Shock blow out: What caused it?

               Hey everyone... So I had gotten to the track a few times lately with our better weather and all, and the slayer had seemed a bit sloppy in the rear.  The response in the corners was just not was I was looking for, and the rear of the vehicle was just sagging more than I wanted, before it was even under power.  SO...I did the responsible thing and looked up the set up guide on Traxxas' website.  But that's about all I did.  See I ended up having a problem with their set up guide.  First it requires you to drill your pistons, second, the guide is for the slayer and not the slayer pro, and third it assumes that your track is a standard well kept American track.  My truck is none of the above.  Drill out your pistons? Ok, that really is not asking all that much so why do I not just jump right on it and do it? well because of the second issue.  Being a Slayer Pro instead of the standard original Slayer, a lot had changed.  My track foot print was both wider and longer.  In order to achieve this larger foot print, it appears they just put in roughly an additional 30mm to the chassis.

So I am not exactly sure what this did to the weight distribution, but my best educated guess is that there is a majority more weight sitting on the rear than on the front, seeing as this empty space comes right after the front shocks.  Definitely explains the massive sag and lack of responsiveness.  But now I am back to square one with the "set up guides" and will have to pave my own path.  I did a lot of asking around, I love to get opinions, even if I can make a rather close educated guess, because you never know if you may get an adverse affect you do not know about.  The answers, of course as expected, varied extremely so.  I got everything from "just tighten your stock suspension preload" to "drill more holes in your piston and run 50k diff fluid".  Of course any of these could potentially work, but I didn't want to take the extreme options with out having a good explanation as to how it was not only beneficial but would not put increased pressure or damage on the equipment over time.  What I decided on was trying to stay close to the Traxxas set up guides, with a few minor adjustments via the assistance of a friend also in school at VT for engineering. (Thanks Tony for the help!).  We decided via a few different diagnostics that the shocks needed to have stiffer damping and stiffer springs.  Unfortunately Tony was not available to see the actual track and we had to go off of general descriptions and pictures, so this was still a best educated guess.  So I get to work and rebuild all of my shocks, with the variable valve kit.  I rebuild the Front shocks to the same stock set up, but slightly raise my rear shock oil wt.  The shock springs presented a problem for me though, and I knew this before I put them on the truck, but decided to try them anyways.  For some reason, I am not sure why, perhaps its a common set up for the Revo or something, but for some reason the local hobby shop does not carry the one step up spring rate, or the 2nd or 3rd step springs that are stiffer.....nope, they carry the 4th heavier spring, than the stock set ups.  You know I could do a whole post on the techs and the guys there.  You stand and wait in line, because they have people who "can not come help you" for what ever reason.  Then they act and pride themselves on the "knowledge" they have...but lets get one thing strait...its the knowledge you "should" have.  Very few of the "techs" there are actually capable of telling you how to properly set these vehicles up.  They seem to learn the band aid fixes for something and never really tell you what is properly happening.  They tell you "oh that will be ok" instead of explaining to someone how it works and what they can do to get it into a premium mode.  I have had to spend an insane amount of time doing my research into just finding out how these engines work, and I have come across some very good information to know, that is just never really said at the hobby shops, or because they give me a wrong "fix"....But hey that's just the rant of a parts guy that worked for a much larger industry in the past (Honda, Polaris, Kawasaki, Yamaha - motorcycles, atv's, boats, jet skis.... you get the idea) ....anyways I ended up trying the gold springs from Traxxas just because they were the only ones available and the ones I already owned.  So I get the truck all back together, the shocks assembled with extreme care to make sure there is no "fod" (military term for ya, foreign object debris, because remember "fod kills").  I take the time to make sure there are no air bubbles and then I carefully place my caps on, ensuring that they are not over filled, or under filled, and lastly before placing them onto the trucks I make sure they compress and rebound without any binding.  Well we got about 2 track days on them and I was not happy with the set up, but mostly it was because of the springs I think.  Nose diving off of jumps, things like that.  occasionally I would have issues just because our track was not smooth though...this tells me not only my springs are wrong, but so is my fluids.  Oh well, I just didn't feel like rebuilding the suspension yet, and wanted to get a few more days of this beautiful sun, at the track.  So track day 3 comes around and I have the engine running strong, there are a few other buggies at the track...race time!  Nothing really special but still a blast to see how you hold up around other drivers.  A few tuning points from the transmission became clear pretty quickly, such as how my slipper clutch was much too tight, and my engine was shifting much too early.  But another thing was happening a bit more gradually.  My truck seemed to handle the track in a less capable manner.  Eventually I was getting to a point where my truck would roll over at this one turn in the track unless I took it extremely slowly, so, not realizing that it was my suspension that was causing the issues, I got tired of my "driving inabilities" for the day and packed it up and headed home.  I sit down with the truck outside to start cleaning it off and see a lot of gunk all over the rear shocks and the engine on the block.  "Great...an engine leak, right after I finally get it dialed in"  First thought that comes to mind.  So I start cleaning everything off and realized that the truck "felt funny", and of course investigate.  It became extremely obvious early on that my "passenger side" rear shock was empty...happy: its not an engine leak ... anxious: did I damage my shocks?  Well I just got them apart late last night, cleaned them out as they were completely covered in rocks and dirt, and started to get them back together. 

What seems to have happened is 1 of 2 things.  First for some reason my damaged shock did not move as smoothly, once cleaned up, as the undamaged...but this seemed to have cleared up once I put a different piston from the variable valve kit. I put the original piston back in, and it was still gone? I originally thought the piston was mis manufactured, because it didn't look damaged at all.  But its possible that a very micro piece of dirt was sticking to the side, that I got off when inspecting it, as like I said, it seemed to have cleared up once I used a different piston than came back to it.  Second, its possible that my lower shock caps were not tight enough, or rattled themselves loose enough to blow out.  Luckily I had a few spares I just took one off of my Jato, as its not running right now anyways.

So instead of getting to the track, we got out and had a family short hike, just to get us all some sun!  Hopefully the weather does not get nasty and cold this week as it is supposed to, and we will be able to get back to the track.  I plan to rebuild the shocks back to stock oil, stock spring, and see exactly how it reacted on the track, and then have another diagnostic session, as I failed to mention my stock shocks were improperly built, discovered when I went to rebuild them the first time.  Since this could have had an affect on our original diagnostics, I plan to run a few tanks through the truck on a stock set up (with roll bars and Variable valve shocks) again, and just see what that does.