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Fork Pressure

  • Thread starter Thread starter TBucket32
  • Start date Start date
T

TBucket32

Guest
Hi folks!

I have an '83 GS550ES.

Recently I had my forks rebuilt because the right one was leaking. Shortly after the rebuild, the right one started leaking again and soon let go completely dumping oil all over me and the bike. I went back to the shop that did the rebuild but they would not warrenty the work because they had written on the work order that the tubes were pitted and polishing had not removed all of it. They figure the pits (which were less severe on the right side then on the left) caused the seals to go again.

I found a local salvage shop that had a fork ready to go. I put it on this past weekend.

My manual says to pressurize to 4 psi. The guy I got the fork from made a comment that most people run 10-15 psi. I put in 7 psi and it feels soft...lots of fork compression under heavy braking.

Any suggestions about what pressure I should be running? [I'm 190lbs, have no bags or anything on the bike and only ride one-up.]

Thanks for any help.
 
You have a couple of options.

Rebuild the forks, as in new springs and oil.

I'm on the larger end of the scale, also on a 1000, but I used Progressive springs in the forks, and 20 weight oil. No air.
Or just change the fluid and run some heavier oil in the forks.
many shops will use 5 or 10 weight oil, try something heavier.


As to the air in the forks, some here, me, will say no air, others use the
air feature in the forks.

By the way, you only replaced one fork leg?

If yes, did you at least change the fluid in both to match?
 
Change to Progressive springs and no air pressure.

It's the only way. The original springs were set up for a 120 pound Japanese test rider, and have had 20-25 years to wilt dangerously.

Air pressure in forks is a rotten, bad idea. It's very unreliable and places way too much stress on those fragile fork seals. Air pressure in forks is a cheap, shameful band-aid for lack of proper suspension setup from the factories.

Ditto on making sure the fork oil and levels match (don't worry much about the quantity of fork oil -- the level of fork oil is what's crucial, and the levels in both legs must match exactly).
 
bwringer said:
Air pressure in forks is a rotten, bad idea. It's very unreliable and places way too much stress on those fragile fork seals. Air pressure in forks is a cheap, shameful band-aid for lack of proper suspension setup from the factories.
Click to expand...

But it just sounds so cool to say "Air ride suspension". :-D

Brad tt
 
Rider weight

Rider weight

I found some Progressive Suspension springs on bikebandit.com for my 78 GS1000. They don't give a rider weight. When I upgraded my SV650 suspension, the first question was how much I weighed. Thoughts?

What brand springs are you all upgrading to? Progressives? My forks are in pieces at the moment so now may be the time for me to get rid of the air system.
 
Thanks for the info guys.

This is my first bike and I'm looking to upgrade to a modern sport bike (likely a GSXR) next spring. So for now I will dump the air pressure to preserve the seals and run the bike for the rest of the season.

Thanks again.
 
TBucket32 said:
Thanks for the info guys.

This is my first bike and I'm looking to upgrade to a modern sport bike (likely a GSXR) next spring. So for now I will dump the air pressure to preserve the seals and run the bike for the rest of the season.

Thanks again.
Click to expand...
If you don't replace the springs and simply dump the air pressure the bike will handle unsafely and be very sloshy and maybe even bottom out the forks. If you do get and install the progressive springs you wont need the air anymore. It's money well spent.
 
Last edited:
Surly said:
I found some Progressive Suspension springs on bikebandit.com for my 78 GS1000. They don't give a rider weight. When I upgraded my SV650 suspension, the first question was how much I weighed. Thoughts?

What brand springs are you all upgrading to? Progressives? My forks are in pieces at the moment so now may be the time for me to get rid of the air system.
Click to expand...

Well, you don't really get a choice in fork spring rates, at least not in springs available for our older bikes, so they don't care how much you weigh.

Other brands may have a few different spring rates available to fit GS forks (Hagon? Race Tech? Hyperpro? Works?), but I haven't researched it.

I use Progressive springs, with longer preload spacers to suit my largeness and fastness... By compressing progressive rate springs, you're using the higher spring rate anyway.
 
Surly said:
I found some Progressive Suspension springs on bikebandit.com for my 78 GS1000. They don't give a rider weight. When I upgraded my SV650 suspension, the first question was how much I weighed. Thoughts?

What brand springs are you all upgrading to? Progressives? My forks are in pieces at the moment so now may be the time for me to get rid of the air system.
Click to expand...

Different times.........well options.

No we don't get different spring rates thru Progressive brand.
Use different weight oil.
I'm over 6ft and 250 lbs, I run 20 weight, no air.
The forks are firm, not spongy or flaccid.
 
Surly said:
I found some Progressive Suspension springs on bikebandit.com for my 78 GS1000. They don't give a rider weight. When I upgraded my SV650 suspension, the first question was how much I weighed. Thoughts?

What brand springs are you all upgrading to? Progressives? My forks are in pieces at the moment so now may be the time for me to get rid of the air system.
Click to expand...

Different times.........well options.

No we don't get different spring rates thru Progressive brand.
Use different weight oil.
I'm over 6ft and 250 lbs, I run 20 weight, no air.
The forks are firm, not spongy or flaccid.
 
I use 10-15lbs in the forks. 155lbs, also with the wife who is another 100.
Works fine for me.
 
bwringer said:
Change to Progressive springs and no air pressure.

It's the only way. The original springs were set up for a 120 pound Japanese test rider, and have had 20-25 years to wilt dangerously.

Air pressure in forks is a rotten, bad idea. It's very unreliable and places way too much stress on those fragile fork seals. Air pressure in forks is a cheap, shameful band-aid for lack of proper suspension setup from the factories.

Ditto on making sure the fork oil and levels match (don't worry much about the quantity of fork oil -- the level of fork oil is what's crucial, and the levels in both legs must match exactly).
Click to expand...

If the quantity of oil you put in is not so important, any idea how you best measure the oil level inside the fork in order to match them both?
 
Longimanus said:
If the quantity of oil you put in is not so important, any idea how you best measure the oil level inside the fork in order to match them both?
Click to expand...

I used a dipstick from a junk car. I cut out a 3" by 3" piece of cardboard, pierced a hole in the middle, then put the dipstick through the hole. The cardboard allows the dipstick to sit on top of the fork tube. The manual for my bike indicates 8.3 oz. of oil per tube. I put 8 oz. into a measuring cup then into each tube. I then used the dipstick to ensure the levels were the same in each tube after adding a little bit more oil.
 
On order

On order

I am going to order Progressives today. Here's a question though, folks mention clapped-out old forks require heavier oil. But I am installing new oil seals and dust wipers, which will increase fork stiction. Would I be wise to drop from 20w to 15w or even 10 oil?

My fork has a factory three inch spacer, do I need this with the new springs or will I lose it and cut a new one to dial in preload?

Incidentally, I weigh about at 160 pounds and push it a just a little when I ride.
 
Longimanus said:
If the quantity of oil you put in is not so important, any idea how you best measure the oil level inside the fork in order to match them both?
Click to expand...

Drain the forks completely, use pre-measured exact amounts when adding back. It's the only way to get the same exact volume of oil in there. If there are any differences in the inside of the forks the oil levels could be different while the volume is the same. It's actually the volume that matters. Pre-measuring is the only way to get it spot on.
 
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