Brake Arms

What's the Difference

by Alan Buehner

This article is to show the what the different brake cams and arms look like that were used on the Penton and KTM bikes - from 1968 thru 1980.

Front Wheel Brake Arms

**Photo 1** showing the front brake arms used on the Penton motorcycles from 1968 thru 1978. They all used the same brake cam with a tapered spline. The end is threaded to use a 6mm nylock nut to secure the arm.

**Photo 2** showing the front brake arm used on the KTM motorcycles from 1978 thru 1980. They all used the same brake cam with a straight spline. A 6mm pinch bolt screws into the arm to secure it to the end of the cam.

Rear Wheel Brake Arms

There were 2 different type of cams and 2 different groups of brake arms used on the Penton and KTM bikes from 1968-1980.

The first group, as shown in photo 3, utilized brake cams with a tapered spline and a threaded end. Parts “A thru C” were used on the 1968-71 Steel Tank Pentons. The 1968 bikes came with the short arm (item “B”) and these were switched over in 1969 to arms with an extension (item “C”) for an external spring. Item “C” shows a front and side view of what they look like.

The cam “D” was used on the 1972 thru 1975 100/ 125s, the 1972-73 175s that use the straight hubs with the cush drives and the 1973 250's with the conicle hub. The arm (item “E”) was used on the 1972 thru 1975 100's and 125s and the 1972-73 175s. A front and side view of this part is shown. It has the extension for the external spring and is bent to keep the brake rod from rubbing on the backing plate.

The arm (item “F”) was used on the 1973 250s. A front and side view of this part is shown. The arm was shortened, eliminating the use of the external spring, and the arm is straight.

**Photo 3** showing rear brake arms that were fitted onto taper splined cams (as shown). These were used on the Penton motorcycles from 1968 thru 1974.

**Photo 4** showing rear brake arms that were fitted onto the straight splined cams (as shown). These were used on the Penton and KTM motorcycles from 1976 thru 1980.

The items show in photo 4 show the different brake cams and arms used on the bikes with backing plates for the 1976+ conicle rear hubs. The cams had straight splines that required new style arms with pinch bolts. Now this is where the confusion comes in. Items H to J have the same casting with the same part number (52-10-033-400) but are different as shown. Item H & I are bent and item J is straight. The casting has a closed loop for the brake rod saddle and the top part of this loop was machined off on some of these (as shown on H & J) to allow quick removal of the brake rod.

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