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abominable z71

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  1. abominable z71
    What ratio is the rear end in your truck? 3.42?
  2. abominable z71
    The best way to think of the shock itself is as a brake for the movement of the spring. Kinetic energy is ultimately converted to heat via friction and dissapated to the atmosphere. Gently apply the brakes and the car comes to a stop nice and smooth over a long distance. Slam on the brakes and you quickly test the lock mechanism on the seat belts. I've talked to fox, king and radflo and they all say the same thing it's not a stiffer ride it's "firmer" lol. Stiff carriers a very negative connotation in the suspension world but firmer implies performance, semantics at work. I've got the rs9000 adjustable shocks all the way around. The lightest setting lets the spring travel further with input and "feels" softer, the trade off is degraded handling and an increase in body roll. one thing for sure, it doesn't matter setting 1 thru 9 the vibration is always the same.
  3. abominable z71
    Shock abosrbers actually damp the spring oscillations. Sorry just couldn't resist after your post about the consul. I know your post was all in fun and so is mine. =) Unless your springs get wetter on bumpy roads. Damp: verb (used with object) 1. Physics. to cause a decrease in amplitude of (successive oscillations orwaves). Dampen: verb (used with object) 1. to make damp; moisten:to dampen a sponge.
  4. abominable z71
    Yeah, I had the tires trued and balanced on the truck, it helped out quite a bit but there's still a vibration starts at 72 peaks at 76 and is gone around 80. It's pretty mild compared to some I've seen and if it was this mild from the start I might have never noticed it but now I know exactly what to look for. It's like a small door ding you only see from a certain angle but once you find it you can't help but notice it.
  5. abominable z71
    I've had this exact same conversation with my dealer. $4k later I've got the vibration down to a minimum. The problem is once you feel it and know what to look for it's all you can focus on no matter how small.
  6. abominable z71
    Simplest terms a thrid order vibration is when the vibration frequency is 3X rotation frequency of the part causing the vibration. Example: tire rotates at 10 rotations per second or 10 Hz, First order vibration detected at 10 Hz is usually a mass imbalance, Second order vibration is detected at 20 Hz, Third order vibration is detected at 30 Hz, and so on.
  7. abominable z71
    The third order tire vibration is always there but even though it can be detected by an accelerometer at all speeds it can't be felt until 72mph, peaks in intensity at 76 mph and falls off at just above 80 mph. The vibration we all feel in these trucsk is always there at all speeds it's amplitude is just so small at other speeds we don't feel it.
  8. abominable z71
    I think the problem with doing an assembly is there is that it can't differentiate whether the tire or rim is the source or both in combination. I'd really love to talk to a design engineer from hunter to talk about the machines capabilities. What I do know, the compression arm can provide a variable force onto the tire up to 1250 lbs, it's resolution is .01 Oz or about 1/4 gram and placement accuracy is +/- .35 degrees. Not sure what it can tell you when it comes to higher order vibrations. I checked the vibrations on the console, seat and steering column at various speeds from 60 to 76 mph always 3rd order tire, checked same speeds in 4th 5th and 6th gear no affect on the vibration. I wish I knew someone with more sophisticated equipment I could borrow to really do some testing and try to narrow down the source. I think even a single channel eva could do it , even though it would be much faster with a 4 channel device.
  9. abominable z71
    I'm running the 4500k morimotos in the stock projectors with Denso ballasts, I'm very happy with the light output from the 4500k. It offers the most usable light without being too yellow and produces more foot candles than the higher K. Everyone looks at lumen output but foot candles is what determines how much light you have per square foot at a measured distance from the source which is really what matters when you're trying to illuminate something. This is where the temperature/color/K rating comes into play which is actually the frequency of the light wavelength the human eyes sees. We see red at 620nm or 400Thz and all colors in between up to violet at 380nm or 780 Thz, infrared and ultraviolet are the wavelengths on either side of the spectrum that we cannot see. Given the same power output from the ballast, the lower frequency waves travel further than higher frequency with identical power. This means the lower K value will have more foot candles the further you move away from the source because the lower frequency light is attenuated less as it passes through the air molecules. This is why infrared works through walls, the low frequency even though unseen by the human eye passes through a wall that visible light waves cannot pass. This is also why lights in the 8k and 10k range are blue and purple and have terrible lumen and foot candle ratings even though they're powered by the same 35 watt ballast. Obviously the better the optics in a projector and higher quality bulbs can help focus more light to where it needs to be. I'm going to open up the head lights and put in the rx projectors and run them with the Osram night breakers which I think are 4200K this should get the most foot candles where they need to be. I want the most light on the road not lights the look cool, function over form if you will.
