[1813254617.th]

My friend just got a Cannondale CAAD2 F900 with a Headshok Fatty D. Seeing what I thought was boatloads of rust mixed in with the grease on the bearing races, I immediately did the unthinkable and tore it down to bits (including all the races and roller bearings). Looks like the imitation pepperoni...er... elastomer has perished.

Ignoring the fact that the fork is(was) in pieces, how screwed is this fork? The spring inside the fork is blue, and feels to be about the correct stiffness for my friend.

The damper was quite anemic and very noisy so I ripped it open (got damper oil squirted all over the place because there somehow was high pressure air inside?!) and put in Motorex 2.5wt fork oil (CST 15). The noise is gone but the damper still feels anemic.

Am I right in assuming that the elastomer also provided some damping and a thicker oil is required? I believe the original oil was Golden Spectro semi-synthetic 5WT oil with a cst of around 15 or 16, so Motorex 2.5wt should be close.

BTW, The fork has been thoroughly cleaned and put back together (I made sure all the races went in the exact same way as from the factory). But I'm willing to take it apart to either change the damper oil or spring some other day.

 

[1813254617.th]

Update:

The fork is alive! wouldn't call it plush, but it's smooth. Alas, another problem has cropped up, I can only assume I messed something up.

The lockout is now extremely speed sensitive. If you stroke the fork slowly the lockout does absolutely nothing, not even an increase in resistance. However, if you stroke it somewhat quickly the fork locks solid with a clunk. Before my service attempt, the lockout had 10mm of play, but would lockout at any speed.

Basically, the fork lockout now behaves the opposite way a blow off valve lockout does. It only triggers with sufficient force.

The only thing I can think of that could be the culprit is the oil. Maybe Motorex 2.5W isn't thick enough? Maybe something is up with the lockout shim?

 

[Notthatbryan]

Try a thicker oil. IIRC we used to use 5 wt, and remove one shim from the rebound side of the damper.

 

[1813254617.th]

Try a thicker oil. IIRC we used to use 5 wt, and remove one shim from the rebound side of the damper.

Will do when I get some thicker oil for a Fox Float R damper rebuild. I don't think removing a shim from a Cannondale DD60 damper cartridge is within my abilities.

I don't think comparing oil weight across brands is fair. 5wt Maxima is close to 2.5wt Motorex, for example. I don't know what the specs are for Golden Spectro 5wt oil, but it might be just that little bit thicker than Motorex 2.5wt and causing my problem.

 

[Notthatbryan]

Will do when I get some thicker oil for a Fox Float R damper rebuild. I don't think removing a shim from a Cannondale DD60 damper cartridge is within my abilities.

I don't think comparing oil weight across brands is fair. 5wt Maxima is close to 2.5wt Motorex, for example. I don't know what the specs are for Golden Spectro 5wt oil, but it might be just that little bit thicker than Motorex 2.5wt and causing my problem.

I used to pull them apart, polish the bearing races, revalve the damper, and fill it with heavier oil. They felt great, but this was 20 years ago when a 75mm fork was hot stuff.

 

[1813254617.th]

They felt great, but this was 20 years ago when a 75mm fork was hot stuff.

Headshoks make a lot of sense for short travel, imo. They're really, really stiff and light. I really enjoy the fact that all the heavy wear items are in theory easily replaceable. I don't know why Cannondale stopped making them.

My friend's 2007 Manitou R7 Super absolutely embarrasses the Fatty D in every metric but stiffness (yes, including stiction). That fork basically has zero stiction, whereas the Headshoks still have stiction caused by grease. I guess the Headshok may shine under heavy torsional or lateral loads, though.

An air Headshok with the Manitou ABS+ damper would be really nice.

 

[Notthatbryan]

Headshoks make a lot of sense for short travel, imo. They're really, really stiff and light. I really enjoy the fact that all the heavy wear items are in theory easily replaceable. I don't know why Cannondale stopped making them.

My friend's 2007 Manitou R7 Super absolutely embarrasses the Fatty D in every metric but stiffness (yes, including stiction). That fork basically has zero stiction, whereas the Headshoks still have stiction caused by grease. I guess the Headshok may shine under heavy torsional or lateral loads, though.

An air Headshok with the Manitou ABS+ damper would be really nice.

The big drawback to headshocks is that the stack height ends up super tall for the amount of travel.
That was the reason the lefty was created. It was to increase travel to 100mm without raising up the front end.

The stiction can be improved by using better grease, or if you are chasing every last little bit of performance removing every other needle bearing.

 

[1813254617.th]

The stiction can be improved by using better grease, or if you are chasing every last little bit of performance removing every other needle bearing.

