Marz Fork Springs

[BrianG]

I've reviewed the posts on fork spring setup for the Marz equiped V11 Sports, and have concluded that I'll need the 1.05 kg/mm units, but I can't find the needed numbers for free length and coil diameter, in order to acertain that I'm ordering the correct units. Does anyone have this information??

[Guest ratchethack]

Brian, I'm also interested in this. Do you or anyone else out there know of a good source? Evoluzione Cyclesports (evoluzione.net) was recommended and their Web site invites email inquiries. I got a prompt reply from Ken Zeller, who said he no longer carries anything for Guzzi's. My email inquiry at Progressive was unanswered.

 

Any known source for progressively wound springs (as opposed to straight rate) that are known to work well on our bikes would be appreciated

 

Thanks in advance!

[helicopterjim R.I.P.]

I don't know if the springs in my V10 are stock but they are much stiffer than my V11. I will investigate.

[Janusz]

I've got mine from Lindemann Eng. in California. 1-408-3716151; just call and ask for 1.05 springs for v11s and they will send you a perfectly matched springs for Marz. forks.

 

If you want to do only one, most important upgrade for your suspension that is the one. Do not forget to back down all the dampings and then set them up carefully avoiding overdamping - the most common mistake made by majority of people. You will find out that you will need more rebound damping on your front though.

[Janusz]

As far as progressive spring I think it would be a mistake. The regular spring works better and 1.05 for a heavy klotz like me is perfect.

[dlaing]

http://www.guzzitech.com/V11SForkSprings_Jason.html

says the FZ1 springs work and are 1/4 to 1/2 inch longer

 

 

http://www.racetech.com

Part number FRSP S373210

RT FRK SPR 36.7x34.5x315 1.0kg

$109.99

 

What is the source for the rear shock spring?

LE?

[BrianG]

I'm looking for straight-rate springs, too. I've done quite a bit of work with Max, at Traxxion Dynamics. He can be a bit acerbic at times but he knows his stuff. His fork springs are superior!

 

I've had him do the fork revalving/springing for my old VFR and for my 900RR, and supply the Penske shock, and the difference from stock was nothing short of incredible.

 

If sprung properly, the fork action is wonderful... if it's wrong it sucks, and progressive springs just feel mushy to me.

 

Picking the right spring is quite easy, it's just a matter of having some to play with, or a table set up from experience. Picking a Honda unit is easy...they have a list. The issue is simply selecting the spring that gives you the desired sag measurements.

 

Valving is another issue, but apparently the Marz units are pretty good. Once sprung properly, minimal rebound damping is set to control "jounce", and I leave compression damping basically off.

 

I'd just like to order the springs now... before the bike arrives on it's sojourn from Pennsylvania!

 

So I needed the numbers!!

 

Thanks dliang!!

[Guest ratchethack]

Great info & interesting comments. I respectfully request additional arguments against progressively wound fork springs.

 

Here's my deal on fork springs. I suffer no illusions about chasing "boy racer" track performance. Compared to some of the local exotic and pseudo-exotic Krotch Rocket mounted Kommandos that scream past my left ear around blind curves in the mountains(!), my Guzzi Sport is more of a Kenworth, and I'm more of a Geezer-Sport with neither much ability, nor inclination to become a knee-dragger. Recognizing this, I tend to humbly ride well within both the Guzzi's limitations and my own, per the sage advice of "Squint" Eastwood (circa 1970?).

 

I weigh 175 lbs., so I'm moving up to .8 - .9 kg/cm, not anything near 1 kg/cm. Truth be told (ego now completes exit stage left ), my fork spring needs are driven by a real-world 99% bias toward horribly boring old "normal" road use, as I probably spend less than 1% of my riding time on roads where I actually pursue anything resembling "sporting" performance. Since my future riding itinerary specifically EXCLUDES following any of the local squids over the armco, I won't be setting my chassis up for that 1% of "sporting" road at the cost of enduring racing-harsh pounding for the remaining 99%. So yeah, maybe I'm suffering from Old Guy syndrome, but I'm afraid that dreaded word of scorn, *compromise* is called for here. Hey - let's face it, chassis set-up is ALL a personal blend of compromises, is it not?

 

I've put Progressive fork springs in 2 previous bikes with very favorable results overall. In both cases, it transformed the bike in a wonderfully positive way once I got the fork and the rear-end set up properly. Though I haven't needed to before with progressive springs, to eliminate excess "sponginess" I reckon I can always go up to the next higher viscosity fork oil to get my compression & rebound damping adjusters in a more effective operating range, if need be.

 

So anyone want to take some more shots at progressive springs? C'mon, pile on! Anyone actually try them on their Marz-equipped LeMans or Sport (or variant)? All experienced thoughts on this are most welcome!

