Marz Fork Springs

[dlaing]

hmmm? I kind of disagree that it adds preload.

I would assume that the air pressure inside the forks is about 1 ATM when the bike is on its side stand, adding no preload.

When you sit on the bike the air pressure builds, and assists the spring.

The higher oil level, like a high compression piston, would result in higher pressure as you approach bottoming out, and if high enough, it would prevent you from bottoming, but you would still hit a

hard air cushion.

Lower oil level might allow for more fork travel if the air is preventing the bottoming, which I suspect it is.

[dlaing]

Dave, your point about the lack of progressive damping to match progressive spring rates is spot-on.  However, you're talking theoretical ideal, and I'm not so sure this is so much of a hard necessity.  However, I take exception to the notion that since we already have the fork air as a working progressive spring, that no further progressive load carrying capacity is needed.  At least with pressures low enough to allow seals to remain intact, it just doesn't add enough load carrying capacity to help the springs very much.

 

OK that's more than enough....It's been raining for how many days now?  And this is gonna continue for how many more days????

 

Ratchethack

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So you don't think varying the air level would help?

 

I like the idea for an air pressure cross over tube. The idea of one tube bottoming before the other bugs me....

 

Fourty Days and Fourty Nights of rain!

edit please excuse my attrocious spelling....should be, Forty days and Forty nights....

[Guest ratchethack]

Yeah, it would be great if you could control the air pressure somehow. If there was a way to do it consistently in the right range, independent of temperature, without blowing large-diameter fork seals, we'd probably all have air forks as an OEM feature. I think that changing fork oil volume to control fork air pressure is a bit of a fool's errand. A few degrees of ambient tempertature change accomplishes much more of a pressure change in the fork than a changing oil volume, without affecting damping valve function in the process.

 

I'm building an ark in my workshop

[dlaing]

I guess it could be worse, and it could all be snow...We are so spoilled her in San Diegocool! I did not realize it, but the link to this image is dynamic and changes...So just trust me when I say that initially the weather looked worse than it does now...maybe.

[Guest Brian Robson]

I think that changing fork oil volume to control fork air pressure is a bit of a fool's errand. 

 

I'm building an ark in my workshop

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I've looked back at my posting and didn't actually state that I was trying to change fork air pressure, rather that by increasing fork oil volume, it would have the effect of lessening air volume thereby preloading the forks.

With your weather causing ark building, the aberration up here means I should be attaching ski's to the Guzzi

[BrianG]

It may or may not surprize you fellows to know that my '86 Lemans has bridged forks with a tire-like air-stem on one. The forks have self-contained damper cartridges inside as well as the spring. The "fork-oil" is simply lubricant (ATF) for the spring to slide on the fork and cartridge, and to lubricate the fork-tube sliding parts. The Owner's manual suggests a pressure of 0-5 lbs.

 

Apparently Guzzi heard this discussion before, tried it, and abandoned it!

[txrider]

It may or may not surprize you fellows to know that my '86 Lemans has bridged forks with a tire-like air-stem on one.  The forks have self-contained damper cartridges inside as well as the spring.  The "fork-oil" is simply lubricant (ATF) for the spring to slide on the fork and cartridge, and to lubricate the fork-tube sliding parts.  The Owner's manual suggests a pressure of 0-5 lbs.

 

Apparently Guzzi heard this discussion before, tried it, and abandoned it!

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Try Dave, help desk at Traxxion Dynamics. He knows suspensions and is friendly and helpful. I've dealt with them before and always got good service and good product. If you can give them the spring specs I bet they can supply springs, front and rear.

[dlaing]

On the subject of progressive springs and the forks, I had my forks apart, and for kicks, reassembled without springs so that I could test how much assistance the air offered....the answer: Not Much at all....Without any oil it took maybe five pounds of pressure to fully compress the forks.

Which leads me back to thinking progressive springs may be a good idea.

Has anyone tried Hyperpro springs or their shocks.

They list the V11Sport for a rear shock, rear shock spring and front springs.

http://www.hyperpro.com

[Guest ratchethack]

Dave, YOU ARE DA MAN!

 

I had given up in frustration on my quest for progressive springs (see prev. discussion in this thread - way back during the time of "the deluge") and was preparing to settle for straight rate springs from Racetech. Racetech expects a stocking shipment on 1.0 kg/mm springs not before next week, and I've been waiting for a couple of months now.

 

After I saw your post, I called the US Distributor for Hyperpro, Micron North America, and talked with Doug. Doug passed the gauntlet of questions I threw at him without a flinch. He's out of the kit (front & rear springs, PN SP-MG10SSC002, which includes their fork oil), for '99+ V11 Guzzi's, but he's putting together a set for me from other stock. The kit is $249. I'll order the set when he gets back to me with confirmation.

