Marzocchi 48mm CC Forks

[markwoodlief]

Have you changed the fork oil and drained the cartridge as described on this thread? Cause as mentioned, outer chamber oil gets into the cartridge and gets stiffer after some hours... Assume you are correctly sprung (front and rear) with proper sag

Sag is right at the moment for the rear, I have a feeling the springs are too heavy for my weight. I'm going to pull it apart today and see what I see. .. THis thread has been very helpful and will refer to it when I pull this apart today.

 

[Anders]

I'm about to order seals and bushings to do my first service of my 2015 Mazocchi 48 PFP fork. I did change the oil previously, but no bushings and seals yet. I have used the bike approx 40 hours now, and the previous owner perhaps 20 hours.

I'm going to use SKF seals and Innteck bushings (unless someone has a better suggestion).

While I'm at it, I'd like to soften the compression damping somewhat. Now, I run 2.5W Ohlins oil (15 cst) and still I don't use the complete stroke with the compression clickers all the way out.

Does anybody have a suggestion on how to alter the shim stack?
Should I change the midvalve or the compression stack? Or both?
Lost of questions...

 

[GGRider01]

I'm curious what weight of oil is in the forks when they ship from the factory. I bought mine from motocrosscenter in Spain, used by some race team in Spain from what I remember. They're amazing compared to the old open cartridge WP43 forks I was running and I'd hate to botch it all up with something as simple as the wrong oil weight.

 

[Jakobi]

I'm about to order seals and bushings to do my first service of my 2015 Mazocchi 48 PFP fork. I did change the oil previously, but no bushings and seals yet. I have used the bike approx 40 hours now, and the previous owner perhaps 20 hours.

I'm going to use SKF seals and Innteck bushings (unless someone has a better suggestion).

While I'm at it, I'd like to soften the compression damping somewhat. Now, I run 2.5W Ohlins oil (15 cst) and still I don't use the complete stroke with the compression clickers all the way out.

Does anybody have a suggestion on how to alter the shim stack?
Should I change the midvalve or the compression stack? Or both?
Lost of questions...

You could post up the base valve stack and we could make some suggestions. Many found that the OEM beta stack was an improvement over the GG one.

I also think the rebound on the stock fork is far too fast. Thinner fluids increase that issue. I'd suggest firming that up.

 

[Anders]

You could post up the base valve stack and we could make some suggestions. Many found that the OEM beta stack was an improvement over the GG one.

I also think the rebound on the stock fork is far too fast. Thinner fluids increase that issue. I'd suggest firming that up.

Thank you Jacobi!
The base valve stack is (earlier in this thread) stated as being:

This is Marzocchi standard , it's not from any tuner.

Compression
2 x 11 x 0,20
18 x 0,15
20 x 0,10
22 x 0,10
24 x 0,10
26 x 0,15
2 x 32 x 0,15
12 x 0,10

There is also a thread here where GMP have a suggestion for a modified stack.

I have found that when using 2.5W Ohlins oil (this has a viscosity of 15 cst, quite close to the Maxima 5W that a lot of people uses), the rebound is about right for my speed and terrain at 4-8 clicks, which is OK with me. On the OEM oil viscosity, I used around 11 clicks.

As I said earlier, I have the compression clickers all the way out (around 25 clicks if memory serves me right) and still have 40-80 mm of unused travel on a normal day. I would like to end up with using all the travel at say 15 clicks under the same conditions. That way, I have some adjustment either way and can even try my motocross skills when setting the clickers at fully closed (or near).

It must also be noted that I am old and slow, in my typical terrain I rarely get out of first and second gear. I ride a lot of rocks and roots and steep hills.
Sometimes, however, there are some races on a faster terrain where I can hit third and even fourth. Under these circumstances I might need to firm it up a bit, perhaps even moving the PFP away from its current "fully out" position.

I did a search, but could't find a description of the Beta stack (apart from the four strokes). Any links to that one?

 

[barossi73]

+1 the rebound is way too aggressive stock.try slowing the rebound clickers by at least 6 clicks(clockwise)from stock
It will still feel pretty firm but itl beat you up about 50% less through the arms/bars(what makes it feel so stiff),and it will cost you nothing to try.most have pfp set at only 1/2 to 1 turn in from full OUT.then address your comp if its still as big an issue.i found that once i got the reb under control it was firm,but much less tiring,and was more in sync with what was happening out back.

