-
TDR Magazine subscribers receive more than the magazine! You also gain additional forum privileges!
Details here: TDR Privileges
Subscribe to TDR Magazine here: https://www.tdr-online.com/
Aftermarket Control Arm And Suspension Info Thread
- Thread starter nps
- Start Date
Attention: TDR Forum Junkies To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.
Thanks, TDR Staff
- Status
Gents,
Control arms are an integral part of your truck's suspension. They're made of rubber and metal, and like most components, they eventually wear out. The rubber bushings rot and fatigue over time. With hard use the arms can even bend. I've bent them by hard forward impacts, but most people who bend them do so by crunching them on rocks or obstacles. It's very rare to bend a control arm because most people just aren't pushing it that hard and the OE units are plenty strong. The 3rd Gen. arms are better than the 2nd Gen. arms because they're boxed. The 2nd Gen. arms are open on the bottom, making them more susceptible to damage - they "taco" pretty easily - I've seen more bent 2nd Gen arms than 3rd.
OE control arms work in a unique way. The bushing is vulcanized to the housing and the sleeve is vulcanized to the bushing. It's a common misconception that the sleeve rotates inside the bushing, but this isn't the case. The sleeve is actually captured by the frame's outer mounting flanges; it's the rubber that twists. There is no mechanical rotation. That's why it's really important to loosen all your control arms when you install a lift kit and retighten them when you get the weight back on the wheels - otherwise you'll put undue stress on the rubber bushings by forcing them to twist when the truck is just siting there at static height.
Control arms link your front axle housing to the frame and allow it to articulate. The function of the bushings is to provide resistance to deflection and a natural return-to-center feature. They also insulate the vehicle against what automotive engineers call NVH or "noise, vibration and harshness. " A lot of good thought went into the design of your stock control arms, from exactly the correct durometer (hardness) and diameter of bushing, to the wall thickness of the metal.
For stock applications, the OE control arms work wonderfully. They provide nice feedback from the steering, good road feel, good NVH insulation and are very strong. I've hit stuff with the OE control arms that blew tires off the wheel and broke motor mounts without actually bending or damaging control arms. I've smashed stuff so hard that when I got out of the truck to check everything I was amazed that nothing was damaged. I've also bent control arms without even knowing it. If you hit something at just the wrong angle, even gently, they'll fail. Another weird thing that can happen is the bushing can avulse or push out of the housing. Stock control arms have their flaws, they're only . 090 wall steel, but in general, they're really tough - especially for a production part. I really think that DC over-designed these pickups. That's what I love about the HD Rams.
The five link on a 4x4 moves the axle housing in a circle, so without tight bushings, steering becomes sloppy and the truck feels like it wants to wander. With hard use it doesn't take long to wear out bushings - and you can't tell when they're gone just by looking at them. After a few years, you can see the rubber rotting, but they can be worn out long before you see anything. It's also hard to tell if you drive the truck every day because you get accustomed to the feel. You need to drive a newer truck to notice the difference. Fresh OE control arms actually make the truck feel "springy" and responsive. Old OE control arms make the truck feel kind of "dead. "
When you add suspension that increases wheel travel beyond stock, you end up fatiguing control arm bushings faster than you would if you were twisting them less while the suspension cycles. The new Powerwagon uses the same control arms that your diesel trucks use and they're getting 10" of travel stock - the same travel good suspension kits offer. This shows a lot of faith in the quality of the original design.
Like I've stated, it's my belief that for average use the OE units are great, so the following discourse applies only to extreme use.
Here are the weaknesses we discovered from racing:
1. Hard use + long travel suspension quickly wears out OE control arm bushings.
2. OE control arms can be bent and damaged. OE control arms seem to have been designed to "crumple" in order to either protect other components or absorb the energy of a collision (i. e. auto accident). When they bend, they usually bend right in the middle (go figure - simple leverage), then your steering gets messed up or the tires start rubbing somewhere. When this happens you simply take off the offending part and chuck it, put on a new one and continue. Or, if you don't have another arm, you just drive home on three arms - don't laugh, I've done it - and I've seen someone else do it too - hundreds of miles.
3. OE control arms limit free articulation. This is especially true on the passenger side. As the axle housing drops away, the twisting of the control arms provides a lot of resistance, so it doesn't move as freely as it could with a different design.
4. OE control arms put a lot of stress on mounting flanges. Because the bushings twist (rotate) and simultaneously flex laterally, they transmit a lot of side-load to the frame mounting flanges. This causes the frame to crack or the mounting flanges to split. I've done this too - more than once. Hit enough stuff hard and it could happen to your truck as well.
So how, you may ask, do you improve on the OE design?
