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Honest opinion on rear control arms

19K views 29 replies 8 participants last post by  2k2wranglerx 
#1 ·
i'm not a drag racer. I autocross and do some spirited back road driving. That's about it. My car does less than 2,000 miles a year.

Current suspension:
H&R super sports
Subframe braces
KYB AGX adjustable shocks
Summit Sway bars front and rear
MM Caster camber plates

The last piece of the puzzle for me is the rear end and maybe some bushings on the steering rack. I know it's a solid rear axle vehicle. I know it's never going to handle like something with independent suspension. BUT, what i am trying to do is make the rear end feel solid. Right now with the 119k mile stock rubber bushings... well you can tell.

I know guys are passionate about this. about solid bushings leading to less traction since the axle can't move. But i'm looking for first hand experience with rear control arms. Which are decent and which are junk. I'd like everything to be as solid feeling as possible. The sway bars i have are already some of the stiffer ones available.

Thanks guys.
 
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#2 ·
I run full UPR suspension on my 03 V6. Double adjustable uppers, and single adjustable lowers. I have poly bushings because its a street car first, drag car second. I love the way the car handles, and would not change a thing with regards to the rear suspension. I also run UPR lowering springs, Mach 1 front and rear sway bars, UPr FLSFC, and eibach shocks and struts.

For the front I have 3 bolt CC plates, and the same springs. I am going to coilovers in front to work with my K-member and A-arms but overall the car handles amazingly. Ride is stiff but it drives like its on rails.
 
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#4 ·
Solid bushings in the lower control arms will improve traction, not decrease it. Any horizontal or lateral movement in the rear axle is bad, and unfortunately with the stock 4-link design, the rear suspension is allowed to move excessively. The use of soft rubber bushings in the control arms doesn't help the situation. Beyond a certain range of motion the rubber bushings begin to deflect, resulting in unpredictable handling and/or wheel hop. With 119,000 miles on the stock bushings, the problem is probably made worse. Solid bushings (either polyurethane or aluminum heim joints) withstand this detrimental deflection far better, meaning the car will handle and accelerate better.

Since you don't drag race, you do NOT want solid bushings in the upper control arms. With what bind there already is, it will be made worse with solid bushings. In addition, NVH will increase and potential damage to the chassis could result. I suggest replacing the upper control arm bushings with new rubber.

The best RLCA design for street performance is one with a 3-piece polyurethane bushing on the chassis end, and a spherical heim joint on the axle end. They will only slightly increase NVH. Maximum Motorsports HD series control arms are very nice, as are Steeda billet control arms. I have the Steeda's installed on my car, and they have performed great.
 
#8 ·
That appears to be a drag racing kit. The upper control arms are adjustable to set pinion angle, and they utilize spherical heim joints. The lower control arms have no provision for a swaybar. All of which is fine if all you want to do is go fast in a straight line, but you said you don't drag race.

Here's what I recommend:

Heavy-Duty Mustang Rear Lower Control Arms, 1999-2004

Mustang Rear Upper Control Arm Bushings, Axle/Differential Side, pair
 
#10 ·
You want traction and handling? Torque Arm and Panhard bar. Get rid of those upper control arms that absolutely ruin the rear end. Maybe not as comfortable over uneven surfaces as an IRS, but it handles.
 
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#11 ·
I ran UPR ProSeries extreme duty adjustable upper and lower control arms for years. I also ran spherical bushings on the differential side of the UCAs. I recently removed the UCAs and the spherical bushings and put MM FRPP-style UCAs with rubber bushing back in. I didn't have the stock ones to put back in. The solid UPR bushings created more NVH than I wanted. They also didn't allow me to get a Maximum Motorsport panhard bar. I daily drive my car so I would never have a torque arm installed. It would give me even more NVH than I had with the XD UCAs.

If you want better handling then put in LCAs and a MM panhard bar. Leave the uppers alone. If you want more information call Maximum Motorsport and talk to the experts. That is what I did when I decided to ditch the XD UCAs that I was running.

