Today’s project is the resurrection of my Bontrager Ti Lite’s Modzilla fork that Speedgoat Bicycles built in 1995. Chris took a Rock Shox Judy SL, replaced the crown with a Paul Components CNC machined aluminum crown that can fit 1″ and 1-1/8″ fork steer tubes, then replaced the original Judy internals with air cartridges by Englund, now Total Air, if they still exist. The 2 massive crown bolts are torqued to 35 ft/lbs.
A round aluminum tool (pic R) is pressed into the cartridge cap and used to unscrew the air cartridge out of the fork tube. I carry it with me on rides in case the cartridges fail to hold air, lowering the bike’s front end 3 inches to unrideable. My untested plan is to remove the failed cartridges with the round tool, carve 2 fat sticks the same length as a cartridge, square off their ends, then cap them off inside each fork leg and huff it home on a woody, um, rigid fork.
Both cartridges out.
Cartridge assemblies after wipe down. Rebound and compression damping are set by 3 internal air valves (soft, medium, and hard) with flow rates tuned by screwing the valve deeper into its slot and constricting flow. Law of Poiseuille, ya know? 4 valves of 6 [2 R N] are @ top R in pic, which didn’t turn out well enough to show them. They are basically polymer allen bolts with differing diameter air channels and o-rings.
Fork food. Forget what the nutritionists say, for bikes, bike grease is mandatory nutrition. Other greases may taste better, but they have viscosities too high for bicycle forks.
Wipers (against crown) and fork seals up outta the sliders for cleaning.
The fork sliders are syringe lubed with silky Manitou Prep M green under the fork seals before they are finger pressed into their slots. Visible is the Bontrager’s downtube gusset, which has a detent either side to maximize the weld surface area for extra strength in a high stress area.
Highlighted is 1 of 2 firm rubber discs I cut from a handlebar grip to place inside the fork tubes under the air cartridges to damp any top out feedback from metal to metal contact.
Both cartridges are screwed into the fork and pressurized to 100 psi, a pre-load setting for my weight of 125#’s and local terrain that has lots of poison oak, steps, railroad ties, scat, and log crossings. And, yeah, that’s a 19 year old King headset before logos were etched on them all. Almost time to flush and re-lube the bearings, a once every decade suggested maintenance. Didn’t think the 1st re-lube was necessary. This upcoming one either. But I’ll do it anyway. It’s fun.
All ready to roll, once I get the wheels built. We’ll save that project for next week . . .
Gears 2 ya,
Cary~
