Marz Fork Springs

[Guest ratchethack]

Dave, I don't think anyone knows how the stock-issue Guzzi springs measure for sure, though I think your estimates are probably close. That's why I'll be measuring the rate on mine carefully and graphing it out, just as soon as I have my fork apart for the new springs (and new oil). I haven't found a local shop that has the ability to analyze spring rates, but I can sure set up an accurate way to measure them in my workshop. Will do so as mentioned before, so I can look very accurately at the delta between 'em over the full operating range.

 

Looking at the chart and tables in your post #65 in this thread, the Wilbers starting rate is below your guestimated stock Guzzi spring rate, as well as the starting rate of all the others. My concern is that as you pointed out, this would give me excessive static sag. To my way of thinking, this would be fundamentally counter to my objectives. I liked the first (wrong) lbf/in. numbers I came up on the Wilbers a lot better [sigh], but this would seem to make me a chaser of unicorns at this point... Possibly, Todd can find me a Wilbers set with the same curve, but higher start and end rates. Will advise.

[dlaing]

I am not sure if I got it right, but this may indicate the effects or preload, roughly...

Keep in mind that as you add preload the lines in the blue green field remain parallel.

The black line (EDIT, I mean gray line) is supposed to represent Guzzi stock.

And for comparison, if pre-load was added to the other curves, they would rise vertically.

[dlaing]

Maybe the HyperPro is what you want

For my money, HyperPro fork springs are too progressive, but that I am only guessing.

The biggest problem I had with HyperPro is that the rear spring is too firm.

Maybe the front is not bad.

In the argument of progressive vs. linear, the Wilbers seems to be a good compromise.

Yes if it was for my weight, I would want it a little heavier.

Maybe,

8.0 N/mm start rate, and 11.0 N/mm end rate.

But for your weight, I think the

7.0 N/mm start rate, and 10.0 N/mm end rate my be perfect.

What are your sag numbers now?

[Guest ratchethack]

Dave, your last illustration of the preload effect was helpful again, thanks. So were a few more Q & A's with Todd today. The man knows the products he represents, and he knows Guzzi's. I'm putting the Wilbers progressives on order. I'd like to thank you and all the Forum readers for all your contributions as well as for your patience through my "extended Marz fork education" process - but hold on, you're not done yet, and either am I. Next you're gonna be subjected to the results - and after that, we move on to the rear shock... I'm going to make a special effort to keep this as concise as possible, promise...

 

Side note: I've decided to drill out, tap & plug the Marz fork lowers for the dual purpose of making both oil viscosity changes and scheduled oil changes a simple 2 minute operation instead of a hour-long (minimum) chore that puts more wear cycles on all the critical steel-in-aluminum fasteners on the front end. Now that I'm about to open the Pandora's box of meddling with suspension, I figure I might as well make it easy on myself...Will advise.

[dlaing]

So were a few more Q & A's with Todd today.  The man knows the products he represents, and he knows Guzzi's.

...and then some!

Yep, Todd is a career motorcyclist, probably one of the top three fastest in the world on a Guzzi Jackal, and he knows alot about Guzzis, and alot about suspension....more than you or I will ever need to know.

Years ago, Computrack resprung and valved JohnT's Marzocchi Forks for Todd to put on his Jackal.

Todd borrowed my bike to test the springs before he went through the trouble of making them fit his Jackal. Unfortunately, we discovered that John T's forks were threaded for the axle and mine clamped the axle...so, my bike did not help him much. We did notice that the computrack shocks felt totally different when we pushed down on them.

I am not sure how he progressed from there, but he eventually got it dialled in for the Jackal.

Not to many Jackals with upside down forks.

Because Todd is a racer, I suspected he might be down on the idea of progressive springs, but he is a smart guy, and open minded enough to choose a Guzzi over a Hayabusa for his daily ride, and probably open minded enough to see the value of a progressive spring for the type of riding we do.

[Guest ratchethack]

Dave, Roger your comments on Todd. He did a great job of finding me a "standard" matchup of a PCIII map for my engine config. 2 years ago, and has always been an open and encouraging resource. I hadn't considered Wilbers as a source for springs, because I always thought they offered complete shocks only, so thanks for your reference.

 

While progressives would not be Todd's first choice for himself, he's way beyond condemning solutions for others that wouldn't be right for him. His own choices of not only springs, but shocks, tires, engine setup, even his entire bike wouldn't be right for me either. As far as I know, his offer on "bituminous modified footpegs" at this link is still good:

 

http://www.guzzitech.com/Todd-Pegs.html

 

This says it all about the way he rides "the Jackalnator" (Highly modified Jackal matched up to a V11Sport motor) on the road - and that sure ain't me. But I think he has the ability and the wisdom based on a great depth of experience to provide solid advice. After he understood my objectives, he thought the Wilbers progressives would be just about right.