It's difficult because the OE units are really good, simple parts that require no maintenance and generally last a long time. We wanted to make arms that would require little to no maintenance, provide good, tight steering, good NVH protection, greater flexibility (free articulation), be rebuildable (unlike OE), provide greater strength, more tire clearance, no noise (squeaking) and limited adjustability.
KORE tested a lot of different iterations while trying to come up with the perfect control arms. The following are some bearing formulas that didn't work for our purposes:
1. Heim front - heim rear. Great steering precision, strength and reliability + articulation - but way to harsh, zero NVH protection, metal to metal feel - bad.
2. Heim front - poly bushing rear. Great steering precision, strength and reliability - limited articulation due to the small-diameter bushing - still way too harsh.
3. Poly Bushings front and rear. Great steering precision, poor articulation and reliability. Soft durometer poly eventually splits, harder durometer poly rides harshly like a heim. Plus they squeak like crazy if you don't keep them greased.
4. Large diameter synthetic rubber bushings front and rear. Great NVH protection, less limited articulation than OE due to the fact that the rubber allows the bushing to rotate inside it. They're not fused by vulcanization. They don't require grease. The only load is lateral so they last a long time and are generally under much less stress than stock.
5. New-style spherical balls front and rear. Excellent everywhere - NVH somewhere between heims and stock but with high steering precision and massive free articulation. All the advantages of heims without the metal to metal harshness. Plus they're much less expensive to rebuild - vice good heims like FK's or Auroras.
We ended up with spherical ball capsules in front and large diameter rubber bushings in the rear. For combined use - street and dirt, the combination of capsules in front and big rubber bushings in the rear works best. Other companies that specialize in rock crawling are using this joint set up. It's a proven combination that works well.
Much like our suspension, the aluminum arms we're making were unprecedented. Nobody has ever made anything like this before for these trucks. FEA (finite element analysis) put these arms at something like 40 times stronger than stock. Of course the real test was mashing them for thousands of miles in Baja. They survived unscathed - so like all parts KORE makes, these arms are guaranteed for life. The shape comes from the fact that we wanted to get a bit more steering clearance for guys running OE wheels with larger tires. The arms provide about enough to run a true 35x12. 50 without rubbing. By making arms out of tube you cut clearance dramatically - that's why the cross-section of the OE units is rectangular. Round arms don't matter if you're running low-offset wheels (4. 5" standard) but if you're running stock wheels it does matter.
Our steel arms will be out shortly. They're rectangular and much stronger than stock. They have the same joint tech that our aluminum arms have but don't offer more tire clearance than stock and aren't adjustable. They should be a good option when it comes time to replace worn out stockers.
That's all for now.
Everyone have a great weekend,
Kent Kroeker
KORE
Control arms are an integral part of your truck's suspension. They're made of rubber and metal, and like most components, they eventually wear out. The rubber bushings rot and fatigue over time. With hard use the arms can even bend. I've bent them by hard forward impacts, but most people who bend them do so by crunching them on rocks or obstacles. It's very rare to bend a control arm because most people just aren't pushing it that hard and the OE units are plenty strong. The 3rd Gen. arms are better than the 2nd Gen. arms because they're boxed. The 2nd Gen. arms are open on the bottom, making them more susceptible to damage - they "taco" pretty easily - I've seen more bent 2nd Gen arms than 3rd.
OE control arms work in a unique way. The bushing is vulcanized to the housing and the sleeve is vulcanized to the bushing. It's a common misconception that the sleeve rotates inside the bushing, but this isn't the case. The sleeve is actually captured by the frame's outer mounting flanges; it's the rubber that twists. There is no mechanical rotation. That's why it's really important to loosen all your control arms when you install a lift kit and retighten them when you get the weight back on the wheels - otherwise you'll put undue stress on the rubber bushings by forcing them to twist when the truck is just siting there at static height.
Control arms link your front axle housing to the frame and allow it to articulate. The function of the bushings is to provide resistance to deflection and a natural return-to-center feature. They also insulate the vehicle against what automotive engineers call NVH or "noise, vibration and harshness. " A lot of good thought went into the design of your stock control arms, from exactly the correct durometer (hardness) and diameter of bushing, to the wall thickness of the metal.
For stock applications, the OE control arms work wonderfully. They provide nice feedback from the steering, good road feel, good NVH insulation and are very strong. I've hit stuff with the OE control arms that blew tires off the wheel and broke motor mounts without actually bending or damaging control arms. I've smashed stuff so hard that when I got out of the truck to check everything I was amazed that nothing was damaged. I've also bent control arms without even knowing it. If you hit something at just the wrong angle, even gently, they'll fail. Another weird thing that can happen is the bushing can avulse or push out of the housing. Stock control arms have their flaws, they're only . 090 wall steel, but in general, they're really tough - especially for a production part. I really think that DC over-designed these pickups. That's what I love about the HD Rams.
