fishboat

I have a 2001 Bianchi Grizzly hardtail with a Marzocchi Bomber "Z.2 Atom Sport" fork. I searched for the fork air pressure range when I bought the bike a few years ago and never did find it. Wonderful bike, though I'm mostly a roadie. I rode the bike a couple days ago and, as usual, I put 30-35ish psi in the fork. The fork is firm with that pressure, but still has some give.

What psi should I be running?

Crankycrank

There is no exact one-fits-all pressure. You should experiment with lower and higher pressures compared to what you're using now to find out what works best for you. Suspension settings are an individual thing depending on weight, type of riding and what feels best to you.

well biked

Put a zip tie on one of the stanchions, slide the zip tie all the way down to the seal. Carefully (might need someone to assist in holding the bike) get on the bike, get in as normal a riding position as possible with the bike sitting still, and once that's done, measure the distance the zip tie has traveled from the seal. You say it's a 100mm travel fork, so I'd suggest playing around with the air pressure until you have your sag adjusted to about 20mm, or 20% of your total 100mm of available travel. Nowadays, with longer travel suspension, sag is usually set on a fork at about 25% of total travel available.

Doing it this way, you're setting the sag based on your body weight. Also keep in mind the rebound adjustment will play a big role in how the fork "feels" and acts on the trail. Regarding rebound (aka damping), I suggest starting with the setting somewhere close to the middle and then play around with it until it feels and acts the way you want. You don't want it to rebound like a pogo stick, but you also don't want it to be sluggish in rebounding to the point that it's still compressed as you hit the next bump (an imperfect science, obviously, but hopefully you get the idea).

Those old 'zokes from that time period were really good forks, although I preferred their coil spring models (aka coil-and-oil) instead of their air forks. One thing about those old air forks from Marzocchi, the amount of air pressure required was much lower than other brands of suspension forks, so your mentioning 30-35 psi makes sense. They were known for being well built and reliable.

fishboat

Thanks folks..your suggestions will get me where I need to be.

SJX426 

Do a search on your fork. I found a manual for my 2003 SL with complete service and settings guide.

RockHopper_ Sprung_2012_018 on Flickr

veganbikes

I would also suggest getting your fork serviced if you haven't already. Help keep it running well and clean out old goo and grime and replace old seals and make it like new again.

fishboat

Would you have a link to the manual for your '03 model? I've looked for any documentation on the 2001 Marzocchi Bomber Z2 Atom Sport and I'm not finding much of anything. I do see a couple references to the Z2 Atom Race (not sure what the difference it between the Sport and Race model).

fishboat

Know anyone that does service on an old fork like this? It seems like it performs well, no oil leaks and holds air. I'm pretty sure the fork has never seen a rebuild yet.

veganbikes

I don't know anyone specifically other than DirtLabs but there is others out there I just cannot think of anyone at the moment but we had DL build us a shock for an old Brain system and it was fantastic.

well biked

The Z2 Atom Race was a coil spring fork, not an air fork, and had 80mm of travel instead of 100mm. The Z2 Atom Race was pretty much a renamed version of the original Z2 Atom Bomb from a few years earlier. Marzocchi was kind of an old school Italian company that had built motorcycle suspension since the late 1940's, so when they entered the bicycle suspension fork market their forks became known for robustness, smoothness, excellent damping, etc. For a moment, they were the gold standard in suspension forks for mountain bikes, IMO. Not long into the 2000's, they were bought out or something, never really the same it seems. Also, Fox entered the bicycle suspension market in the very early 2000's, and that certainly changed things also.

cobba

Page 14 the 2001 All Models or the 2001 Instruction Manual has air pressures for different riders weights.

Marzocchi manuals: https://public-repository.org/

It says 27–37 psi for a rider that's 155–180 lbs / 70-80 kg

fishboat

DANG!

Serious amount of documentation. Thank you! That's what I was looking for, but nothing close to this came up in my searches.

They made a huge selection of forks..nice stuff.

thx!

cpach

Many local mechanics could likely do it, particularly if it really just needs new dust wipers and oil (I service old Marzocchi forks like this semi regularly), but the expert on these is mtbforksbymark.com