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Gearing

Final drive ratios are a very important factor in creating a successful hot rod or touring engine.  We feel the best overall ratio for any of our engine combinations is 3.36:1.  Taller gearing (2.91:1) will cause the bike to acclerate slower and be prone to detonation.  Lower gearing will allow the bike to accelerate quicker, but you will find it revving too high for freeway cruising.  Big Twins from 1985-92 came from the factory with 3.36:1 final drive.

The 1993 Softail can b3e changed to 3.36:1 by replacing the rear 61 tooth belt sprocket to a 70 tooth sprocket (HD-40221-85A).  A new 132 tooth belt (HD-40023-86) will also be required.

 In 1994 and later, all Big Twins final drives were affected by a change in primary gearing.  The 24 tooth engine sprocket and 37 tooth cluth sprocket were changed to 25 and 36 teeth respectively.

The results were all models with rubber mounted motor became 3.15: final drive.  The Softails were given a new 65 tooth rear belt sprocket to maintain 2.92:1 ratio.

To bring the rubber mounted motor bikes back to 3.36:, the front belt sprocket must be dropped from 32 teeth to an Andrews 30 tooth sprocket (AP-290304).  The stock drive belt can stay.

The 1994-up Softails will require a 30 tooth front belt sprocket and a 70 tooth rear belt sprocket.  The stock belt can be used.

Belt Drive Sprocket Ratios 1985-93

(37 T clutch - 24 T Engine Sprocket)

Belt Drive Sprocket Ratios 1994-Up

(36T clutch - 25 T Engine Sprocket)

*Information obtained from Head Quarters Performance Products & Service