Minimal/No Lift Suspension Upgrade

[KJowner]

Curiosity got the better of me, I've just been looking at suspension pictures to see what's going on. This one grabbed from on here shows it perfectly.

You must be registered for see images attach

If you move the shock relative to the pivot points on the wishbones then you change its position relative to the bump stop as they are both fixed points on the car body. So a boiler plate lift would allow the shock to reach maximum travel before the bump stop hits the top of the upper wishbone.
However a clevis lift will not change the upper limit but will affect the lower end of the stroke, a spring lift should be the same.
At least that's the way I'm seeing it unless someone else has any ideas?

 

[u2slow]

Longer front bumpstop needed... to compensate for the top spacer. Otherwise the problem is the same as no factory bumpstop; the stock shock would bottom out within itself before the arms/knuckle stops moving.

Edit: doesnt matter if its a top plate or a longer fork. More is more, and the coilover assembly gets longer overall (compressed state) either way.

 

[YukimeS]

is there a difference in the rear in the before and after?
If so how much, looks to me if I replace my front springs I should be level

Oh for sure. My old suspension, not being changed for over 120k miles, was sagging bad and bottoming out on even the tiniest bumps. My old bump stops were worn basically flat. So it already had about an inch a half sag from factory. Driving on the new suspension, it definitely feels more level. I haven't done any measurements since, and right now there's snow out the door and I don't feel like freezing my toes off.

Funny enough, I always pull my dashcam footage when I have someone service my Jeep, and the shop guys were saying to each other "is it alright to pull the rake out of the suspension like that?" "You definitely don't want to do it on a truck, but on a vehicle like this it's fine."

 

[u2slow]

"Level" is an opinion on the KJ. The wheel wells are different heights and the body lines are not parallel.

Edit: its also a bit of a teeter-totter game. When you lift the front, the rear typically squats a little.

 

[JustSumDad]

You've got me thinking there, my gut says it's increasing the potential upwards swing so risking shock damage when it hits the end of travel.
I'm off shift today so I'm going to have a look and do some drawing when I get home, to see exactly what's going on when you shift the coil over down.

a spring only lift does change the upward swing but not the total swing. The total travel is unchanged, the max and min locations are unchanged, the system will bottom out and top out in the same location. Thus bump stop alteration is not needed. The difference is where the vehicle rides within the total travel. Such as lets say there is a total travel of 8" and stock the ride is right at the 4" mark then you put in a spring that gives 1.5" lift but with no other changes to the system - then the ride hight is at the 5.5" mark so more upswing ability but the drop out is reduced by the same amount. All that has been done is to trade off part of the down travel for up travel, and as I said, top out and bottom out points are unchanged. Your going to hit a bigger bump better, but may find your high speed crossing of a hole to be a bit more rough as your wheel/tire cannot drop in as far as it could before.

 

[KJowner]

a spring only lift does change the upward swing but not the total swing. The total travel is unchanged, the max and min locations are unchanged, the system will bottom out and top out in the same location. Thus bump stop alteration is not needed. The difference is where the vehicle rides within the total travel. Such as lets say there is a total travel of 8" and stock the ride is right at the 4" mark then you put in a spring that gives 1.5" lift but with no other changes to the system - then the ride hight is at the 5.5" mark so more upswing ability but the drop out is reduced by the same amount. All that has been done is to trade off part of the down travel for up travel, and as I said, top out and bottom out points are unchanged. Your going to hit a bigger bump better, but may find your high speed crossing of a hole to be a bit more rough as your wheel/tire cannot drop in as far as it could before.

Yes, that's the way I thought too, however Tom Mudd the old suspension guru on here was adamant that every lift needed more bumpstop.

 

[JustSumDad]

Yes, that's the way I thought too, however Tom Mudd the old suspension guru on here was adamant that every lift needed more bumpstop.

I have not read his posts, but I am 100% certain of what I said. If the top out and bottom out points do not change the only reason to add a bump stop is to allow for larger tires to prevent rub. In doing so however you are reducing the overall amount of travel.

This is regarding stock length spring upgrade only, that is a spring that is the same length as stock both compressed and relaxed, but with higher spring rate to increase lift.



IF using a spacer or clevis lift, bump stops MUST be adjusted as this changes the geometry of travel vs the mount where the bump stop is.