Tuesday, April 10, 2012

TECH: Part 1 of 4 - How to do an annual service on Fox Forks

So for many parts of the world spring is fast approaching or is already here. This means you probably need to get your ride tuned up for the upcoming race season. Hopefully you also kept your body tuned up too.

This multi-day post will focus on what you need to do to service your Fox 32mm F-series fork to ensure consistent reliable performance for many years.

This guide is just the full blown annual service. It will not explain how to fix problems and assumes your fork was in proper working function before this service.

Just remember routine regular maintenance means less cost over the long run as you don't need to replace expensive parts to get it working again.

First order of business is to gather up on supplies.

Walmart for this:

Then go to an autoparts store (Canadian Tire, Parts Source, Pep Boys, Autozone, etc). Go ask the guy at the counter for vacuum caps. You want the small assorted package on the right. You will trim the rubber cap end off so it becomes a plug/adapter for the syringe to the FIT dampener cartridge.

Buy new seals. For 2012 Fox contracted design of new seals to SKF industries. Whatever you do make sure you buy these new seals as they are miles better than the previous ones for sealing and a lot less drag.

Buy fork oil aka Fox Float fluid. Depending on year of your fork you either need 7.5wt or 10wt.

Fox Flat 10wt Red is the same as silkolene pro rsf 10wt and probably a lot cheaper. Call around to various motorcycle dealers and inquire.

I went with Redline suspension oil as I have been using their oils for a very long time when I used to race cars. If you live in the greater Toronto Area you can buy it from JRP. If you go the redline route you will need to buy their heavy weight and medium weight and mix the two so that you get the same viscosity index as 10wt Fox fluid.

Peter Verdone talks about how to mix the two redline oils together to get the same viscosity as Fox 7.5wt you need. If you want to read up about the theory of dampers and oil viscosity go here:

To ease in the math on how to get Redline Medium + Redline Heavy to be at the same viscosity as Fox 7.5wt you need to mix:

81.1% Redline Medium + 18.9% Redline Heavy = Fox 7.5wt. 

If you have a newer Fox fork it will call for Fox 10wt or silkolene pro rsf 10wt. Silkolene Pro RSF 10wt has 47.36 cSt @ 40C. Therefore to replicate this with redline oil you need to mix:

42% Redline Medium + 58% Redline Heavy = Fox 10wt =  silkolene pro rsf 10wt
(reference Suspension Oil Blend Viscosity Calculator)

Tools you are going to need:
  • Metric allen key set (hex keys)
  • Small rubber mallet or block of wood
  • old ice cream container or yogurt container to contain the used oil
  • torque wrench
  • hex bits for torque wrench
  • metric wrenches (8mm and 10mm)
  • shock pump
First order of business is to remove your fork from your bike. Remove your front brake caliper from your fork, Undo the aheadset cap bolt, remove the aheadset cap, loosen the stem bolts, remove your fork. Tie or tape everything to your frame so it's not just left hanging in mid air and in the way.

Take your fork and go wash it with hot soapy water. You don't want to have dirt and sand fall into critical areas when you take apart the fork. Towel dry your fork or allow to dry overnight.

with all the loose bolts, thread them back into where they came from so you don't loose them. Here is a pictorial guide on what you need to do.

Next post will discuss taking apart your fox fork to get to the seals.

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