Jtek Shiftmate 6

Jtek Shiftmate 6

If the number of inquiries on the subject that land on Cycle’s desk says anything, it is that building a derailleur transmission using components not originally designed to work together is a popular pastime.

There are doubtless many reasons for this, ranging from the understandable desire to build, say, a range of gears not offered as standard by any manufacturer right through to a quixotic urge to construct some sort of Frankenshift. In any case, the process generally depends on the fact that many unexpected combinations of shift lever, rear mech and cassette do, in fact, work in harmony. Some, however, do not, which is where Jtek’s Shiftmate series comes in. The basic concept is the same as that of the classic Travel Agent linear-pull brake adaptor, which comprises a pulley wheel with two cable grooves of different diameters, in a housing that forms part of the cable’s outer casing. The inner wire wraps around the pulley, entering on one groove and exiting on the other to alter the input:output cable-pull ratio according to the two-groove radii.

Accurate indexed derailleur actuation depends on the amount of cable pull required to make the rear mech align precisely with each sprocket in turn; if an incompatible shifter pulls, say, 10% less than needed, then compatibility can be achieved by having the inner wire exit the Shiftmate on a groove of 11% larger radius than the entry groove. Of course, the same principle works in reverse. There are currently nine versions of the Shiftmate, each made for one or more specific combinations of shifter, rear mech and cassette; in other words, there is no universal solution, since any desired combination requires a specific ratio. Peruse the Shiftmate website compatibility chart – jtekengineering.com/resources/shiftmatecompatibility/ – to find the right model. In most cases, the device works in either direction depending on the desired component combination.

Some combinations are apparently impossible. I paired a Shiftmate 6 with Shimano 10-speed Ultegra 6600 STI lever, 10 speed 11-32 cassette and 10-speed Deore XT MTB rear mech. Despite sharing the same number of gears, the MTB mech is incompatible with the road shifters. The Shiftmate can, in principle, go anywhere in the outer casing run and is supplied with a small spacer tube that fits a standard frame cable stop. Once an initial failure to note the offset of the outer casing stop holes had been overcome, I got the device cabled up nicely. The inner wire switches grooves via a flat in the intervening ridge; getting this snug proved the only real difficulty. Once all slack was removed, the Shiftmate worked! If not as slick as with the ‘correct’ rear mech, it was accurate right across the cassette.

Back issues of cycle free (for longstanding members) Somewhere in there will be the answer to almost every derailleur compatibility query. 

Dia Compe Ene Ciclo Shifters from £41.99 These friction-shift levers work with almost any mech and cassette up to 10-speed. Available as a down tube shifter or as a bar-top thumbshifter (£59.99). ison-distribution.com

Richard Hallett

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