 

Thanks in advance!

[dlaing]

I have some inexperienced thoughts.

So speaking out of here:

1) Progressives are THEORETICALLY superior if well engineered.

The problem is that they are never built correctly.

Ideally the progressive spring would create an initially high sag number of maybe 1.1" and it would bottom out with the same force as it would take to bottom out a straight rate spring offering maybe, a 0.5" sag.

So for a 200 lb rider, we might be talking a progression going from .60Kg to 1.10Kg/mm.

But the progression must be true. ie half way through the stroke the spring should be at about .85Kg/mm.

Sorry my math is not great, so don't take these numbers as gospel, especially since I am only being theoretical and your mileage will vary.

2) That being said, there are some gotchas.

a)The damping will not be progressive in a telescopic fork, so you will be over or under damped depending on where you are in the stroke.

b)The forks already have a progressive effect from the air inside the fork, so there is no need for progressive springs!!!

If anything, I have suspected that our forks are overly progressive, and I was considering lowering the oil level to allow for greater room for the air to expand.

How low can we go!?

 

 

Any thoughts?

[Janusz]

I think your theoretical explanation is right on the money dlaing, but what really matters, at least for me, is what works and brings desired result and what not.

 

I am a true believer of experimenting and finding out by trial and error when considering any changes to a stock vehicle. All I can say that I've given a try to progressive springs on two bikes before and they both sucked.

 

Only regular spring of proper hardness gives me control and feel I want. I am a true control freak as far as riding/driving is concerned and only the bike which gives me as much feedback as possible will satisfy me. No soft seats, mushy grips, rubber mounted handlebars, flexible footpegs or progressive springs will do.

 

As far as oil levels go I prefer vary its viscosity first and keep the level stock. Again, I do not know or care why but it seems to work better for me.

 

My real pride and joy of seat of the pants adjustments is PC fueling map which took me a long time of minute changes after each ride but the result is truly fantastic. No commercial dyno operator will ever achieve even similar result on paying customer's bike I believe unless he spends all day on your bike perhaps and charges you exorbitant amount of money. He also has to be able and willing to do it.

[BrianG]

I too favor experimentation in things mechanical, and I have found some things seem counter-intuitive. Tangling up With Max, of Traxxion Dynamics, is itself a lesson in counter-something-ness!

 

In the case of motorcycle forks, I have found that using the firmest spring which gives the desired sag numbers...... 20-25% free-sag, and 30-35% loaded sag, with minimum preload.... provides the best feel and responsiveness. The counter-intuitive part of this is that I have found this to also provide the cushiest ride, as well. It is FAR cushier than an under-sized spring preloaded to a high degree.

 

End-point compression progression is another function and feel, and is a consequnece of another independent issue, as Janusz pointed out....... being the air-chamber size.

 

Damping is another separate issue, and it contributes at least as much to the feel of the ride. I'm not certain why this part seems counter-intuitive to a lot of people, but the less damping one can get away with, the cushier the ride will be. That sounds logical to me! The other part of that, that seems counter-intuitive, is that rebound damping is the primary damping of relevance to vehicle handling. Control comes from the application of the gentlest of forces required to maintain tire/road contact. The spring and fork-tube friction contribute quite a bit of compression damping, while one desires as much bump-absorbing compliance as possible, hence as little compression damping as possible. Rebound damping is added just enough to prevent cyclic rebound.

 

So my philosophy is; appropriate spring rate with as few other added forces as possible, to attain the most compliant (cushiest) and best controlled ride.

 

This is how I set up my old VFR, and my current CBR 900RR, and will be for the V11 Sport that's on the truck, somewhere out there! I'm 52yrs old, 225lb (hence the 1.05 springs), and spend the majority of my time cruising around town and some of the outlying side-roads. I spend a little time in the mountain twisties near here, and occasionally have the opportunity to go to the track and spank my 20 yr old son's ass...... (not!!) I want the cushiers ride that I can get, along with great control, because, while I'm old and decrepit, it IS a Sport Bike!

 

Make sense to anyone else?

[Guest Brian Robson]

I was considering lowering the oil level to allow for greater room for the air to expand.

How low can we go!?

Any thoughts?

40668[/snapback]

 

I'm not quite sure why you think that the air would expand. Wouldn't that occur only because of heat? Would the forks get that hot?

Increasing the amount of fork oil will lessen the air gap and therefore add a small amount of preload (which isn't adjustable on the 02 LeMans), somewhat similar to adding a spacer on top of the springs. I wished to increase preload slightly and added extra oil to each leg which lessened the sag.

