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post #1 of 52 Old 01-20-2010, 09:33 AM Thread Starter
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The Great Strength Versus Weight Suspension Component Debate

Guys

Here is a little bit of information you might find helpful when looking at the strength of materials versus the weight of the material or weight added to you Jeep. These compare most common materials used by manufacturers that support JK Owners... Of course, if you are a do it yourselfer, you might also want to factor in processes to make your own arms or things of that nature...

Rock Krawler uses 2" Dia. Solid 1020 CR Steel for its long lower control arms. We are also testing arms made from 2" Dia. solid 7075-T651 Aluminum which you will see at Easter Jeep Safari this year. They are intended to go in our Pro JK Systems if they test successfully! The new Pro Systems will be pretty expensive however, concidering the high cost of 7075-T651 Aluminum these days. On to the facts.

The biggest concern customers have is the control arms bending. The easy way to take a look at bending properties of material without being concerned over arm length etc. is to compare the cross sections resistance to bending.

For 2.00" diameter solid material I = 1/4pirexp4 = 1/4*3.14*1.000exp4 = .785in4

For 2" diameter 1/4" wall tubing I = 1/4piroexp4-1/4piriexp4= 1/4*3.14*1exp4 - 1/4*3.14*.75exp4 = .537in4

For 1 3/4" diameter .188" wall tubing I = 1/4piroexp4-1/4piriexp4= 1/4*3.14*.875exp4 - 1/4*3.14*.6875exp4 = .283in4

What does this mean to you? Basically 2" solid round material is more resistence to bending based on geometry along, followed by 2" - 1/4" wall, followed by 1 3/4 - 1/4 wall. Please note, this is based only on geometry and does not factor in the material properties.

When doing a material comparison the above is merely a reference on the geometric properties of the cross section to resist bending.... To get an accurate comparison of relative strength you will also need to account for the specific material strength... For doing so, we will concider all long arm to be relatively the same length and all mid or short arms to be relatively the same length so the bending moment from the bending force will be equal for all manufacturers.

Our suppliers 1020 CR Steel has a yield strength of 76,000 psi.

Our suppliers 7075-T651 Aluminum has a yield strength of 66,000 psi.

The average yield strength of 1026 DOM tubing according to Matweb is 70,000 psi.

So now you have to figure out what kind of force it takes to bend each cross section for all conditions being equal.

stress = MC/I. For now we will consider the stress level to be the yield strength of the material since any stress above the yield strength will allow the arm to bend. M since we said each arm is the same length will simply be the bending Force (F) times a constant which we can throw out for comparison sakes. C for will have a specific value for each cross section and I will be as stated above for each material.

2.00" Solid 1020 Cold Rolled Steel

76,000 pounds = F * 1.000/.785 therefore F = 76,000*.785/1.000 = 59660 pounds of force

2.00" Solid 7075-T651 Aluminum

66,000 pounds = F * 1.000/.785 therefore F = 66,000*.785/1.000 = 51810pounds of force

2" Diameter 1/4" Wall 1026 DOM Tubing

70,000 pounds = F *1/.537 therefore F = 70,000*.537/1 = 37590 pounds of force

1 3/4" Diameter 3/16" Wall 1026 DOM Tubing

70,000 pounds = F *.875/.283 therefore F = 70,000*.283/.875 = 22640 pounds of force

What does this mean to you? This means that arms made out of 2" solid 1026 CR steel are stronger for a given length arm than any other material shown above and are more than twice as strong as 1 3/4 - 3/16 wall 1026 DOM tubing for a given length.