 

NOTE: Despite outward appearances from their Web site, Hyperpro progressive springs are NOT a "one size fits all" consideration. For you Big Boys and Boy Racer types, they have higher-rate progressive springs available via special order.

 

NOW THAT'S WHAT I'M TALKIN' ABOUT!

 

Will advise.

[dlaing]

Dave, YOU ARE DA MAN!

Glad someone found this info useful I almost did not post because of the popularity of straight rate springs, and the fear of ridicule.

NOTE:  Despite outward appearances from their Web site, Hyperpro progressive springs are NOT a "one size fits all" consideration.  For you Big Boys and Boy Racer types,   they have higher-rate progressive springs available via special order.

Did the sales guy give an idea what the weight/sport range is on the non-special order springs?

I am about #210, naked and am looking for sporty sport touring firm but compliant, not road racer stiff and I rarely ride two up.

I was thinking a #500 straight rate spring was about right for me.

I am just looking for the rear spring now. (Anybody in San Diego want to save money and split a kit?)

I suppose if I just tell them that, they can set me up right, with something like a 400/600 rising rate spring.

[BrianG]

I just got my Marz forks back from Traxxion Dynamics. They gave up on the Marz damper valves and installed Max's new valves, giving me rebound damping control on both sides, with preset (not variable) compression damping on both sides as well.

They also resprung the forks with 1.05 kg springs.

 

It's a very nice ride, but I can't comment about the before/after differences. I have them do the forks as a matter of course, after experiencing the before/after differences on my old VFR and CRB 900RR.

 

Penske rear shock is next!

[Guest ratchethack]

Did the sales guy give an idea what the weight/sport range is on the non-special order springs?

I am about #210, naked and am looking for sporty sport touring firm but compliant, not road racer stiff and I rarely ride two up.

I was thinking a #500 straight rate spring was about right for me.

I am just looking for the rear spring now. (Anybody in San Diego want to save money and split a kit?)

I suppose if I just tell them that, they can set me up right, with something like a 400/600 rising rate spring.

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Dave, they don't rate their springs except by weight of rider, weight of usual gear carried, passenger/no passenger, and sport riding, racing, etc. When I asked about a chart to look at rising-rate curves, he said, "that's proprietary". Now this put me off a tad, (a false illusion of marketing mysticism applied to hardware just bothers me - Guzzi's excepted, of course - nothin' false about that Guzzi Mystique! ) but I learned enough about what Hyperpro is all about to get an impression that they know their business.

 

One thing I learned from generic research on progressive springs is that progressives give a wider range of load carrying capability than straight-rate springs. I'm looking for the same range rear spring you are. I'd expect that if you gave your weight, type of riding, weight of gear normally carried, etc., they'd probably match you up to the standard rate rear spring, rather than point you toward a higher rate special order spring. (You don't weigh enough. ) Just my take, though. I'd give Doug a call and see if he can earn your interest. 888 963-1212.

[Guest ratchethack]

On the subject of progressive springs and the forks, I had my forks apart, and for kicks, reassembled without springs so that I could test how much assistance the air offered....the answer: Not Much at all....Without any oil it took maybe five pounds of pressure to fully compress the forks.

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See my prevous posts from the era of the deluge. As Inspector Clouseau once famously said, "It is what I am telling you!"

 

BTW - Doug didn't call back, which means he couldn't match up a kit today. Hopefully he'll be calling in the nxt few days...

[dlaing]

... damping on both sides as well.

 

Penske rear shock is next!

cool!

I am glad it worked out.

I am pretty positive that the irregular wear on the front tire is caused by uneven damping right to left.

I'll bet the work they did will work very well.

Mike Stewart has a Penske listed for sale that you might be interested in...see Classifieds.

He was very happy with it after a return or two to dial it in right.

 

 

See my prevous posts from the era of the deluge. As Inspector Clouseau once famously said, "It is what I am telling you!" laugh.gif

I think you are right about the Marzocchis on our bikes. Unless one put a liter of oil in each tube the air spring would not be strong enough to make much of a difference and the seals are not exactly air tight so down hill mountain runs with lots of braking could result in the front losing air and bottoming out.

On the other hand I was looking at the Ohlins R&T manual and they provide a pretty good guide on how to set up the oil level to get progressive damping out of the forks.

Here is a chart of the effects of oil level. Oil level measured from the top, so, lower mm +higher oil level and smaller volume of air.

For Larger graph click here http://www.imageshack.us

[Guest ratchethack]

Hmmmmm......the plot thickens! It seems that over a drop in air volume displaced by only 30 mm of oil, the Ohlins gain nearly 200 kgf of force from compressed air at full stroke. That IS significant, but I have to wonder about what the pressure measurement you took on the Marz forks would be on the Ohlins - the change in pressure over this range? It must be substantial - a LOT more than 5 lb. As you're suggesting, the Marz and Ohlins are entirely different animals.