The stiction is still good enough. I care far more about durability than low perceived friction.

Yes, I do need better grease. I've been tolerating my vat of Lucas Red N' Tacky for far too long. I used to use Mystik JT-6 and it was so much better at staying put and resisting washout. Too bad it's no longer widely available in my region. The Red N' Tacky is quite tacky, though. It was so tacky I didn't need anything to hold down the races and roller bearings during assembly, the grease held everything together. Of course there would be some stiction...

What greases do you use, may I ask?

 

[Notthatbryan]

The stiction is still good enough. I care far more about durability than low perceived friction.

Yes, I do need better grease. I've been tolerating my vat of Lucas Red N' Tacky for far too long. I used to use Mystik JT-6 and it was so much better at staying put and resisting washout. Too bad it's no longer widely available in my region. The Red N' Tacky is quite tacky, though. It was so tacky I didn't need anything to hold down the races and roller bearings during assembly, the grease held everything together. Of course there would be some stiction...

What greases do you use, may I ask?

I haven't rebuilt a headshock in years, but IIRC we used Judy butter (slickoleum is probably close) for other forks I use slickoleum or Ohlins grease on their forks.

 

[1813254617.th]

I haven't rebuilt a headshock in years, but IIRC we used Judy butter (slickoleum is probably close) for other forks I use slickoleum or Ohlins grease on their forks.

Slickoleum, eh? I have a tub coming my way for fork maintenance. Is that thing only good for fork seals, or is it good for bearings, too?

BTW, from what I'm gathering. Nothing about the hardware of the fork should have any problems, I just need a thicker oil. Am I right?

Thanks!

 

[Scott O]

If I didn't know what that was I would say it looks delicious. Actually, now that I do know what it is, it does look delicious!

 

[1813254617.th]

If I didn't know what that was I would say it looks delicious. Actually, now that I do know what it is, it does look delicious!

The forbidden salami, encased in an impenetrable (for the average biker) container known as the "Headshok".

Fresh ones look even more delicious, if I do say so myself.

 

[BadgerOne]

The forbidden salami

Let's keep it clean here, folks

 

[Philco]

Wrong grease, need a Anhydrous calcium grease, food grade grease made from mineral oil is usable. Correct example, Slickoleum for suspension forks.

Automotive greases bad. May dissolve your new elastomers.

 

[wolfmw]

been a long time since I messed with a Headshock, but your lockout issue may be due to air in your oil? I seem to remember it being a real PITA to get all the micro bubbles out of the damper. You might try refilling the damper cartridge, being super careful to keep any air out. But it's been 20+ yrs, so I may be way off here.

 

[127.0.0.1]

If I didn't know what that was I would say it looks delicious. Actually, now that I do know what it is, it does look delicious!

now I know where all that dried paste ended up in grade school....

 

[1813254617.th]

Wrong grease, need a Anhydrous calcium grease, food grade grease made from mineral oil is usable. Correct example, Slickoleum for suspension forks.

Automotive greases bad. May dissolve your new elastomers.

Thanks, I did not put in a new elastomer so don't worry about my grease choice destroying a new elastomer. I strongly suspect that is how the old elastomer disintegrated.

My only current concern is my grease destroying the boot and the seals in the damper. It's hard keeping the grease from reaching the damper.

Is slickoleum good for the roller bearings? I thought it was designed for seals and such.

 

[1813254617.th]

been a long time since I messed with a Headshock, but your lockout issue may be due to air in your oil? I seem to remember it being a real PITA to get all the micro bubbles out of the damper. You might try refilling the damper cartridge, being super careful to keep any air out. But it's been 20+ yrs, so I may be way off here.

Given how solid it locks when it does kick in, I believe I've done a decent job at bleeding the thing. Won't hurt to do it again, though.

 

[1813254617.th]

It's alive! The lockout actually does work fine, it's firm and the speed sensitivity doesn't matter on the road. You really have to go really slow to bypass the lockout, something that isn't difficult on the shop floor, but isn't possible under riding conditions.

Damper performance appears to be slightly better (still a bit anemic, though) than the foamy old oil. I guess Motorex 2.5W can work in these. I don't know how it compares to stock performance, though.

Gotta replace the pedals since my friend doesn't do clipless.

This bike sure is in excellent cosmetic condition. Mechanical condition was...bad... The bottom bracket is completely siezed, my 2 foot breaker bar cannot budge it. Oh well, it spins smoothly so I don't need to change it anyways.

 

[OldMike]

What did you use for a replacement elastomer?

Also, I the rider feels he's too low (in the front), the stem can be flipped to raise the bars.