Fork striction

[Guest hyper]

When I got my rosso last year I noticed that the forks were extremly harsh, on my first ride down avery bumpy winding road I got a couple of nasty head shakes. I thought ,OH OH I may have made a mistake buying this thing. When I got home I started to check things out. If I pushed lightly on the forks they would not rebound , I decided to check if someone at the factory or dealership had tightened up the axle pinch bolts without first pumping up and down on the forks. So I loosened up the pinch bolts, applied the front brake and pushed down hard several times. After tightening up the pinch bolts I tried lightly pushing down on the forks and they were much better. Any time the front end is apart you should do this as it allows the forks to find their neutral position. If you guys try this and find the same thing let the rest of the members know as forks wear out alot faster and effect the handling. Thank, Hyper

[Janusz]

So whats your front stiction now, Al - lets compare notes. I did not measure it straight from the factory but after first 1,000 km forks disassembly and new oil etc. mine is at 13 mm. I think its quite good.

[dlaing]

How do you measure stiction?

Also, I have heard that some bikes ship from the factory with the incorrect amount of fork oil. Too bad it is such a pain to change or check the fork oil.

[Janusz]

I hired a dealer to do the forks - easy but tedious work.

 

You push down on the forks and let it extend SLOWLY. Then you measure them using your favorite method. Next you lift the front up and let it settle again very SLOWLY. Then measure again. The difference in mm is your stiction which represents the mechanical drag of your seals. If you neglect the stiction your sag measurements will be imprecise.

 

Simiarly the rear stiction represents the friction of your linkage and/or swingarm.Normally it's markedly less then front.

 

Anything less then 15mm of stiction at the forks I consider good, the good rear is almost negligible, maybe 2 or 3 mm on my bike.

[Guest hyper]

Janusz and Dlaing, Striction is not really something you can measure, its the amount of "stick" in your suspension caused by seal drag, bushing drag, Stuck valving and contamination. What you are measureing Janusz is the amount of free sag (no rider). I can see where you are getting the striction part into the equation because like you said you have to gently neutralize everything when you put the tire back down on the ground to get repeatable measurements that you trust. Our V11s are not as easy as some of the japanese bikes because try as I might they don't seem to be as free from striction and repeatable results are not easy to get because of the striction. I am going to take my forks apart and see whats up, I love a challenge, anything to make a guzzi a better weapon. Thanks, Hyper

[Janusz]

Al, the stiction can be measured as a function of a different height of your suspension when you release it in an UP direction as opposed to the DOWN direction. I did not make a mistake and my method describd above is the right and precise one.

 

In short, you take TWO measurements as described above, both with the rider, gear etc. on. Then you have to add them of course and divide by two, which of course will give you the closest approximation of the reading if the stiction was zero. Is that clear now?

 

The difference between these two measurements is a precise amount of your stiction then.

 

Lets disregard the free sag in our discussion since it really is not needed in a process of measuring of the sag.

 

I do not really know how to express it better in order to make it clear. Thats the problem of English As A Second Language people like me,I guess.

[Janusz]

The people measuring their sag disregarding stiction are introducing a random error to their measurements. If they repeat their measurements few times the results may and will vary up to the amplitude of the unaccouted for stiction.

[Guest Scura Owner]

I think the dealer is responsible not the factory as the dealer puts the front wheel on.

[Guest hyper]

Scura owner, Thanks for the info, The bike shops I worked at some bikes came with the front wheel on and others didn't. Hyper

[Guest hyper]

Janusz, I think were both on the same page but we don't know it so I'll run through the procedure I use to set front sag.

Step 1, Jack up the front of the motorcycle so that the front wheel is off the ground.

Step 2, All measurements will be taken on the sliding part of the fork, shiny part.

Step 3, Measure from the wiper seal on your fork to the bottom of the shiny part near your axle, write this number down, eg. 100mm

Step 4, Take the bike off the stand and with the bike straight up and down, no rider, slowly pump it up and down, take a measurement several times so your confident with the number, eg. 88mm, this is bike only sag

Step 5,Sit on the bike in full riding gear, have someone hold the bike straight up and down so your feet can be on the pegs. Slowly pump up and down and take several measurements. When you have repeatable numbers write it down. eg. 70mm

Step 6 , 100-70=30mm sag

This number will be how much front suspension sag on your bike, you will have to get the a couple of helpers to do it accurately. This number will contain the spring movement and whatever striction there is. If you have a well set up set of forks in primo condition there will be almost 0 striction but to measure the sag it won't matter as long as you get the desired number. 30mm is a good race number by the way.

Hopefully this helps our little barrier. Thanks AL

[Guest hyper]

Janusz, as an add on to the letter above. On the last measurement, eg.70mm there is enough spring pressure at this point that it would take a of striction to not get repeatable numbers. I can appreciate your high and low number theory but its hard to get repeatable numbers for both. When you take your first measurement, eg. 100mm the fork is topped out so its a true number. Because of the incresed spring pressure the 70mm is very accurate. Racers are a weird bunch, if you get a set of forks that no matter how light the pumping action it will always return to the same spot moving fluidly,we'll yap it up, good for a pissing match. We remove seals from the rear wheel,torgue up the axle to the number that takes up all the free play but dosen't cause any unnesacary binding, why? So when your bike is on your rear stand, if you give your tire a good spin it will continue to rotate 3 or 4 revolutions. More speed yeehaa.

You can imagine with our guzzis that don't have state of the art suspension ,how much striction there must be when were braking hard over bumps or hard cornering over bumps in other words,the forks would almost bind up in these situations. Hopefully I can figure something out.

PS>Scura owners, you have the best chance to get it right , Ohlins are very tunable and parts redably available. You can be sure some suspension shop will get it right. Hyper

[dlaing]

Thanks Guys,

Now I know how to measure stiction and get a more accurate sag measurement.

I think you guys are pretty much on the same page. The only little disagreement is that Janusz would do step 4 slightly differently. But You should both end up with the same degree of accuracy, give or take a couple millimeters.