(Updated) Is Voyager XII Tech Tips Fork Springs Correct?

[ghostler]

On tech tip: https://amervoyassoc.org/techtipsXII.ph ... %20Springs

Subject: Installing Progressive Fork Springs, Step 18 states,

Before you install the new fork springs, you must add the required amount of oil. As mentioned under the tech tip "Front Fork Oil", the best way to bring the oil up to the required level for the Voyager is to measure from the top edge of the fork inner tube to the top of the oil level (it should measure 145mm for Progressive Springs, 140 for stock OEM springs). Use some kind of measuring tool or improvise to accomplish this, I used a heavy plastic zip tie, and put a piece of tape 145 mm from the tip of the tie. I lowered the straight zip tie into the fork inner tube till the tape lightly touched the fork tube. I then added oil till the fork oil just showed on the zip tie. Note: Progressive recommends 160mm ± 2mm of oil level. Carl Leo has determined that 145mm works best for Progressive springs in the Voyager XII (1200). I had originally used the 160mm level, and found that it indeed was too much oil, use the 145mm measur{e}ment. <-- typo

We are basically measuring the air gap from the top of the collapsed tube down to the oil level. Following detail is from the Service Manual, Section Suspension, Page 12-5:



145mm air gap would allow more oil to reside in the reservoir than 160mm. How does then 160mm provide a taller oil level?
Inquiring minds want to know.

[chevyman1]

I think that a typo 160mm is less oil.
you will probably will notice some ride difference between 160mm and 145mm.
The more important thing is to have them both the same (air volume not oil volume), I use a hand vacuum pump over fill them and then suck the oil out to the height I want (I use 145mm).
you don't want to have to much oil in there that the forks bottom out on the oil.

[ghostler]

So far in 900 miles of riding, I've gone with the 160mm gap from top of strut tube to oil level on both sides, and ride is fine. In the progressive springs instructions it mentions about the springs taking a greater volume than the OEM, so it will increase the oil level. It does leave a caveat to use no more than 145mm if motorcycle manual mentions a lesser value, although. 0.6 inch or about 5/8 inch isn't much but I thought it would be worth clarifying.

The B1 - B17 Supplement on Page 12-2, Specifications mentions 177mm for B1 through B3, 158mm for B4 through B17. It supports the logic that a greater air gap uses less oil as the B1 - B3 is 336 ml, whereas the B4-B17 is 352 ml. I don't know why 1987 through 1989 would use less oil even though the same strut assembly is specified for all years except the 1986.

And, if the 145mm value is the appropriate value regardless, I have no disagreement with that. I just wanted to point out there appears to be a logic error in the Tech Tip, perhaps even a misquote from Carl Leo. Using the 160mm air gap value, I haven't had any oil shortage problems and my 2001 B15 properly dampens so far.

[ghostler]

Haven't gotten a reply from others besides chevyman. Thus I gather that it is probably a mute point. 145mm air gap would provide maximum permissible oil, so there'd be no shortage of damping. 160mm provides a touch over OEM oil for damping (due to greater volume of thicker and more coils per length progressive springs), so still provides OEM shock performance.

I think chevyman is right, doesn't make much difference as long as both shocks have the same amount of oil. Thus I'd consider case closed.

However, I think it would be beneficial in the next update to the Tech Tips, to correct the logic error as 160mm air gap is less oil than more oil as stated. The 145mm air gap is greatest permissible oil level to have and probably most optimal as alluded to.

[Highway Rider]

Thanks for bring it to attention so it could be worded correctly. It has been confirmed, and changes have been made to the last two lines of step #18 to read as fallows.

Carl Leo has determined

that 145mm air gap works best for Progressive springs in the Voyager XII

(1200). I had originally used the 160mm air gap level, and found that it

was not enough oil. Use the 145mm air gap measurement .

[ghostler]

Thanks for bring it to attention so it could be worded correctly. It has been confirmed, and changes have been made to the last two lines of step #18 to read as follows.

Carl Leo has determined that 145mm air gap works best for Progressive springs in the Voyager XII (1200). I had originally used the 160mm air gap level, and found that it was not enough oil. Use the 145mm air gap measurement .

Thanks Jim for the clarification and you are welcome.

Next time when I have the forks out (need to verify I put the seals in right, not upside down), will set oil level to 145mm.
Best I can say at this point is the Progressives were a definite improvement to front fork handling. I didn't want to exceed the factory air levels and still had some front end dive at stops and damping wasn't all that great with the weak OEM springs. For all I know, the OEM's could have lost some of their springiness over time. I don't get the dive with the Progressives and ride on rough roads has really smoothed out.

Next time around, I'll be able to compare the difference even further when I up the oil to 145mm air gap.

[chevyman1]

I went from Progressives to the Race Tech setup and noticed a big difference there also.
On the PA. roads the Race Tech gave me a smoother ride then the Progressives on the sharp bumps, and PA. has a lot of them.
The only thing is there twice the money

[ghostler]

I went from Progressives to the Race Tech setup and noticed a big difference there also. On the PA. roads the Race Tech gave me a smoother ride than the Progressives on the sharp bumps, and PA. has a lot of them. The only thing is they're twice the money

Work sent me to Claysville, PA, 46 miles south of Pittsburgh some years back for training. It was a very pretty area in Fall, but you're right, PA has bumpy roads, too. Law of diminishing returns, on a retirement income the Progressives improved ride enough that it satisfies me for now.