The five link on a 4x4 moves the axle housing in a circle, so without tight bushings, steering becomes sloppy and the truck feels like it wants to wander. With hard use it doesn't take long to wear out bushings - and you can't tell when they're gone just by looking at them. After a few years, you can see the rubber rotting, but they can be worn out long before you see anything. It's also hard to tell if you drive the truck every day because you get accustomed to the feel. You need to drive a newer truck to notice the difference. Fresh OE control arms actually make the truck feel "springy" and responsive. Old OE control arms make the truck feel kind of "dead. "
When you add suspension that increases wheel travel beyond stock, you end up fatiguing control arm bushings faster than you would if you were twisting them less while the suspension cycles. The new Powerwagon uses the same control arms that your diesel trucks use and they're getting 10" of travel stock - the same travel good suspension kits offer. This shows a lot of faith in the quality of the original design.
Like I've stated, it's my belief that for average use the OE units are great, so the following discourse applies only to extreme use.
Here are the weaknesses we discovered from racing:
1. Hard use + long travel suspension quickly wears out OE control arm bushings.
2. OE control arms can be bent and damaged. OE control arms seem to have been designed to "crumple" in order to either protect other components or absorb the energy of a collision (i. e. auto accident). When they bend, they usually bend right in the middle (go figure - simple leverage), then your steering gets messed up or the tires start rubbing somewhere. When this happens you simply take off the offending part and chuck it, put on a new one and continue. Or, if you don't have another arm, you just drive home on three arms - don't laugh, I've done it - and I've seen someone else do it too - hundreds of miles.
3. OE control arms limit free articulation. This is especially true on the passenger side. As the axle housing drops away, the twisting of the control arms provides a lot of resistance, so it doesn't move as freely as it could with a different design.
4. OE control arms put a lot of stress on mounting flanges. Because the bushings twist (rotate) and simultaneously flex laterally, they transmit a lot of side-load to the frame mounting flanges. This causes the frame to crack or the mounting flanges to split. I've done this too - more than once. Hit enough stuff hard and it could happen to your truck as well.
So how, you may ask, do you improve on the OE design?
It's difficult because the OE units are really good, simple parts that require no maintenance and generally last a long time. We wanted to make arms that would require little to no maintenance, provide good, tight steering, good NVH protection, greater flexibility (free articulation), be rebuildable (unlike OE), provide greater strength, more tire clearance, no noise (squeaking) and limited adjustability.
KORE tested a lot of different iterations while trying to come up with the perfect control arms. The following are some bearing formulas that didn't work for our purposes:
1. Heim front - heim rear. Great steering precision, strength and reliability + articulation - but way to harsh, zero NVH protection, metal to metal feel - bad.
2. Heim front - poly bushing rear. Great steering precision, strength and reliability - limited articulation due to the small-diameter bushing - still way too harsh.
3. Poly Bushings front and rear. Great steering precision, poor articulation and reliability. Soft durometer poly eventually splits, harder durometer poly rides harshly like a heim. Plus they squeak like crazy if you don't keep them greased.
4. Large diameter synthetic rubber bushings front and rear. Great NVH protection, less limited articulation than OE due to the fact that the rubber allows the bushing to rotate inside it. They're not fused by vulcanization. They don't require grease. The only load is lateral so they last a long time and are generally under much less stress than stock.
5. New-style spherical balls front and rear. Excellent everywhere - NVH somewhere between heims and stock but with high steering precision and massive free articulation. All the advantages of heims without the metal to metal harshness. Plus they're much less expensive to rebuild - vice good heims like FK's or Auroras.
We ended up with spherical ball capsules in front and large diameter rubber bushings in the rear. For combined use - street and dirt, the combination of capsules in front and big rubber bushings in the rear works best. Other companies that specialize in rock crawling are using this joint set up. It's a proven combination that works well.
Much like our suspension, the aluminum arms we're making were unprecedented. Nobody has ever made anything like this before for these trucks. FEA (finite element analysis) put these arms at something like 40 times stronger than stock. Of course the real test was mashing them for thousands of miles in Baja. They survived unscathed - so like all parts KORE makes, these arms are guaranteed for life. The shape comes from the fact that we wanted to get a bit more steering clearance for guys running OE wheels with larger tires. The arms provide about enough to run a true 35x12. 50 without rubbing. By making arms out of tube you cut clearance dramatically - that's why the cross-section of the OE units is rectangular. Round arms don't matter if you're running low-offset wheels (4. 5" standard) but if you're running stock wheels it does matter.