Now, when you concider the weight differences;

2" solid alloy steel is approximately 10.6 #/ft

2" solid aluminum is approximately 3.5 #/ft

2" O.D. 1/4" wall tubing is approximately 4.7 #/ft

1 3/4" O.D. x 3/16 wall tubing is approximately 3.13 #/ft


For a given set of long arms that are all approximately the same length;

A 2" solid steel arm would weigh approximately 27.60 #'s

2" solid aluminum arm would wiegh approximately 9.11 #'s

2.0 O.D. x 1/4" wall tubing would weigh approximately 12.24 #'s

1 3/4" O.D. x 3/16" wall tubing is approximately 8.25 #'s


A long arm system upfitted with 2" solid alloy steel versus the lightest material 1 3/4" x 3/16" wall tubing is only approximately 77.4 pounds heavier over all for the long arms. That is not even the weight of a spare tire. Is it really that big of a difference given the strength difference? That is up to you to decide. Not to mention our arms made of 2" solid alloy steel carry an abuse proof lifetime warranty, where the others do not....

If you are a do it yourselfer, weigh out all the options above and pick what is best for you!

If you are a consumer, also wiegh out the above, price, customer service and everything else that may be important to you and make the best choice you can for you! Hype and BS are just that, facts are facts!

We hope that aluminum tests out well. We know some JK Owners would really like to see the ultimate in strength to weight ratio for their components!

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post #2 of 52 Old 01-20-2010, 09:48 AM
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Are only your lowers solid? Because 77 pounds only cover 4 arms.

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post #3 of 52 Old 01-20-2010, 09:53 AM Thread Starter
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Our uppers are solid as well, but they are much smaller in diameter so the weight ratio's are not as significant as the lowers.

On our X Factor systems we do the independent three link conversions, so there are only three links instead of 4 so it is hard to provide an accurate weight comparison when talking full systems and strength to weight ratios.

We were simply posting for imformational purposes so people had real world comparisons and the only way to truely do so is with the lowers since there it is 4 arms to 4 arms no matter who's kit you look at.

We hope this sheds some light on the subject matter for all.....

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post #4 of 52 Old 01-20-2010, 10:05 AM
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Good info hoss. Ya know, I've had my eye on one of your mid-arm setups for quite some time.

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post #5 of 52 Old 01-20-2010, 10:17 AM
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Less than 8,000 pounds of force difference and less than half the weight.

Lets go Aluminum...
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post #6 of 52 Old 01-20-2010, 10:25 AM
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edit by camo


let's refrain from the pimping please

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post #7 of 52 Old 01-20-2010, 10:27 AM
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Originally Posted by PBach View Post
Off-Road.com will be doing testing and a review on the new aluminum Pro Kit soon. Watch for it on a new JK Project.
Do you need a 4 door Rubicon to test it on?????
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post #8 of 52 Old 01-20-2010, 10:33 AM Thread Starter
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Aluminum is pretty salty though when it comes to price....

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post #9 of 52 Old 01-20-2010, 10:38 AM
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Do you need a 4 door Rubicon to test it on?????
We have a new, blue, four door, soft top, automatic, Rubicon.
THanks though.

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post #10 of 52 Old 01-20-2010, 11:06 AM
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Good info.


Anybody have an idea of how much force a JK can generate falling off a rock?

The "rule of thumb" I have always read in race suspension texts is that unsprung weight has roughly 10x the effect over sprung weight. This is HIGHLY vehicle dependant through.

So in theory 1lb added under the springs is equal to 10lbs in the passenger seat. Some suspension components are 1/2 sprung and 1/2 unsprung because they attach at both ends.

So (again, in theory) 77lbs of added unsprung weight has the "effect" of adding 770lbs to the Jeep (for @ speed manuvers, stopping, turning, etc). Which for a control arm should be cut by 1/2 so 385lbs of "effect". (only based on the rule of thumb and not the actual ratio for a JK) I would imagine the effect would be less on a vehicle like the JK which has a larger ratio of sprung to unsprung mass to start with.

Sounds like the aluminum arms could be the best of both worlds!!

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post #11 of 52 Old 01-20-2010, 06:23 PM Thread Starter
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Quote:
Originally Posted by Xtremjeepn View Post
Good info.


Anybody have an idea of how much force a JK can generate falling off a rock?

