Ohlins Fork Adjustments

[Greg Field]

The Guzzi service manual says the adjuster in the center of the top cap is compression damping, and the one at the bottom of the slider is for rebound. The Ohlins manual says the opposite. My own adjust and push experiment tells me the Ohlins manual is correct. Any of you know for sure?

[mark.gilmore]

The Guzzi service manual says the adjuster in the center of the top cap is compression damping, and the one at the bottom of the slider is for rebound. The Ohlins manual says the opposite. My own adjust and push experiment tells me the Ohlins manual is correct. Any of you know for sure?

Hi Greg.Ohlins manual is correct.

[Greg Field]

Hi Greg.Ohlins manual is correct.

 

Thanks. Is there anything those effing Aprilia retards couldn't get wrong?

[dlaing]

Thanks. Is there anything those effing Aprilia retards couldn't get wrong?

Yah, damn Aprilia retards were so stupid they put phreakin' Ohlins on a two wheeled tractor.

What a waste.

You should sell your Ohlins and put some shocks off a Ural in place of the Ohlins

[profWacko]

>>Yah, damn Aprilia retards were so stupid they put phreakin' Ohlins on a two wheeled tractor.

 

Does anyone have the link for that guy in Germany that had a bunch of the Guzzi OEM Ohlins forks for sale?

 

Also, does Race Tech have replacement valves for the Marzocchi's?

 

I might jump ship from my Marzocchi's because I'm getting a little tired of the battle.

 

My tractor needs better suspension in the front mesathinkin.

 

-Jack

[Greg Field]

Yah, damn Aprilia retards were so stupid they put phreakin' Ohlins on a two wheeled tractor.

What a waste.

You should sell your Ohlins and put some shocks off a Ural in place of the Ohlins

 

Akshully, I'm the retard who put Ohlins on my tractor.

[Guest ratchethack]

I might jump ship from my Marzocchi's because I'm getting a little tired of the battle.

 

My tractor needs better suspension in the front mesathinkin.

 

-Jack

Jack, I've set up my Marz fork by the generic setup drill recommended by most Pro's, with a relatively low expenditure on substantially up-rated springs, and have been more than pleased with the results. IMHO these are very good road forks, certainly more than capable of delivering excellent road performance and long service life for 99% of Guzzi riders.

 

WARNING: DANGER ZONE!

 

You are about to enter The Bermuda Triangle of V-11 lore. The lattitudes of the Forking 40's are dark, treacherous waters of evidently very low navigation skill by most riders. Sea monsters of various descriptions, capable of swallowing Guzzi's whole endlessly ply the fathomless depths. These waters are fairly boiling with ignorance, rumor$, $ale$ hype, entirely unfounded opinion$, half-truth$, outright lie$, and emotional ju$tification$ for relatively extreme expenditure$ of many thou$and$ of dollar$! Enter here at y'er own risk with a keen eye to weather, my friend!!!

 

But if'n y'er willing to take the slings & arrows that I've learned to ignore hereabouts in the interest of common sense, and if y'er at all interested, I'd be willing to share wot I've learned, which may be at least amusing, if not actually useful. It ain't rocket science, but by my experience, basic knowledge of these waters these days is mighty scarce.

 

Wot's the battle y'er fightin'? Wot're the symptoms?

 

Cdr. Hatchracket, U.S.S. MarzGuz, Road Geez Fleet

[profWacko]

>>Wot're the symptoms?

 

Generally, a lack of compliance over any kind of bumps.

 

If I dial out the rebound (the only adjustment I have, right?), the front gets really mushy and bouncy, but it is still harsh.

 

When I dial in some rebound to get rid of the bounciness, it's better overall, but I still get pounded over bumps, like the expansion joints on the freeway, or worse in bumpy turns where you don't know if the bike is gonna bounce left or right.

 

Basically, the rebound setting has no affect on the harshness over bumps.

 

I believe that what I am experiencing is waaaaayyyyyy too much high-speed compression damping, which is endemic to these forks from what I read here and elsewhere.

 

What I have done so far is switch to the heavier progressive springs from Wilbers (thanks, Todd), and I have changed the fork fluid to 7.5 wt, with a 100mm air gap.

The higher spring rate has really helped a lot, as the bike no longer nose-dives under braking.

 

Speaking of air gap, here's how I set it (assumes you have the fork leg totally compressed and vertical in a vice on your work bench:

1) Take a short length of 3/16 steel brake line and mark lines from one end every 10mm or so until you get to 150 or 160.

2) Connect a few feet of clear plastic tubing to the opposite end tube from the marks.

3) Use a pair of needle nose vise grips (or some other kind of clamp) to hold the tube vertical in the fork leg with the desired air gap mark even with the top of the leg.

4) Over-fill the fork with fluid of choice so that there is fluid up in the steel tube.

5) Siphon out the excess fluid through the clear tubing. When the fluid stops flowing, you have the air gap that you want.

 

So, what's my next step? (with apologies to Steve Jobs >8])

 

-Jack

[Guest ratchethack]

Jack, it sounds to me like y'er on the right track and you've gotta be very close to getting things right, but I'm a little dubious about y'er air gap measurement technique.

 

Rebound damping will have no effect on harshness over bumps, and you shouldn't expect it to. It only acts in extension of the fork, or "jounce" -- 'nother words, it only acts in "recovery" after a bump.

 

Only compresssion damping will have an effect on felt resistance to a jolt.

 

Back to air gap now.

