Rear suspension numbers as measured at ride height with approximately 7.5" of
shaft showing on the rear struts.
I have an alternate position for the rear lower links to try a higher anti-squat
number as well which I tried while we were away at the 2011 KOH race.
After 5 days of driving I noticed this setting seemed to hook up better on
climbs and the front end would not rise up when the front tires encountered an
obstacle. Pretty sure this is the new default setting.
Front suspension numbers as measured at ride height with approximately 7" of
shaft showing on the front struts.
One major issue I have been fighting is with the inner beads burping air.
For these tires to really work they need to be run around 5-6psi when off-road
for maximum traction. Currently I get burping even at 10-11psi and not just when
the rig is all bound up. Even pulling onto an obstacle like Backdoor in JV
which has a nice flat launching area I was getting air hissing from the rear
tires. Before leaving for KOH I grooved the inner bead protector to hopefully
make the tire more flexible.
I also grooved the inner sidewall protector. My mods didn't help at all.
After talking with various people I am now thinking the rim shell just isn't
compatible with these tires based on some measurements I was given. I
think the beads on the PBR's are so thick that they are setting on top of the
inner bead retainer of the rim which would result in much less contact area.
More on this later when I get a chance to do my own measurements.
Just before KOH while doing rig prep I discovered a bent lower link mount bolts.
These were all brand new grade 8 bolts purchased from McMaster Carr with no
country of origin listed on the box.
One other fix I did before KOH was to replace my torque converter bolts with
some low head socket head cap screws so I could get a lock washer under the bolt
head. The original bolts looked like standard grade 8 hex head bolts and
despite the red loctite they kept coming loose. Even with the new low head bolts
I had a minor clearance issue which self clearanced itself after a few minutes
at 4000 rpms.
One of my goals on our
KOH trip was to come up with a go fast setting for the ORI's. Here's my
impressions after wheeling on them for 6 days straight at the Hammers. Tires
were set at 10-11psi the whole week to minimize burping and help hold up the
sidewalls in the desert.
Internally the ORI's
have multiple bypass tubes to change the dampening as the strut collapses. If
you drop the initial ride height down too low you will be riding on the second
compression stage which will result in a rougher ride. Keeping this in mind I set
the struts up so I had 8" of shaft showing when I left Phoenix (which barely fit
out of the garage). It was at this point we discovered I had a defective strut.
We were unable to extend the passenger side strut more than 10" and after some
calls and a test it was determined that the strut was somehow leaking internally
so essentially the lower chamber was filling with oil from the top chamber
causing the strut to hydro lock. Since we were to leave for KOH the next morning
the only thing we could do was reset the oil levels in the strut, hopefully the
leak was slow enough that I could wheel for a few days before the strut travel
was noticeably affected.
For the initial go fast
setting the lower chambers were set at 100psi, slightly less than my first
couple trail rides (120 psi). I was going for softer ride, lower pressure equals
more plush but increases body roll, higher pressure is the opposite. One of the
first things we did when we got out to the lakebed was bomb out to the sand
dunes and back with some razors; I never drove one before and I liked the ride
quality. We made it out there in well under 5 minutes with the throttle mostly
pinned and the independent front and rear suspension soaked up the bumps very well with no jarring or harsh
impacts. My first thought was if an IFS/IRS rig rode like that my solid axle buggy
was going to ride like a!$. We did the same route with the buggy on Sunday
morning and was amazed it rode better than the razors. We were getting some rear
wheel hop on the medium bumps at around 40-50mph so we started playing with the rebound screw,
dialing the screw up helped and we easily picked up 10-15mph in the small to
Despite the monster
truck stance I never felt tippy on the trails or dunes all week and it worked as
good or better than the old rig going up FOH despite not having stickies or
water in the tires. All the other trails we ran were pretty much a cake walk. My
brother in law has raced IFS short course style trucks and he was impressed with
how the shocks worked after witnessing the "tuning" session before we left
(essentially changing pressures). He observed we were using the full strut
travel thru the foot wells and despite them going all the way to the bottom
there was no hard impact, instead you'd get a soft pillow like bounce at the end
of travel. Some people have described this feeling as a
"cloud-o-titties", never having been in a cloud-o-titties I'll have to take
their word for it. the bottoming was a 100 times better than the feeling when an
air bump bottoms or even starts to engage. There were quite a few bumps where we
both flinched on impact only to laugh afterwards after there was no impact.
There has be some sort of velocity sensitivity in the valving because on the trails
it rarely bottomed when crawling but it appeared like we were using all the
travel based on the dust mark on the shaft. Overall I was pretty impressed
with how these things handled both extremes.
When Jack was shock
tuning on Sunday we tried some bigger whoops (2-3 foot deep) and quickly found the struts
limitations. It didn't take much to get the back end bucking. You can do things
to get them to rebound faster at the expense of stability but this is the main
limitation of these things. Honestly I revalved my previous coilovers several
times looking for a sweet spot for go fast and crawling and never really got it.
Having the rear bench complicated things because you could potentially have an
extra 300lbs of people at times so the final valving/shock combo rode kind of
rough on the fire roads. The last time out at JV with the 4 seater I remember
maybe driving 20-30mph in the medium chop to keep the bouncing down, it was way
slower than what we were doing last weekend. I used 3rd gear high range several
times which rarely happens down here due to not having enough road. With the
ORI's I feel like I can outdrive my steering and the new valve theoretically
should be faster than my old one.
I know other people who
ran ORI's in the past who experienced shock fade pretty quick. I never felt any.
It was in the 70's the day we hit the dunes and with the travel time and ripping
around in the sand we were driving hard for at least 3 hours. I stopped after
getting the trans and steering really hot but never felt the shocks fading. Planning on trying some
lower pressures in the lower chamber just to feel the difference in the rocks.
A lot of people had fuel issues on our trail runs. in my case my pump was
overheating due to the hot air from the radiator cooling fan creating a hot
pocket like environment. Relocating the pump in front of the radiator solved the
problem so I just need to come up with a more permanent mounting solution.
I also noticed my fuel cell breather was puking a lot of gas at times, going to
try upping the filter size to keep the breather line from pressurizing.
The last evening of wheeling I made a crazy save on Backdoor
caught on video. I initially thought I turned in the wrong direction
but after watching the video a few times it looks like I held the tires straight
but the drivers side rear tire suddenly grabbed which kicked the rig sideways
and start a roll. I quickly hit reverse and gave it just enough gas to
pull out of the roll. I was totally disoriented due to it being so dark
and I honestly thought we were going onto our lid. When the rig came down
my foot landed on the gas pedal and we shot backwards, in a panic I put the rig
in first, then neutral while I fumbled for the brake pedal. That is about the
worst case scenario as far as impact go and it resulted in some bent strut
mounting tabs. I suppose this is one downside to having the strut be the
bump stop, it is much easier to beef up a lower mounted bump can than it is an
upper strut mounting point.