Topic: Am I Missing an Inch?

[Really?]

Got new -2 tubes from cyclex and I decided to lay the tubes side-by-side.  There is only about an inch difference.  The old tube measures about 10 3/4 inches and the new one is just under 10 inches.  There is a cutout that is not in the same place.

Anyone know where that other inch is?

This cutout is further up the tube.


This is the difference in length.


These are side-by-side.

[Tower]

Looks like the new tubes are for a much newer bike. 1980+ (could be as early as 1979?) and your old tubes appear to be 1973-1975

Edit: The newer tubes may have an integrated oil lock (hence the extra length at the bottom)
You will need the newer matching pipe bottom and seals as well.

As for missing an inch, perhaps your wife is best qualified to answer that question. sorry.

[Really?]

There is a hole in the cutout of the new tubes where there is not one in the old tubes.  The inch is not internal as I put the dampening rod and top out spring in both and measured.

Newer matching pipe bottom?  Are you talking about the lower tubes?

I can't reply to the last part, this thread might get deleted, lol.

[Tower]

Nope.  The pipe bottom is the piece that's inserted into the tube below the spring.  A newer pipe bottom will be shorter and probably have fewer pressure relief holes.

If you use the old pipe bottom, the spring dampening effect will be quite different - not necessarily bad, just much stiffer and easier to bottom out.

[Really?]

I think you mean dampening rod that the top out spring goes on.  I guess, lol.

Well, I found the inch.  I measured the new tubes and they are what cyclex says they are, about 21 3/4 inches.  I measured the old tubes and they are about 22 3/4 inches.  And stock is about 23 3/4 inches (13/16 for all the die hards, I can't read that on measuring tape, lol).

So, the old tubes were already an inch shorter, darn.  Or, maybe they came from another bike before me purchasing it.  Can't always trust the story from the PO.

Makes me want to go get some PVC to be satisfied.

BTW, what is the stock length for the springs.  I noticed the preload was like nothing.  These are about 18 1/2 inches.  I might not have to cut them, woo hoo.

Edit:  Yanno, that may have been the bang I was hearing when I slid the tubes up the trees to begin with.  No preload and when fully extended, they got loose.  I just changed to tapered bearing but the stock bearings were fine and tight.

[Really?]

I found 19.00x inches is stock length.  So, hmmm someone has been here before, lol.  Maybe 550 springs as I have read they are about 3/4 inch shorter.  Maybe the tubes and lowers are too.

Thanks for your help Tower!

[Tower]

No problem.

The other important consideration when swapping out to a shorter front fork is the rear shock height.  What is the eye-clevis distance of the shocks now?  If you reduce the front height, you may want to consider reducing the rear shock height as well.  Otherwise, the bike will want to track straight and have a marked under-stear in the corners.

[Really?]

The rear shocks are the 11" shorties.  Hoping to have the 16" rim on it this week, going away from the 18' rim.

[Tower]

You are right, it appears the suspension on your bike (I'm assuming a CB750) has been shortened by 2" by the previous owner.

Consider that when using the newer tube, its designs place more pressure on chamber "B" in the dampening section of the lowers, which in turn places more pressure on the upper oil seals.  I think that means either plugging the cutout hole or replacing the inner (damper rod) with the newer one - but I'm not sure which is better in a mix and match situation like this one.