Progressive front springs, solid spacers, and oil level--what should it be?

[BumbleBee]

So, after having my bike on the track and having some folks with lots more experience than I tell me my front forks, well, left something to be desired, I took them apart to see what was going on.  The fork oil was gross, and probably no where near correct levels.  (Where does the muck come from and the oil go? Just enough leakage at the seals over time?)

Anyhow, as I half-expected from the bike's history, it had the progressive springs (I assume they are Progressive brand).  However, there was no spacer with them.  From my reading of the Progressive installation instructions, looked like it should have about a 1" spacer in there.

Went to Tapp Plastics (across the street from my office, and one of my new favorite shops) and bought two 1.25" diameter and 1" long segments of solid pastic rod.

I set the oil to be the recommended 5.5" below top of the tube (per Progressive's install sheet) with the spring out, etc.  Assembled the whole thing (and learned that the top clamp bolts do deform the tube enough when tight to prevent a 1.25" solid rod from sliding in).

So, if the problem/question I'm now worried about isn't obvious to those reading along, it is thus:

Since my spacer is a solid  rod I've lost a full 1" of air space along with preloading the springs 1".  Should I have reduced the oil depth another 1" to compensate for this?  Are my forks going to go into hydraulic lock before bottoming out?


-B.

[Kasumi]

No your just likely to force oil through your seals because there will be too much pressure, solution is to reduce the amount of oil or replace the spacer with tubing.

[coll0412]

You will be fine....

[GeeP]

No, don't reduce the oil level!  The fork has plenty of air space inside.  You won't experience hydraulic lock unless you SIGNIFICANTLY overfilled your forks.

However, it is important that the spacer be assembled on top of the existing spacer, just below the fork cap, if it fits the fork tube tightly.

[Flywheel]

Yeah, old fork oil turns into nasty snot somehow. The air space inside your forks acts as a (weak) progressive, pneumatic shock when compressed; by adding a solid rod spacer instead of a tubular one, you have reduced the air volume inside a sealed fork a bit, but I doubt it would be noticeable at 1". 

[RichDesmond]

So, after having my bike on the track and having some folks with lots more experience than I tell me my front forks, well, left something to be desired, I took them apart to see what was going on.  The fork oil was gross, and probably no where near correct levels.  (Where does the muck come from and the oil go? Just enough leakage at the seals over time?)

Anyhow, as I half-expected from the bike's history, it had the progressive springs (I assume they are Progressive brand).  However, there was no spacer with them.  From my reading of the Progressive installation instructions, looked like it should have about a 1" spacer in there.

Went to Tapp Plastics (across the street from my office, and one of my new favorite shops) and bought two 1.25" diameter and 1" long segments of solid pastic rod.

I set the oil to be the recommended 5.5" below top of the tube (per Progressive's install sheet) with the spring out, etc.  Assembled the whole thing (and learned that the top clamp bolts do deform the tube enough when tight to prevent a 1.25" solid rod from sliding in).

So, if the problem/question I'm now worried about isn't obvious to those reading along, it is thus:

Since my spacer is a solid  rod I've lost a full 1" of air space along with preloading the springs 1".  Should I have reduced the oil depth another 1" to compensate for this?  Are my forks going to go into hydraulic lock before bottoming out?


-B.

They won't hydraulic lock, but you're making a bad situation worse. Waaay too much progressivty in your overall spring rate. Get rid of the solid rod. Go to Lowes or Home Depot and buy a piece of 3/4" Schedule 40 PVC. Only be a couple of dollars. Use that to make spacers according to the directions here, in the Note A section

http://www.sonicsprings.com/catalog/damper_rod_forks_tech_article.php

Use 15w oil, set the level at 110mm.

[BumbleBee]

The only spacer in the tube now is the 1" one I installed.  There was no sign of the stock spacer when I opened-up the forks.  So it is: Cap->solid rod->spring.  I did loosen the top clamp enough during install to get the spacer seated in there with no gaps between those various parts, etc. (Then tightened the top clamp again when everything was together).  I decided against putting washers in with the solid spacer, as it seemed to have a reasonable bearing surface for the spring. 

-B.

No, don't reduce the oil level!  The fork has plenty of air space inside.  You won't experience hydraulic lock unless you SIGNIFICANTLY overfilled your forks.

However, it is important that the spacer be assembled on top of the existing spacer, just below the fork cap, if it fits the fork tube tightly.

[GeeP]

Ahh!  Yeah, the progressive springs are much longer than the stock or other straight rate springs.

Leave the spacer, go for a ride. 

Progressive springs will still feel soft compared to straight rate.  There's nothing to do about that except replace the springs.