06 April 2016

Stardate 2016.263

Fresh Seals

In 2011 I blew the Nitrogen-charged portion of the rear shock on my Specialized FSR mountain bike. I can tear into suspension to change oil and air seals, but my shop isn't quite equipped to deal with Nitrogen charging – yet.

I also had just built-up a Giant XTS hardtail (no rear shock) 29er (29 inch wheels). So, the FSR has been stabled for a while – a long while; as in 5 years. Anyway, I finally sent the shock off to the FOX factory for a rebuild. In the process, I've decided to resurrect the FSR as well. The resurrection begins with new air, oil and dust wiper seals for the blown seals on the front Marzocchi MX Pro + TAS shocks.

This was the first time I'd torn into this model of Marzocchi fork. The left leg top cap required utilizing a free hub tool that normally is used to remove the cassette (rear sprockets) from the rear hub. I thought this was a good idea because you can get a good bite on the top cap.

After removal of bottom bolts, the air/oil-pumping element, spring and the extension travel adjustment (ETA) and travel adjustment system (TAS) cartridge can be removed. ETA allows fork rebound and damping to be controlled on-the-fly from full rebound, to lock out or something in between. TAS allows suspension travel to be preset at a minimum of 100mm (3.9 inches) or a maximum of 120mm (4.7 inches).

After draining the oil and pulling the sliders off of the stanchions, I let them drip residual oil overnight.

Residents of the left leg are the ETA/TAS cartridge, spring and top cap. Left leg pump is not shown. Oil is collected and given to appropriate handlers.

After popping the old seals out, the fork races are cleaned and await fresh seals to be pressed in.

New air/oil seals are pressed in tightly and further held in check with stiff snap rings.

The new dust wiper seals are also tightly pressed in. At times, it can be a battle to get seals pressed.

My basement floor is designed to "float", thanks to our local clays. To complicate matters, bicycle suspension performance characteristics are very sensitive to air pressure, oil weight and oil quantity. Hence, I use a tripod, 4-square metal blank and level to find level ground for measuring volume.

Into the forks goes the new elixir.

TA DA! The fat lady won't sing until I get to test everything.

Thanks to a recent "mini blizzard" dumping over a foot of snow, followed by yet another storm adding an additional 8 inches of very wet snow, conditions to ride are slow in returning. Trails have melted fast but require additional time to dry. Maybe I'll saddle up a road bike and venture into the foothills to see how wet and sandy the roads are.

Stay tuned, and thanks for reading!


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