TEEJ, I have to disagree... its not just one tire going up... The tire that is planted on the ground will sink into the springs. The more its sinks, the greater the angle of the jeep, the greater the chance of flipping. The wheel in the air become less and less loaded and does not sink into its springs.

This is not only true with a left tire vs right tire, but also front tire vs back tire. Why do you think they have winches wrapped aroiund the front axle. Its to pull the axle into the springs, so as to reduce the jeeps angle partially casued by the rear suspension sitting on its springs. The axle in the air won't compress on its own. But since most of us don't have a wench, we just work around that risk.

 

Interesting...a wench to perform that sort of thing... We used to use a winch, but the wench thing has other possibilities....



OK - Lets run with a taller spring on the down hill side to prevent the jeep rolling down the hill from settling too low on the down hill side due to weight transfer.....that certainly does happen.

Um, does that mean you set up your jeeps coils like a circle track racer, with shorter coils on the UPHILL SIDE?



Or - are all 4 coils the same length...so that the UNWEIGHTED up hill side's coils are actually PUSHING the jeep over onto its downhill side?

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Breaking it down-

OK, you are climbing a rock on the diver's side....the front tire is going up the rock, and life is good...

As the front tire goes up the rock, the P side tire is on the ground, and the coil is uncoiling as the opposite side is climbing.

Sounds normal so far, right?

OK - Key question - Is the P side coil un coiling because there's less weight on it to support, or because it is PUSHING the frame up as the D side tire climbs the rock?



Remember, the coils are set to support that corner of the jeep at a preselected ride height and weight....make the corner lighter, and the coil has less to support,and, based upon its spring rate, uncoils more.

As the jeeps coil didn't get stronger, and the jeep' s weight did not change...it is reasonable to conclude that the coil was lengthening because the frame was being lifted...just like if you were merely jacking up the other tire's side in your driveway with a jack, etc.

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OK - So the D-side tire's been climbing the rock, and the P side tire's been on the ground with its coils lengthening as the weight's being lifted from it.

Now...the d-side tire's uptravel is interrupted, say by a bumpstop....or, by a stiff coil that will not compress/allow further uptravel, etc...

NOW we are tipping the jeep to the down hill side, as the FRAME is now rising, instead of just the tire stuffing.

OK - As we are now tipping the jeep's weight BACK to the down hill side, the coil on the P-side will start to compress. If the jeep continues to climb the rock, raising the D-side further and further...the P side can become more compressed, until it is supporting the ride height it was chosen for....and holds up whatever weight it was designed to, etc....

This is where it gets interesting....the break point - depending upon the jeep's set up...it has a 3 dimensional place, somewhere inside the jeep, on the TJ's, it was traditionally about at the radio volume knob...where the center of gravity lives (COG).

Obviously...if you are fat, have special cargo, passengers ,a Saint Bernard bounding about inside the Jeep, that exact COG point moves...but, where ever that exact point ends up BEING...that's the COG we mean.

If the tire's contact patches can be considered to make a box drawn between the 4 tires...and the "knob" ends up passing out of the borders of that box...the jeep will flip over, no matter what tires, suspension, etc...it has....its just physics...when the COG is outside of the support box...the object will tip....period.

If the driver continues up the rock, and the same length bumpstops he had that made the jeep start tipping to the down hill side - will then hit on the down hill side....and the same forces on the uphill side, like the uphill coils' spring rates, wil be pushing back on the down hill side.

Obviously, unless the down hill side gets stronger coils than the uphill side....and you KNEW which side would BE down hill...the jeep will tilt based upon its spring rates...if the uphill side pushed with long coils, it pushed the jeep over more at he down hill side, etc.

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Now - if the jeep had longer coils/more lift height, all around...well, the COG is higher...and, less tilt is required for it to "pass out of the box", and flip the jeep more easily...so - the less lift, the less likely the jeep is to flip....so, shorter coils = more stability.

Stiffer coils might mean more tilt, as the uphill side coils pushed the jeep over to the down hill side harder....and, as weight is naturally transferred to the lower side (IF moving furniture...the guy on the bottom of the stairs with the couch has to carry more weight that the guy at the top of the stairs with the couch, etc...) more....a stiff set of coils uphill, will over power a set of same stiffness coils down hill.

In real life, this is why you should AVOID getting into a side hill position....

Now - about the leverage - if you pick one tire up, you push the other one down...and, the jeep's TOTAL weigh remains the same....

So - if you transfer weight to one side, its less on the other...if you raise the front end to climb a rock with one tire, the weight goes to the other three based upon their positions.

