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Gates Carbon Drive Timing Belt System




Gates Carbon Drive Timing Belt System FAQ

What are the benefits of a Gates Carbon Drive?

Will the Gates Carbon Drive fit my tandem?

Cranks must be 130 bolt center distance cranks. 
     Measure directly from one chainring bolt to the next. If very near 3" then the Gates sprockets will mount to your cranks. 
        If the measurement is near 2.5" you will need to update your crankset.

Frame must have the right boom tube length. Take these 2 dimensions.
        1)  Measure from bottom bracket center to bottom bracket center in millimeters 
                with the eccentric in the loosest possible chain position.
        2)  Measure from bottom bracket center to bottom bracket center in millimeters
                with the eccentric in the tightest possible chain position.
        3) Does 739mm, 726mm, or 706mm fall between the 2 dimensions just taken from your tandem? If so, choose the correct system below.

   739mm 66T CDX system = Tension Point is 739mm. Install point is 729-732mm. These frames measure close to 736mm or 29". 
                    Typically these would be Precision Triplets and some Cannondales.

   726mm 69T CDX system = Tension Point is 726mm. Install point is 719-722mm. These frames measure close to 724mm or 28.5". 
                    Typically these would be Co-Motions, Calfees, and Paketas.

   706mm 74T CDX system = Tension Point is 706mm. Install point is 699-702mm. These frames measure close to 704mm or 27.7". 
                    Typically these would be Santanas since about 1999, some Burleys, and maybe older pre 2000 Co-Motions.

There is only one size belt and only 3 choices in sprocket sizes.

The tension point must be reached without the eccentric being rotated all the way forward. Older 9sp era Calfees are border line. Some will work with the eccentric rotated all the way forward. Others are a bit too short.

See our current sale on Gates belt drives on our [ HOMEPAGE ]


[ ORDER ] the correct belt drive system from Precision Tandems. The Gates sprockets require 2 sets of the longer FSA alloy chainring bolts and spacers ($52.50 total) for proper chainring bolt engagement.


How do I install a Gates Carbon Drive on my tandem?

The below assumes you have equal length captain and stoker bottom brackets and symmetrical alignment.

Nearly all frames permit mounting the rear Gates sprocket to the inside of the spider. Check to make sure the belt and sprocket clear the frame. If you do not have a minimum of 2mm clearance between the sprocket/belt with the chainring spacer on the outside of the spider, then the sprocket must be mounted to the outside. The sprockets have an internal alignment tooth (similar to those found on chainrings) to be installed aligned with the crankarm. Mount the sprocket using the longer chainring bolts and spacers (not included with Gates system and purchased separately). Spacers may be installed in any position to facilitate alignment or whatever position is best for your application. It is common to slip the spacer over the chainring nut, slide the nut through the sprocket, then the spider, and then thread in the bolt. 

Mount the front Gates sprocket exactly the same as the rear with the same spacer and spider orientation.

Loosen the eccentric and rotate to the shortest effective position. 

Use a metal straightedge to verify that the sprockets are in plane. If lateral adjustment of your sprocket is needed, you may reposition the chainring spacers, slide the captain's eccentric laterally slightly, or install a spacer under an older style Octalink, ISIS, or square taper bottom bracket. The newer CDX system is not super critical to alignment but getting it very close is recommended.

Install the belt. Slide it on from the side. Never roll it on like a derailed chain as belt damage could happen. Pay attention to the crank orientation, i.e., in phase or out of phase. Check the orientation by squeezing the top and the bottom of the belt together thus tensioning the belt. Adjust the orientation as needed.

Rotate the eccentric to bring up the tension on the belt. Rotate the crank looking for tight and loose spots. If needed, loosen one of the sprockets and retighten when in a tight spot attempting to balance out the rotating tension.

The Carbon Drive's belt tension is significantly higher than that of a chain. With about 10 pounds of force, press with your finger against the center of the belt between sprockets- with the belt tensioned properly the belt should deflect about 1/2" (12.7mm) and strumming the belt should elicit a musical tone, but not a high one, nor a dull thud. Think base fiddle.


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