The "rule of thumb" I have always read in race suspension texts is that unsprung weight has roughly 10x the effect over sprung weight. This is HIGHLY vehicle dependant through.

So in theory 1lb added under the springs is equal to 10lbs in the passenger seat. Some suspension components are 1/2 sprung and 1/2 unsprung because they attach at both ends.

So (again, in theory) 77lbs of added unsprung weight has the "effect" of adding 770lbs to the Jeep (for @ speed manuvers, stopping, turning, etc). Which for a control arm should be cut by 1/2 so 385lbs of "effect". (only based on the rule of thumb and not the actual ratio for a JK) I would imagine the effect would be less on a vehicle like the JK which has a larger ratio of sprung to unsprung mass to start with.

Sounds like the aluminum arms could be the best of both worlds!!
"So in theory 1lb added under the springs is equal to 10lbs in the passenger seat. Some suspension components are 1/2 sprung and 1/2 unsprung because they attach at both ends." Where did that theory come from? There used to be a design factor of safety of 10 used for components that stated the components of a vehicle need to be able to withstand a 10g impact which would give you a factor of 10, however, biomechanical engineers figured out that if your body took a 10g impact, your brain would be mush so you were dead anyway!

If people really want to get involved with the Theory of what happens as you add weight to your vehicle, alter its center of gravity, go to larger tires etc, here is some good practical theory for you.

The basics of it and the world starts with Newton's Law or F=MA but to also take it further with angular acceleration effects of the vehicle itself you must also take into account I times alpha so the equations stretchs to F=MA+I*Alpha. F is simply a force, m=mass of the vehicle, I in simple terms for now is relative to the center of gravity of the vehicle and alpha is the angular acceleration of the body relative to its center of gravity.

So people can can quickly figure out from the above, the following logical deductions....

The acceleration of a vehicle is effected by weight! But, we are pretty sure everyone here knew that. But, how is it effected? One component is simply a ratio of the masses of the vehicle. Concidering it has the same power plant the Force remains constant thus the new ability of a vehicle to accelerate would simply be a ratio of the

original mass of the vehicle (before mods) divided by the new mass of the vehicle (after mods) times the old acceleration... So you tell us. Does the difference in weight of suspension components make a huge amount of difference based on the above? Not in a major way.

You also need to account for the changes in center of gravity and its effect on angular acceleration and how that effects the over all effect on vehicle acceleration and nimbleness. Like Xtremejeepin said, since some of the weight of the suspension is concidered sprung and some unsprung, then you need to concider what effect it has on the center of gravity of the vehicle. Usually, when you add weight down low, the center of gravity goes down, but then you have to take into account your increase in tire size and over all lift height. So by in large the center of gravity has gone up and that will effect acceleration as well. That certainly is not a huge effect when concidering the 77 lbs mentioned above. By in large our weight added is below the OEM center of gravity of the vehicle.

The last item that needs to be accounted for and this is a well debated topic now a days is the angular acceleration of the body. Suspension Geometry plays a huge part in this by having good roll center (track bar geometry for the most part), you are helping control the angular acceleration of the body or how it is allowed to roll over while cornering, this effects handling obviously and is the last part of the overall equation.....

All of the above items effect handling and acceleration. This is leaving out the effect of larger tires on greater rotational mass and their inertial effect without gear changes on basic acceleration.

So when it comes down to it, the overall weight of the components is by in large not a huge issue when you are comparing one system to another as their differences are small relative to all the other weights concidered. However, the strength and durability to the end consumer are certainly a point of concern.

Sure high strength aluminum will make for great suspension components, but that strength to weight ratio will come at a steep price that alot of people cannot afford or simply do not need!

Hopefully this sheds some light on the subject for alot of people!

