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Lift Mathematics

Discussion in '80-Series Tech' started by landtank, Apr 14, 2003.

  1. landtank

    landtank SILVER Star

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    With all the 35" questions and do to me also understanding what everyone is saying I wanted to see better for myself how everyone is calculating the amount of lift their trucks have.

    Ok, first we start with a 80 that is completely stock except for the heavy non J springs from OME. At this point I think we can all agree that the truck has lifted about 2 1/2".

    Now we add an ARB BullBar, 12k winch and a second battery. Lets say the nose drops an 1" from the additional weight.

    Now we go out and buy Slee's 1 1/2" front spacers and install them to compensate for the drop in height.

    How much lift do we now have?

    Sorry for sounding like a 4th grade math question.
     
  2. Beowulf

    Beowulf

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    Landtank,

    +2.5
    -1.0
    +1.5
    ===
    +3.0 "

    Theoretical of course.

    -B-
     
  3. woody

    woody Internet Fireman Staff Member

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    IMO, lift is defined by the height of the springs/spacers you install, then qualified by stating you have a ARB/winch which compressed it....

    If I install 4" lift packs in my truck and 2" overstock shackles, that's a 5" lift....350 or inline 6 regardless, winch or no winch regardless....

    Your "raised height" in this case does not equal your lift...

    (too many damn definitions.....lol)
     
  4. landtank

    landtank SILVER Star

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    Raised height Woody...I like that! Now that is something I can understand and apply to my truck as it is sitting now. All these lengthy posts and debate over caster bushings what's needed to run 35s would make alot more sense to me if things were stated in that manner. This would also help everyone when building up their trucks so they could better determine the path of the upgrades. Such as what is exactly needed to run those 35s on their truck depending on what other changes have been made. So anyone (Christo :G) out their who is running 35s on their 80 what is your raised height? And how/where you measured it?

    Thanks
    Rick
     
  5. sleeoffroad

    sleeoffroad Supporting Vendor

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    Again, there is no simple answer, and people have different expectations etc etc. The bottom line with tire fitment & lift is to experiment and limit travel if needed. I have 6" of raised height on the Yellow truck and will still rub the rear tires. They are 315 GoodYear MT/R's mounted on 10" wheels with 3.25" backspacing. Others report that they don't rub with 3" of lift and running 315's on stock wheels.

    The way we normally do it, is choose tire size and adapt the supsension to match. Taking into account how high the customer wants the truck, what it is used for etc etc. We have found the that the system we list as 5" is a good combination in running 35's. It will not rub in 99% of the cases, it is stable on the road, and gives good ground clearance.

    If you measure your truck from the center of the hub to the bottom of the flare, vetrically up, then I can tell you what mine is. We just don't have a stock truck arround right now that I can check.

    measuring this way takes any tire differences out of the picture.
     
  6. landtank

    landtank SILVER Star

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    Thanks Christo for the reply. I measure 23" from hub center to the flare as you described. That is for both the front and the rear. As I've been concentrating on drive line mods the only added feature is a rear Kaymar with single carrier and nothing up front.

    Thanks
    Rick
     
  7. sleeoffroad

    sleeoffroad Supporting Vendor

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    Rick, did you measure straight down to a line extending from the hub or did you curve the tape around the tire?

    Mine is 24.5" in the front and 26.5" in the rear. From center of hub to bottom of flare with a straight measurement. Also note my front spacers are turned down at the moment and I normally raise them by 1-1.5" when on the trail.
     
  8. landtank

    landtank SILVER Star

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    Christo I did have a slight bend in the tape so the actual straight measurement is 22.75". I'm running stock rims with the 315s. I think I'm getting a clear picture as why I'm not rubbing even though I only have the heavy non J springs. Your truck has the bar, winch, 2nd battery, SC and who knows what else in the front and the rear bar and aux gas tank also if I remember correctly. That's a crap load of weight over mine and as the suspension flexes and the weight transfers to one side the extra raised height quickly evaporates as the spring takes on that extra load ove mine.

    Make sense?

    Rick
     
  9. sleeoffroad

    sleeoffroad Supporting Vendor

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    Rick

    Actually the truck has no SC, single battery, but does have a Extreme Air compressor, bumper & 12k Winch.
     
  10. landtank

    landtank SILVER Star

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    Oh...must be one of the many other trucks you have ;). Thanks for taking the time with me. All these extensive posts on what you need and I wasn't having any problems. But with a little luck and the basement finished I can resume my mods in earnest.

    Thanks again
    Rick
     
  11. sleeoffroad

    sleeoffroad Supporting Vendor

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    Rick, it is important to remember that what is problems to some is just par for the course for others. Also, lift is not the only think that determines if tires fit. At some point, more lift will just hurt you and you won't gain anything.

    Also, you have to set your truck up the way it works for you. All the theoretical measurements, ramp testing etc etc means very little on the trail. I had the ShortBus on the ramp, checked if the 40's cleared. Twisted it all the ways we could with the ramp & forklift, and yesterday on the trail it still rubbed the front tire. Nothing a hammer & sawzall will not fix :D

    Just to point out, it is a trail and error thing, but then that is part of the fun.
     
  12. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    "a trail and error thing"

    Christo, did you mean to say that?... 8)
     
  13. sleeoffroad

    sleeoffroad Supporting Vendor

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    Yup,

    sometimes we think the tires don't rub, then we get it twisted up and we rip a flare or mudflap off. We try to experiment a lot at the shop, to make sure that the errors are on our side before we make recommendations. :D