Project Hellraiser 3

Page 30

   
 
 

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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 medium chop.

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 which was 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.

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