GeoShift Compatibility Will it work on my bike? Frame must take press-fit headset cups. Frames with integrated headset cups are not compatible.Nominal inner diameter of top end of the head-tube must be 44mm (43.95-44.00 mm measured).Inner diameter of bottom end of head-tube must be within one of the following:44mm (43.95-44.00 mm measured ID)49mm (49.57-49.61 mm measured ID)56mm (55.90-55.95 mm measured ID)Head-tube must be between 90mm and 140mm long. Head-tubes outside of this range are not compatible.GeoShift headsets may have a taller stack height compared to traditional headsets. Refer to the sizing table for stack height measurements to ensure your fork's steerer tube will be long enough to accommodate the GeoShift cups.All GeoShift headsets are designed for forks with 1 1/2" - 1 1/8" tapered steerer-tubes. Forks that have 1 1/4" - 1 1/8" tapered or 1 1/8" non-tapered steerer-tubes may be used with a Wolf Tooth 1 1/2"-1 1/4" or 1 1/2"-1 1/8" adapter crown race (sold separately) Traditional ZS44/EC44 headset in 44mm head-tube Many GeoShift headsets use an EC44 upper bearing cup. That is, the upper bearing cup sits outside of the head-tube, and is pressed into a 44mm inner diameter tube. These are used in applications where a traditional (non-angle adjusting) headset would typically use a ZS44 upper bearing cup. The reason for this is purely spatial - by moving the bearing outside of the head-tube, more angular movement of the steerer-tube can be achieved. In fact, a 2-degree angle change in a 44mm head-tube with a 1 1/2"-1 1/4" tapered steerer-tube is only possible with an EC upper bearing cup. GeoShift 2-Degree EC44/EC44 headset installed in same 44mm head-tube The only drawback to using an EC upper bearing cup instead of a ZS bearing cup is added stack height. GeoShift EC44 upper bearing cups have 10mm more stack height than a comparable ZS44 cup. If you currently have your stem slammed on the headset (no steerer-tube spacers used) with a ZS44 upper cup, it's a good bet that your fork's steerer-tube will be too short to accommodate the GeoShift headset. If you have at least 10mm of spacers, which is most often the case, you will simply need to remove 10mm from your spacer stack.