Suzuki Volusia Forum banner

1 - 20 of 54 Posts

·
Registered
Joined
·
1,719 Posts
Discussion Starter #1 (Edited)
Finally just went ahead and tried it after years of debate with myself as to whether it was a good idea or not.

So far I've had it aired up for 24 hours and emptied a full tank of fuel testing it. Handles bumps and cracks better, even a couple nasty ones around here that used to bottom out the fork and get the rear airborne (now I need to figure out how to improve the rear suspension). All in all the front is much smoother. A side effect is an increase in front ride height of .75" @20PSI slightly more at higher pressure. Personally I like the height increase and the extra 3/4" inch of available wheel travel. While it doesn't seem like much I noticed it immediately when I got on, it does seem to improve the steering geometry (there is a noticeable improvement in cornering that I suspect is a combination of the change in rake and trail as well as the more progressive behavior of the fork). At 30PSI the fork does not feel stiffer as one would expect, in fact it takes bumps far more smoothly than stock.

I will post any issues should there be any, but so far there are none. This seems like a winner for folks unhappy with the stock fork's shortcomings.

This is a very easy and cheap mod, no special tools required, and the parts are available at most auto parts stores.

Step 1. Purchase bolt in valve stems for alloy wheels.


Step 2. Remove the fork caps. (easy enough eh?)
Step 3. Select a drill bit the same size or slightly smaller than the bushings in the stem kit.
Step 4. Set the caps upside down on a hard surface, locate the center and drill them.
Step 5. Remove any rough edges.
Step 6. Install the stem kits in the caps. (A dab of gasket adhesive couldn't hurt.)
Step 7. Reinstall the fork caps.
Step 8. inflate to 10 PSI (after a test ride you can increase or decrease pressure as desired. I have mine at 30PSI.)
Step 9. Take a test ride Adjust pressure as needed.



As you can see by the less weathered area the front forks extend a bit when the pressure is upped. This is at 30PSI at 60 they extend fully at lower pressures they extend a little less.
 

Attachments

·
Registered
Joined
·
1,719 Posts
Discussion Starter #3 (Edited)
Yes, Immediately.
Awesome. The bike has never handled or rode better. As I said above now i need to sort out a cure for the lousy rear suspension. As far as I'm concerned the front is as perfect as a cruiser suspension can get. In the works is sorting out plumbing to add a compressor and a deflate valve in my fairing. For the compressor I'm going with a cheapy $10 dollar store unit as it only takes 10 seconds at most to inflate the forks to 60PSI (way overkill). Stripped of it's case it would easily fit where the Suzuki tool box is. So far the trick seems to be finding the airshock fittings like Gabriel uses.

Apologies to all for no pics yet, the stupid uploader keeps crashing. I will get some up just as soon as I figure out why they won't upload.

EDIT: Pics added to the opening post.
 

·
Registered
Joined
·
818 Posts
Great job, I would never have thought of doing this on these bikes.

This was standard on my old V45 Sabre, be careful not to run too high pressures as you may blow fork seals, compressors or service station pumps may overinflate very quickly.

I would use a small bicycle pump like this Tioga Alloy Dual Head Bike Bicycle Pump Gauge Schrader Presta Road MTB 120PSI | eBay

In the end I replaced the springs with aftermarket progressive springs and done away with the air altogether.

As for the rear, mine was terrible, it felt like the rear was bottoming out and therefore bucking on big potholes. The more I increased the preload the worst it got.

I eventually fixed it by reducing the preload on the rear coil to let it soak up the bumps, it hasn't bottomed out once.
 

·
Registered
Joined
·
1,541 Posts
I'm getting a pretty well balanced ride in the rear on notch 3 with the hard Commander II tires.

I'm still mulling over the air system for the front. If I understand the system correctly the aspects to consider are:

1. Spring - rate, and whether intentionally progressive or not
2. Preload of the spring - adjustable by putting in shims on our machines, or a special mod
3. Hydraulic Damping - our adjustment is oil kinematic viscosity
4. Compression preload / damping - air.

