Vorsprung Suspension from Canada come with bold claims for a small part: Get more out of your fork - more compliance, more support, more grip and more control! The Luftkappe, or air cap, is a simple fork modification available for Fox and Rockshox forks. Costing around 100 €, can this small part really improve your 1000 € fork? I got mine from the best suspension part dealer in Finland, Jukka at 4130.fi
Basic function
What the Luftkappe does is it increases the volume of your fork's negative chamber. The negative spring force is what helps the fork ease into its travel while the positive spring force is what extends the fork. The balance between these is a function of volume and pressure. Most modern forks equalize the chamber pressures though a dimple in the chamber wall, for example, so chamber volume becomes the adjustable factor. Other manufactures, like MRP or EXT do this differently by adjusting the pressure difference between the chambers, so this only applies to "Single air" Fox and Rockshox forks.
As you increase the volume of the negative air chamber, the fork becomes easier to move early in the travel as the spring rate decreases. This is similar to what Fox are trying to achieve with their EVOL air chamber, or Rockshox with their Debonair springs. At the same time, the spring rate increases as the fork moves deeper into the travel to offer more mid-stroke support and ramp-up, so the fork essentially becomes more progressive earlier.
 |
| Spring rate comparison: Original vs. Luftkappe. Graph courtesy of Vorsprung. |
Installation
Installing the Luftkappe can be done by a competent home mechanic while servicing the air spring. At the minimum, it's recommended to also borrow or purchase the roll pin removal tool with the Luftkappe as it makes removing the existing air piston head much easier. It can be done without the tool by using a drift and a hammer, but you need to be very careful. A set of shaft clamps is also recommended, but most people working on their own suspension will likely have these.
Vorsprung have an excellent DIY video on YouTube on how to install the Luftkappe, and I recommend checking it out as it shows the entire process, but the basics is you remove the existing piston head and replace it with the Luftkappe. The piston head is held in place by a roll pin, which needs to be pressed or punched out to remove the OE piston head, and then pressed back in when you are mounting the Luftkappe piston head mount. Removing it is a delicate operation as you need to be careful not to scratch the air spring shaft, but installation is rather simple. It helps to get the roll pin started if you compress it with a pair of plies first, insert it into the mounting hole and then press it in in a vice.
 |
| Removing the white nylon OE piston head with the Vorsprung roll pin tool |
 |
| Pressing in the new roll pin and piston head mount for the Luftkappe. |
 |
| The roll pin correctly installed and protruding from both sides of the piston head mount. |
 |
| Luftkappe installed on a Fox 2020 EVOL air spring |
The Luftkappe comes complete with a new piston seal so once you have it installed and the roll pin pressed in, all that is left is to screw in the cap and secure it to the mount with a dab of blue Loctite. The seal should be lubricated with a liberal amount of appropriate suspension grease, such as Slick Honey, but not quite as liberal as Fox does it from the Factory to prevent blocking the equalization dimple in the fork leg.
Vorsprung have several different versions of the Luftkappe to fit various Fox and Rockshox forks. Make sure you get the right version and once installed, check for any interference with possible installed volume spacers. I fitted mine to 2020 Fox 36 EVOL with 0 spacers and had no issues at all.
Performance
Can such a small part make a difference? In short, yes, it can! Increasing the negative volume will clearly make any but the newest 2022+ Fox forks much more supple and progressive. Enough so that you will likely need to decrease air pressure and readjust your damper completely to account for the totally different fork behavior.
I have no experience with installing the Luftkappe on newer RockShox forks, but on older DebonAir models the difference is immediately noticeable just like with Fox EVOL forks. I have fitted several Luftkappes on Fox forks and frankly if you have one of the new 2022+ Fox forks, the difference is minimal to non-existent. Earlier forks with smaller negative chambers can enjoy the benefits but the difference with the new ones is simply not worth the price and hassle.
2 things are immediately noticeable as you ride a fork with a Luftkappe installed: Small bump compliance is greatly improved and the fork feels like it can just float through chatter! At the same time, the fork will become significantly more progressive so if you run the same air pressure as before, it will run taller but also most likely not use up all travel. I had to decrease the pressure in my Fox 36 by about 8-10 PSI to get full travel, even on big hits.
Conclusion
In short: The Luftkappe is well worth the price, relatively easy to install and a fit-and-forget upgrade. Regardless of what type of riding you do, the Luftkappe can only offer benefits. The only situation I can think of where it may not work if you are a very light rider and already have trouble using full travel at minimum air pressure. For normal and especially for aggressive riders the benefits are clear. Recommended!
Comments
Post a Comment