Oops,missed your last post while drafting mine.i see you have already explored your clickers/pfp options.

 

[Jakobi]

15cSt is a good viscosity to be working with IMO.

Given that you are OK with the rebound being where it is I'd leave the midvalve for now and work with the BV. You'll probably find that dropping the 32.15 in exchange for 4 to 8 x 32.1's and maybe a 21mm crossover somewhere between those face shims will be a good starting point.

I'll search for the beta info later.

 

[Anders]

15cSt is a good viscosity to be working with IMO.

Given that you are OK with the rebound being where it is I'd leave the midvalve for now and work with the BV. You'll probably find that dropping the 32.15 in exchange for 4 to 8 x 32.1's and maybe a 21mm crossover somewhere between those face shims will be a good starting point.

I'll search for the beta info later.

Thanks a lot for the advice. Can I use Kyb shims? I have some Kyb shims laying around as well as Racetech shims for Kyb. Or do the Marzocchi use another ID?

According to Paul Thede in the suspension bible a .15 shim is 3.4 times as stiff as a .10 shim so then it would seem that 7x32.1 is approx the same as 2x32.15.

With that in mind, your suggestion replacing 2x32.15 with 4-8x32.10 makes good sense to me. I think i will start out with 5 (or perhaps 6 plus a cross over)? Now I feel that I understand a little bit more.

Thanks again.

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[Jakobi]

That's where I was going. Use .10mm shims to give you more flexibility when adjusting and fine tuning. Perhaps a crossover to give it some more LSC compliance.

All shims in the 48mm Zoke are 8mm ID. KYB only uses 8mm ID on the mid comp.

 

[Anders]

I found the Beta standard stack at the Beta forum. I didn't read the complete thread until now, as it was named 4T and discussed the fourstroke suspension. Anyway, GMP has listed his 2013 RR300's stack in the same thread here.

It's kind of a three-stage stack where the first stage provides some bleed via a 28mm shim. The Beta thread also discusses the reasoning behind this type of bleed as opposed to the GG bleed that has just a 12.1 on top.

I have no 8mm ID shims available, but have started asking around locally. If I cannot find any, I'll just have to wait for shipping from abroad. It's still some days until I have time for doing any suspension work, the coming week I'll be busy repairing the roof of my old workshop.

Jacobi, when you suggested using a 21mm crossover, was that a typo for 12mm or do you suggest to use as big as 21mm as a crossover? Of course, there is quite a difference between 32 and 21 in any case.

 

[Jakobi]

The crossover is a variable. It depends how you set the whole stack up and what you wish to achieve.

I personally don't like to go too small on the crossover as it can give very different feelings depending on the force you hit things. A straight stack (or larger OD crossover) gives a more progressive feeling.

The GG uses a 12mm bleed on the BV. The Beta uses a staged 28, 12 bleed setup so it bleeds less. I think I may have totally removed the bleed on the base in my setup but would need to check my notes to confirm.

 

[Anders]

Haven't received any shims, seals or bushings yet, so no progress here so far. However, I have started thinking about also adjusting the rebound shim stack. I was out on the local MX track the other day, and ended up at 2 clicks out on the front rebound. I also did a enduro training yesterday and left the rebound at 2 clicks. It seemed better than before in a uphill climb with lots of loose 10cm to 20cm round stones with that setting.

So my conclusion is that I am very close to not being able to close the rebound any more, should the need arise.

I'm afraid I didn't order any suitable shims for the rebound, so I'll have to shuffle around the ones I find inside the cartridge.
Should I start out just reducing the bleed or perhaps remove another shim as well?

 

[Jakobi]

You might have some fun with that. Won't be too many shims available in the size you're working with.

Believe stock was
Rebound (from piston)
12x.10 - bleed
20x.10 (2)
18x.10
14x.10
11x 2.5 - collar

A start is to remove the bleed shim, and it makes a decent crossover if you're that way inclined. You'll then want to significantly beef up the HSR portion of the stack.

 

[Anders]

You might have some fun with that. Won't be too many shims available in the size you're working with.

