There is a lot more to come on this thread as we are documenting and entire shock rebuild as well as fork rework, but I figured some of you might be interested to see the actual rate of the OEM 919 fork spring.
In truth the spring is not as non-linear as this graph would make it appear. The lightness of the spring combined with the length of it causes it to move a little more than we would like it to and of course the massive sensitivity level of the spring rater we use feels everything. Splitting the difference it would appear the rate of the OEM springs is somewhere around 7.3Nm
First off, lets again thank LDH for even doing the test.
Next, allow that it is a simple force reaction vs displacement curve.
It does not account for whatever the friction component is as function of the unit being in acceleration or at constant velocity.
This is not a criticism, just a simple observation and I have no idea as to what the friction component might be.
Obvious is that the springs are extremely soft in the initial and normal travel zone.
Note the chart goes to 60 mm of travel, while displaying a noticeable upwards slope.
Now have a look at the attached pictures.
Then allow that total travel is 109 mm
The shorter spring is out of rickards 2002 fork set that he loaned me for a look see.
The longer one is from the stockers I removed from my 05.
Both are obviously classic dual rate springs with one transition wind between the two spring wind pitch zones.
My guess is that the spring change came in 2004 when the adjustable front came out.
The 02 has 7 tight coils and 24 in total, with a free length of 281 mm.
(I'm assuming no sag over time, and the spacer lengths support this)
The 05 has 8 tight coils and 23 in total, with a free length of 302 mm.
(I'm assuming no sag over time, they have little time on them)
See how the shorter spring actually has one more coil in total, but has one less coil in the lower portion where the coils are closer together.
I didn't check the overall wire length, but sense that they are not that much different, for sure no day and night difference, and as long as there is no coil bind, total wire length dictates the overall spring rate.
It appears that Honda got Showa to retune the front springs to alter where in the stroke that lower coil bind begins, and what the revised rate is once the lower portion is in coil bind.
For sure, the effective front spring rate at 100 mm of travel will be way more than LDHs chart depicts.
The short story is this :
Insanely soft mush spring in the normal range of travel designed for a plush ride.
Stiffer spring rate once into significant travel, otherwise the suspension would be out of control and clanging the hard mechanical stop.
If one is happy with the stockers, ride on !
If you want more front end stability and less bobbing about, and do any degree of "sport riding", get yourself as set of stiffer springs.
Look at this way, LDH's chart shows a nominal 7.25 N/mm = 0.74 kg/mm rate.
Meanwhile, I'd suggest that a reasonable range of rates that many sporting or high gross weight riders would be happy with, would be in the nominal 0.90 to 0.95 kg/mm zone.
By the way, coil bind reduces the effective total spring wire length, thus increasing the spring rate.
Late addition : I just did a crude check and now ballpark the 05 spring as being about 5 % softer than the 02 spring BEFORE coil bind effect and about 5 % stiffer AFTER coil bind effect.