Our steel arms will be out shortly. They're rectangular and much stronger than stock. They have the same joint tech that our aluminum arms have but don't offer more tire clearance than stock and aren't adjustable. They should be a good option when it comes time to replace worn out stockers.
That's all for now.
Everyone have a great weekend,
Kent Kroeker
KORE
Last edited:
Kent- Thanks. Alot. I had about 6 questions that got answered, and only one that didn't. Does it make sense to box the 2nd gen arms? Why or why not? O. k. , one more: who makes the spherical balls?
Another approach would be a long arm conversion. I understand why the big lift guys go for it, but it seems like most high speed offroad vehicles have longer arms than the CTDs. Did you consider them, or do you have to keep stock suspension to race in a certain class?
I don't get to the 3rd gen posts, so I really enjoy it when you educate the rest of us on tech matters. I realize that this kind of knowledge is expensive to come by, and sharing it takes balls (not exactly sperical ones).
Thanks. Alot.
-JJ
Another approach would be a long arm conversion. I understand why the big lift guys go for it, but it seems like most high speed offroad vehicles have longer arms than the CTDs. Did you consider them, or do you have to keep stock suspension to race in a certain class?
I don't get to the 3rd gen posts, so I really enjoy it when you educate the rest of us on tech matters. I realize that this kind of knowledge is expensive to come by, and sharing it takes balls (not exactly sperical ones).
Thanks. Alot.
-JJ
JJ,
Good joke :-laf .
It would make a lot of sense to box 2nd Gen arms, but I think you would end up introducing too much heat into them - even with gentle TIG. Above all things you've got to keep heat off the bushings or you could de-vulcanize them. Even if you boxed them, I still think the material is a bit thin for hard use.
Our spherical balls are proprietary - they're not parts anyone could buy; they're ours. I designed them - got the prints right here. I wish the Dodge trucks used a common size bolt - like 1/2" ID by 2. 5" wide; it would make things much easier (and cheaper) on us, but they don't. Our big trucks use weird metric ID's with odd imperial widths, so we had to design our own balls. Now, here's what we've discovered; some of the older 2nd Gen. trucks use sizes that are pretty close to what is being commercially offered by Rubicon Express, Daystar, etc. If you have an older truck (pre 97) and you have fabrication skills, you may be able to buy these parts and put together your own steel arms. Do not buy the kind of joint that uses poly capsules - these require constant greasing and they have a sticky, kind of lack of smoothness. Do not buy the kind that use a circlip on both sides. They are a royal pain to install and rebuild. Use the kind with the nylon/delrin capsule, chrome-plated ball, zerk fitting and screw-in side plate. The screw-in side plate allows you to adjust tension with a simple pin spanner. Then you lock it with a set screw. It's a great design.
If you have a newer 2nd Gen. or 3rd Gen. Ram, the closest thing you'll find is a 9/16 ID ball. If you grind this down to narrow the width for the top arms, you'll grind off much of the flange and mess up your purchase area. If you bore it out to 16mm for the bottom and weld a spacer or use a washer for the width, you'll be making the walls dangerously thin. We tried this to test one company's spherical balls. It was a bad move. Stuff failed. Essentially, there's no way to cleanly Jerry rig these for late model Rams.
Long arm conversion.
The purpose for this design is to make the arc upon wich the axle travels as oblate as possible for the given amount of suspension travel. The more wheel travel you have the bigger the arc, so the longer the arms have to be. Imagine very short arms with 15" of travel. The axle would move very far back and very far forward (relative to the longitudinal axis of the vehicle). Now imagine 15" of travel with very long arms. The closest point aft to the farthest point forward (on the arc) is greatly reduced. This helps with a lot of things - steering, caster angle changes, shock angle changes. Basically, long arms greatly reduce the operating angles of major components. A common (and very tired) misconception is that longer arms by themselves equate to a smoother ride. There is only one reason this would be true. If everything else were equal (i. e. springs, shocks etc. ), then the reduced operating angles of certain bushings, and the greater leverage on the bushings could contribute to a smoother ride due to reduced relative resistance. Some may argue this but I think they would be hard-pressed to put forth empirical data to back up their point.
There are a couple of "long arm" kits for Dodge trucks running around out there. They require a lot of welding and rigging. Basically, all they're doing is relocating where the wheel travel occurs - lift kits. You've got to cut off, or notch one cab mount on each side of the truck to permit the upper arm to clear. We once notched a forward cab mount to clear a reservoir and the front of the truck eventually collapsed about 3". To prevent this they may offer reinforcements with the kit. Drop pitman arms and the usual lift kit stuff completes the picture.
