The silver “knee” highlighted here is one of the first insert levers ever tested. When you live on a motorcycle as much as the top pro’s do, the smallest aggravation is huge. The front brake must be a sensitive area due to all the special parts we have made to accommodate. The insert lever refines the feel of the brake or clutch without needing a full machine shop to make a change.
The distance from the lever pivot center to point of contact with the master cylinder piston is the ratio. Most stock brake levers have a ratio around 15mm’s. The ratio drastically effects how the brake feels and functions. Above left is the early method of changing the ratio with a ball bearing at the point of contact. This style vastly improved feel by just adding the bearing. Instead of metal to metal skidding, this lever rolled across the face of the piston. Different ratios are achieved by adding a .5mm different location of the bearing. The right image shows some pushrod style brake levers with the dimple machined in different locations. Shown are 13.5mm, 15mm and 16mm ratios for a CR master cylinder.
On the left is a tray of blank Magura hydraulic clutch knees. On the right is the shelf with all of the blank knees waiting a special ratio. You can see we have quite the collection just waiting for the phone to ring. It was very frustrating!!! We would get a call from a riders mechanic requesting a different ratio than the rider was using that day. I would go in the shop and tear down a setup to make a handful of different ratio knees. They would be sent red label to get there the next day. By the time they got the lever on the bike a day or three later, the conditions were not the same. The ratio lever allows ratio changes on the spot in a couple of minutes.
This is the solution to making ratio changes on the quick. We added a box to house the replaceable inserts. Each insert has a different ratio and by rotating 180 degrees you have another ratio.
The inserts are marked with the corresponding ratio. On the backside you can see the different location of the dimples that create the ratio.
Shown is a 14-19 insert in two orientations. The engraved number closer to the lever pivot is the functioning ratio. This adds another element of setup to the bike. If the conditions are dry and slick you can back off the brake ratio to prevent locking the wheel. If the dirt is like chocolate cake then increase the ratio so you can take advantage of the extra power.
Each time an insert is changed the freeplay must be adjusted. As the angle of the pushrod is altered with a ratio change, the distance also changes and needs to be adjusted. Depending on whether a “harder” or “softer” ratio is selected you may have too much play or too much pre-load. It is very simple and takes less than 30 seconds. Back off the locknut of the adjuster screw. Loosen the set screw until some freeplay is felt. Place a piece of paper at the stop contact point. Turn the adjuster in until drag is felt on the paper and tighten the locknut. Be careful the first few times you activate the brake because it will function differently than the previous setup.
The insert levers refine control function. For over 15 years we have been making special ratios for the top riders and now you can have the same adjustment options as the factory guys. The brake levers can go from feeling like there is air in the system with a 14mm insert to “something is wrong, the lever is hardly moving” with a 19mm insert. The clutch levers compensate for Rekluse style clutches. The slipping type clutches seem to need a pinch more “pull” at the lever to get full disengagement. Hydraulic clutches benefit greatly from the ability to overdrive the master cylinder and get that “pinch” more pull needed.