double butted spoke features a 1.5mm center section for weight reduction. Wire diameter is 2.0-1.5-2.0mm (neck-body-thread). Available in odd lengths from 241mm to 303mm with black or silver finish.|
Sapim butted spokes have two major benefits: less weight and more strength. Cold forging “stretch” the spoke, retaining the linear molecular structure of the material, thereby increasing the spoke strength at the middle by at least 48%.
The CX-Ray and Laser had a few features that made them clear winners for our FLO wheels.
- Light Weight (equal to titanium spokes)
- Constructed from high tensile Stainless Steel
- Unparalleled fatigue resistance (specifically the CX-Ray)
- Reliable precision
Let's look at these features...
Below is Sapim's weight chart. You can see that the CX-Ray and the Laser are the clear weight winners amongst the Sapim line-up. We also compared these spokes to the weights of other popular spokes used by other wheel companies and Sapim was comparable or better in every case.
|Sapim Weight Chart - Weight of 64 spokes|
For our FLO 60 and FLO 90 race wheels we chose to use the CX-Ray for it's aerodynamic benefits. Sapim doesn't post any aero data on their spokes but there have been independent studies by others proving the CX-Ray's aero benefits. There is a reason the nearly all other leading wheel companies use the CX-Ray.
Our FLO DISC uses Sapim Laser Spokes simply because they will be covered by a carbon fiber fairing and not exposed to the air.
First, let's start with a description of strength and fatigue.
Strength, to put it simply, is the maximum weight/force that something can hold before it breaks. This is known as the maximum tensile strength. Fatigue causes an object to break when it is repeatedly exposed to a weight/force that is less than it's maximum tensile strength. When an object is continuously loaded and unloaded it can "fatigue" and break.
While maximum tensile strength is clearly important when choosing spokes, it is rarely the limiter. Fatigue is more important. Here is why...
Every time your bicycle wheel makes one revolution each spoke experiences a loading and unloading of your weight. On a 50 mile ride this happens roughly 39,000 times! It becomes pretty clear that we would want spokes that have a high fatigue strength. Let's first take a look at a competitors spoke. I won't name the brand simply because I do not want to put down another company. Many "affordable" wheel companies use this spoke. We chose not to. You'll soon see why.
|Competitor Spoke Data|
There is a lot of data in this picture but the thing I want you to take note of is the fatigue. This particular aero spoke (a CX-Ray look-a-like) will fatigue at 300,000 revolutions. Now we have to be careful... if our calculations were correct from above, it means this spoke would break at 384 miles right? No, you have to remember that the fatigue test only tests a single spoke at 180 kg/f (396 lbs). In the real world there are 20+ spokes in each wheel and most triathletes or cyclists weigh much less than 396 lbs. So in reality this spoke will last much longer than 384 miles.
Let's see how Sapim compares...
Yes you are reading that correctly. Sapim CX-Ray spokes last longer than 3,500,000 revolutions. This is more than 10 times the fatigue strength of the competitor. This fact alone was enough for us to choose Sapim. The Laser on the other hand is rated for 1,200,000 revolutions. While this isn't as good as the CX-Ray it is still a remarkable fatigue strength and suitable for our FLO DISC wheel since disc wheels are typically not used during training and get much less use as a result.
When building wheels it is important to achieve a uniform spoke tension on all spokes. Typically, you are aiming to get all of your spoke tensions within about 10% of each other. This ensures a wheel will stay truer longer and helps prevent any of your spokes from breaking prematurely. Sapim builds all of their products to conform with DIN (Deutsches Institut für Normung) which is equivalent to America's ISO Standards. All spokes are constructed with tight tolerances and accurate threads, which means well built wheels using Sapim spokes will be long lasting and require relatively low maintenance (ie. hold true). For the wheel, owner these are two very important characteristics.
We hope this component series on spokes has helped you better understand why we at FLO Cycling chose Sapim spokes. For more great content, please register for our free monthly newsletter at the top of the column on the right. We send links to all the articles we post during the month. As always, comments and questions are more than welcome.
All the best,
Chris and Jon