I'm just trying to work this out. Based on racetech discussions, a linear rate spring does nicely for bikes, a softer one than stock on touring type bikes to soak up little stuff. I'm not convinced that a heavier bike doesn't like progressively wound springs.

I'm convinced that we have too much damping in the stock system, primarily in the oil. Without replacing the system, less viscous fluid in combination with progressive springs might well give a great ride quality, but offer very poor progression under load, allowing bottoming.

That's where I suspect the air adjustment might be great to have. Now we have the option of less headspace (higher oil level) for greater compression resistance. With an active air pressure control system, a more compliant suspension could be adjusted nicely to give a highly progressive response, providing very comfy level ride, but rapid stiffening up under load (braking - cornering).

I could see something like a progressive spring with somewhat shorter than standard spacer (say 1"), slightly lighter oil than standard (perhaps 10 cSt), plus air. The optimum oil level and air pressure would have to be figured out (past me) or experimentally determined (That I could do).

Seems like a really fun project!!
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #7
Great job, I would never have thought of doing this on these bikes.

This was standard on my old V45 Sabre, be careful not to run too high pressures as you may blow fork seals, compressors or service station pumps may overinflate very quickly.

I would use a small bicycle pump like this Tioga Alloy Dual Head Bike Bicycle Pump Gauge Schrader Presta Road MTB 120PSI | eBay

In the end I replaced the springs with aftermarket progressive springs and done away with the air altogether.

As for the rear, mine was terrible, it felt like the rear was bottoming out and therefore bucking on big potholes. The more I increased the preload the worst it got.

I eventually fixed it by reducing the preload on the rear coil to let it soak up the bumps, it hasn't bottomed out once.
I'm using a cheapy 12V compressor, it's quick but not so quick that I can't dial in the pressure right where I want it.

It's worries about the fork seals and only worry about the seals that's keeping me from plucking the springs entirely. I suspect that air pressure alone would be adequate, BUT the pressure required might very well blow out the seals...doing my homework and investigating the differences between our forks and air pistons....if I like what I see them springs are coming out for further experimentation....our forkseals aren't too expensive right? (I hope)
 

·
Registered
Joined
·
818 Posts
I'm using a cheapy 12V compressor, it's quick but not so quick that I can't dial in the pressure right where I want it.

It's worries about the fork seals and only worry about the seals that's keeping me from plucking the springs entirely. I suspect that air pressure alone would be adequate, BUT the pressure required might very well blow out the seals...doing my homework and investigating the differences between our forks and air pistons....if I like what I see them springs are coming out for further experimentation....our forkseals aren't too expensive right? (I hope)
Every air suspension system I have ever seen is based on a sealed bladder system, I have serious doubts that a seal designed to hold back fork oil that is not under any pressure would come close to supporting the forces required for an air suspension system.
 

·
Registered
Joined
·
70 Posts
I myself am very curious to see how long and if there are any problems with the fork seals, short or long term, due to adding extra pressure in the system.
Please keep us informed, very, very interesting.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #11
Every air suspension system I have ever seen is based on a sealed bladder system, I have serious doubts that a seal designed to hold back fork oil that is not under any pressure would come close to supporting the forces required for an air suspension system.
Yeah, most of what I've seen for air shocks/springs involves bladders, Haven't found a good exploded diagram for air ride forks (I've seen the forks, just not how their internals are designed). An air piston though is an entirely different animal more akin to a steam engine's or a hydraulic piston.

