Innovative Spanish component manufacturer Rotor’s product range includes cranks, non-circular chainrings – and handlebar stems. There are, in fact, two current models: the S2 and the SX. The S2 is almost identical to the old Rotor S1 stem, the difference being the adoption of T25 Torx-headed Dual Thread Technology clamping bolts in place of the plain 3mm Allen-head DTT bolts of the S1.
The SX, the stem shown here despite the S1 logo on its side, which is explained by the fact that this was a pre-production sample, mainly differs from the S2 in the use of four bolts for the front face plate rather than the two of the S2. Furthermore, it has a rise of 2.5deg instead of 7.5deg, is slightly heavier by about 5g and is not made in length 130mm. It does come in 70mm and 80mm lengths in addition to 90mm, 100mm, 110mm and the 120mm shown. Bar bulge diameter is 31.8mm; oversized, in other words.
Stem material is 7075 aluminium alloy with a hard-anodised black finish and choice of red or black for the face plate. The DTT bolts are in stainless steel. They way they work is explained fully in the S1 article but basically a DTT bolt employs separate coarse and fine threads to apply a high clamping force without the need for a bolt head, saving considerable weight.
That for the 120mm stem is a meagre 119g, making it as light as the all-carbon Bontrager XXX Lite stem it has replaced, for positioning purposes, on the RCUK test Trek Madone 6.9.
In exchange for that lack of excess weight, the face plate requires careful assembly. Each bolt threads simultaneously into both the plate and the stem. Since the plate begins to be pulled towards the stem as soon as both threads are engaged, all four must be engaged at the same time and equally before subsequent tightening begins. In practice it is not a difficult task for the mechanically-skilled but care and attention are required.
Once installed, the SX feels robust, reliable and slip-free and looks great, the white lettering matching that of the machine and going well with many current colour schemes. Initial ride sensations are very promising; update soon on RCUK.
Rotor SX stem £125.00.
