fork stiction

[dlaing]

I measured stiction with no tank and no rider on my Ohlins Fork equipped bike and after a little bit of practice got pretty consistent 5mm difference, or more specifically 105 - 100 = 5mm (FWIW...assuming 120mm travel, this indicates 22.5mm static sag albeit with no tank)

I did readings ranging from 97 to 107, but after about a dozen readings wrote them off as errors, as well more than half the down push readings were between 99and 101mm and all but one of the up readings were between 104 and 106mm.

Note that I was trying to get as big a difference as possible by not yanking up nor pushing down too hard.

Also note the Ohlins is supposed to be coated with gold nitride or nitrite which is supposed to be slicker.

And also note, I have not ridden in over a month

[Guest ratchethack]

Dave, measuring unladen, I would expect 5 mm stiction or more. It's measured laden to show what happens under real-world "working" conditions. Unladen stiction will be 2-3X laden stiction.

 

Didn't we measure stiction on your rear shock when measuring your laden sag number - way back when??? As I recall, it was just a few mm??

[Guest ratchethack]

I wish I knew!

90453[/snapback]

Chris, have you done any measurements to check for parallel? How about visually checking for twist?

 

NOTE: It can be out of parallel but not twisted. But if it's twisted, it's out of parallel.

[dlaing]

Dave, measuring unladen, I would expect 5 mm stiction or more.  It's measured laden to show what happens under real-world "working" conditions.  Unladen stiction will be 2-3X laden stiction.

 

Didn't we measure stiction on your rear shock when measuring your laden sag number - way back when???  As I recall, it was just a few mm??

90492[/snapback]

It sure is easier to measure unladen sag stiction.

I agree that laden stiction would be more valuable, but I am too lazy to help out with a laden sag stiction measurement.

I don't recall the stiction difference that we got, but I am sure we would have noticed if it was extreme.

[beauchemin]

Dave, measuring unladen, I would expect 5 mm stiction or more.  It's measured laden to show what happens under real-world "working" conditions.  Unladen stiction will be 2-3X laden stiction.

 

Didn't we measure stiction on your rear shock when measuring your laden sag number - way back when???  As I recall, it was just a few mm??

90492[/snapback]

I'm taking an unladen measurement.

 

 

 

Chris, have you done any measurements to check for parallel?  How about visually checking for twist?

 

NOTE:  It can be out of parallel but not twisted.  But if it's twisted, it's out of parallel.

90497[/snapback]

I've checked this. I used a piece of glass to ensure that the legs are parallel.

[Guest ratchethack]

Chris, if you're getting 10 mm stiction unladen, you might be not as far out as you think. Your laden stiction might be ~3 mm. Still seems a bit much to me........

 

I used a piece of glass to ensure that the legs are parallel.

A piece of glass can tell you if the fork is twisted or not, but it can't tell you if the stanchions are parallel, as I noted. I mention this because it should be checked.

[beauchemin]

Chris, if you're getting 10 mm stiction unladen, you might be not as far out as you think.  Your laden stiction might be ~3 mm.  Still seems a bit much to me........

A piece of glass can tell you if the fork is twisted or not, but it can't tell you if the stanchions are parallel, as I noted.  I mention this because it should be checked.

90550[/snapback]

 

Are you referring to the possibility that the distance between the forklegs might be different at the axle and at the lower triple clamp? Given that the right forkleg floats on the axle until the two pinchbolts are tightened leads me to believe that it is nearly impossible for this to occur. I loosened those 2 pinchbolts and pumped the forks with the wheel against a wall before re-tightening the pinchbolts. Am I missing something?

[dlaing]

Did you try cleaning the fork tubes and dust covers with some silicone spray?

Note:

1. Don't get any silicone on brake disks. spray on to rag and then clean the fork tubes.

2. Some think the silicone will attract dirt. It is a trade off. Squished bugs will slide away, but more grime will accumulate at dust cover. Regular cleaning with WD40 or better silicone spray, should help reduce pitting on the forks and keep the seals working properly, and reduce stiction.

I think you mentioned the stiction seemed to worsen after service.

Can anyone think of something else that could cause the increase in stiction?

Wrong fluid level???

Replaced something incorrectly????

threaded rod connection???

springs upside down???

Spacers???

adjustment rods?????

Maybe the seals just need time to re-wet??? If you don't like the idea of silicone, clean tubes with fork oil, work the forks, clean again, work forks, clean off excess.

[dlaing]

Are you referring to the possibility that the distance between the forklegs might be different at the axle and at the lower triple clamp?  Given that the right forkleg floats on the axle until the two pinchbolts are tightened leads me to believe that it is nearly impossible for this to occur.  I loosened those 2 pinchbolts and pumped the forks with the wheel against a wall before re-tightening the pinchbolts.  Am I missing something?

90555[/snapback]

If it did not feel like it was binding with the pinchbolts and axle nut loose, it probably is not an alignment issue.

I suppose you could pull your springs, dump your fork oil and then put the forks on the bike without springs and oil, keeping the bike on a stand, see how it moves with just a free floating axle, and see how it moves with a tightened up axle and wheel.

But that is alot of work

[Guest ratchethack]

Are you referring to the possibility that the distance between the forklegs might be different at the axle and at the lower triple clamp? 

Yes. I'm here to tell you that this and stranger things than this can and do happen.

it is nearly impossible for this to occur. 

Not so nearly impossible. I'm not saying that I know what your situation is, Chris - just trying to suggest things to check - however remotely likely - all of which I'd do in your situation. I've had slightly bent fork tubes several times, and straight tubes that mysteriously get knocked out of parallel in the clamps, which were re-set parallel by backing off all clamps and re-setting 'em in sequence.