Late night musings about control arm bushing design

Guest · **Posted:** Sat Jul 14, 2007 1:18 am

Articulation. We all want it, right? I've dismantled the IFS on several cars & this KJ & my observation is, once the sway bar is disconnected, the largest resistance comes from the upper & lower control arm bushings located where the control arms secure to the frame of the vehicle. In short, the way they are designed is the center metal cylinder is squeezed & held stationary by the U-bracket mount & the attaching bolt & nut. then the rubber surround flexes as the "free" control arm moves around this stationary pivot point.

There are 4 of these on each side of the Liberty. & if you loosen the mounting bolts & nuts while the KJ is up on jacks, you can see the wheel drop more, & I'd bet you could stuff it further into the wheel wells too. But I doubt that driving with loose bolts on the suspension is a good idea. :shock:

So here's my idea: can the bushings be made using a bearing of some sort? I'm thinking of a spool shaped inner race, so the mounting bolts & nuts can be secured, surrounded by a cylindrical outer race, this assembly would then have the rubber bushing around it, then that would be pressed into the control arms. Voila, IFS with articulation.

What's wrong with this idea?

tjkj2002 · **Posted:** Sat Jul 14, 2007 1:29 am

Here you go,about the best you'll find----http://www.4wheelparts.com/PPT4764T100129.aspx

Guest · **Posted:** Sat Jul 14, 2007 1:39 am

Close. If you totally eliminate the rubber, the ride is going to be quite rough. Where would these Johnny Joints typically be used? Solid axle control arms?

tjkj2002 · **Posted:** Sat Jul 14, 2007 1:45 am

KJpilot wrote:

Close. If you totally eliminate the rubber, the ride is going to be quite rough. Where would these Johnny Joints typically be used? Solid axle control arms?

yep

Guest · **Posted:** Sat Jul 14, 2007 1:50 am

I just found Currie's web site. I don't need the side to side movement they are designed for, but they certainly do have the vertical movement I'm looking for.

Guest · **Posted:** Sun Jul 15, 2007 7:32 pm

All the engineers & fabricators here & no one has any thoughts or opinions???

DaveKJ02 · **Posted:** Sun Jul 15, 2007 7:51 pm

This is going to be a 2WD KJ, or did you figure out a way to float the axle to accomodate the extra travel, cuz you know the CVs wont.

Jeepjeepster · **Posted:** Sun Jul 15, 2007 8:22 pm

The bushings are not keeping the suspension from traveling any further.

I understand what you mean with the bushings, but they are not limiting the travel. If you take the sway bar off and flex it, one side will hit the bumpstop and the other side will droop till the shock stops it(Or the bumpstop on the spacer for those people that run a franken lift)..

Guest · **Posted:** Sun Jul 15, 2007 10:31 pm

Ah, finally! Conversation!

Jeepster- I don't have first hand experience with the bump stop on the upward travel, but on the downward side I do. When doing the clevis lift, even with the bar disconnected, I could get a bit more "droop" with the CA bushing bolts loose. The up ward side bump stop is a bit disappointing. These poor KJs look so arthritic when they have one front paw on a rock!

TJKJ: How does the Humvee control arms attach to the frame?

tjkj2002 · **Posted:** Sun Jul 15, 2007 10:42 pm

There are reasons for the stiff rubber bushing though.First they transmittes less road shock while driving,those Johny Joints would give you a very,very harsh ride,plus the LCA's have alot of stress on them(and take) that tube LCA's in our case would never be as stronge and safe as the cast one's,hence the lack of tube LCA's(IT's been thought through by a few places,but scraped due to safety).Aslo like DaveKJ02 stated it's to limit front articulation to keep the CV's from self destucting,bump stops should be a last resort safety check foe a IFS setup.

Quote:

TJKJ: How does the Humvee control arms attach to the frame?

The same way the LCA's attach to the KJ.Stiff rubber bushings.Be thankfull,the H1 has less travel then the front IFS on the KJ,but with 3000+lbs rate springs(up to 5000 on the heavy and armored models) don't expect alot of travel until loaded to the max.

Guest · **Posted:** Sun Jul 15, 2007 10:57 pm

tjkj2002 wrote:

There are reasons for the stiff rubber bushing though.First they transmittes less road shock while driving,those Johny Joints would give you a very,very harsh ride,plus the LCA's have alot of stress on them(and take) that tube LCA's in our case would never be as stronge and safe as the cast one's,hence the lack of tube LCA's(IT's been thought through by a few places,but scraped due to safety).Aslo like DaveKJ02 stated it's to limit front articulation to keep the CV's from self destucting,bump stops should be a last resort safety check foe a IFS setup.

Quote:

TJKJ: How does the Humvee control arms attach to the frame?