  10. abominable z71
    Yup the stock projectors are meant for Halogens which do not have the electrode that runs parallel to the arc tube. What you are seeing is the shadow from the electrode. Well that's what I assume it to be anyway
  11. abominable z71
    It is my understanding from the owner of a hunter road force touch that the machine is not capable of diagnosing anything third order, and it cannot do a second order on a wheel/tire assembly only a wheel by itself. It's been a while since I had this discussion with him but I believe this is what he said. Typically 2nd and 3rd order tire vibrations diminish in amplitude compared to the first order and no one worries about them that is until you put it on a truck with a natural frequency that matches it and you get harmonic resonance. Changing the mass of the system can shift the natural frequency and that's probably what happened to the guy that had 5 people in the truck with the arbitrator, when he was told there's no vibration. When I have 4 adults in the cab (roughly 800-850 lbs) There is very little vibration felt. Perhaps I just need to replace the floor board with 1/2" steel plate
  12. abominable z71
    Did replacing the right front fix the vibration?
  13. abominable z71
    "Some people have a perceived vibration" you just think it's vibrating and so does the PICO scope. My guess is the typical PICO reading is a T3. Which I think but can't confirm is a 3rd order tire vibration which really just means that something is vibrating at 3 times the tire frequency, this is why they constantly road force the tires but it rarely solves it because they are not the issue.
  14. abominable z71
    Manufacturing variances should be accounted for in the design of the vehicle. If you know a part you plan on using is going to vary and that variance can contribute a negative effect if out of spec you better account for it or tighten the QC inspection frequency to catch the part before it makes it's way into an assembly. Engineering isn't merely designing something to perform a certain task or sets of tasks it has to account for a whole list of other variables that can affect it's ability to accomplish that task. I understand it's impossible to account for everything that could happen and not cost effective to inspect every single part. But this is not a 250 dollar bicycle from Walmart that you just replace with something else when it provides subpar performance. It's a 50 thousand dollar truck and to tell someone like Paxton he can only be pissed at himself for not taking a $10,000 loss to get out of a poorly built truck is BS. If you've read the posts of people who have traded it in or looked into it, the results are terrible, some dealers will not even consider accepting them as a trade in, or they offer well below a reasonable trade value because they know about the vibration issue in this platform. So even if your truck doesn't vibrate it's value is still affected by it.
  15. abominable z71
    Over engineered is when the design is capable of performing well beyond its working rating for example rated to tow 10k lbs and haul 1.5k lbs but could easily tow 15k and haul 2k and still deliver acceptable NVH levels. Under engineered is when it cannot deliver on it's working rating while still providing acceptable NVH levels. Great I have a truck with a light super stiff frame that can tow 10k lbs but its going to vibrate at freeway speeds when unloaded because the engineers didn't do anything to damp the vibrations transmitted by the stiff frame. Hardly over engineered. I bought a Lexus a few years ago and while we were car shopping we looked at an E class Mercedes. The salesman for whatever reason felt the need to show us how well the door hinges were designed, put the window down put all his weight on the door with it fully open and bounced up and down and claimed they can handle 600 lbs of additional weight with the door fully open. No where in the Mercedes brochure did they advertise this as a feature. That's over engineered. GM did tell me I was getting a truck rated to tow this and haul that while providing a smooth ride with the most quiet cabin, they delivered on this for about 2k miles. Window sticker, brochure or salesman didn't mention the latent vibration feature though.
  16. abominable z71
    The PSD is the power spectrum density . It is what you think, takes the square of frequency divided by the frequency that it occurs. I was more curious as to the frequency which the primary vibration occurs than the amplitude of the vibration to try and narrow down which part could possibly be the source. The readings in the graph were taken at 76 mph. First order vibration at 13.3 second at 26.6 and third at 39.9 and the first order drive line would be 45.5. Taking into account it is just an accelerometer in a phone, mounting, the FFT algorithm and truck speedometer accuracy the results are pretty much spot on for the vehicle speed, small spikes at 13, 27 and 40 and a small drive line vibe at 46 Hz. Its pretty safe to say the vibration is a third order related to the tire angular velocity. To test the app I induced a large drive line vibration by putting a few hose clamps on it and it indeed generated a larger spike and caused a beating vibration when it combined with the 40 Hz what was really interesting is even with a significant amount of unbalance on the drive line the PSD at 46 hz was still nowhere near as large as it was at 40. The tires have less than 10 lbs force variation checked on 2 different machines at different shops they have been trued and balanced on the vehicle (lateral and radial run out were low even before truing) and it continues to vibrate I keep going back to the rear end because its the only assembly that has parts turning at the same velocity as the tires that also have surface contact that could generate something third order that and the front hub bearings it just seems like a bearing issue would have gotten much worse after 15k miles. Assuming the data is accurate what besides tires caould cause it, any thoughts Wrench? A few people claim a fix after replacing the rear some said it was only temp and the vibe came back. It's maddening I tell you.