 

Though I can (sort of) follow y'er numbered procedure, and it actually sounds like it could be correct, I don't see any need for any tubes or graduated marks on a brake line tube?? Also, y'er reference to 150 or 160 mm throws me f'er a loop here...... Seems to me you could easier mark something to use as a 100 mm dipstick and skip the pipes & tubes??

 

My concern here is that you may have ended up with something considerably less than a 100 mm air gap. This would explain y'er harsh riding conditions!!!

 

I think its simpler than you've made it here.

 

Whether the fork assemblies are on or off the bike, the procedure is the same.

 

With the springs out and fork lowers in full bottom-out position relative to the stanchions, fill forks until the level of oil is 100 mm of the top of the fork stanchion (the top of the part where the caps thread in).

 

It's very important to pump the forks as you fill to get ALL the air out. Lots of bubbles will appear at first when you pump it, allowing more oil to be filled. When the oil level stabilizes -- that is, when no more bubbles appear and the level no longer drops when you pump the fork, add more oil until you have a 100mm measurement.

 

That's it, my friend. If you need to draw off excess oil, you can use y'er brake tube and/or tubing.

 

With both compression and rebound damping adjusters fully backed off LEFT, you should have a fairly decent ride already with plenty of compliance, assuming you've assembled the fork in proper sequence and there's no binding. You might want to check this, unless y'er certain about the sequence. Add comp and rebound damping to reduce cycling, per usual procedure.

 

A general rule o' thumb that I like to use f'er starters with damping is to start very low with rebound only, take a ride and get a feel for it, and only if necessary add in compression later to half rebound setting. I agree with your observation of Marz forks providing lots of compression damping. This isn't a fault, IMHO! You've gone to 7.5 wt Fork Oil, probably since this is wot Wilbers instructions recommend. I did this also, coming from 10 wt., which reduced the damping effect, then went to synthetic 125/150 CARTRIDGE FORK FLUID on the next fork oil change, which cut the damping by an equal amount AGAIN. Even so, much of the time I still use no compression damping at all in my Marz 40 mm USD. A zero setting starts you off with significant damping already.

 

FYI - Here's some o' the best linked generic procedure I know of:

 

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

 

http://www.racetech.com/articles/SuspensionAndSprings.htm

 

Pete Verdone's write-up on air gap is good also, though I think the above are better resources for everything else than wot Verdone's got on his site:

 

http://www.peterverdonedesigns.com/oilheight.htm

 

Hope this helps!

[Greg Field]

Ratchet:

 

I think he has the later forks, which have adjustment for rebound and pre-load only. These are what I originally had on my Billy Bob.

 

FWIW: I went with 5w fluid in my set, and they were still harsh. That doesn't mean they can't be tuned to work well. I just was offered a set of Ohlins for relatively cheap, so I went that route. I'll be putting the marzocchis on my Eldo pretty soon, so I will be playing with them a bit more then.

[Guest ratchethack]

I think he has the later forks, which have adjustment for rebound and pre-load only. These are what I originally had on my Billy Bob.

Mea culpa. I should've known this, since my Pal's '04 LM has the same ones, I think.

FWIW: I went with 5w fluid in my set, and they were still harsh. That doesn't mean they can't be tuned to work well. I just was offered a set of Ohlins for relatively cheap, so I went that route. I'll be putting the marzocchis on my Eldo pretty soon, so I will be playing with them a bit more then.

A Marz graft on the Eldo sounds challenging, Greg.

 

But wot a ride if you can pull it off successfully!!

 

I'll be keepin' an eye peeled f'er the results. . . .

[dlaing]

Rebound damping will have no effect on harshness over bumps, and you shouldn't expect it to. It only acts in extension of the fork, or "jounce" -- 'nother words, it only acts in "recovery" after a bump.

 

Only compresssion damping will have an effect on felt resistance to a jolt.

 

Excessive rebound dampin' can cause the suspension to "pack" and thus become harsh.

In addition to damping having an effect on felt resistance, stiction and spring rate also have an effect.

But bottoming has the worst effect on felt resistance to a jolt

High speed compression damping is most notorious for passing the jolt.

But too little high speed compression damping is bad for reasons that I don't fully understand.

[profWacko]

>>If you need to draw off excess oil, you can use y'er brake tube and/or tubing.

That's the whole point of the tubing/siphon procedure. Plus, you get very repeatable levels. Motion Pro sells a fork fluid level setting device that I have seen used in a lot of shops. My version is just a lot less expensive.

 

>>Excessive rebound dampin' can cause the suspension to "pack" and thus become harsh.

I could not agree more.

 

>>FWIW: I went with 5w fluid in my set, and they were still harsh.

That's a pretty revealing fact, which is why I may be looking for the link to that German guy with all of the forks. I was beginning to think that I have some kind of mechanical binding going on, but after reading about the 5wt still being too harsh, that might not be the case.

 

-Jack (still bounding down the roadway...)

 

 

 

Here's how the siphon thingy works.

 

Just pretend that the roll of paper towels is your fork tube.

[raz]

Does anyone have the link for that guy in Germany that had a bunch of the Guzzi OEM Ohlins forks for sale?

http://www.hmb-guzzi.de/html/teileangebot.htm

[Guest ratchethack]

Here's how the siphon thingy works.

Got it. It's a slightly "streamlined" version of the turkey baster and depth gauge method I use.

 

Can't f'er the life of me figure out wot's givin' you fits with this thing, Jack -- unless as mentioned above, you've bound up the fork assembly. I don't want to insult anyone with assumptions about lack of knowledge, its pretty obvious you know a thing 'er 2 about wot y'er doin', but did you follow proper sequence in assembling the fork to assure no binding or twisting?

 

Just askin' in the interest of chasin' down every angle.