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post #12 of 52 Old 01-20-2010, 06:58 PM
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What are you going to do for Joints? There are considerations that should be looked into with dis-similar metals and Aluminum. The comp guys run their rigs in a pretty restrictive environment (though brutal). With Lay JK quy, they will want to install and leave it. It will see more water and grime for extended periods then the average comp rig that usually runs Aluminum links. Also the average Joe may not understand this and in a bind change out Stainless components for Mild steel, which would cause problems in the long run. I've been curious about the Aluminum but I've had to deal with mistakes of the wrong fasteners in Aluminum aircraft parts, white powder isn't fun. I thought stainless HeliCoils might do the trick, and keep things seperated if unspec'd materials are used?

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post #13 of 52 Old 01-20-2010, 07:12 PM
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There's no question that solid is usually stronger than tube.
As a fair comparison use real world DOM yield strengths. The mill certs on our tubing is often in the 85-90 ksi range. That puts 2 x .250 DOM at F=45,650, not as much difference now, your 2" solid is still stronger, 20% more, but still more than twice the weight. You use solid because is cheap and you can just thread the end and not weld a threaded bung. Like they say in racing, you can have cheap, light and strong, pick any two.

When I look at stock JK's I notice how light some of the components are, the bumpers don't weigh any thing, there is a cast magnesium spare tire mount, the body panels are very thin, etc. Jeep engineers went to great lengths to keep the weight down. There must be a reason?? We do nothing but add weight to our modified jeeps, I just try to keep it to a minimum. 2 x .250 DOM lower control arms are a good compromise of weight and strength IMO, see I have this annoying tendency to engineer things.

When our 2dr JK had stock axles, short arm suspension, light wheels and tires, it would haul ass in the desert and would climb very well, it was really fun to drive, pretty amazing how well it worked with 4" lift and 35's. Now it has Rock Jock 60s, 40's, heavy bead locks and it is a dog, not nearly as much fun to drive any more.

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Aluminum is pretty salty though when it comes to price....

Rock Krawler
what kinda price jump are we talking?
or what would the price be to "upgrade" a current RK offering?

Would the end be a welded on tube like your current arms or would they be threaded both ends?
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what kinda price jump are we talking?
or what would the price be to "upgrade" a current RK offering?

Would the end be a welded on tube like your current arms or would they be threaded both ends?
It would have to be threaded, 7075 is not considered 'weldable'.

Those of you that think you know everything really annoy those of us that do!
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post #16 of 52 Old 01-20-2010, 07:26 PM
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Thanks professor RK!.......Geeeeze!

Simple version.

Rock Krawler JK systems = Uncompromising hardcore suspension

Now take off that lab coat, get off the computor and go work on your rig

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post #17 of 52 Old 01-20-2010, 07:29 PM
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Quote:
Originally Posted by Broncojohn View Post
What are you going to do for Joints? There are considerations that should be looked into with dis-similar metals and Aluminum. The comp guys run their rigs in a pretty restrictive environment (though brutal). With Lay JK quy, they will want to install and leave it. It will see more water and grime for extended periods then the average comp rig that usually runs Aluminum links. Also the average Joe may not understand this and in a bind change out Stainless components for Mild steel, which would cause problems in the long run. I've been curious about the Aluminum but I've had to deal with mistakes of the wrong fasteners in Aluminum aircraft parts, white powder isn't fun. I thought stainless HeliCoils might do the trick, and keep things seperated if unspec'd materials are used?
stainless and aluminum cause more galvanic corrosion than mild steel, you have less reaction with a zinc plated steel than stainless. (wider space on the galvanic series) Even less with a cad plated steel.

The rate of galvanic corrosion is related directly to the ratio of cathode area (less noble stainless) to anode area (more noble aluminum) and seeing as the aluminum surrounds the bolt you need to kinda pay attention to this.

For your issue (aircraft) place an epoxy paint first and install the fastener while it is still wet. The same could be done with a link if worried. But like I said, a cad plated joint (most common plating on them) is less corrosive than stainless by a LOT
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It would have to be threaded, 7075 is not considered 'weldable'.
juuuust making sure
Hey, he could start with an oversized rod, drill out the joint pocket and then turn it down to the OD of the control arm looking like a dog-bone.
It would be nuts, but I never underestimate nuts
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So Thats why I like my RK lift so much


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post #20 of 52 Old 01-20-2010, 09:32 PM
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[QUOTE=GOAT1;321852] You use solid because is cheap and you can just thread the end and not weld a threaded bung. Like they say in racing, you can have cheap, light and strong, pick any two.