Since, above all things, going fast off road requires wheel travel, longer arms just don't make sense for a truck using stock steering and drivelines. Unless you're fabricating some crazy stuff (and we can't because we're racing a "Stock" class that requires OE steering and OE control arms) true wheel travel is limited by steering and u-joint angles, not control arms, longer or not.
During the 1000 I bent two control arms, snapped an upper mounting flange and blew a bushing out of a housing. We drove back to California (over 1000 miles) on only three control arms. When we did the forensics on the truck we discovered what we needed to do to prevent stuff like this from happening again. We're not allowed to race with special control arms, but when we go to Baja for fun, they're on the truck.
Cheers,
Kent
Good joke :-laf .
It would make a lot of sense to box 2nd Gen arms, but I think you would end up introducing too much heat into them - even with gentle TIG. Above all things you've got to keep heat off the bushings or you could de-vulcanize them. Even if you boxed them, I still think the material is a bit thin for hard use.
Our spherical balls are proprietary - they're not parts anyone could buy; they're ours. I designed them - got the prints right here. I wish the Dodge trucks used a common size bolt - like 1/2" ID by 2. 5" wide; it would make things much easier (and cheaper) on us, but they don't. Our big trucks use weird metric ID's with odd imperial widths, so we had to design our own balls. Now, here's what we've discovered; some of the older 2nd Gen. trucks use sizes that are pretty close to what is being commercially offered by Rubicon Express, Daystar, etc. If you have an older truck (pre 97) and you have fabrication skills, you may be able to buy these parts and put together your own steel arms. Do not buy the kind of joint that uses poly capsules - these require constant greasing and they have a sticky, kind of lack of smoothness. Do not buy the kind that use a circlip on both sides. They are a royal pain to install and rebuild. Use the kind with the nylon/delrin capsule, chrome-plated ball, zerk fitting and screw-in side plate. The screw-in side plate allows you to adjust tension with a simple pin spanner. Then you lock it with a set screw. It's a great design.
If you have a newer 2nd Gen. or 3rd Gen. Ram, the closest thing you'll find is a 9/16 ID ball. If you grind this down to narrow the width for the top arms, you'll grind off much of the flange and mess up your purchase area. If you bore it out to 16mm for the bottom and weld a spacer or use a washer for the width, you'll be making the walls dangerously thin. We tried this to test one company's spherical balls. It was a bad move. Stuff failed. Essentially, there's no way to cleanly Jerry rig these for late model Rams.
Long arm conversion.
The purpose for this design is to make the arc upon wich the axle travels as oblate as possible for the given amount of suspension travel. The more wheel travel you have the bigger the arc, so the longer the arms have to be. Imagine very short arms with 15" of travel. The axle would move very far back and very far forward (relative to the longitudinal axis of the vehicle). Now imagine 15" of travel with very long arms. The closest point aft to the farthest point forward (on the arc) is greatly reduced. This helps with a lot of things - steering, caster angle changes, shock angle changes. Basically, long arms greatly reduce the operating angles of major components. A common (and very tired) misconception is that longer arms by themselves equate to a smoother ride. There is only one reason this would be true. If everything else were equal (i. e. springs, shocks etc. ), then the reduced operating angles of certain bushings, and the greater leverage on the bushings could contribute to a smoother ride due to reduced relative resistance. Some may argue this but I think they would be hard-pressed to put forth empirical data to back up their point.
There are a couple of "long arm" kits for Dodge trucks running around out there. They require a lot of welding and rigging. Basically, all they're doing is relocating where the wheel travel occurs - lift kits. You've got to cut off, or notch one cab mount on each side of the truck to permit the upper arm to clear. We once notched a forward cab mount to clear a reservoir and the front of the truck eventually collapsed about 3". To prevent this they may offer reinforcements with the kit. Drop pitman arms and the usual lift kit stuff completes the picture.
Since, above all things, going fast off road requires wheel travel, longer arms just don't make sense for a truck using stock steering and drivelines. Unless you're fabricating some crazy stuff (and we can't because we're racing a "Stock" class that requires OE steering and OE control arms) true wheel travel is limited by steering and u-joint angles, not control arms, longer or not.
During the 1000 I bent two control arms, snapped an upper mounting flange and blew a bushing out of a housing. We drove back to California (over 1000 miles) on only three control arms. When we did the forensics on the truck we discovered what we needed to do to prevent stuff like this from happening again. We're not allowed to race with special control arms, but when we go to Baja for fun, they're on the truck.
Cheers,
Kent
- Status
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
