Marzocchi ETA cartridge leg minimum oil levels?

TuckerUK

Just fiddling with my 2006 Marzocchi MX Pro ETA & TAS fork setup.

Regarding oil levels on the ETA cartridge side, does the top of the cartridge body have to be covered? If I go lower than this, cycling the cartridge piston rod doesn’t sound too good (metal to metal contact, although that could just be the oil making an excellent suppressor). ETA works perfectly BTW.

Before anyone suggests it, Marzocchi‘s 135ml per leg spec is useless if you are doing a quick oil change as some of the old oil is impossible to drain from the legs without a full strip-down, so I'm using the old height spec of 45-55mm from top of stanchion.

nicklouse

with the fork compressed having the oil at about top seal level is a fair guess.

TuckerUK

Hmmm, I guessed that too, still not achieving full travel though.

Pretty sure the rebound leg oil level isn't to blame because even running that leg at 0psi (well actually some psi because the leg sucks in air when it extends) doesn’t yield full travel either. 25mm travel unused with my correct preload air, 16mm travel unused no preload air. I didn’t measure it (unfortunately) but when I played around with no spring above the ETA cartridge I got very nearly full travel (not sure whether that’s actually because of the spring rate, of just because of the extra air space having no spring creates). Is running with no spring on the ETA side wise/possible?

nicklouse

yes it is possible. just treat as an air fork.

you still have the ETA spring at the base.

TuckerUK

Righto, I'll experiment some more and try no spring, thanks.

nicklouse

Errm just had a thought there did not do an air only ETA. so maybe an issue.

let me have a look at a cart later.

It might be a TAS issue....

TuckerUK

For the sake of accuracy, I should update the thread to add I've been a complete twat!

I do that sometimes! :roll:

For some completely unfathomable reason, I decided to measure the ETA leg oil level with the cartridge fully extended! Whole different ball game with the cartridge fully compressed (as it would be when the fork is fully compressed)! Doh! No wonder I wasn't getting full travel, hardly any air space at all!

Still some experimenting to do, but I'm down to about 15mm travel unused with 155mm rebound side oil height, and 150mm ETA side. Will try 155mm both sides tomorrow.

All the Marzocchi docs state 135mm oil in each leg.

P.S. The no spring plan was a no go, as to get correct sag I had to run prohibitively high air pressure in the other leg. Still, all good fun experimenting to get a feel for the fork behaviour.

Thanks for your help.

Edit: lol at 'fool', not quite what I wrote!

nicklouse

but with the no spring you need to run air in both legs.

Just been looking at a 150mm ETA cart and it should not make much difference as to how much oil is in it as the orifices are in the lower part of the cart.

I would be looking at the TAS cart for issues.


what travel MX is it?100mm?

TuckerUK

100-120mm.

After further experimentation:

ETA doesn't fully work with an oil level of 55mm below, but 50mm below is fine.

With an ETA leg oil level of 55mm, and no air in the rebound leg, I pretty much get full travel (actually just under 3mm remaining). Putting the required 54spi that my 101kg needs to run 25% sag means I miss out on 16mm of travel, and I think that is an unavoidable consequence of running the positive air pressure I do for my weight. I’ll have to cut down on the dark choccy digestives!

I can’t pressurise the ETA leg because of this version of the fork there is no air valve for that leg.

TuckerUK

Whoa, just had a thought (I'm on a roll here), do Marzocchi do different spring rates for the ETA side? If I could get a stronger spring, I could run less air preload, and then I'd get more travel.

nicklouse

dont think so.

will have a look in the "book"

nicklouse

Mmm the 2006 MX Pro TAS ( full name) with ETA 120mm lists the spring as 5141411/C
while the MX COMP ETA 120mm has a 5141276/C SPRINGS KIT K= 6,50

as you can see there is some difference but the top caps have different numbers but....

Call Windwave in the AM as see if they have something.

TuckerUK

Ah, interesting, 0.5kg harder spring then. I'll give 'em a call tomorrow.

TuckerUK

0.5kg?

Hmm, based on a quick down 'n' dirty test (fork compression with my weight on handlebars over zero air preload fork), I reckon the standard spring is around 71 lb/in, which would equal 1.27 kg/mm.

I wonder what Marzocchi's 'K' measurement refers to?

nicklouse

http://www.engineersedge.com/spring_comp_calc_k.htm

http://www.calculatoredge.com/mech/hspring.htm is better (scroll down).

but I dont know if they are using metric or Imp.

TuckerUK

After some head scratching and a wee Google, it seems they are using N/mm. So that's 34 lb/in versus 37 lb/in. I presume my 71 lb/in result was because I didn't take into acount the air pressure building in each leg on compression.