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 Pen Spring Mod
With the accumulation of dirt / sand, the rear brake pads have a tendency to drag on the brake rotors. When shims (#87437) are used sand can also easily accumulate between the loose shim faces, decreasing the pad / disc clearance, resulting in the pads binding with the discs.

The installation of two small springs (the kind that are found in a variety of 'click' type pens will suffice, though preferably good quality steel springs that will retain their 'spring' are recommended), will help prevent this binding by keeping the shims tight, pushing the brake pads apart and clear of the brake disc rotors.

Note - Sometimes a pen spring may not be strong enough to push the pads back - particularly if the brakes are new and the cam sticks (and stock bushes are being used instead of bearings eg. as on some of the upgraded brake kits).

In such a case the stock spring (HPI part # 85462 / e) that is used at the rear of the linkage is an ideal spring for this use. It is stronger than most of the springs found in pens and as such will make easy work of pushing the pads away from the disks, as well as forcing the cam to the neutral position should it bind. This spring will be made redundant if the fuel tube mod is carried out.

The spring should be cut into two equal parts, each cut slightly longer than the distance between the pads at rest, so that they exert just enough pressure to comfortably push the pads apart, but are easily compressed when the brake is applied.

Further reading