Wilderness Trail Bikes produces an unusual B/B that implements their famous Grease Guard principle. Designed by Mark Slate, it uses SKF 6003-RS1 sealed bearing cartridges with the inner seal removed. Behind each bearing cartridge is aluminum ring, cut on the edge, with a specially created rubber ring that forces grease injected into the cut area into the open ended sealed cartridge.
The outer seal on the cartridge is made so the inner lip of the seal moves away temporarily under pressure, permitting old grease to be purged from each bearing cartridge. To prohibit grease from migrating back into the center of the B/B, there is an aluminum tube that slides over the spindle, making a tight seal with both the rubber ring and the inner bearing race, leaving the spindle to revolve freely. The aluminum ring is cut on edge to create a 2mm wide gap, that is nearly an inch long that permits a wide target to inject the grease into. This B/B doesn't come with standard threaded bearing cups. Instead, the user reams their B/B shell with a 1 3/8" (1.375") reamer, to give the interior a smooth surface. The aluminum ring is pushed in with the cut edge facing the direction you intend to inject the grease from. The bearing cartridge is then pressed in, with the seal out. On the other side, the aluminum sleeve is inserted, the spindle is carefully pressed through, then the other aluminum ring, and the remaining bearing.
The outer diameter of the bearing and the alloy ring is 35.0mm, and they fit tightly within a round properly reamed B/B shell. If the shell is slightly oval Loc-Tite adhesive may be required. The cut edge of the alloy rings should face the same direction, to meet a 1mm hole that will have to have been previously drilled 11mm from each end of the B/B to pump the grease into the assembly, (there wasn't a way to explain their need earlier). The holes on a aluminum frame can be Zerk fittings, for steel, it is suggested that electrical tape be used to close them off between grease applications.
The WTB bottom bracket is available with either a Cro-Moly spindle, (made for them by Chris King), or Titanium spindle, (made for them by Doug White at White). Both spindles have the required two degree taper to fit all aluminum crank arms, and both are drilled through to reduce weight. The Cro-moly spindle is made in either 116mm or 122mm lengths. The Titanium spindle comes with matching Titanium crank arm bolts, and is available in 108mm, (for XTR), 115mm, or 122mm. The weight of a WTB Cro-Moly B/B with a 122mm spindle is 267 grams. A Titanium version wasn't at hand for weight at the time of writing.
Cro-Moly Spindle Length-16-22 $Price in Catalog
Titanium Spindle Length-08-15-22 $Price in Catalog
