CLASS system, 6 psi minimum in the forks?

[CaseyJ955]

I have recently added Progressives, no more need for pressure. I put CLASS in manual mode and tried air down the forks all the way but it would appear that 6 lbs is as far down as it will go. What gives? Do I have to DC and plug the hose?

 

Thanks.

[camos]

You have discovered the hidden danger of having tight fork seals.

Airing down the front forks to zero was not an option the design covered.

You can easily do it manually by loosening the equalizer hose fitting between the forks. Can't think of a reason that hose cannot be left loose on a permanent basis.

[MiCarl]

You don't want to leave the equalizer open. Aside from getting dirt and moisture in the trapped air is part of the suspension system.

[camos]

You don't want to leave the equalizer open. Aside from getting dirt and moisture in the trapped air is part of the suspension system.

Well, I didn't say open, I said loose so dirt is not a problem. Since progressive suspension apparently does not require any air pressure to operate well then air is not really part of the equation. Preload is provided by the spacer above the spring and damping is provided by oil moving through the valving.

[MiCarl]

Well, I didn't say open, I said loose so dirt is not a problem. Since progressive suspension apparently does not require any air pressure to operate well then air is not really part of the equation. Preload is provided by the spacer above the spring and damping is provided by oil moving through the valving.

 

Loose is open.

 

While you might not need to pressurize with the progressive springs (many forks don't have a way to add air) the trapped air on top of the oil does act as a spring. You're right that the "air spring" might not be necessary. But if the system isn't sealed when the forks compress air will exit and air will re-enter when they extend. That will bring in dirt and moisture.

 

I have yet to see a fork that is vented, which is what you're proposing.

[CaseyJ955]

I have a supply hose that was severed and I had to replace it, I kept the old hose for some reason odd reason, so I can fashon the ends into plugs. I figured if I let the air out by loosening a hose then the pump would simply resupply the 6 lbs back into the forks upon next start, or continuously pump trying to regain that 6lbs. It is nice to know that it is not a system defect and this is normal operation. I'll let it pressurize the plugged hose, that'll teach it who the boss is!

 

I have another concern that I think might be related to air pressure in the forks and a possible defective internal air seal. I have blown the right fork seal, sprung a decent leak. I rode for 45 minutes and had to stop and wipe the fork clean twice to keep the leaking fluid from reaching the brake. All the seals, bushings and dust covers are new OEM and the forks were in great shape, it was wearing the chrome plastic rock shields to protect the forks from rock chips and appears to have worked great. During reassembly of the forks I was very careful to measure the fluid 5.5" from the top with fork collapsed and springs out. It's not just a little weep, it's a damn significant leak, I want to RO air pressure from within pushing the fluid out through the seal via defective internal air seal, reaching I know but I really super duper dont want to tear this thing back apart if I dont really have to. I'm hoping that fixing the issue of the CLASS system introducing PSI into the fork against my wishes will also magically and mysteriously cure the heinous seal leak.

 

Aside from this, the bike is completely ready for some awesome long trips.

 

EDIT, effitt, it's coming apart again, no reason a new seal should leak this badly, something is amiss, I'll replace the front air supply line with an obstructed one while I'm on there. dernit, I was hoping I was past all the oily pieces rolling around on the bench.

Edited April 21, 2017 by CaseyJ955

[camos]

I figured if I let the air out by loosening a hose then the pump would simply resupply the 6 lbs back into the forks upon next start, or continuously pump trying to regain that 6lbs.

The CLASS doesn't work that way. A normal turn key on then push start will not activate the CLASS. It only operates when in ACC position and it is necessary to select Front or Rear then Manual or Auto to get it to come on.

 

Loose is open.

Seems to me you are quibbling on this. Loose will let air in or out but not necessarily allow dirt in. When I bought it, my 90 had a cut in the balance hose that prevented the forks from pressurizing. I rode it for three years before getting around to fixing it and who knows how long the cut had actually been there. The fork oil was also of an unknown age and it when I changed it a year later it was pretty dark but there was no grit in it and the seals still worked with no leaks. I'd say having a joint cracked is not an issue.

[Condor]

I'm not sure why this is even an issue.... Getting all the air out of the front forks to zero they would need to be pumped out to create a vacuum. Atmospheric pressure is 15psi at sea level. Even with aftermarket springs there's nothing wrong with fine tuning the pressure. I left my AD and CLASS as is and my '83 was one the finest riding bikes I've ever owned... and I've owned a lot... Just because there are new springs doesn't mean all riders are equal...

[CaseyJ955]

Cool, I thought it would auto adjust as was needed. I plan to still use it for the rear shock so I'll probably just DC/plug it in the back by the system. There really is very little room to work by the forks. Thanks for the enlightenment, there was no air in it when I took it apart. I would like to keep it functional and completely manual but that minimum 6 lbs is a little taller minimum than I want to start with. Again I'm sure I'll have to turn it on to add air to the forms when I'm loaded with stuff and wifey is on the back. Each time I turn it on it seems to default to automatic mode but that could be because I had the battery out between rides last year.

 

When I indicated no air pressure I meant atmospheric pressure. It's not a huge deal but I do prefer it to be slung on the soft side for crappy pavement and max comfort. Even with a nice cushy front end it seems quite competent around the curves. At the moment I have diverted my attention to why it blew a brand new seal and I have metal shavings around the lower seal spacer, bit strange but I'm heading into town to get a new seal now.

 

I guess some miles will tell me if I need to add any air but at this point it sure doesn't feel like it.

[camos]

Cool, I thought it would auto adjust as was needed. I plan to still use it for the rear shock so I'll probably just DC/plug it in the back by the system. ..... Each time I turn it on it seems to default to automatic mode but that could be because I had the battery out between rides last year.

It isn't necessary to disconnect the plug. Automatic does not mean the CLASS will turn on by itself. It does mean it will automatically set the pressure at one of the three preset levels when turned on for either the front or rear systems. You can pump up the rear without also pumping the front.

 

When I indicated no air pressure I meant atmospheric pressure.

Hahahaha, yes you have to watch out for the few folks on here who are literally literal. Similarly, when I was referring to zero pressure when bleeding brakes it also was assumed to be atmospheric pressure at a zero differential.

[CaseyJ955]

It isn't necessary to disconnect the plug. Automatic does not mean the CLASS will turn on by itself. It does mean it will automatically set the pressure at one of the three preset levels when turned on for either the front or rear systems. You can pump up the rear without also pumping the front.

 

Hahahaha, yes you have to watch out for the few folks on here who are literally literal. Similarly, when I was referring to zero pressure when bleeding brakes it also was assumed to be atmospheric pressure at a zero differential.

 

It's all Disneyland here! I appreciate all the input and I'm hard to offend. So thank you to everyone for the input.

 

I wanted to make sure I didnt accidentally get air in the front when trying to mess with the rear so I just unplugged the front air line at the compressor and plugged the hole with a short bolt and O ring, then ran a flanged bolt and nut with an O ring through the end of the hose to seal it up from moisture and dust. Now I can use the rear air without worry. I managed to fix the blown fork seal today and got a nice long ride in. She runs nice but I still have a few things too deal with. I'm only getting 29.3 mpg and shes awful wiggly and loose at 75+.