I got in an actual ride yesterday (snow & bike upgrades have pretty much shut me down this winter) and everything worked OK, so I'll start posting about the recent round of mods / repairs. Some good news on the bearing front... I finally found a source I trust for quality precision bearings -
Ortech:
These are double-sealed (2RS) hybrid stainless/ceramic ABEC-rated precision bearings, handmade in the USA (6904 '13?-'14 wheel bearing on the left, 6204 '15-'17 wheel / '13?-'17 swingarm bearing on the right). You can pick and choose options at the Ortech site to design your own bearing. I chose full-complement type (max # of balls, no cage) as I wanted the highest load-carrying capacity; this explains the ball-loading notches in the races. These 6904's are ABEC 5 (medium precision) and the 6204's are ABEC 7 (medium-high precision, for less swingarm play). The notches made seal removal easy, so I repacked them with my go-to grease for lo-temp wet conditions (Bel-Ray); I use Silkolene Pro RG2 for everything else.
Wheel bearing replacement ('14 FX, 6904 bearings); Removal was pretty straightforward, as I have a
Motion Pro blind bearing removal kit. Pullers like these are the only way I know of to remove wheel bearings without risk of damage to the hub or center spacer; they pull against the small chamfer on the inner-race I.D. Years ago I used to bring my wheels into my ICE dealer for bearing work, but after one wheel came back with a 2mm gap to the center spacer and another was nearly destroyed by a "service manager" with a giant screwdriver & sledge, I decided it was less stressful & cheaper in the long run to get the proper tools and do it myself. The OEM wheel bearings removed were rusty and notchy, but they appeared undamaged and still had a nearly-full grease pack.
Installing the new wheel bearings wasn't as easy (front wheel was OK, rear not so much). All my '14 hubs had issues with brake rotor & sprocket flange alignment - which I finally fixed last month, and will address in another thread at some point - but I didn't realize the bearing pockets were bad too (my '16 FX wheels are
much better on all these counts). Precision bearings are not forgiving of alignment problems, and it wasn't until I'd driven the inner LH rear wheel bearing fully into the (tilted-bottom) pocket and then installed the outer bearing on top of it that I knew something wasn't right. Despite carefully driving the outer LH bearing in (with a large socket - I'm working on a press) until it just made contact with the inner one's center race - and then having both bearings turn as one without binding - once the axle was in & tight, both LH bearings bound up. As always, I made sure to drive the RH bearing in until it contacted the center spacer without binding. I was able to free things up on the LH side by using the bearing puller and tapping the center races a bit, but I really wasn't happy doing that (and never needed to before). If I'd left it as it was, the inner LH bearing would've destroyed itself within a few thousand miles, possibly locking up and ruining the pocket as well. I installed all bearings with unslotted sides out, for best axial strength & dirt rejection.
Swingarm bearing replacement ('14 FX, 6204 bearings): I needed a large breaker bar to remove the M20 'stub axle' swingarm pivots (impact gun couldn't budge them). Both bearings were totally roached (dry, rusty, notchy as hell; I was barely able to rotate them, and bearing corrosion had etched the frame pockets). I believe both bearings had their inner races pulled outward against the SA by stub-axle torque, opening a gap to the bearing seal and letting water in & grease out, eventually destroying the bearings. Once both pivots were out, there was a visible gap from the SA pivot extensions to the bearing races, and an orange wash of rust all round.
After hammering out the OEM bearings with a small sledge & socket (I won't be doing that again), I wanted to find a way to install them perfectly straight to the proper depth without stressing the frame side rails or moving the motor. I came up with the bearing press below, which closely 'cups' the bearing and presses it straight into the frame pocket, pulling against the frame around the bearing-seal holes; when the cup bottoms against the inner frame rail, it's removed & reversed to press the bearing the rest of the way in. It works extremely well, & I'm currently working up an extension & collar to allow it to do bearing removal too. I pressed the LH bearing fully into its frame pocket, then pressed the RH one in incrementally until I was just barely able to get the swingarm in between them (both SA extensions were in intimate contact with the inner races, but exerting barely any pressure on them). No way I was going to leave any gap, like the OEM install. The stub-axle pivots had a few drops of blue Loc-Tite applied & were torqued to 50 ft/lb.
Here's the bearing press, with a 6204 bearing in the 'cup' (RH side). The 51204 thrust bearing and M20 x 1.5 fine-thread bolt let it turn easily & precisely even under heavy loading, and the white PTFE (Teflon) ring gasket protects the frame's powder coat:
Diagrams:
I realize few Zero owners would be interested in this, but a dealer might - especially one doing a large volume of Zero service (bearing replacement is surely commonplace, and motor-bolt removal is a pain). I'm working one up for the wheel bearings too, using the axle as a puller. It's a whole lot better to press bearings in rather than hammer them, especially ceramic types.
As with any of my posts, if anyone wants to add some or all of this to the wiki manual, please feel free.
Ray
Author
Topic: Precision bearings & replacement (Read 5807 times)