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Marzocchi’s new Roco air shocks.....we chose the WC
version with external rebound and high speed compression adjust, bottom
out resistants via Schrader valve at the reservoir head and air spring
preload adjustability. Our chassis to mount and test the shock was brand
new Specialized FSX Trail, with a newish ( modified ) 07 Marzocchi 66 ATA
air fork.
Once the rear shock was mounted the first impressions were
not good, the Roco air shock slurped and gurgled on every compression
stroke, and what could have been thought stiction, was the response of the
damper piston as it slipped through aerated damping fluid, it felt ( and
sounded ) like crap. We also found the detent
ball and spring on the rebound adjuster loose, the grub screw that holds
the ball & spring in place ( situated in the tumbler ) had unwound,
therefore no tension on the ball ( the rebound tumbler will spin
randomly with out it )
It was a good excuse to pull down the Roco WC for a look
see inside....although I didn’t contemplate the service before using
it....having said that Marzocchi are not the only rear shock manufacture
to inadvertently introduce aerated
damper internals, and half the bikes in NZ will have air bubbles floating
around their rear shock dampers anyway.
Back to the Roco WC air, the internals look reasonably
well made, servicing the air sleeve wont be a problem, it unwinds
relatively easy, the damper itself is accessible and all moving
sacrificial parts are replaceable. The Roco air is a big shock, it has an
acceptable amount of volume to retain suspension oil, which also
circulates through the damper shaft and then into the reservoir. The
damper piston is ported and shimmed to control both high and low speed
inputs, compression or rebound, and low speed control is aided by both
external adjusters.
As I mentioned the shock has a large volume, for both
air spring and oil capacity but the separate volume behind the internal
floating piston in the reservoir is small in comparison to other shocks
with reservoirs, and as deceiving as it might be the reduced air pocket
appears to not only control bottom out successfully but resists the
excessive travel inherent in most air shocks.
Shocks with reservoirs need to be stripped completely to
avoid air cavitation, this means the reservoir needs to be accessed, the
FTP removed and oil circulated through the housing that joins both main
shock body and reservoir, the Roco is no different and requires complete,
and airless oil medium replacement for correct operation.
With the air shock mounted back in the bike, the obvious
silence and smooth consistent feel obliterated my initial response of
disappointment early on, and once I was riding the shocks performance
planted a seed of favouritism, and Marzocchi’s design equalled the
best of the air shocks available at present.
Having both a bike park and short down hill trails right
outside the door is a treat when it comes to testing bicycle suspension, I
most often attempt the pedal up to the trail head when riding the DH, if
the bike is a pig, or is not a climber I’ll walk. The Marzocchi equipped
Specialized was a little active but pedalled up the climb ( as far as my
legs and lungs could carry its 35 pound weight ) surprisingly well, ( the
Roco with TST would be more suited to climbing ) the compression
adjustment on both the WC air and the 66 ATA would have been useful too,
but I was too slack and did not intend on racing up the hill anyway, I was
more interested in the Roco WC air shocks ability to take on big hits at
speed.
Which it did nicely on consecutive runs, and as I
mentioned early on it didn’t have the tendency to blow through its travel
like other air shocks, interestingly I used slightly lower air pressures
than the manufactures recommendations so I was pleased to see the travel
indicator ring not pushed to full travel.
The shock performed as well as any other large volume air
shocks, the Roco Air has a 35mm shaft, its bulky and could be an
issue in some frames when mounting ( The Specialized SX Trail required
fettling on the rear stay to accommodate the large diameter shock
shaft/eyelet housing )
The Roco demands high air pressures ( 170 - 210 psi ) in
the reservoir, the shocks correct operation relies on high pressure behind
the IFP….Not to be confused with the main spring Schrader
valve.
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