To some extent our fork seals are designed to hold back oil under pressure as there are no vents in our forks to bleed of pressure. The evidence to support this is the fact that with no other modification (aside from adding the valves to the caps) the forks hold pressure. Just like in our engines, as the forks volume decreases during compression, the pressure inside increases. I've no doubts that the sliders and tubes can hold back at least 200PSI without failure, air assist shocks have much thinner shells and add 500 to 1000 lbs. per shock of additional support/lift at around 100PSI for similar surface area (far above our needs). The question falls to the difference in seal design between air pistons not typical air suspension design and our forks. A good example of the force that can be generated with an air piston of similar bore is the actuator piston from the 1969 Roper/White Spot welder at our shop which at 100PSI is capable of 900lbs of compression force according to the builder's plate. The seals on this unit are "O" rings, one on the piston, two on the cylinder. The piston is 1.25".

There's a lot to be researched before I'm ready to make any claims related to ditching the springs entirely, including actually removing them and testing whether it will be reliable. But that's a ways off, at the very least not until I have some spare seals on hand, and have determined that a catastrophic failure will not result in the bike being rendered unrideable (IE> with the forks completely compressed the frame hits the ground) or wrecking. Looking for an elastomeric bumper that will fit inside the fork to at least prevent damage to hard parts and make it capable of limping home if the seals were to fail...might even resort to using valve springs held in place by lengths of hydraulic tubing. I dunno, we'll see where things lead me.

Today marks more than 48 hours of the forks being pressurized (I think. I'll have to double check.). Still at 30 PSI still no leaks after two full tanks of riding on them deliberately choosing rough roads to really give the suspension a workout. Very hard on the rump, even at the lowest preload on the rear the back's ride is to stiff. The front is still awesome. I've discovered riding off a low curb the front makes the transition much more smoothly than stock, the rear still sucks. A tiny bump VS a big thump.

I have pushed the front to 80PSI but wouldn't ride it that way, even putting all of my 260lbs on the front end the forks do not move. This of course leads me to believe it might only take 45 or 50 PSI to support the front end without the springs.....Again much more homework to do before trying it.

More status updates to follow. Any issues will be reported honestly and as accurately as possible. Would be pretty ****ing stupid to claim no problems if it turns out there are, after all if someone else tries it and horrible things happen....Well it wouldn't be good for all involved.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #12 (Edited)
A correction to the above post, today at 2:30 will be 48 hours of having the forks pressurized to 30PSI, so it's not more than 48 yet.

The clock started Oct/01/13 @ 2:30PM.

EDIT: 11am Day 3, Still no issues to report, still holding, still rides nice, still no leaks. Yeah, I know it won't officially be 72 hours till 2:30PM (3.5 hours from now), but I have errands to run.

EDIT: 3:30pm Day 4, and all is well. Still no leaks or unusual behavior.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #13 (Edited)
Oct 6, 3:30pm Still no issues, still holding pressure, still no leaks, still rides well.

On my fourth tank since upgrading, and thanx to unbelievable weather for October will be on my fifth by monday.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #14
Oct. 8, 7PM- Still rides nice still no leaks of any sort at 30 P/SI. Seriously thinking of removing the springs entirely and testing how much pressure is required to run strictly on air pressure. Still wagering it only needs about 40 or 50 P/SI for the front to ride like it does with the spring in. Worst comes to worst I limp home with no front suspension or running the compressor as needed...not the happiest thought for a long road trip, but I won't be taking any any time soon, maybe a short ride into the hills for the fall colors....nothing more than 90 miles either way, maybe 250 or so round trip.
 

·
Registered
Joined
·
1,945 Posts
On my Honda GL500 Silverwing the front shocks have springs with air pressure adjustment recommended pressure is 11-17 PSI.
With Rear shock adjustment range 0-70 PSI.
 