  17. abominable z71
    There is riding like a truck and feeling the road and there is vibration. So either this road I was on when I took these readings was perfectly imperfect or something is vibrating at 40 Hz.
  18. abominable z71
    Yeah hunter calls it smart weight, but you can turn that feature off. I request it when I have mine done. At the shop where I have mine done the owner let me get up close and personal with the machine and explained the smart weight feature and it does exactly what you suspect and widens the acceptable margin for unresolved dynamic balance. But its a machine like any other and non-detect doesn't mean the same thing as not there but even a static balancer is going to have it's resolution thresh hold and a small imbalance still has to create a large enough moment to overcome bearing friction. All in all it's still an interesting experiment. I think everyone calls it a road force balance because 99 percent of the time its accompanied by a balance but I get what you're saying the force variation cannot be balanced out this is true for any tire vibration second order or higher. The real fact of the matter is numerous trucks do not vibrate and of the non vibrators you can't tell me they all have tires with less than 15 lbs of force variation and perfect dynamic and static balance, there is something else wrong with the ones that shake.
  19. abominable z71
    Well join the dumbass club, I kept saving my settings to position 1 but was using key 2 and it kept resetting so I saved the settings to both 1 and 2 problem solved. When you use the RKE to unlock the truck that's what lets the truck know which key (person) is about to operate it and moves all the positions accordingly. My acura was the same way but the RKE fobs were marked 1 and 2 I should have 2 and 2 together sooner but oh well I'm part of the dumbass club.
  20. abominable z71
    The sets of keys are matched to the memory settings for 1 and 2. One set of key's is paired to the memory settings for 1 and the other is paired to #2. But the fobs are not marked denoting which is which though.
  21. abominable z71
    I'm trying to wrap my head around this one. Not sure that I buy that an assembly or single part can be dynamically balanced but not statically balanced. I would believe the opposite before that. Did the article offer any form of evidence to support this mathematically or at least empirically? Parallel axis theorem doesn't support this claim, the CG for a solid body is the CG. But there are a few equations used in fluid mechanics that that we know work for calculations but are not proven or understood mathematically like the navier-stokes equations that are a millennium prize problem. This would be interesting to check though I'm going to ask Les Schwab if this is something they can do. Perform an RFB on the hunter then check the static if there is indeed a difference how do you fix it would be the million dollar question.
  22. abominable z71
    There's something janky about these new rear ends. Its odd that after 3 years there still isn't aftermarket gear sets available, your only option for gears outside of the 3 OEM ratios is to retrofit using parts from the old 9.5's which I've been tempted to try to see if it makes a difference but 2.5k dollars is an expensive experiment.
  23. abominable z71
    Unfortunately you're going down the road we all know to well. The problem is that the problem is not the tires but GM refuses to look elsewhere. My guess is everyone is get a third order tire vibe on the pico scope which typically points to excessive force variation where as a first order tire vibration is typically dynamic balance or a weight issue moving the tires rotation axis relative to center. I think the problem is in the rear end not necessarily the ring gear though. Possibly poorly machine housings. I'd really like to swap an old 9.5" 14 bolt in and see how it rides compared to the redesigned 9.5".
  24. abominable z71
    What you describe is known as creep, but these are not seeing nearly the radial velocity or temps, Creep is a problem in compressors and turbines with extremely tight tolerances high speeds and high temperatures. We had a turbine compressor touch off at 38000 rpm and obliterate the air end one time not a pretty sight.
  25. abominable z71
    The new hunter road force touch self calibrates every 4 hours, it's usually tech error versus machine error although my RFB numbers changed after several thousand miles, same machine same tech, watched him do it both times. The tire is just rubber that looses its flexibility over time and the thermal cycling probably contributes as well.
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