The same way the LCA's attach to the KJ.Stiff rubber bushings.Be thankfull,the H1 has less travel then the front IFS on the KJ,but with 3000+lbs rate springs(up to 5000 on the heavy and armored models) don't expect alot of travel until loaded to the max.

Yeah, those johnny joints wouldn't be the way I'd go, but it was nice to see them. If I did anything like this, It'd be part of a bigger plan, that would include addressing the CVs. But if I can't get decent articulation, I may as well throw a solid Dana 44 on the front of the thing & call it a day!

tjkj2002 · **Posted:** Sun Jul 15, 2007 11:15 pm

HEH,HEH,HEH

Jeepjeepster · **Posted:** Sun Jul 15, 2007 11:44 pm

What are you going to do about the drums tj?

If you look in the fender well pilot, you can see the bumptop that limits upward travel...

I have two conduit nuts for the clevis lift and I have right around a 1/4 to 1/8 of clearance between the balljoint and spring at full droop. I have a bumpstop to stop it from getting that close though. I didnt like the angles on the balljoint when it drooped all the way..

There is alot of weight on the suspension when its under compression and when its drooping. It probably doesn't take 100lbs of force to twist those bushings.

tjkj2002 · **Posted:** Mon Jul 16, 2007 9:44 am

Quote:

What are you going to do about the drums tj?

They have been thrown in the trash,disc's are going on all around.

Jeepjeepster · **Posted:** Mon Jul 16, 2007 11:30 am

Im alittle confused as to why people always want to loose the 8.25 when they put a SFA under the kj.

Why dont you just make new upper A-Arm's with heim joints like Al did..

pixeldzn · **Posted:** Mon Jul 16, 2007 11:41 am

Jeepjeepster wrote:

Im alittle confused as to why people always want to loose the 8.25 when they put a SFA under the kj.

Why dont you just make new upper A-Arm's with heim joints like Al did..

More gearing choices? Stronger by some degree, even if small?

Guest · **Posted:** Mon Jul 16, 2007 12:06 pm

Jeepjeepster wrote:

What are you going to do about the drums tj?

If you look in the fender well pilot, you can see the bumptop that limits upward travel...

I have two conduit nuts for the clevis lift and I have right around a 1/4 to 1/8 of clearance between the balljoint and spring at full droop. I have a bumpstop to stop it from getting that close though. I didnt like the angles on the balljoint when it drooped all the way..

There is alot of weight on the suspension when its under compression and when its drooping. It probably doesn't take 100lbs of force to twist those bushings.

Sorry for the miscommunication... I know about the bump stop, I've just not examined the front wheel at full "up flex" so to speak. Like I said, I'm looking at ideas for a complete front suspension. With parts like the one I mentioned, I'd need to know if it's feasible or reasonable before I need to think of how it interacts with the whole system. The way it's looking, by the time I'm done I'd have been better off doing the SFA. I can't wait to see the lift coming from Al's. That will help cement my thoughts.

tjkj2002 · **Posted:** Mon Jul 16, 2007 1:43 pm

pixeldzn wrote:

Jeepjeepster wrote:

Im alittle confused as to why people always want to loose the 8.25 when they put a SFA under the kj.

Why dont you just make new upper A-Arm's with heim joints like Al did..

More gearing choices? Stronger by some degree, even if small?

You hit it on the head Pixeldzn,with the D30A you can only go to 4.10's,the lowest you can go with the 8.25 is 4.56's.For my setup I need at least 4.88's,but going to 5.13's for a little more low end power(better mpg's in the city).

BeepBeepJeepJeep · **Posted:** Mon Jul 16, 2007 2:09 pm

tjkj2002 wrote:

pixeldzn wrote:

Jeepjeepster wrote:

Im alittle confused as to why people always want to loose the 8.25 when they put a SFA under the kj.

Why dont you just make new upper A-Arm's with heim joints like Al did..

More gearing choices? Stronger by some degree, even if small?

You hit it on the head Pixeldzn,with the D30A you can only go to 4.10's,the lowest you can go with the 8.25 is 4.56's.For my setup I need at least 4.88's,but going to 5.13's for a little more low end power(better mpg's in the city).

5.13s? What the heck? Are you planning on putting 40s on that thing???

tjkj2002 · **Posted:** Mon Jul 16, 2007 4:06 pm

Quote:

5.13s? What the heck? Are you planning on putting 40s on that thing???

35"s,to bring it back to "stock" like performance I would need 4.88's,I want a little more low end for all the city driving I do,plus it will really help out more on the trails.Don't want or need to go past 80mph anyway,plus the 3.7 makes all it's power in the higher rpm range so 5.13's will preform much better than 4.88's.It's all in the gear ratio,you don't need 500hp to turn 44" tires,I've seen a totally sick Samuri with 2 1/2ton military axles running 53" tires with a 100hp 4-cylinder,was also running 6.72 gears.

Late night musings about control arm bushing design

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