[BrianG]

Brian, I think you are correct... adding oil brings in the "air-spring" effect earlier, and firms up the end-of-compression-range spring rate. There will be a little effect upon sag because of this shift. Did it have the effect you desired?

 

Does the Sport have preload adjustment? I sure hope so!

[Guest Brian Robson]

BrianG...I used a lighter weight oil as well for the overall movement to be quicker and the extra oil gave a better sag measurement. It also feels better (this being a little ambiguous...."I've changed something, so it must be better/faster/smoother etc").

Over the stretch of road I use, the front is smoother and there is minimal cupping at the end of front tyre life.

[Guest ratchethack]

Ahhhh, great stuff. Thanks fer the input, Guys.

 

A few items in reply:

 

I think we'd all agree that OEM-issue springs are notoriously weak, Guzzis included. On top of this, most are also made from nororiously low-grade spring steel, and therefore are quick to become sacked-out. When we have individuals of shall we say (ahem) more generous "gravitational endowment" than the lower weight rider that mfgr's actually select their spring rates for, these 2 facts lead to a prominent and widespread belief, correct though it may be in many if not most cases, that "all stock springs are crap." I have no doubt that in general, heavier guys always benefit, tremendously so and immediately, from installing quality, higher-rate springs.

 

Though I'm of average weight, I also find that for the most part, I need to go up-rate on springs both front and rear to reach anything close to chassis potential.

 

I agree that commonly available progressively wound springs will be worse than useless to those of more generous heft. I think the reason for this is that for a heavier rider, the initial sag on most improperly-matched over-the-counter aftermarket progressive springs is far in excess of ideal, which entirely destroys chassis geometry, handling, and road manners. It leaves the rider suspended on the last fraction of effective operating stroke - a very poor substitute indeed for a properly matched, beefier straight rate spring.

 

But for a lighter rider, this would not necessarily be the case, as even quality progressive springs are a relatively low-volume item, and tend to also be mf'd for average weight riders. As Dave pointed out and Janusz concurred, the correct theoretical match would be achieved for a heavy rider only with a higher-rate progressive spring exactly matched to the rider's weight. Of course, due to the complexities and vagaries of the motorcycle aftermarket involved here , a perfect match is unlikely outside the purview of a good suspension specialty shop - hence the tendency of both heavy and performance-oriented riders toward more commonly available and easier-to-match straight-rate springs, where you might actually have better than an even shot at getting the operating stroke properly matched to your weight.

 

Dave, when you said,

 

Ideally the progressive spring would create an initially high sag number of maybe 1.1" and it would bottom out with the same force as it would take to bottom out a straight rate spring offering maybe, a 0.5" sag.

So for a 200 lb rider, we might be talking a progression going from .60Kg to 1.10Kg/mm.

But the progression must be true. ie half way through the stroke the spring should be at about .85Kg/mm.

Sorry my math is not great, so don't take these numbers as gospel, especially since I am only being theoretical and your mileage will vary.

 

Allow me to disagree, por favor. A straight rate spring adds it's rated load capacity with every cm of travel, which makes a straight travel/load capacity line on a graph. Progressive springs make a pronounced curve on a graph, where the load capacity increases by (for example) a geometric, or even exponential progression, depending on design. As you pointed out, air in the fork adds a perfect progressive load-carrying capacity to the fork, being a perfect progressive spring itself. It's an exponential curve, if memory serves. But without the ability to charge the forks with additional pressure, the amount of pressure generated from ambient pressure at zero fork stroke to full stroke doesn't add significant carrying capacity to the springs.

 

30 years back, the progressive property of compressed air was used to advantage by dirt and some road riders, who pressurized their (then) relatively small-diameter forks. All manner of air hose linkages between forks and expansion chambers were tried. Ultimately I think this fell out of favor when it was discovered that there was too much compressible volume inside ever-expanding diameter fork tubes (as has been the trend in design since then) to ideally match the spring requirements - that and the fact that larger-diameter forks eventually led to seals blowing out (literally) right & left.

 

Note to Janusz - In pursuit of a less progressive, low-pressure fork, you might consider linked air forks with a remote expansion chamber, or even vent your fork tubes to atmosphere through snubbers, but then you might have to put air filters on 'em to avoid contamination.

 

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 real-world necessity. However, I take exception to the notion that since we already have "unpressurized" fork air as a "working" progressive spring at near-ambient (negligible) pressure, that no further progressive load carrying capacity is needed. At least with pressures low enough to allow today's relatively large-diameter seals to remain intact, it just doesn't add enough load carrying capacity to help the springs very much. Consider that at 0 bar unloaded, and at probably something around .01 bar with the fork fully compressed, air could hardly contribute in any significant way to keeping our forks from bottoming ('specially for you big Guys).

 

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