I was running something like this but the lowers still had the sway bar mounts:

Link:http://www.uprproducts.com/mustang-chrome-moly-pro-series-uppers-lower-spherical-package-79.html

I replaced the uppers with this:

Link: http://www.maximummotorsports.com/Rear-Upper-Control-Arms-1979-2004-Mustang-P544.aspx

You already have changed the springs. I'm thinking of doing that and adding this panhard bar:

Link: http://www.maximummotorsports.com/Panhard-Bar-1999-2004-solid-axle-equipped-Mustang-P482.aspx
 
#28 ·
I ran UPR ProSeries extreme duty adjustable upper and lower control arms for years. I also ran spherical bushings on the differential side of the UCAs. I recently removed the UCAs and the spherical bushings and put MM FRPP-style UCAs with rubber bushing back in. I didn't have the stock ones to put back in. The solid UPR bushings created more NVH than I wanted. They also didn't allow me to get a Maximum Motorsport panhard bar. I daily drive my car so I would never have a torque arm installed. It would give me even more NVH than I had with the XD UCAs.

If you want better handling then put in LCAs and a MM panhard bar. Leave the uppers alone. If you want more information call Maximum Motorsport and talk to the experts. That is what I did when I decided to ditch the XD UCAs that I was running.

I was running something like this but the lowers still had the sway bar mounts:

Link:79-04 Mustang Pro-Series ™ Adj Control Arm & Spherical Package

I replaced the uppers with this:

Link: Rear Upper Control Arms, 1979-2004 Mustang

You already have changed the springs. I'm thinking of doing that and adding this panhard bar:

Link: Panhard Bar, 1999-2004 solid-axle equipped Mustang
79-04 Mustang Pro-Series ™ Lower Control Arms Sway Bar Mount

their LCA's are pretty tempting....
 
#13 ·
As I said, I wouldn't do the torque arm but with the Maximum Motorsport panhard bar you leave the the stock upper control arms in place.
 
#14 ·
MM HD lowers for sure. Been mid 12's in the GT and daily drove on them for 7 years. Great control arm. Have them on the Mach as well. For uppers I had Frpp uppers on the GT which are the same stock replacements that MM sells. On the Mach I have J&M uppers. I couldn't tell you if one is better than the other.
 
#15 ·
Mg 2v summed it up pretty well.
For handling purposes, you want stock rubber bushing uppers. Poly will increase bind and create snap oversteer during hard cornering if you aren't careful with throttle control.

I have the mm HD lowers that are poly on the chassis side and heim joints on the axle side. Hook well and no noticeable increase in NVH. The mm arms are very well made and pretty beefy compared to the cheap ones I pulled out of the car.

Cheap poly bushing lowers like LMR/Am sell are crap. I destroyed the bushings on the axle side.

As said above, the ideal setup is a torque arm and panhard bar setup, but it is very expensive and requires running dumped mufflers. It also hangs kind of low.
You can run a panhard bar and a single stock upper control arm for what they call a "poor man's 3 link". Only issue is that it seems to wear out the upper bushing more quickly and it doesn't handle quick side to side transitions well, like what you will see in autox with tight slaloms or essess.

Hope that helps. The solid bushed and adjustable length stuff is typically for drag racing and trying to get a high horsepower car to hook up. You kind of sacrifice handling with that stuff. You can run all heim joints which allows the rear axle to articulate correctly, but it is terribly loud and harsh.

Maximum motorsports has a decent amount of good reading about suspension on their website.
 
