impact on center of gravity

hello

New be from Montreal
I saw a cherokee the mount braket for the shock on the rear axle were relocated on top of axle and lower control arm mount braket were relocated dead center on front axle.I was woundering the impact it has on the center of gravity or what are the negative impact.I Know it provide for greater clearence.
Sory for scatching english
Thank you
Zzzz the Frenchi

I would say little to none. Alterations to the vehicle centre of gravity are usually caused by shifting large amounts of weight (removal of seats or battery relocation, for instance) or adding/subtracting large amounts of weight (like improving/removing bumpers, adding a winch, or similar.)

While the mod you describe would improve ground clearance, its major impact would likely not be on CG or roll centres, but would be on suspension geometry and how the linkages would react to outside forces. It would be an interesting exercise to see what effect the LCA relocation would have...

5-90

xj95 said:

hello

New be from Montreal
I saw a cherokee the mount braket for the shock on the rear axle were relocated on top of axle and lower control arm mount braket were relocated dead center on front axle.I was woundering the impact it has on the center of gravity or what are the negative impact.I Know it provide for greater clearence.
Sory for scatching english
Thank you
Zzzz the Frenchi

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If you move your lower control arm mounts up, you need to raise you upper mounts up the same amount. If you don't, you will have a lot of brake dive (the front end will nose dive when you hit the brakes hard)

Raising the LCA mounts up will make the ride much less harsh as the angle of the LCAs are not as steep.

Dan

you will gain some brake dive if you move the CA to the center of the axle. the CA's do a better job in the over/under configuration

yotaparts said:

you will gain some brake dive if you move the CA to the center of the axle. the CA's do a better job in the over/under configuration

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What do yu mean over/under?

Dan Turner said:

What do yu mean over/under?

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I think he means the LCA mounted beneath the axle and the UCA mounted above.

Look at the geometry under dynamic conditions. Under braking (or under acceleration, for that matter, especially if it's a drive axle) the axle wants to rotate in the opposite direction from the wjheel rotation. A horizontal control arm attached below (or above) the vertical centerline of the axle is perfectly positioned to resist that movement. For argument, picture it attached at 6:00 o'clock, viewed from the driver's side of the vehicle.

Now picture the same axle with the control arms attached behind the axle, on the horizontal centerline ... the 3:00 o'clock position. The control arm has a joint that's free to pivot where it attaches to the axle, and another where it attaches to the chassis. In this configuration it is useless to resist rotation of the axle -- it just acts like a hinge.

OK...I understand now.On mine, I raised the LCA mountsso that the arm is even with the bottom of the axle tube. This really induced brake dive. Next unforeseen mod was to change the UCA mounts.I had an old RE drop bracket kit, so I used the parts for the UCA frame mounts, with a little re-working and fabbing. Worked beautifully until the rubicon trip. With the frame end lowered, when the drivers front tire got fully stuffed, the pinion yoke rubbed on the UCA, chewing a big gouge in the UCA, and broke the yoke. Changed yoke, took off UCA (and left it off) finished trail and drove home. When I got home, I put the UCA in the bender, to make a little clearance. Now it works great, no more rubbing, with just a hint if anti-dive, better angles, and better clearance.

Dan

Eagle said:

I think he means the LCA mounted beneath the axle and the UCA mounted above.

Look at the geometry under dynamic conditions. Under braking (or under acceleration, for that matter, especially if it's a drive axle) the axle wants to rotate in the opposite direction from the wjheel rotation. A horizontal control arm attached below (or above) the vertical centerline of the axle is perfectly positioned to resist that movement. For argument, picture it attached at 6:00 o'clock, viewed from the driver's side of the vehicle.

Now picture the same axle with the control arms attached behind the axle, on the horizontal centerline ... the 3:00 o'clock position. The control arm has a joint that's free to pivot where it attaches to the axle, and another where it attaches to the chassis. In this configuration it is useless to resist rotation of the axle -- it just acts like a hinge.

Click to expand...

okay before i say what im about to i have a disclaimer : i am not a suspension genius, nor do i have a degree in physics, nor do i claim to know a ton about link suspension setups, altho i do know enuf to understand them and know how they work for the most part.

now, i would like to question what it was you said, in the way that you described moving up the lca made it like a hinge where i would not be able resist the rotation. if we were dealing with a haveing no UCAs then no matter where the lcas were on the axle it would act as a hinge. but having uca's keep the axle from rotating, as u put it, as a hinge. IF the uppers and lowers where mounted on the same horizontal centerline (looking from the front or rear) then yes it would act like a hinge, but if there is any verticle separation between the uca and lca axle mounts, then it will not let the axle rotate like a hinge. however if you didnt repostion the uca mounts then i can see how the castor changing thruout the suspension cycling could cause some sort of problem. the castor change might be what causes the brake dive but i dont know, i havent done that much research on that yet. im not attacking you or any of your ideas, but i would like to be educated on this some more so please explain the faults in my thinking to me.

kolby

Dan Turner said:

Worked beautifully until the rubicon trip. With the frame end lowered, when the drivers front tire got fully stuffed, the pinion yoke rubbed on the UCA, chewing a big gouge in the UCA, and broke the yoke. Changed yoke, took off UCA (and left it off) finished trail and drove home.

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When did that happen? I don't remember you swapping out the yoke and taking off the UCA?

Kejtar said:

When did that happen? I don't remember you swapping out the yoke and taking off the UCA?

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While Joe was rebuilding his engine.

Rabbit and I work like the Penske Pit Crew.

Dan Turner said:

While Joe was rebuilding his engine.

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LOL You did it all quiet to avoid geting any pictures taken didn't you....

Dan Turner said:

Rabbit and I work like the Penske Pit Crew.

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LOL git 'er done

Kejtar said:

LOL You did it all quiet to avoid geting any pictures taken didn't you....

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The pics would have been blurry anyway, because we were moving so fast.

Kind of like trying to take pics of Bigfoot.

Or our 6 minute axle change on Big Sluice.