If solid is cheaper, why don't more of the inexpensive kits on the market use solid?
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Originally Posted by GOAT1 View Post
When our 2dr JK had stock axles, short arm suspension, light wheels and tires, it would haul ass in the desert and would climb very well, it was really fun to drive, pretty amazing how well it worked with 4" lift and 35's. Now it has Rock Jock 60s, 40's, heavy bead locks and it is a dog, not nearly as much fun to drive any more.
No chit... I miss it

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Quote:
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You use solid because is cheap and you can just thread the end and not weld a threaded bung. Like they say in racing, you can have cheap, light and strong, pick any two.

If solid is cheaper, why don't more of the inexpensive kits on the market use solid?
Very good question.


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post #23 of 52 Old 01-21-2010, 08:53 AM
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To me, this thread is something akin to 3 degrees of irrelevance.

We're talking Wrangler control arms here, not passenger jet wing structure bulkheads. When's the last time anyone saw a Jeep taco a control arm from a major manufacturer? I've seen a picture of one in a test, from Trailmaster (low buck), and a trashed stocker. Even for those stock/low-buck parts, the Jeeps were getting pounded pre-runner style with absolutely no mercy. Does it really matter if one is 20% stronger when control arms failures to your average wheeled (or even hard rock crawler) Jeep are almost non-existent to begin with - especially if it comes at a weight penalty?

And aluminum? Why bother? These are layman wheeler's rigs for the most part, not circuit racers. I could lose an equivalent amount of weight from my Jeep by eating a few less chimichangas per week. Seems like bringing a SCUD to a knife fight. The fact that RK is considering this for public JK kits just tells me that JK owners at large just have WAY too much money to burn. Not that I can blame RK for that - if I was in their shoes I'd do the same thing.

I think a well-designed kit with corrected geometry and maximized articulation capabilities makes the utmost sense. RK and Poly (and a number of others) already offer this. Four-wheeling, anyone?

It's interesting information, sure. But for a lot of people this whole wheelin' thing seems to have moved from 'Hey, let's go hit the trails with what we've got!' to complete and total obsession over inconsequential minutia that make no real-world difference.
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post #24 of 52 Old 01-21-2010, 09:08 AM Thread Starter
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Wow, the educational post has now turned into the same old BS which is not what it was intended to be at all!

Goat1 To Address Your and PIG's Statements or Questions.

"There's no question that solid is usually stronger than tube.
As a fair comparison use real world DOM yield strengths. The mill certs on our tubing is often in the 85-90 ksi range. That puts 2 x .250 DOM at F=45,650, not as much difference now, your 2" solid is still stronger, 20% more, but still more than twice the weight. You use solid because is cheap and you can just thread the end and not weld a threaded bung. Like they say in racing, you can have cheap, light and strong, pick any two.

When I look at stock JK's I notice how light some of the components are, the bumpers don't weigh any thing, there is a cast magnesium spare tire mount, the body panels are very thin, etc. Jeep engineers went to great lengths to keep the weight down. There must be a reason?? We do nothing but add weight to our modified jeeps, I just try to keep it to a minimum. 2 x .250 DOM lower control arms are a good compromise of weight and strength IMO, see I have this annoying tendency to engineer things.

When our 2dr JK had stock axles, short arm suspension, light wheels and tires, it would haul ass in the desert and would climb very well, it was really fun to drive, pretty amazing how well it worked with 4" lift and 35's. Now it has Rock Jock 60s, 40's, heavy bead locks and it is a dog, not nearly as much fun to drive any more."

