surfercross

Member
Jan 6, 2001
15
0
I was wondering if anybody could explain to me how this new air suspension idea is supposed to work I know that the air is used in place of the spring is the shock just pressurized with more nitrogen than normal or is it more complicated than that I know there are some very intelligent people that use this site. Just curious
 

WhiPit

Member
Mar 16, 2000
236
0
:silly: Don't believe everything you read in magazines......

I know what you're referring to and I have it from a very good source that there is no such thing being tested by KTM - at least, not anything from the suspension company that KTM currently owns.
 

HiG4s

~SPONSOR~
Mar 7, 2001
1,308
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This is right from the KTM website!!!

In the past, we used air forks on KTM’s (no fork springs!) and used very small air chambers, (around 40-45mm) with about 30 psi of static air pressure. Believe it or not, these ‘no spring’ forks could take the biggest hits and jumps without any problems.

Here is the link to the rest of the article.
http://www.ktmusa.com/ugvol11no1/ug16.htm
 

380EXCman

Sponsoring Member
Sep 15, 1999
721
1
:(
 
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WhiPit

Member
Mar 16, 2000
236
0
Dear HiG, surfer and 380.....

Funny how things get switched around when taken out of context.

Notice that what Mr. Rosso actually wrote in his article are the words, "IN THE PAST we used air forks on KTM's".

The forks he is referring to were known as "Muller" air-forks. Yes, they could take any hit - but only once! The second hit was the one that blew all the seals out of the fork!

CURRENTLY, there is no such fork being tested by the factory, as was "reported" by one of the monthly off-road publications.

"OOpppss" :D
 

Jeremy Wilkey

Owner, MX-Tech
Jan 28, 2000
1,453
0
Crow sure tastes bad dosent it! I never followed up on that..Did not even know, but was going man why would WP do that! I'm glad I did not have to entertain such thoughts..

:p
 

BrentBlain

~SPONSOR~
Aug 21, 2000
67
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i thought air in suspension was bad becuase it changes denisity with alititude. Wouldn't it handle different at sea level than like 8000 feet? That's just what i always thought but i am no expert.

-Brent
 

MTRHEAD

Member
Oct 26, 1999
41
0
Do none of you remember FOX AIR SHOX, or are all of you that young?

Back in the late seventies it was very common to use FOX air shox in the rear and remove the fork springs and install air valves in the forks. We ran like very small air chambers in them too.

Guess what. It worked.

FOX air shox were a "must have" item for years. All the factory bikes had them. They were a dual air chamber shock.
 

P_Taylor

Uhhh...
Jun 17, 2000
106
0
Seals have come a long way in the past 20 years.

We use nitrogen cylinders to replace springs in the dies at work. The nitrogen cylinders look like a late 70`s FOX air shock with the mounting holes cut off each end of the shock. They hold 2000 psi of nitrogen with even higher pressures at full compression. They run tens of thousands of cycles before needing a rebuild that takes all of ten minutes to finish.
 

MTRHEAD

Member
Oct 26, 1999
41
0
Seals weren't an issue 25 years ago, so I don't think the would be now.

We did it, it worked and we didn't even realize all the tuning options we had at the time.

I'm with Mace on the weight savings. I'd take a lot of Ti and CF to knock off 12lbs.
 

Jeremy Wilkey

Owner, MX-Tech
Jan 28, 2000
1,453
0
The Fox shocked worked? At the time yes but.. The biggest hurdle I can see is one getting enough intial "preload" and yet not suffering from massive midstroke harshness. A spring is a linear, using a air spring would cause massive problems due to a masive pressure rise late in the stroke. Forks with 12 inches of travel with a high intial pressure (for static ride ht) would encounters some huge pressure..

A shock with a linkage ratio and reduced shaft travel would not be such a big problem as the total volume change would not be so large. An intresting concept but I need to see some ideas . concepts before I give up my springs.. How about we hot wind some fork springs.. That would do it.. We could reduce the amount of wire a good 20-30%..

Jer
 

vern#19

Member
Apr 23, 2000
126
0
Fox airshocks

I ran fox shox on my Maicos they had 2 chambers High preasure 137psi and low preasure 35 if can remember right.The big problem with those shocks was they topped out very harshly and when they got hot they got stiffer.They did work better than the Corta cosos that came on the bike.
 

