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Ok Driving me nuts. Any ideas?

Discussion in 'The Garage' started by Grim-Reaper, Oct 9, 2002.

  1. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    When I put my truck together I ramped it about a year later. It pulled a 752 on a 25deg ramp. Limiting factor being Shocks on droop and bumps stops on compression.
    This year I ADDED two leaves in the rear to stiffen it up because it was too soft in the rear. I Put in 1 inch Zero rates on both ends. SAME shocks that have been on the truck since I put the truck together before the first ramping. Truck gained 3 inches suspension hight in rear and 1 in the front. By all my figguring if anything my RTI should have gone DOWN.
    Ramped it on exactly the same ramp at 25 degrees as the first time........839.63 /forums/images/graemlins/confused.gif HOW did I GAIN 87 points when I made the truck have stiffer rear suspension and did not change the shocks?!?!?!?!?!?!
    I rolled around under the truck looking and I cant' figure out how I managed that much better. Granted the front springs had more time to break in but I added a lot of spring rate to the rear set and it should have more than offset that.
     
  2. Depdog

    Depdog 1/2 ton status Author

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    Bigger tires have something to do with it as well. I would also venture that the rear locker is helping out a little as well.

    Depdog
     
  3. Chaz88K5

    Chaz88K5 1/2 ton status

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    ya know what it might be...since you are gettin older and makes it harder and harder to loose weight...maybe you just got a little heaver and its keepin the wheels on the ground /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif..i am just messin with ya....now really i dont have a clue
     
  4. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I agree with Dep and it could be the added height changed geometry and/or center of gravity. It's probably not one thing, but a combination of several things. I wouldn't complain though, those numbers are sweet.
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well the truck did get heavier but the front Zero rates the bump stop still hits at the same spot. THere would be 1 inch less available travel at least. Probably more because I moved the axle forward 1 inch.
    The truck also has a full cage now that should stiffen the body up more so take out some of the frame flex. SO I am kind of discounting the weight because the suspension really should have less available travel now.
     
  6. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    different tire pressure?
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Different tires all together but even so 80+ points from tires?.....A few points I could buy with the tires but 80+!
     
  8. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    Yeah you got it!! Tires can change your score alot. I changed mine by fifty points just changing the tire pressure by 10 lbs. /forums/images/graemlins/eek.gif /forums/images/graemlins/truck.gif
     
  9. Twiz

    Twiz 1/2 ton status

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    Is it makeing the front springs work harder? - maybe.

    Included in the longer wheel-base too I assume.
     
  10. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    Since you lengthened the wheelbase, wouldn't that make you score higher too?
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well the difference is 4" under a tire...what PSI were the tires at the first time versus the second time?

    Also...is the ramp adjustable? I did a little quick math and the 863 on a 23 would be near enough to identical to a 752 on a 25.

    Rene
     
  12. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    The ramp has Three possisitons 20, 25 and 30. VERY well designed ramps so the ramp did not change angles at all. Both times it was on level ground.
    Totaly different tires. I had 32's on it before and it now has 35.s Bother were at Trail pressure of 20 psi on the 32's and 18pst on the 35's. I used 106 as a wheel base both times. I have moved the front axle forward and that got me back up to 106 (Shackleflip moves rear axle forward). That 1 inch is not going to make a 87 point difference. Then there is still the fact the shocks are now too short and I made the rear pack stiffer. I can account for only a few points with the tires.
     
  13. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Strange...but cool/forums/images/graemlins/smile.gif

    I'd have to go with Dep's suggestion that the locker had a lot to do with it then. When my truck was open front and rear it ramped pathetically...as soon as i welded up the rear it did much better. It also really depends on who is running the ramp and how accurately they measure (even the method used)

    Before my 57" rear spring swap I ran my truck up the ramp and the guy running the ramp took a fairly aggressive approach to geting my truck as far up as possible. I'm sure I could feel it doing the 'tip' you feel as one tire leaves the ground. He swears the other three were touching the ground and measured using a carpenter square to find the center of the tire on the ramp and then ran the tape down the ramp. 1065 on a 20 degree. That's 38.8" off the ground for one tire. Using a forklift I was never able to get more than 35" under a tire though so who knows...

    With the 57's I ramped the same ramp but a different guy did the spotting and measuring. He was much more conservative and I felt the truck had more to go when he stopped me. *shrug* The number wasn't as important to me as seeing my limiting factors was and it ramped an 1113.

    Seat of the pants tells me the 57's made more than a 48 point difference...

    Rene
     
  14. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Are you still using the same rims as you had with the 32's. If you went from say an 8" rim to a 10" rims with the same back spacing you should definetly gain some RTI points. First of all the wider rims puts more leverage on the springs, and also the wider track will basically allow the tire to be higher off the ground for the same amount of actual axle flex. The 35's with taller sidewall also have more potential to flex. Raising the rear of the vehicle will also transfer more weight to the front, also the rear springs shouldn't be drooping as much so may have more room to move. Softer springs are not always better.

    Overall, there are a lot of factors involved in determining the RTI of a vehicle, and setting up a ramp in a field and having some guy hand measure the distance is not really an accurate or repeatable method.
     
  15. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Rene,

    Of course to establish a "baseline" you could always have a few different people spot you up the ramp, and have each of them calculate the score. I'm willing to bet that the scores are different! /forums/images/graemlins/smile.gif

    The only other idea I had, was that maybe the extra weight of the tires themselves helps to create more "droop" in the suspension? Perhaps there is enough extra "sprung weight" now to offset the stiffer springs...?

    Just a W.A.G. on my part! I only played with an RTI ramp once.....so I know EXACTLY what my truck can do! LOL /forums/images/graemlins/grin.gif


    Remember that old expression: "A man with a watch always knows the time, the man with two watches is never sure."????
     
  16. Blue85

    Blue85 Troll Premium Member

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    How about the spring rates? Perhaps stiffening the rear got the whole truck to stay a little straighter? When you go up the ramp, the front axle wants to twist while the rear axle wants to stay flat. Soft rear springs would let the front dominate and twist the whole truck more. Stiffening them might reduce the twist of the truck and keep you from lifting that left rear tire until the front was stuffed harder.

    I don't really know, just a thought.
     

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