So - bottom line...an airborne tire is airborne for a reason...lets say it hung from too little down travel...and the weight is transferred to the other three tires....they will compress based upon their spring rates....as the total jeep's weight s now on 3, instead of 4 tires, etc. (It did NOT hang, and then transfer its weight...it hung BECAUSE the the other tree tires TOOK its weight, UNTIL it hung...)

Lets look at the one axle with a hung tire...the hanging part is a weight, and, its cantilevered out....unweighting the down side tire by that cantilevered amount....

And - therefore transferring more weight to the tire on the opposite side of the the other axle...like you would on a see saw, front to back though.

A hanging tire acts as a counter weight...cantilevered out away from the compressed side, and will not push the jeep over....its leverage can only be applied in the opposite direction....

...that (Flipping) will only happen if the driver let his COG pass out of his support box.

The tire in the air cannot be less and less loaded, once its weight is transferred to the other tires, - and its hanging there - its pretty much an ornament / counter weight after that.

Remember - its not about the springs...the bottom line is keeping the COG in the box, and if you hang a tire...there was a REASON it ended up airborne....the jeep was ALREADY tilting too far to keep that tire on the ground....and - whatever suspension forces it had to fight a roll from the down hill side, are WHAT IS PUSHING IT OVER from the uphill side.





So - not enough droop, or the COG already passing out of the box to the down hill side, etc...eitherway...the down hill coils are typically the same as the up hill coils...and the answer to to too little droop on one side, is rarely to take away uptravel on the other side too. (Hell, NO coils, a Little Red Wagon Suspension would be best then if that were how it worked, etc.) I've seem more stiff sprung rigs flip than soft sprung ones...the uncompressing side flips the rig over, etc.

Since most of us, if going to end up side hilling, rarely set up the jeep ahead of time to be longer on one side and shorter on the other...you set it up level, and try to stay out of off camber traps.

 

TEEJ,

You are typing way too much. It's statics 101. A distributed load placed at an angle will apply a greater load to its lowest point. I am not going to argue over it. Been an engineer for a long time and what I indicated earlier is correct. You can't theorize logic until you turn blue in the face, but it basic physics, and all your typing isn't going to change it.

I'll give you an experiment to try... take a heavy chest of drawers up a flight of stairs and tell me who is carrying the greater load... the guy at the top of the stairs, or the guy at the buttom of the stairs.

And as for the compressing your rear axle. Most of those buggies have winches tied to both front and rear axles. And yes they will compress the rear axle when going down hill.

Ok, that's all I am going to say. You folks can make up your own mind... If anyone out there owns a true ORV, please pipe up. T'hanks

 

I think we are saying the same thing...I even used the same furniture carrying analogy you did.

Maybe I did not know the context of what you were responding to?


I think I was responding to this:

And my response was that a lack of uptravel simply raises that side as it ramps up an object, tipping you over to the downhill side....

Your point seems to be that this doesn't happen...and a bumpstop won't do that, as per simple statics...101 IIRC?

I've seen it happen...I understand how it happens...I think you do too, but were really talking about something else?

Please clarify - maybe I was addressing three point cantilevered leverage, and you were addressing simple "Raise one side, and it increases the weight on the other side" issues...not sure why that was your topic...but, OK...I agree with that 100%.

After that - I guess the overlap was me saying a lack of uptravel on the uphill side tips you down hill...and you saying a lack of uptravel on the down hill side might help prevent tipping down hill...and me saying sure, but the same lack of uptravel is on the uphill side anyway...so its a wash, and that keeping the COG in the support box was really the issue.



OK - we agree on the furniture carrying up the stairs...we both want to carry the top, so if we move in together....I suppose a flat would be best.



If we have to side hill on the way there....I'll take the bumpstops off the uphill side, and leave them on the down hill side.

That should cover it I think.

 

we are good... I just now have a headach from all that reading.

 

If you take the bottom of the couch, I'll roll you a few aspirin.

 

great info. now going back to shock lenghts on a BB. I too am on the same boat as you i actually already purchased front shocks for my BB Collapsed length (in.): 15.56 Extended length (in.): 26.750 they are the skyjacker softride hydro shock part #H7075. IF i run into over compressing my shock then i will cut up my 2in body lift pucks that i have left over and they will act as my LONGER BUMP STOPS. now i might need longer breaklines. it was funny when i ordered them over the phone through 4wheelparts the guy was like SIR ARE YOU SURE YOU WANT THOSE SHOCKS THEY ARE MENT FOR A 6" LIFT.

 

i think there are a couple of us that have a headache from reading too much. I WILL MAKE SURE TO POST PICS OF MY JK FLEXING WITH THE SHOCK EXTENDERS/STOCK SHOCKS AND ONE WITH THE NEW SKYJACKER SHOCKS W/OUT SHOCK EXTENDERS