In the spirit of WTB technology found in other companies' products, this week's Throwback Thursday highlights SunTour's 1991 XC Pro Headset with GREASE GUARD®. When many think of historic WTB products, they immediately gravitate toward Grease Guard hubs, which will indeed see their time in the limelight and are more than worthy of their praise and accolades awarded. However, just like the Specialized Ground Control tire featured in last week's post, this week's focuses on WTB technology used under a different brand, this time SunTour. WTB licensed GREASE GUARD® technology to SunTour in 1989 and in 1991, The GREASE GUARD® Challenge, pictured below, hit the streets, focusing on the ease with which one could service their headset in a pre-ride pinch. Aside from the ability to easily run fresh grease, which was remarkable in itself, GREASE GUARD® was also particularly special because it allowed one to completely fill the voids, or bearing cavities, around individual ball bearings, effectively completely packing grease into the entirety of the bearing as a whole. Why was this important? As changes in temperature occurred between the outside of the bearing from something like water or mud, the inner cavities or air pockets surrounding individual balls of bearings would cool as well and as air molecules condense, they effectively pulled moisture in from outside of the headset, much like fog creation in the San Francisco Bay when a temperature gradient between land and water is hit. Packing the headset full of fresh grease allowed GREASE GUARD® users to eliminate air pockets from the headset, which removed the ability to pull moisture in from the outside while also freshly lubricating the seals of the headset. Genius? We think so along with many other steadfast followers. Enjoy the following challenge, it's bold but beautiful, just like the headset it touts.