  • Like
Reactions: njvolusia

·
Registered
Joined
·
198 Posts
Oct. 8, 7PM- Still rides nice still no leaks of any sort at 30 P/SI. Seriously thinking of removing the springs entirely and testing how much pressure is required to run strictly on air pressure. Still wagering it only needs about 40 or 50 P/SI for the front to ride like it does with the spring in. Worst comes to worst I limp home with no front suspension or running the compressor as needed...not the happiest thought for a long road trip, but I won't be taking any any time soon, maybe a short ride into the hills for the fall colors....nothing more than 90 miles either way, maybe 250 or so round trip.
i would think this is a bad idea. for the fact "IF" it does fail there will be nothing there for it to fall on and could be a very dangerous situation. i would assume that they would not fail at once but if they did at same time of a serious breaking situation... what then? that would probably be the time they would fail, when you needed the suspension to work at its best. i love the idea as additional support for the weak suspension we have but i find it hard to believe the old Kawasaki (i think that was the bike i had with air assisted forks) didnt have any springs in there at all. i would hate to hear anyone getting hurt trying something like this. only safe test would be on some kind of a suspension machine that put the bike under extreme conditions as it was stationary. please dont put your self in any dangerous situation that we have to send you mail hoping you heal up quickly.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #17
That is definitely a concern and a matter not to be taken lightly. I'm not at all eager to have my second major accident. But, I'm nearly convinced that if they were to fail it would be a relatively slow failure. Still haven't found a good schematic for our forks, the key to determining if they would even fail at all lies in how they are built and sealed. If it's an "O" ring or two and a dust seal like I think it is, pressures in excess of 100 P/SI (higher if the tolerance between slider and tube are tight enough) can be reasonably expected to be held back safely as long as the seals and surfaces are not allowed to get dry.

Still holding at 30 P/SI, still rides awesome.
 

·
Registered
Joined
·
1,719 Posts
Discussion Starter #18 (Edited)
Well ladies and germs, here's the deal (and oh I'm ever so happy). Best exploded images and diagrams say.......Big f'n seal, "O" ring type, clippy thingy, and crud seal...this is great f'n news for your's truly and anyone else dreamin of air ride. I see exactly one weak spot, the clippy thingy. BUT it already holds back the forces of the rebounding fork as well as the pressure from the spring when the bike's on a lift. Simple fix, make or obtain a heavier snap ring to replace the simple wire spring type clippy thingy. By design it is practically impossible to blow out the seal in a spectacular "OH F***!!!!!" manner. With an improved retaining clip it goes to totally impossible. The fork tube and slider are heavy enough as-is to hold back 200 P/SI at least without failing. By thickness I'd estimate failure pressure to be at least 300 P/SI for the alloy slider and closer to 500 P/SI for the tube. (for about the same thickness pressure tanks, air and hydraulic pistons hold back up to 1000 P/SI before approaching failure ratings)


Edit: screw making a snap ring didn't realize just how wide a variety there is of them...easier and cheaper to buy two of them.
 

·
Registered
Joined
·
390 Posts
i would think this is a bad idea. for the fact "IF" it does fail there will be nothing there for it to fall on and could be a very dangerous situation. i would assume that they would not fail at once but if they did at same time of a serious breaking situation... what then? that would probably be the time they would fail, when you needed the suspension to work at its best. i love the idea as additional support for the weak suspension we have but i find it hard to believe the old Kawasaki (i think that was the bike i had with air assisted forks) didnt have any springs in there at all. i would hate to hear anyone getting hurt trying something like this. only safe test would be on some kind of a suspension machine that put the bike under extreme conditions as it was stationary. please dont put your self in any dangerous situation that we have to send you mail hoping you heal up quickly.
I second that. Making suspension components do what they are not designed to do is just a bad idea.
 

·
Registered
Joined
·
1,541 Posts
I'll have to disagree. I've been re-configuring components for decades. Very few one-off racing conversions use entirely "stock" parts. Reconfiguring components is fine and dandy if done with the limitations of the materials and design in mind. And a consideration of what the mod may do to lifespan and safety.

Certainly adding 20 psi air pressure is a minimal thing. 200 psi takes more consideration, of course.
 
1 - 20 of 54 Posts
Top