MTRHEAD

Member
Oct 26, 1999
41
0
Jer- That's because you are looking at the present suspensions physical constraints.

I'm afraid you're going to have to look outside the box on this one.

Fox was able to build a decent system with 70's technology. Someone should be able to build a better system with today's technology, but I would think it would require a dual pressure system like Fox used. KYB built a single pressure shock that did not work as well.

Bump absorption was the main focus back then.
 

MACE

LIFETIME SPONSOR
Nov 13, 1999
441
0
If we have an infinitely large accumulator we get no pressure rise, right? It's all P1V1=P2V2, right? Whether or not you get a pressure spike is dependent on your initial and final chamber volumes.

Let's get stupid.... What if you had sealed damping cartridges separate from your spring air chambers. Now how about using steel sealing rings (like an engine piston) on your air springs with total loss high pressure source. What I mean by "total loss" is that you expect some blow by and you have to recharge your source about as often as you have to fill the gas tank. Let's use the frame for this gas reserviour. A pressure regulating valve maintains the fork spring pressure within a set range. The steel sealing rings are low friction and not prone to stiction under pressure.

If we are really stupid we also use our high pressure source to power our air shifter and our air driven starter motor.

Hey, I'll throw out 100 ideas and 99 are stupid. I'm still looking for number 100.
 

HiG4s

~SPONSOR~
Mar 7, 2001
1,308
0
If volumn is a factor maybe it is time for dirt bikes to take a chapter from BMW front suspension and use a swingarn, linkage, and single shock? I suspose in that instance with the forks only doing steering and not taking any real force they could be very small. If the front shock volumn still needed to be increased it could be done by moving all the rebound damping back to the fork leaving the shock only doing the compressions chores.
Just a thought.
Probably another of those 99 ideas.
 

Jeff Howe

Member
Apr 19, 2000
456
1
Hey Pat, sounds pretty cool too don't it? Pressure relief valves and all. I'm looking forward to more on this stuff. Pretty neat what a guy can accomplish when he puts his mind to it.
 

P_Taylor

Uhhh...
Jun 17, 2000
106
0
I agree , it does look pretty interesting.

If the pressure relief valves take care of heat caused pressure build up and the oil they have takes care of the seal drag then who knows ? If the relief valves work well enough at keeping the pressure right air might work as well as nitrogen?

Looks like Dirt bike mag was right on these being tested , just shows not to trust everything you read on the net.
 

WhiPit

Member
Mar 16, 2000
236
0
:confused: Yeah, right......."don't believe everything you read on the net".

I WAS correct in my assertion that the suspension company that KTM currently owns (WP), is not testing this air suspension!

Jobe' is testing it and just because it's shown as mounted on a KTM does not mean that KTM is testing it. Jobe' somehow got a hold of one of Shayne King's old practice bikes.

Again, don't believe everything you read in magazines. :D
 

Jaybird

Apprentice Goon
LIFETIME SPONSOR
Mar 16, 2001
6,452
0
Charlestown, IN
I think the biggest problem of the early air shocks was the variences in altitude, temp, pressure, etc...seems Jobe is on to something with the pressure relief valves.
In the same issue of MXA you'll find the Enzo Racing "sub tanks". I find those very interesting and I'm very curious what Jeremy thinks of the theory behind them.
 

shed

Member
Dec 9, 2001
40
0
Fournalis already make an air shock for dirtbikes. UK mag TBM tested one a few years back.

They work, they are light, I want one. A Ti spring and aluminium shock body will do for now.
 

Robcolo

Member
Jan 28, 2002
342
0
I've been using an air spring on top of a very light steel spring to achieve an on-the-fly "tuneable" spring rate. Air is added by a plumbed in mini bicycle pump. To avoid the non linear increases in pressure [and resultant spring rate] I'm using an Enzo type subtank-but about 230cc. We ride in Co and Utah and go from 1st gear trials terrain [very soft spring rate] to wide open 6th gear sand washes which require much stiffer rates to keep one upright. It's actuallyworking quite well --just have to keep dust and sand out of the air pump.
 
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