First to address your strength of material concerns. Your Poly Performance website states that your lower long arms are made from 1 3/4" O.D. .188 wall 1026 DOM tubing.

Copied right off your website:
•Poly Performance Front Long Arm Lower Control Arms for 2 Door & 4 Door Jeep JKs
•Suspension components feature an abrasive resistant powder coat finish for maximum durability and corrosion resistance
•Made from high quality crush resistant 1 3/4" X .188 Wall 1026 DOM tubing
•Arms are designed and manufactured to maximize ground clearance
•The arms will allow the use of OEM wheels with larger tires without the requirement of an additional wheel spacer

•Features an OEM style bushing for extended permanence & minimized road vibration
•Incorporates the tried and true Currie Enterprises Johnny Joints® for paramount performance
•Poly Performance Double Adjuster Sleeve & Pinch Bolt Assembly: allows for adjustment of control arm length without removing control arm mounting bolt
•100% bolt on components assures an easy, trouble free installation with the use of basic hand tools
•Sold in pairs

The 2" O.D. 1/4" wall thickness will be a conciderable improvement over your current offering if you are indeed upgrading or changing the material. The yield strengths that we posted are all based off ASTM standards. Sure, there are going to be mill runs where it will run higher, that statement goes for all materials, but the ASTM standards are the minimum! That is why we posted those numbers and it can be quickly referenced through matweb. Again, this was done for the people. Not to have a pissing contest. We have also seen some rediculous numbers on our 1018-1020 CR during our mill runs, but we are not going to base anything on that knowing that does not have to be the case! You have no control over that. Especially if you do not order mill runs of material.

To address your concern over weight. Weight is always a concern. You are talking about your JK handles poorly now because it is heavy! You probably added over 1500 pounds to your JK in axles, going with 40" tires, your long arm suspension, all of your Poly Body Armor, Bumpers, etc. Alot of things will contribute to the poorer handling. Could be suspension related? We would imagine a huge effect would be the rotational inertia and mass of the 40's from 35's? Another huge effect will be all the weight you added up top further raising the CG of the vehicle with all your armor, roll cage, etc.

If you want to bad mouth us for our system being a little heavier, on a relative scale we are talking what here, 70 to 80 lbs, call it at worse 100 as the difference between our full long arm system and your Poly kit! To put it into perspective for the average consumer, that is the equivalent of approximately 12.8 gallons of fuel at most. That certainly won't make your JK handle like crap! Not to mention, this weight difference is down low where it actually aids in lowering your vehicles effective CG. When we come out with our body armor if we do, it will be all aluminum. Nice and light weight up top designed to protect! In our opinion, in some places it is ok to add weight and in some cases better methods should be sought out!

What are we seeing JK 4 Doors tipping the scales at these days on 40 or 42" tires all armored up and accessorized. Say 5500 pounds plus? That will contribute significantly to poorer handling, acceleration loss, but if that is how the consumer wants his or her rig, then the basic equations above apply and if you want it move faster, then you will have to have great Force. This is why hemi swaps are so popular and almost needed at that point in our opinion. Power adders are certainly nice for a JK tipping the scales in that range!

Sure Jeep tried to save weight where they could on the JK. Look how much heavier they are than a TJ. They had to do something where they could to help out their fuel economy numbers someplace. The new frames are stronger and heavier, the axles are larger, the brakes are bigger, the body is physically bigger, so sure. Chrysler designed a few parts that were hopefully based on weight savings. Notice, all their weight savings was mostly on the body and accessories. They did not skimp on the frame or major structural components!


"Originally Posted by GOAT1
You use solid because is cheap and you can just thread the end and not weld a threaded bung. Like they say in racing, you can have cheap, light and strong, pick any two.

If solid is cheaper, why don't more of the inexpensive kits on the market use solid?

Very good question"

PIG, really is that your arguement? That is a poor way to judge just about anything. You guys do some things that other companies do not do.