#16 ·
You can run a panhard bar and a single stock upper control arm for what they call a "poor man's 3 link". Only issue is that it seems to wear out the upper bushing more quickly and it doesn't handle quick side to side transitions well, like what you will see in autox with tight slaloms or essess.
Jazzer used to talk about removing an upper control arm to create a "poor man's 3 link." But he was running a Griggs suspension. There is nothing that I've read in any of the Maximum Motorsport documents that says to remove one of the upper control arms. It's been a while since I've talked to them about panhard bars but neither they or the installer I called said anything about removing a UCA and the installer had installed dozens of them. The note in their advertising says "when installed with the OEM 4-link rear suspension..." and everywhere else they talk about upper control arms (plural). I'm not sure that a "poor man's 3 link" applies to the Maximum Motorsport panhard bar.
Panhard Bar, 1999-2004 solid-axle equipped Mustang

Tech report: Why your 1979-2004 Mustang needs a panhard bar
Installation instructions: http://www.maximummotorsports.com/Assets/install/pdf/rear_susp/MMPB99Ar4.pdf
 
#18 ·
While a PHB does a far better job of centering the rear axle laterally than does two upper control arms, it alone is not an ideal solution. A stock 99-04 GT has a pretty high roll center defined by the upper control arms. After installing a PHB, a new, lower, roll center is defined. As a result, the upper control arms are forcibly made to comply with the new roll center of the PHB, causing the stock rubber bushings to deflect and bind as they are now operating outside their normal range of motion. This symptom is referred to as roll bind.

Maximum Motorsports did a study on roll bind in several rear suspension configurations. They found that by adding a PHB with stock upper and lower control arms, rear wheel rates increased by 47 lb/in in the first inch of suspension travel. This number decreased to 30 lb/in between 2-3" of travel. That's a significant amount of wheel rate added to the rear, all because of bind in the upper control arms. Despite this increase in upper control arm bind, MM still recommends a PHB because of the increased predictability and stability. By eliminating one upper control arm, however, roll bind–and by extension snap oversteer–is reduced (this is the main reason S197 Mustangs came equipped with a single upper control arm with the factory PHB).

So why doesn't MM overtly recommend the PM3L (poor man's 3-link)? Because it isn't a true or durable (or even safe, for that matter) solution to eliminating upper control arm bind–it's merely a trick road racers on a budget came up with to combat snap oversteer. The main concern with the PM3L is the resulting damage to the bushings in the remaining upper control arm. On a stock rear suspension car, the forces from engine torque, acceleration, braking, and handling are transmitted through two upper control arms and their respective chassis mounts. Remove one of those arms, and now all those forces are passing through a single control arm, a single set of bushings, and a single chassis mount. This will destroy the bushings, and worse the upper control arm mount, in short order. A lot of MM customers drive their cars on the street, so you can only imagine the danger involved if a bushing or chassis mount fails while cruising down the road.

To safely utilize the PM3L, the chassis mount needs to be reinforced, and the stock rubber bushings in the remaining arm should be replaced with spherical heim joints. A few people have designed their own bushings out of steel. This is quite a bit of work, especially for someone that doesn't competitively race their car. The best solution for a street driven car is to leave both upper control arms in place with the PHB, or better yet, remove them entirely with a torque arm.
 
#19 ·
Well, you guys have convinced me that I do not want a panhard bar on my daily driver. I'm glad we had this discussion. It would have ended up being one of those mods I'd regret.
 
#22 ·
I suppose I should have clarified that when MM did their testing on roll bind, they did not account for the lateral loads encountered during cornering. There's fairly little correlation between roll bind and how a car actually feels and performs. Even a torque arm induces some bind, but a TA and PHB combination is still one of the best performing configurations available.

Eagle, I encourage you to stick with your plan of adding a PHB. It will improve the handling of your car.
 
#24 ·
When you put on the LCAs you can take off your quad shocks. They aren't needed anymore. My have been off for years.
 
#26 ·
Yes. The quad shocks are there to prevent wheel hop. The aftermarket lowers are designed by themselves to stop wheel hop.
 
#27 ·
ya i get that. I just figured with the rubber bushings in the uppers that you'd still have enough flex to allow the axle to rotate (hence wheel hop).

I've dealt with wheel hop in jeeps and poorly set up 4 links before lol. it's more obvious on a large vehicle on 42's or whatever but watching that pinion bounce is always wild.

i figured with stock uppers you'd need to keep the quad shocks since the axle could still technically pivot on the new more solid bushings and flex on the soft upper bushings.
 
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