fork stiction

[beauchemin]

OK - all you fork tuners, what stiction measurements are you getting with your Marzocchi or Ohlins forks?

 

I am getting 10mm with my Marzocchis.

[Guest ratchethack]

YIKES! I get 1-2 mm.

[luhbo]

Why in mm ?

 

I found this:

 

Main Entry: stic·tion

...

Etymology: static + friction

 

Anyway, the bike alone sets for 10mm, me and the bike make 20mm.

 

Hubert

[Guest ratchethack]

...... the bike alone sets for 10mm, me and the bike make 20mm.

 

Hubert

Hubert, fork stiction is measured with a zip-tie or similar around the fork stanchion. It's the difference in laden sag measurements between where the fork "settles" in it's range of travel in each of two conditions:

 

1. Fork extended, then slowly allowed to come to rest.

 

2. Fork compressed, then slowly allowed to come to rest.

 

It usually takes 4 or 5 reads to get consistent numbers.

 

FWIW, an accurate laden sag measurement is taken half-way between the above 2 measurements.

[Paul Minnaert]

I still don't get it, are we talking sag with bike, or just the leg without anything attached to it, alone?

[Guest ratchethack]

I still don't get it, are we talking sag with bike, or just the leg without anything attached to it,  alone?

Paul, I'm referring to laden sag. Rider on-board.

[Paul Minnaert]

Ok then you 1-2 mm is way to little. Or the forks are like shit, or your weight is like a baby.

 

When you stand next to the bike, bike rightup, not on sidestand, push with your hand downwards on the back of the tank, front and back should go down the same amount.

[zoltan c]

OK, we should have some of our more experienced guys give us a lesson on basic fork set up! I'm an infant when it comes to suspension set up.

Where do you start? What is the factory setting? I'm 5' 10" and 180 lbs and my forks seem very stiff, I haven't measured but they don't move much.

 

Any takers, Paul? Please

[Paul Minnaert]

the basic starts with having the right spings, combined with preload. front and rear I think something like 30 mm sag should be ok. Where rear is measured beween rearwheel axcle, and a framepart above it. Over here, in the öhlins manuals you get a discerption about what should be done. http://www.v11lemans.com/forums/index.php?showtopic=1427

 

Compression and rebound valve settings are of no use if the springs don't fit. Best thing to do is to go to an experienced race suspension shop. They have done it a zillion times, and springs are not expensive. It's the most well spend money you can put in your bike.

[Guest ratchethack]

Ok then you 1-2 mm is way to little. Or the forks are like shit, or your weight is like a baby.

 

When you stand next to the bike, bike rightup, not on sidestand, push with your hand downwards on the back of the tank, front and back should go down the same amount.

90426[/snapback]

Paul, I assure you that my forks are working perfectly, as designed, and they're properly set up. They've been re-sprung with spring rates (~50% higher than the OEM .6 kg/mm springs) matched to load, and pre-load spacers properly set, and BOTH laden and unladen sags are set in an ideal range for me (15-20% of full travel unladen, and 30-35% laden). I weigh 180 lbs.

 

The 1-2 mm is referring to fork stiction, per the title of the thread. The way to measure it is to use laden sag, per my post above. In case we have definition trouble here, I try to use the most common terms, but they vary a little bit.

 

The following link (see Definitions lower down the page) is pretty good:

 

http://www.strappe.com/suspension.html

[Paul Minnaert]

Ok, I think I understand, we know 3 positions of the forks,

 

1: wheel in the air, maximimum extension

2. wheel on the ground, no driver on the bike

3. wheel on the ground driver on the bike.

 

1-2 gives static sag

1-3 gives laden sag.

 

Now the stiction is the difference when I come to the measured position in situation 3, when the forks come from extended versus compresed spings.

 

Is this last value what we are talking about now?

[Guest ratchethack]

Now the stiction is the difference when I come to the measured position in situation 3, when the forks come from extended versus compresed spings.

I think you're saying the same thing I've said above.

 

Stiction is a measure of the "friction factor", that is, the resistance of the fork to move, or "break free" of stationary. It's mostly due to the resistance of fork seals on the stanchions, though friction at the fork sliders contributes to it as well. If there is binding or twisting of the fork, dirty and/or old, depleted fork oil, this will contribute.

 

The link I provided above defines it this way:

 

Stiction: the tendency of the fork to "stick" when compressed or released because of friction.

 

It's measured as I described above (post #4).

[Guest ratchethack]

EGAD! No wonder no one wants to tackle suspension. Just getting together on definitions can be such a chore...... and then it's out of the frying pan and into the FIRE when it comes to the concepts......

 

But hey - I'm game!

 

Suspension set-up should at least have it's own thread..... leave us stay on track, shall we, Gents?

 

I'm worried about Chris now......

 

Chris Beauchemin, my man -- What the heck is goin' ON?!?!?!?!

[beauchemin]

YIKES!   I get 1-2 mm.

90404[/snapback]

 

Wow - that's really good. Are you sure? I would be happy with 4 or 5 mm.

 

My fork tubes are straight and the triple clamps and axle are correctly aligned. What do I check next?

[beauchemin]

What the heck is goin' ON?!?!?!?!

 

I wish I knew!