Stock shim stacks for the Marzocchi Shiver 48 on 4Ts

[Leon_RR250]

Hi!

I started today's practice in the place I described above with 20 out on comp and 18 out on reb and I left it there (PFP at 1 and 5/6 turn in). It was really good and generally this is the setting that it has worked well in many different places (except that I had the PFP at 2 turns in). Any other adjustment from now on will be only on the shock if I can still improve the balance with the front. It is really close now.

Leon

[GMP]

I did some slower more technical stuff yesterday, big rocks, local stuff I ride when not focusing on racing. Fork is stiff but still well mannered enough with less PFP, and I used most of the travel on some big hits. Rear was a bit rough but a lot of that could have been the hard crappy tire I used. It would be nice to have a shock with the adjustable scope of the fork! All to be expected as the best setup for this terrain is a bit too focused for general use, trials tire and very soft setttings F&R.

[celler]

Glen, how much are you changing the PFP between sand and rocks? I'll end up going to Wisconsin and riding some sand this summer so will need some adjustments from my rock set up.

[GMP]

I go from .5 - 1 turn for rocks to 2 turns for sandy stuff, but that is closed course so includes some sharp edge braking bumps and holes. Pure whoops I'd try even stiffer.

[Leon_RR250]

Hi!

Time for new seals (I will install the same green SKFs...) and time for trying the almost stock valving in my forks without the bleed shims on the comp and the rebound stack. It has been generally Ok to Very good (depending on the place) but I feel (after about 35 hrs on this setting) there is room for improvement on the heavier 4T...

Leon

[Leon_RR250]

Hi!

Because of the blown seals I found the opportunity to test ride my WP Cone Valve forks after I resolved an issue with a broken preload spacer. Valving is what I prepared (after two trials) for my ex-250 2T Beta last summer and never tested it before due to the spacer. 0.48 springs in and 350 ml of oil in the outer chamber. WPs are at least 1 level better in average than the Marzocchi from sand whoops to slow rock gardens, being more precise (no wondering in sand), offering a firmer/racier ride without beating the hands. This is one advertisement characteristic for the cone valve which it seems it works in practice. I do not write this here to say how bad the Marzocchi fork is (actually they are very good) or how great the WPs are (they are still not perfect anyway), but to state that there is definitely room for improvement for the Marzocchis, especially on the rebound side. From the information on the other thread that just started here, it seems that I was off on the PFP setting and also on the clicks... I will continue for a while with the WP fork before going back to the Marzocchi and I will still keep the current valving on the Marzocchi to test a bit more.

Leon

[Leon_RR250]

Hi!

After long time using the Cone Valve I put new SKF seals to the Marzocchi and did what dirtbird said about the factory team settings in the other thread about having the PFP at +1 turn in. I remembered that when I was testing my valving I had to go really in for the comp clickers when I was reducing PFP. So yesterday I was really happy with PFP +1 turn and 10 clicks out on both reb and comp (and 370 ml oil as before). Magic! Really good in deep sand with lots of whoops and a short section with clay and embedded sharp small rocks. Smooth and controlled action without any deflection. This PFP setting allowed much better reaction on fast sharp hits and the new clicker settings reduced bleed (too much with bleed shims and 20 clicks out previously).

So the high speed compression damping can be mainly controlled with the PFP, not so much by the actual valving/shims. The idea is similar to the Cone Valve fork where the actual damping is happening with the cone valve and spring supporting it and the comp valving (with only 3 x 20mm face shims) are really secondary just for fine tuning.

P.S. There was a good feeling watching live so many top riders on the red Marzocchi forks during the EWC round in Finland.

Leon

[GMP]

Leon,

Good to hear from you. How I beleive this system works is simple, but again I'm sure some will disagree. Its a cavitation threshold control. There can and will always be some cavitation, the higher the pressure from more PFP preload or a stiffer spring the less there is, valving being the constant. PFP preload will affect this primarily in initial travel, spring rate overall. I suppose you could use the analogy that its a lot like actually changing the oil viscosity, because the size and amount of the voids vary. So, if we valve light, that means that a higher PFP preload will provide a more stable fluid with less voids and act like stiffer valving. Comp adjuster will also have more effect at higher PFP settings but by this time it too stiff for rocky stuff overall.

Backing up a little, have you ever noticed that with an OC fork thats set up as good as it gets, the ride quality is a bit rough first thing out in the AM and settles in quickly? I have to climb a gnarly rocky mtn. first to get anywhere, and always noticed this with WPs, 45 Zokes, didn't matter. We used to think that it was the seals need to free up. Now I'm thinking it has always been about the cavitation. First section of bumps the oil is "clean", so damping is stiff, gets softer when the oil is all foamed up, but thats what the basis of all settings and valving have been based on.

Thats why I beleive valving these forks too stiff is just compounded by higher PFP settings. Many are quick to turn it into a KYB with lighter PFP springs and stiffer valving, and it works, but its not the only way and you loose versitility, which is the best thing about this fork.

Next time your forks are apart measure the free length of your PFP springs. From all accounts I have so far they vary from 102 to 108mm, which has a big affect on actual PFP pressure with the same setting.

[dirtbird]

.....

Next time your forks are apart measure the free length of your PFP springs. From all accounts I have so far they vary from 102 to 108mm, which has a big affect on actual PFP pressure with the same setting.

Glenn I think that your last sentence might help us to explain some inconsistency that I have observed between different setsof forks.
Since I do basic periodic maintenance for quite a few Marz 48s, I've noticed that on some, the PFP spring seems to be really loose (inside the PFP-CC unit).
I am always unwind the PFP adjuster before opening the forks but I only took out the spring a couple times (quite a PIA job...) but I am pretty sure that on some, the spring was moving more freely than others. I guess that I will start measuring.

One problem is that the PFP spring itself, is not available from Marzocchi (therefore from Beta as well), hence some cross-reference would be useful.

Do you believe that is the spring setting or that is just inconsistent spring production?

[GMP]

I have had several sets apart and have spring length measurements from others. Your findings are the same as mine. So far mine and a guy in Australia with a GG have 102mm springs, others 108mm. Installed preload via shaft length adjustment is all over the map, and in most cases different from leg to leg on the same bike. As far as the rates being different, the springs I have had out and measured were the same except for length so I would assume they were the same rate. Here in the US we can get PFP springs made by a US spring maker. Some of our tuners here change the springs so there must be a decent source. I had planned to use a set of KYB ICS springs that were shorter, not lighter, to acheive less total preload and a greater range of adjustment but the ID was too small to fit the Zoke piston spring guide washer, and they were a little too close to the shaft for comfort. Maybe Showa springs are a closer fit, not sure, but its being done here for sure. I ended up using the stock springs and adjusting the shaft length for -1.5mm preload(freeplay) with PFP backed adjuster out full CCW. This allows a softer setting for extreme stuff and no compromise on the stiffer settings. Now what was zero turns is about three turns and I'll never use ten! As you can see by the numbers if you have 108mm springs you will not be able to do this and your PFP preload force starts out much higher, so discussing PFP settings between bikes means nothing unless you know whats inside and how its adjusted. I'm pretty happy with the result and there is a big diffference in feel from 0 to 3 turns now. I can ride some some really rough slow stuff, stop and add a couple turns, and feel the fork instantly firm up for some faster sections.

You can remove the tap from the end of the compression unit shaft as an assembly, piston and shims intact, if you want to measure the springs. This will not affect the shaft adjustment. You probably know this having had it apart. It is a delicate assembly with those fine threads, detent ball, circlip, etc. but its worth breaking down and greasing the orings and threads as it turns much easier and smoother.