Overdrive vs. Direct Drive

Generally, the DD6 is designed for touring riders who put on miles, and the OD6 is for the speed freaks and custom bikes. Study the information below and/or consult our tech department to make the decision which 6-speed is right for your application. 

The OD6 offers more gear ratio choices than the DD6. These ratio choices are tailored towards the more aggressive rider with more aggressive engines. As engine output increases, the utility of the stock 1st gear ratio diminishes. In other words, a stock 1st gear will only get you partially across the intersection from a dead stop, before you have to shift into 2nd gear. Precisely the reason why we developed R-ratio 1st and 2nd gears for OD6. Also, bigger engines can pull a steeper 6th gear ratio and this is why we developed deep overdrive for OD6. The 6th gear ratio in the DD6 is fixed at 1:1, by design, and can’t be changed. 

DD6 4-5 Dog Clutch Shown with Dog Tooth Angle

The undercutting on the side of the dog teeth (highlighted with red line on image below) is an important distinction between DD6 and OD6. OD6 undercut angle is 4° and the DD6 angle is 1°. The function of the undercut is to hold the transmission in gear, along with the shift system detent. 4° undercut angles, as compared to 1° angles, have slightly increased shift effort and slightly compromised shift quality but is necessary with aggressive engine tuning. For reference, some pro-stock V- twin applications run undercut angles as high as 10°. In contrast, Japanese motorcycles usually have undercut angles close to 0° but they can get away with that because their engines lack the violent power pulses of a 45° V-twin.