Air in forks??

[Anonymous]

Hi. After geting my bike runing so so I put the recomended amount of air in the forks "1979 GS850G" The ride was the most horable ride ever. I blame this on my 135LBS and looking like an elff on the big bike. I took all the air out and the thing rides like a catilac. My question is am I doing any damage to anything at all by ruing with no Air in the forks? Thanks a million in advance.

[tfb]

Jason,
I don't think you'll cause any damage by having no air in the forks. The main danger is when folks pump too much air in, and burst the fork seals, etc. Therefore do not use your typical garage air hose; it's too easy to go way over the recommended pressure.
I have had two bikes which required air-assisted suspension: a '79 GS1000S and an '89 GPz900. The GS needed a bit of air in the forks to help keep things firmer up front, but with the GPz I always found the suspension was stiff enough, and the air used to slowly leak out anyway.
If you like the 'cadillac' ride, fine!
In the long run, some people recommend dispensing with the air assistance, and putting in a set of firmer fork springs to compensate. But that's more a personal preference, I'd say.
Mike.

[saaz]

Agree with tfb.

I run around 14 psi in my forks (GS1000) but my springs are original and quite soft without any air assist. Use a proper air fork pump to do the pressure. Make sure you have the right fork oil level. I linked my air forks years ago as it is far easier to set the pressures. I also run air shocks on the back (Fournales) so the air suspension front and back matches up quite well.

I find the air rides very nicely over a large range of road surfaces, but not that great for track work.

[KGB]

Agree with both replies.

You do not NEED to run air, it's there to help.

My E model, no air, new fork springs and 15 weight oil, rides fine.

My S model about 5-8 lbs in the forks,new springs and 15 weight oil, rides a little stiffer, but fine.

Some people will discuss that mixing air and oil will break down the
viscosity of the oil causing it to foam and not work correctly.

As was pointed out too much air will work against the seal causing it to leak or even blow right out.

So bottom line, no air is ok.

[Anonymous]

i too found that running air in my gs 750 made the ride too stiff. i've run without air and with 10 weight oil since i've had the bike with no problems (at least that i know of! ) i went back to stock springs from the progressives and like it much better. i'm about 130 with gear. i know the "elf" feeling well!

[Anonymous]

Some people will discuss that mixing air and oil will break down the
viscosity of the oil causing it to foam and not work correctly.

Adding air pressure to your forks makes no difference to the oil, since the forks are full of air anyway. Yes, the oil foams and breaks down and performance suffers. The latest generation of MX forks run a nitrogen filled bladder and function the same as a shock, with no air inside to mix with the oil. This is to gain more consistent damping over a race distance. Ohlins have a set of pressurized road race forks similar to this in concept, as well. I believe Kawasaki ran them the last year it raced AMA Superbike with Eric Bostrum.

Running air pressure will do several things:

1) Assist a set of soft springs in holding things up.
2) Add to seal wear and possibly cause early leakage by blowing the seals out.
3) Add to stiction, resulting in a harsher ride over small bumps.

Air pressure really is a crutch to cover up springs that are too soft. The best answer is to put in the correct springs and run no pressure at all.


Mark

[Anonymous]

Ok good thanks for all the replyes. All in all its exactly what I wanted to hear. I have never had a problem with poor suspention performance up front and a bic pen pring is enough to hold my 135lbs up The bigest problem I have is the rear rides way to stiff but thats a whoile nother post all together LOL Thanks agan for the help.

[earlfor]

I do not run any air in the forks on my 1150. I use 20 weight oil and stock springs and that is plenty firm for my 165 lb bodyweight.
Not using air in the forks will not harm anything.

Earl

[Anonymous]

The reson I ask is becasue I was told it would. My forks leak oil awfull bad. I replaced the seals but it did not help, I am fairly sure my forks are bad they do have marks on them from road debris. I am sure I wasted my new seals the first time I hit a bump. I was told they continued to leak because the air helps creat a seal. I put air in it but that did not seem to help.

[earlfor]

Are your fork tubes badly rusted and pitted? If they are, that is your problem. Are you sure the new fork seals are installed correct side up?
You can polish the fork tubes if they are rusted. If pitted badly, you can fill the pits/holes with J. B. Weld and wetsand the J B away leaving on the filled holes, then polish the forks and you will be fine.

Earl

The reson I ask is becasue I was told it would. My forks leak oil awfull bad. I replaced the seals but it did not help, I am fairly sure my forks are bad they do have marks on them from road debris. I am sure I wasted my new seals the first time I hit a bump. I was told they continued to leak because the air helps creat a seal. I put air in it but that did not seem to help.

[tfb]

Rusted and pitted forks are indeed the usual culprit, but they are not the only cause of leaking fork seals. The bushes insided the forks may also have had their day; if they are excessively worn then there will lateral 'play' at the seals which will cause them to fail.
In any case, the bushes can be examined when you dismantle the forks to change the seals; if you find worn bushes, it's easy to replace them at the same time. And not only will you get forks that have stopped leaking: replacing the bushes also helps cut down fork 'judder' under hard braking.
Mike.

[Anonymous]

well there is somthing I can relate to. My forks do not judder at all under hard breaking. I know this because some P.O.S pulled right out in front of me yesterday afternoon and I darn near locked up both tires trying to avoide him. The dum @#$% looked right at me then hit the gas. My tubes are pited badly. They have no rust on them at all but they are pited. We tryed every polishing method we could think of to cut the pits down but it did not work, however we did not try JB weld

[tfb]

Jason,
Yes, it's the sharp edges that will chop the seals out. If you have already tried polishing things back then there goes that idea.
I'm not sure what 'JB weld' is, but if it is some sort of epoxy filler for filling the pits, then maybe it might work. However if your forks are too far gone, you might just have to get some newies.
But hey, maybe a set of USD forks would look quite nifty on the 850?!
And glad to hear that you have avoided an untimely death.
All the best,
Mike.

[earlfor]

J.B. Weld is an epoxy filler that sets hard enough to be tapped or machined.
It would easily withstand the wear of the forkseals sliding over it.

Earl

Jason,
Yes, it's the sharp edges that will chop the seals out. If you have already tried polishing things back then there goes that idea.
I'm not sure what 'JB weld' is, but if it is some sort of epoxy filler for filling the pits, then maybe it might work. However if your forks are too far gone, you might just have to get some newies.
But hey, maybe a set of USD forks would look quite nifty on the 850?!
And glad to hear that you have avoided an untimely death.
All the best,
Mike.

[saaz]

You can buy JB weld in Australia. I got some in Canberra from Autopro.

Air forks should not leak any more than normal ones. I have only put in about 3 sets of seals over the life of my bike, but I do have 2 sets of forks to play with. Make sure there is no play in the sliders, and that the fork surface is very smooth