Oleo-pneumatic suspension

JAR · Post by **JAR** » Wed Dec 16, 2009 12:48 pm

Hello,

can anybody tell me what the operating pressure range is for these suspension units, what would you advise as a typical pressure start point for
an 80kg solo rider, riding at a brisk pace ? (79 Darmah SD)

Any additional feedback regarding IKON (koni) units ?

Thanks
Andy

machten · Post by **machten** » Wed Dec 16, 2009 7:02 pm

The AG Strada manual for April 1980 (which I think is the red units as used on MHRs rather than the finned grey ones of the Darmah - I don't know if it would be different) says "Bellows should be inflated to a pressure of 28 - 42 psi and a pressure reading taken."

The trick with these things is because the volume is so small, just taking a reading drops the pressure significantly. In the manual they go on to say:

"Recheck the reading and ascertain the amount which was lost when taking the first reading. In flate the bladder again to a reading which allows for the amount of air which was losy in removing the inflation apparatus. Please note, excessive presuure may damage the bladder and force the damper oil past the seals."

I'm not sure that the pressure is at all relevent to weight and ride. The purpose of the air unit is to seperate the oil and air so that bubbles don't form in the oil reducing damping performance. Setting for weight and ride preferences are more determined by altering the spring preload and/or piston washer diameters between 14.6mm and 15.2mm.

I have Koni's on my Darmahs now and they work really well. I changed to them rather than rebuild my originals because they were cheap and I didn't care about originality much at the time. Some day I'll rebuild the Marzochs, but meanwhile they work well and have never given me any trouble.

Hope that helps.

Kev

Lumpy · Post by **Lumpy** » Wed Dec 16, 2009 8:11 pm

Another way of doing it if you have a compressor in the shed is set the outlet regulator to the desired pressure. As the gauges are notoriously inacurate I have cut the valve stem of an old tube and I set it with a digital pressure gauge. Then put it on the suspension and let the pressure equalise and pull it off quick.
However at the end of the day as you point out machten I don`t know how much a few PSI affects them anyway. I used to pump mine up with a bicicle pump to the "one pump two pumps she`ll be right" mark and to be honest did`nt notice any real difference to doing it with pin point acuracy.

machten · Post by **machten** » Thu Dec 17, 2009 9:12 am

My main point is that air pressure into the bellows over a point is irrelevent to damping performance. The theory of them is that once there is enough positive air pressure to prevent bubbles forming, the Oleas have done their job. The air pressure is nothing to do with direct damping performance. I did the same thing as Lumpy and used a bicycle pump to set the pressure - but setting pressure won't control damping (if at all) like:

1. Washer diameters
2. Oil viscosity

Kev

JAR · Post by **JAR** » Thu Dec 17, 2009 4:09 pm

Thanks for the replies,
mine had 0 psi and I was under the impression that this adjustment was directly related to the damping performance. From your report it seems that there is no significant improvement to be had with the konis.

andy

BEVEL DAVE · Post by **BEVEL DAVE** » Fri Dec 18, 2009 2:47 pm

Ikons (Koni's) work heaps better than std. shocks.

They are worth every cent.

Dave.

Peter Mille · Post by **Peter Mille** » Sat Dec 19, 2009 11:55 am

I've ridden my Mille for about 25 years now, and never ever pumped any pressure in the rear Marzocchi AG Strada shocks....
I know people who did, and all they suffered were leaking shocks....

Kickaha · Post by **Kickaha** » Sat Dec 19, 2009 11:25 pm

BEVEL DAVE wrote:Ikons (Koni's) work heaps better than std. shocks.

They are worth every cent.

Dave.

A lot of that is because the spring rate on the original shocks is crap, you need to measure your sag settings and work out an appropriate spring rate from there

BEVEL DAVE · Post by **BEVEL DAVE** » Mon Dec 21, 2009 11:59 am

Same as any other suspension component regarding the spring rates.

The damping is crap, they regularly leak & to fix a rooted set cost's as much as a new set of shocks that rarely leak & work well.

Dave.

machten · Post by **machten** » Mon Dec 21, 2009 4:42 pm

The damping is crap, they regularly leak & to fix a rooted set cost's as much as a new set of shocks that rarely leak & work well.

Yep, that was my experience too and why I just put Konis on.

Kev

mgh1955 · Post by **mgh1955** » Tue Dec 22, 2009 1:37 pm

Andy,

When I bought new my 1982 SD900 it came with Paoli oleo-pneumatic shocks (unlike the marzocs, no remote reservoir though). They started leaking after 2-3 years. Ended up replacing them with a set of Koni's (7610 series). They are still going strong after 20 years or so with just the one rebuild to replace springs that had got tired. Aside from that everything else was still in great condition

Mick

Kickaha · Post by **Kickaha** » Tue Dec 22, 2009 11:29 pm

BEVEL DAVE wrote:Same as any other suspension component regarding the spring rates.

The damping is crap, they regularly leak & to fix a rooted set cost's as much as a new set of shocks that rarely leak & work well.

Dave.

The damping can be changed with the internal shim stack but you'd have to know what you're doing I guess

$380NZ to rebuild with all new seals,bladders etc compared to NZ$1200 I spent on Ohlins

BEVEL DAVE · Post by **BEVEL DAVE** » Tue Dec 22, 2009 11:41 pm

I have Ohlins too, the Ikons work as well in 95% of situations for not much more than your Marzocchi rebuild costs ($440-ish). As stated they dont leak either, even after lots of years service.
Luckily I didnt pay the Ohlins I have or I would be pissed wasting the money.

I have played with the damping in the shocks & made up fork components to give adjustability.
I have also built modern bikes that have won national championships in a variety of classes so I do know have a clue when it comes to suspension.
Unless originality is the goal I would recommend anyone (customer or otherwise) who pays for the work to be done to just buy the Ikons.

Dave.

sevicke · Post by **sevicke** » Sat Dec 26, 2009 1:43 pm

yip that what i did put the konis on and that fixed it, the old shocks were nakered and i just want a bike that goes well. No point raving on about the brill handling and all the time theirs oil leaking out your back shocks. Shocks are consumables like tyres, they wear out get some new ones.

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