Fork oil weight

[NemisusDM]

I ordered some parts to rebuild my forks.
New progressive springs, piston ring, oil seal and air gasket.
In the manual it says to use 10wt oil. What would happen if I used 15wt oil?
I assume that the oil is there to slow the piston down while lubricating it so the 15wt would make it stiffer?

Thanks,

[prometheus578]

Yes.

[jwoell]

I'm about to upgrade to progressive springs and change out the fork oil at the same time. I was thinking about trying out the 15w oil, but I just wanted to see if it's a bad idea. Has anyone else out there has tried the 15w oil instead of the 10w that is listed? What did you think of it?

[mason79]

i'm 135 lbs, i had 15wt with progressives, and the fill was as per progressive measuring from the top with a guage method not the, measuring cup method and it was too stiff,

without the progressive springs the 15 wt was good but not as good as the pro/ springs 10wt combo


mine is a hard bagger and loaded front fairing now and the suspension is very tunable as per the preloads up front, so no need for 15 wt....stay with the 10 wt
good luck!

[DeanR]

10 wt has worked well for me with the progressives.

[jwoell]

Thanks for the info guys, I'll stick with the 10w then.

[GtrMn]

and the fill was as per progressive measuring from the top with a guage method not the, measuring cup method

Just got a set from progressive....and they do mention that the springs displace more oil.

What should that measurement be...and from what point? My manual doesn't say anything.

[mason79]

the instruction sheet from progressive is detailed in how to measure the fork oil, more is stiffer less is softer

[petejw]

ATF

Has any1 used auto fluid as a replacement
for fork oil.
Thought i read some where that some1 had used it.

id assume it would be a softer
feel, lighter than the 10weight?

Ive got progressive springs in the front
but the suspension feels a little stiff, the bike is naked.

[GtrMn]

i had 15wt with progressives, and the fill was as per progressive measuring from the top with a guage method not the, measuring cup method and it was too stiff,

As I read it. It says the measurement should be 5.5 inches from the top with the forks collapsed. I assume that means compressed? Wondering if I should make it around 6 inches...don't want it too stiff.

[GtrMn]

Oh yeah..one other thing...the measurement is without the springs installed...wondering where the level is with the springs installed. I would guess about an inch from the top?

[GtrMn]

Oh yeah..one other thing...the measurement is without the springs installed...wondering where the level is with the springs installed. I would guess about an inch from the top?

Meant to add....where the level would be with the springs installed AND the forks in the normal position....not compressed.

[pggg]

I drilled three extra holes in each fork and widened the others on the dampers, rods and stuff inside, there's even tiny pinhole breathers or whatever they are in there, I left them alone, also I'm pretty sure my progressive springs are unintentionally in upside down with the tight coils at the bottom, got the thickest fork oil going, 20 or 25, the front end is springier but stiffer if that makes any sense.

[skids]

That absolutely makes no difference from the laws of physics.

Originally posted by pggg
I'm pretty sure my progressive springs are unintentionally in upside down with the tight coils at the bottom,

[chopwatchagot]

actually it does make some difference, just not much. I don't know what the progressive instructions tell you to do but the difference would be in the amount of unsprung weight moving up and down with the wheel. If the springs are wound progressively then there is more mass in the end that has the tighter coils. The center of balance of the spring is not in the center of the spring lenghtwise. If the tighter coils are at the bottom of the tube then more mass is moving up and down with the wheel than if the other (lighter) end were down. It's just like progressively wound valve springs. The more massive end (tighter coils) needs to sit still (against the head) while the lighter end does the bouncing up and down.