Believe stock was
Rebound (from piston)
12x.10 - bleed
20x.10 (2)
18x.10
14x.10
11x 2.5 - collar

A start is to remove the bleed shim, and it makes a decent crossover if you're that way inclined. You'll then want to significantly beef up the HSR portion of the stack.

EDIT: Yes, My stack was like you describe.

I have now rebuilt my forks, and for some reason, the rebound seems to be faster (less damping) than before. Perhaps lower friction from the SKF seals? or just me that can't tell if it's different? I don't know.

In any case, I have concluded that I need to to something. I would like perhaps 10 clicks more damping from what I have, to be able to place my clickers somewhere near the middle of the scale.

Edit: I have some 20mm x 0.12 shims, so I have something to install in addition to the OEM shims. The question is whether to use one single 0.12 or one 0.12 + 0.10?
According to the math, a 0.12 shim is approx 1.7 times a 0.10 in stiffness.

On the positive side, my compression damping now handles trail trash a little better, while I still would like some HSC less (I think).
I built a stack like this:

28 x 0,10 ( got this idea from the Beta stack)
12 x 0,10
2 x 32 x 0,10 ( replaces the 2 x 32 x 0,15)
21 x 0.10 ( here comes Jacobi's suggested crossover)
3 x 32 x 0,10 ( replaces the 2 x 32 x 0,15)
26 x 0,15
24 x 0,10
22 x 0,10
20 x 0,10
18 x 0,15
2 x 11 x 0,20

I think my next iteration will be to either remove one 32 mm shim from the HSC side, or try replacing the 26 x 0,15 with a 28 x 0,10 (as I have these in stock).

In reducing the compression bleed as described, I would have expected that the rebound would also give slightly more damping. That didn't happen as far as I can tell.

While building and testing stacks, it would have been nice to use some simulation software like the Restackor program or similar. Did any of you measure up the pistons in the Marzocchi and if so, are you willing to share the measurements as used in the Restackor?

 

[Herdy]

Hi
I stripped down the rebound shims stacks and found they were different in each leg (guessing they have been on the floor and just threw back in ?)
i could do with some guidance in the best way to put them back.
hopefully the pictures will explain it better Thanks

Update: have set rebound to standard and altered the cartridge stack slightly...been out today and they are working really good now.
video of one of the tracks i was finding the suspension to harsh

https://www.youtube.com/watch?v=BIxalNGWBe0&feature=youtu.be

 

[Anders]

Update: have set rebound to standard and altered the cartridge stack slightly...been out today and they are working really good now.

That's good news. Would you share how your compression stack was altered? And what oil you are using?

I'm rebuilding my own stacks at the moment. This my second attempt.



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[Anders]

Believe stock was
Rebound (from piston)
12x.10 - bleed
20x.10 (2)
18x.10
14x.10
11x 2.5 - collar

A start is to remove the bleed shim, and it makes a decent crossover if you're that way inclined. You'll then want to significantly beef up the HSR portion of the stack.

Jacobi, you were right. There were 2x 20 x 0.10 shims in the rebound stack in mine as well.

I now removed the bleed and replaced one of the 20 x 0.10 with a 20 x 0.12. I will test this on Wednesday I hope.


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[Jakobi]

Good work Anders.

Quick question to stimulate some thoughts.. What, if any, effect do you think the PFP preload and cartridge pressure have on the rebound stroke?

 

[Anders]

Good work Anders.

Quick question to stimulate some thoughts.. What, if any, effect do you think the PFP preload and cartridge pressure have on the rebound stroke?

That is a good question. I really do not know. But I have read GMP's explanations on the Beta forum where he states that he believes that the PFP is a kind of "cavitation threshold control". If that is the case, I think the PFP will have an impact on the rebound as well as the compression. If you get cavitation, the oil will act as if the viscosity is lower, and that will affect both direction of travel / damping.

 

[Jakobi]

That's one way to look at it and very well could be something. But you would then imagine that with less preload/pressure acting on the cart at full extension that the oil would be more likely to cavitate and as such offer less damping.

However, the oil pressure acting on the cross section of the damping rod and rebound piston would increase with PFP preload (being more noticeable towards full extension). I would expect the more PFP you wind on, the more force will be required to get the damper rod moving, and the faster it will return as well.