Too much dart like, ass swaying at 80-85 - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 8 Old 09-08-2017, 11:39 PM Thread Starter
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Too much dart like, ass swaying at 80-85

I know I'm asking for the best of both worlds, but yesterday the wife got pretty upset.

82 mph, hard and quick brake and partial turn and the jeep swayed so I countersteered. It fought back some and I was able to calm everything down.

I know it's not a Porsche but damn.. that rear end went wild. No weight in back. 2015 JKUR on 2 inch spacer with 35 MTRK, 4.5 backspace. Longer front end links. Everything else stock

Rear sway need replacement for 2 inch? It feels too heavy at that speed. 65 and under is perfect Steering has been heavy with some slack since 35s

Thanks for any input.

Ton of shit, and not listing it all..
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post #2 of 8 Old 09-09-2017, 02:36 AM
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Keep it at the LEGAL speed limit. It's that simple.

And if you can't do that return it to 100% stock.


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post #3 of 8 Old 09-09-2017, 05:33 AM
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@Bumpstick is offering sound recommendation but it isn't always possible. I can and have swerved in avoidance like you went thru on I-78-85 junction in Chatanooga one night but at 90mph I swerved when some [email protected] just stopped at a split for those two freeways in the middle of the road. My wife and two kids were all asleep and I swerved at 90mph ,went across three lanes and back but the rear surprised me by a combo hang-on resulting from my having JUST the weekend prior installing (1) quality , heim jointed ,correct length rear endlinks for the stock swaybar , (2) simultaneously replaced all swaybar bushings with much firmer Prothane polyurethane swaybar bushings * and all this coincided with the 37" sticky , grippy KO2s having just been installed a month prior.

The thing felt and held like a Porsche but it scared the living f*ck outta me and my quickly awakened family . It took me a while to calm down but I was never so happy to have done a little moderate mods ahead of that trip back home to Georgia since it pretty much saved our lives. (* I give the most credit to the polyurethane swaybar bushing upgrade since it really reduced the sway out back that the OEM rubber ones durometer allows. Much firmed up and higher control offered by them. So much difference, in fact , I've been highly surprised more folks have not commented on how much an improvement replacing the bushings can actually make. I figure everybody must keep the lame rubber stock bushings but it's night and day difference as far as handling swapping for PU bushings . . ) .


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Last edited by j3ff3ry_j33p; 09-09-2017 at 05:37 AM.
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post #4 of 8 Old 09-09-2017, 07:15 AM
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OP, consider yourself lucky to have the added WB of a 4 door in that situation. A longer WB adds directional stability.

Quick braking transferred a lot of weight off the rear. Add a turn and, presto, the rear wants to come around.

Whatever you do, don't get a stiffer rear swaybar...it will only exacerbate this effect.
The rear will want to come around more readily anytime you unweight the rear, like just chopping the throttle during a turn in a spirited drive through the twisties. It'll happen more readily under heavy throttle while exiting, too, if one of the rears loses traction.

It's possible your short-for-a-2"-lift rear sway links topped out, effectively turning the bar into a solid connection and denying the axle its articulation.
First thing I would do is get longer rear links.

When you say "it fought back", are you saying the stability programming kicked in?
I hate that shit...causes nothing but handling problems for those that know how to drive.
Glad to hear you had a clue about driving and were able to keep it together...it coulda been a yard sale.
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post #5 of 8 Old 09-09-2017, 07:59 AM
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Did you raise the track bar mount on the rear axle?
This is your anti squat in rear terms. The weight shift from one end to the other because of acceleration or braking.

One way to increase anti squat is with geometry of the links. Raising the upper links will triangular the upper and lowers and force more of the weight transfer into the links vs the coils.

You can also run a higher coil rate that will counteract the weight being forced into them by the transfer.

Adjustable shocks can be set up with valving stack that can limit the compression. A bypass shock with a dual compression zone could be adjusted to limit the compression of the coils during sudden stops.

I don't see the sway bar having much affect except for controlling the body roll. I don't know if the increase of force on the side you are steering into is increased enough to offset the amount of lift you would be creating on the opposite side would equal enough tire grip to prevent the slide. Tires may have a pretty good impact on the sliding as well. An AT tire vs a MT tire should handle a slide better since there is more rubber on the road.

Glad you got it pulled back and everyone was ok.

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post #6 of 8 Old 09-09-2017, 08:55 AM Thread Starter
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Thank you all for the relief and advice. As far as speed, it was a herd of us around 80 on a rural two lane stretch of 99SB to Merced. Roads are terrible, but you will be limited to the 3 lane in California if your not at 75 minimum.
The CPU did kick in and scared me some. Taken a ton of EVOC courses but not in my fat girl.. lol and again no nanny.
As far as fixes, it appears I may have hit the performance limits at speed. What I'm looking for, and the direct purpose of the post, was to limit nose dive. How much tighter can that poor rubi spring with spacer be? Lol. With your input, I believe you guys are correct. A shift in weight and a sudden turn is our risk. I may just have to remind myself to hang with kiddies around 65-70.
As far as the links.. the front is a teraflex and is appropriate. The rear Is stock. I guess I could get one of those sway bar adjustment pieces..

Ton of shit, and not listing it all..

Last edited by Tierhog; 09-09-2017 at 09:00 AM.
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post #7 of 8 Old 09-09-2017, 09:58 AM
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85mph in my 2 door on 35s feels as scary as 140+ does in my old sports car.

Rarely do I even hit 60mph now a days. While I wouldn't say I drive like a grandpa, its still not a vehicle you want to be speeding in. a JKU will be more planted than a 2 door but also weighs minimum of 400lbs more than a 2 door so it wont be as responsive. I'd never think of swerving at 85 in my jeep. think i'd be safer just plowing into something at that speed then swerving and going for some massive tumbles.

Keep in mind, many people have flipped wranglers from a lot lower speeds. Mines pretty planted at lower speeds but anytime i think im hauling ass around corners, I have some old lady in a prius tailgating me so yea, they don't handle well.

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post #8 of 8 Old 09-09-2017, 10:18 AM Thread Starter
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Quote:
Originally Posted by mvjeeper View Post
85mph in my 2 door on 35s feels as scary as 140+ does in my old sports car.

Rarely do I even hit 60mph now a days. While I wouldn't say I drive like a grandpa, its still not a vehicle you want to be speeding in. a JKU will be more planted than a 2 door but also weighs minimum of 400lbs more than a 2 door so it wont be as responsive. I'd never think of swerving at 85 in my jeep. think i'd be safer just plowing into something at that speed then swerving and going for some massive tumbles.

Keep in mind, many people have flipped wranglers from a lot lower speeds. Mines pretty planted at lower speeds but anytime i think im hauling ass around corners, I have some old lady in a prius tailgating me so yea, they don't handle well.
Strange...my Jeep is a Prius magnet too. I'd love to drive over one. I laughed about plowing through as opposed to around things. Probably safer in some instances. Yeah. I guess the whole experience is a subtle reminder to slow down.

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