Sunday, May 22, 2011

Rebuilding a Ballistic 600 AII front suspension fork


Recumbent bikes are a ton of fun and the Vision R45 is the second that I've owned.  I consider the Vision R45 a nearly perfect bike for me.  Mine has front and rear suspension, aerodynamic wheels, a short wheel base design, and under-seat steering.  It even has a fairly nice component group.  There is only one problem:  it is more than 10 years old and the company that made it (ATP) is now out of business.

I'm not about to buy another recumbent bike and if anything breaks on it, it is up to me to fix it.  Recently I went about doing a complete overhaul on it to get everything back into top shape.  Bike maintenance really isn't that hard and it is really enjoyable with the right tools.  See this article for how I first got started doing my own maintenance.

One of the biggest challenges in overhauling the Vision R45 was rebuilding and servicing the suspension systems.  The rear shock (a Cane Creek AD-5) isn't a problem as you can still get a rebuilt kit for it (with instructions).  However, the front shock (a 20" Ballistic 600 AII) is another matter entirely.  It seems there is almost no information about this shock online even though it was a very common shock for recumbents with suspension.

So, in the hope that it will help others, I'll share my complete rebuild instructions and even a tip to make a minor improvement.

Why not just buy a new one?

This is a good question.  Let's ignore the fact that I hate to throw away perfectly repairable parts.  Front suspension forks aren't hard to find, but keep in mind this is a 20" fork designed for a smaller than normal front wheel.  Nevertheless, there are still a few choices in 20" suspension forks (by MEKS / SASO, White Bros., Spinner, etc.).

However, one major problem with these other forks is that they don't have crown pinch bolts.  My bike uses these bolt to also attach my under seat steering (see the pictures below).  Obviously, without the bolts, I have no way to steer the bike!  Many (or even most) recumbents come in above-seat-steering configurations which do not have this requriement (they simply clamp to the top of the fork steerer just like any other bike).

So, unless I want to convert my bike to above-seat-steering or I want to try to custom fabricate a solution, I'm stuck with a single model of suspension fork that is no longer being made!  A further complication is that newer suspension forks often only support disc brakes (v.s. cantilever rim brakes which I need).

The bottom line is that I better figure out a way to make this fork last!

Tools you may need

Besides a good set of bike tools and such (see here), the only additional tools that I needed was a set of snap ring pliers and a P-handle hex wrench set.  If you are really clever, you might be able to get away with using regular pliers with the snap ring, but I wouldn't recommend it.  A P-handle wrench is needed because most hex wrenches aren't long enough for this application.




Remove the fork

Each side of the fork has a snap ring locking the stanchions to the top of the crown.  Use the snap ring pliers to remove the rings.  See the green arrows below.


Next, you can remove the two allen head (pinch) bolts that bind the stanchions in the crown.  You'll need to loosen them enough so that the fork stanchions can be lowered (you might need a mallet or other tool to gently tap them out of the crown).

Note: I wouldn't try to overhaul the fork while it is in the crown as the compression from the crown bolts will make it hard to take the rest of the fork apart.

Here is a picture of the fork removed from the crown:


Start disassembly from the top

The red pre-load adjust knob at the top of the stanchion is easily removed by removing a tiny allen head bolt.  With this removed, it initially looked to me like I might need a special tool to take the rest of the assembly apart.


I was stumped at first and took the fork to a friend of mine for advice.  After thinking about it for a bit we realized that a 14mm nut would fit perfectly into top and allowed us to use a wrench to loose the top cap.


With the bolt in place, the top cap is easily unscrewed and the rest of the fork comes apart.



(Optional) Remove bottom spacer

At the bottom (underside) of the fork arms, you will notice there is an allen head bolt.  When I first tried to figure out how to disassemble the fork, I removed this bolt thinking the fork would come apart (I was wrong).  Turns out this bolt secures a long spacer with a green elastomer bumper.  I believe this bumper dampens the rebound when the shock bounces back from being compressed.  I don't think you really need to remove this piece when you are rebuilding the fork (so I think this step is optional).  However, if you do loosen this bottom bolt, you are committed and will need to fully take apart the shock in order to reassemble it properly.  This is due to the fact that there is otherwise no way to tighten the bolt again.

You will need one regular hex wrench on the bottom bolt and a long hex wrench inserted into the stanchion to keep the spacer from turning while you tighten the bolt.  My hex wrenches were short and this is where the p-handle hex wrench set comes in handy.  It was probably a good thing (for me) to take this apart as I found that one of my green bumpers was loose.  I ended up using some black electrical tape to "shim" it so it stayed put.


Cleaning and Reassembly

With the fork fully disassembled, I examined everything to make sure nothing was worn or broken.  I then cleaned off all of the excess/old grease and got it ready to reassemble.

I liberally covered all contact points with grease (including the yellow elastomer itself).  I also made sure that the pre-load adjuster turned freely.  I normally would have used a light oil on the threads, but mine was already pretty well oiled.

I used blue (medium) strength Locktite on the bottom bolt that secures the lower spacer to the fork.

I also applied some Tri-flow on the stanchions as they were pretty tight and I felt that heavy grease would only cause them to bind.

Finally, I was a bit concerned about what torque to use for the crown pinch bolts.  As I couldn't find any assembly manual.  I did find a old Manitou 2 fork manual that recommended 90-110 in-lbs for what is a similar fork design.  If anyone knows the proper torque setting, please let me know.  To be safe, I also used medium Locktite.

Fixing the pre-load adjustment

When I finally got the fork back together I noticed that the pre-load knobs were really hard to turn.  As soon as I snugged the securing bolt, they bound up right away.  I also recall them being the same way on my old Vision R-45 as well so I decided to investigate a bit more.

I took the assembly apart again and didn't find anything wrong.  The pre-load bolt turned freely without the knob attached.  Turns out that the knob itself was being smashed down on to the top on the stanchion cap.  Well, it seemed to me that a thin washer might be all I need to fix this problem.  Unfortunately, a washer small enough to fit into the existing hole might be hard to find.


Well, I headed back to my friends' house and he custom filed some small washers (thanks Kevin!).  You can see it installed here:


With the washers inserted, I could snug down the bolts and the knobs still turned freely.  I think I may have also used a bit of blue Locktite on the allen bolts as well to make sure they didn't come loose.

Done!

Well there really wasn't anything wrong with my front shock when I started, but now I know that it is well serviced and working great.  I even fixed the pre-load knob and it is working better than ever.

Best of all I know that I can keep this shock in good shape for years to come.

4 comments:

  1. Saaaweeeeet!!!

    ReplyDelete
  2. This comment has been removed by a blog administrator.

    ReplyDelete
  3. I agree recumbent bikes are a lot of fun. Ever since my first ride I have been hooked but I never tried taking one apart before. I supposed it would be beneficial to see exactly how it works as you did. Thanks!

    ReplyDelete
  4. I think this will be very useful as I have some Ballistic 450aII on my recumbent that I don't want to die. Thanks for your time in posting this. Ed

    ReplyDelete

Copyright (c) 2010 CuttingTheBills.com. All Rights Reserved.