Z1 Light RC2 ETA/ECC tuning
I've picked up a second hand Z1 Light to go on a burly FR/DH hardtail.
I've had a couple of rides on it now, including the Megavalanche qualifier course (25 minute DH run - loads of rocks, loads of roots) and I've got a few issues.
I'm not getting the last 3/4" of travel, despite pounding the bike into the floor pretty damn hard (5' ish drop off a shed roof), so that says less oil.
The rest of the travel is being used a bit too easily, which implies more air pressure to make it more progressive. Or more RC2?? ( I assume its low speed compression?)
BUT small bump is appalling. I ended up stacking at the bottom of one run because I simply couldn't feel my hands (the last mile of trail was a flat out blast over 2" high roots). This is the biggest issue I've got - the fork feels really stictiony. It also got noticeably stiffer over the course of a run - I guess the air heating up?
I weigh 140lb + kit, Currently running 15psi in the air chamber and 2 or 3 clicks of compression. The fork was supposedly professionally serviced shortly before I bought it. I haven't torn it to bits yet - would like to get some idea of correct oil heights before I start...
I basically want it to feel like my coil lyrics (soft spring) which are super plush on the little stuff, but very rarely seem to run out of travel.
I've seen suggestions about removing the remaining coil spring and relying soley on the air spring?? That might sort the progressivity issues (running higher pressure to ramp up faster), but that will probably make the small stuff worse?
Answers on a postcard please!
-If you have a Z1 Light, which has RC2 damping, it does not have ECC. That was several years in the past.
-ETA is not a damper, and it's not for tuning. It's only a "soft" rebound lockout, unlike ECC, which has some confusing iterations, such as a damper with a hard rebound lockout.
All the other symptoms are showing a fork that still needs a service and oil height tuning. I bought my Z1 Light from the classifieds here and the guy that owned it before pretty much reassembled it like a monkey, and it was sticky as hell. I changed the oil, reassembled it properly, and it ran fantastic.
Also, my gf runs an 07 z1 RC2 and she runs no air pressure. In fact, I even removed the coil altogether and she runs only 1-2 pumps of air, which doesn't really register on the guage, and gets proper sag. She weighs less, but she still is in the ball park and nowhere near 15psi. I think I run 20 psi in mine, so something is wrong.
I'd take it apart, put the right oil in it, clean it out (could be sludged because you don't know if the PO actually had it cleaned, or the oil changed out).
Sorry - my bad I meant TAS - the twiddly knob on the bottom of the LH leg to adjust travel.
I'm aware the ETA is not a damper - I just used that to describe the fork, as it is a US only version - the Z1 light Windwave (importer) brought into the UK didn't have ETA.
Certainly a tear down is in order, but it always helps to have a starting point for the rebuild!
Ok, got it. You had some stuff in there that was somewhat conflicting, like a possible low damper side oil level and a high ETA/TAS oil level, but really, I tghink a full teardown, degreasing, and reassembly is in order.
Add a second coil - Marzocchi has a kit that converts to dual coil.
Won't work if he's a superlightweight.
read Jerk_Chicken's 2006 Z1 light rc2 service article
Absolutely brilliant writeup that I refer to whenever I crack my 2007 Z1 open. I can never thank him enough for that write-up.
Couldn't agree more...
Originally Posted by Jerk_Chicken
I weight around 140 too and indeed, I ran my AM1 with Z1 HSCV damper with only the ETA spring... just like 15-20 strokes of a pump and the gauge would not even read.
Setting it up it's a tricky balancing act, though. Don't go too low on the ETA side oil or it will creep up, but if you put in too little, you will not bottom it.
Now, once you have figured the minimum oil level on the ETA, go for the monimum oil level on the damper (look down and check that at full extension the top of the RC2 cart is still immersed in oil.
Set sag with the minimal oil levels you can run and try from there... balance air and oil height on the damper side preferably (to keep the ETA working at it should and remove one variable that could affect your tuning) as this will give you the largest air volume chamber to work with and with the best small bump compliance.
Remember... oil height makes the air chamber larger or smaller. Big air chamber makes a linear fork that MAY wallow at mid stroke or feel buttery smooth. Small air chamber gives a progressive travel that MAY ramp up fast by the end.
Be patient, write down your settings and you'll get a beautiful working fork.
OTOH... your fork may need just a couple clicks off rebound damping. Sounds like it could be packing up. Take a look at that also.
Ok, so I've done the teardown and rebuild.
Took it out for a decent ride yesterday.
Small bump is much improved (LOADS of Prep-M in the seals). The insides & oil of the fork were pretty much mint, so I think the fork was serviced and had new seals not long back, which might explain it feeling a bit tight.
I set the fork up originally as per Warp's suggestions with just enough oil to make the ETA work, and to cover the RC2 cart when bled through.
I needed 20psi in the air chamber to get ~30% sag when in the attack position with riding pack on.
Riding up and down the street showed this set up to be WAY too soft - I could bottom out just punching down on the bars. Eventually added another 30ml of oil to each leg (did both legs as adding that much extra to 1 leg would surely result in travel loss). Didn't hit anything truly unpleasant yesterday - 4' to flat and a few 6' to transition and it was coming within 1/2" of full travel, so that's about right. The fork felt really nice on these hits - I could feel the fork slowing down the impact in a really nice, controlled fashion.
Big problem is that the midstroke feels soggy. Given that the fork is on a hardtail, I end up riding the front pretty hard, and once on the steeps it sits too far in its travel for my liking. It's also a little bit divey. How should I go about tuning this out? The beginning and end of the spring rate I'm happy with, but I'd like to firm up in the middle. More oil would presumably stiffen up the end stroke further, whilst less oil/more air would compromise the small bump?
I'm running 4 clicks of RC2. I tried more, but the fork then started to feel harsh on the chattery stuff.
Overall it's liveable with now, just not yet perfect.
Thanks for the advice!
...and for the hell of it a couple of pics...
For the most part, I treat oil levels differently per leg because air volumes are different due to the different equipment inside each leg. To some extent, the ETA side (especially if you're still running a spring) is a bit more progressive, and small increments of added oil can make a bigger difference. I try to use that side to tune the bottom out, but it can also help the mid range if you add smaller amounts of oil at a time. The air side has a larger chamber, less inherent progressivity, and to make a difference in mid range ramp up/support, it sometimes creates too much progressivity at the end stroke.
I wish I could offer more specific help, but I haven't tuned mine in some years, and didn't follow through with tuning it when I reinstalled it a few weeks ago. My gf's 07 has nearly the minimum oil levels due to her light weight, and she also runs no spring, and just a couple shots of air.