Tolle's Adjustable Triple TreesPR Inox Forktube plugs 84 up f39mm Tolle patented these famous adjustable triple trees in 1986. Their Number One advantage is that they allow you to adjust the fork angle to achieve the optimum trail. Nobody knows exactly what the correct trail is, guideline for rigid frames is between 2" and 4" (50 and 111mm), where frames with rear suspension need a trail between 3" and 6" (75 and 152mm). You can adjust these triple trees from zero to 17 degrees,