The Colnago-badged headset from Acros was the stock headset shipped with C59 framesets prior to the C60 release. Some riders prefer the Acros "clamp" design and use it on other compatible frames as well. With high quality steel cartridge bearings and finely machined components, the Acros matches the pedigree of the C59 frameset. This headset was designed for 1⅛ fork/frame upper and 1¼ lower interfaces. The Acros headset design is very different from other models you may be familiar with, as it does not use a compression plug within the steerer. There can be some confusion as to how to both adjust and keep the Across clamp design working properly. In essence the unit quite simple, but requires the installer to set aside traditional expectations. Given the lack of information online, we have decided to include some basic instruction and tips for installing and using the Acros clamp system.

The upper and lower bearing races have the bearings pre-pressed. The crown race is a split style unit and is easily installed or removed without tools from the fork crown. Once the crown race is installed, drop the lowering bearing down on the race. Slide the fork into the frame. Place the upper bearing in place and hand-press down, then install the upper split ring down onto the steerer tube- it will sink flush into the bearing.

The next fitting is a two-piece clamp design. There is a hex set screw in the lower half. Back the screw out until it is flush with the threaded wall. Identify the grooves and place the top half onto the lower half. It will sit almost completely flush. Add spacers or just your stem depending on your bike fit. Here is where as an installer you have to think differently. If the steerer tube needs to be cut, you will need to establish fit now. Use spacers and use stem bolts to hold assembly together. Cut steerer as needed. When at proper length, or close, you can proceed. With your stem and spacers in place, tap down with a rubber mallet on to take out any gaps or play. Center your stem on your wheel, keeping downward pressure. Torque stem/steerer clamp bolts. There is generally slight play in your bearing system at this point. Using your hex key tighten the bolt in the lower half of the Acros clamp. This will turn the wedge on the grooved inner surfaces to take out slack, creating a safe pre-load. Check your assembly as normal- hold front brake with off hand on head tube at upper and lower races for movement as you attempt to push the bike forward and backward. If you still have some play, tighten the hex bolt more.

The trick is truly removing as much play as possible before fastening your stem/steerer bolts. If you can't get the Acros clamp tight, back the bolt off again, loosen stem bolts, tap the system back down again, tighten the stem bolts and start over. Instead of a top cap that get secured within the fork, your stem becomes the clamp point, and the two piece wedge system is your adjustment. Please keep in mind that if you loosen your stem to adjust or change, you will need to go through the full Acros adjustment process. The long cylindrical top cap just slides into the top of the steerer. You can keep your steerer long and use spacers above the stem if necessary. As long as the top cap can sink onto the flush cut of the steerer tube, it will work properly.

The Acros clamp design may seem more challenging than you'd prefer, but properly installed it works extremely well, and there is zero chance of damaging or creating a weak point inside a carbon steerer tube. The cup and bearing design features a 90° bearing specific to the Colnago C59 head tube design. While it may work with other frames, most of today's headsets of this style use a 45° bearing, so don't make the assumption you can mix or match products without carefully investigating first. As with any headset system, it is important to check for play after first use and adjust as necessary.