The SLP Helix/Spring Shim will help maintain peak RPM riding at extreme elevations (8000 ft. and above). This shim spaces the hub of the clutch in 0.070" which raises the spring pre-load and rate by 8 to 10 pounds. It also shortens the length of the intial (steeper) angle on a multi-angle helix (ie. 58/38.46 with a shim would become a 58/38.40). This improves backshift characteristics at high elevations in very steep conditions. It is especially beneficial when using long, aggressive tracks.
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