We own all the machines to manufacture all of our arms and components in house! We are a machine shop by nature, we own all the lathes, bending equipement, welding equipment, and even in house powder coating equipment. We also manufacture for other companies. That is how we are set up as a company. Most other suspension "manufacturers" really don't manufacture anything. They might design it, then they source all the parts and put them into a box, not really manufacturing anything. We would imagine the up front costs keeps this process away from alot of other manufacurers.

Sure solid alloy steel is more cost effective. Not by much for us! We order mill runs of material since we manufacture in house! We own all the machines to perform the work and since we own the machines and equipment it is easy for us to simply machine the ends of the bars, bend them and weld a tube on for the bushings! It is strong, which cannot be denied, however it is also a more robust and a cost effective process. We do not have to machine a threaded bung, we do not have to fixture and weld in a threaded bung, so two hole operations are ommitted where a possible mistake could be made. This creates a more robust and cost effective product! In the end, in our opinion, the consumer wins! They get a very robust product as cost effective as possible!

The above reasons is probably why not alot of other companies do it! The capital required to buy all the equipment neccessary to perform all the operations would be a major hinderance! And, like most, if the components are simply designed then sources (and especially if they are coming from over seas), the shipping of the components in would be a major overall expense and a significant cost of the bill of materials relative to the raw cost of goods!




Now, to help out those that actually tried to bring some relavent information or offer good questions!

Yes we are concerned about the corrosion causing issues. On things like bridges and stuff, zinc blocks are used for sacrificial anodes. Our first thought is that the zinc plating on our joints will hopefully act like that sacrificial anode and prevent the joints from freezing into the aluminum material. We are in the perfect enviroment to test this out. In NY, our roads are covered with salt from Oct some years all the way through April.

For those questioning the welding of 7075; it is similar to that of welding heat treated chromoly. It can be done, but you must be concerned with the change in material properties in the "heat effected zone", so if you are at home triing to weld any high strength material, be aware of that and make sure it will not be a cause for concern.

Sorry for all of those who are actually triing to learn something and educate themselves on the basics of materials, process, etc. We hope you can read through alot of the BS, take in the facts, and think for yourself. We truely started this post to help educate and help out the entire JK Community.

Rock Krawler
Rock Krawler Suspension is offline  
post #25 of 52 Old 01-21-2010, 09:27 AM
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Quote:
Originally Posted by PBach View Post
Off-Road.com will be doing testing and a review on the new aluminum Pro Kit soon. Watch for it on a new JK Project.
You mean a paid infomercial for RK? Do you "review" any other suspensions?

I would honestly love to see one.

Quote:
Originally Posted by Co4Lo View Post
Seriously dude?
Don't you ever stop?
No. Unlike others here I would actually like to participate in a suspension discussion and possibly learn more.

Quote:
Originally Posted by Rock Krawler Suspension View Post
"So in theory 1lb added under the springs is equal to 10lbs in the passenger seat. Some suspension components are 1/2 sprung and 1/2 unsprung because they attach at both ends." Where did that theory come from? There used to be a design factor of safety of 10 used for components that stated the components of a vehicle need to be able to withstand a 10g impact which would give you a factor of 10, however, biomechanical engineers figured out that if your body took a 10g impact, your brain would be mush so you were dead anyway!


Hopefully this sheds some light on the subject for alot of people!

Rock Krawler
You totally missed it. I was talking about the suspensions ability to control oscillation of both the sprung and unsprung mass as it relates to keeping the tires planted on the ground for control.

Where did you get all this bio mechanical impact stuff from? Totally unrelated to what I was talking about. ( I think maybe you read my first question about how much force the JK can generate, and blended it into the next paragraph on the unrelated sprung vs. unsprung mass, and that may be the source of the confusion)






Quote:
Originally Posted by X-Defector View Post
To me, this thread is something akin to 3 degrees of irrelevance.

We're talking Wrangler control arms here, not passenger jet wing structure bulkheads. When's the last time anyone saw a Jeep taco a control arm from a major manufacturer? I've seen a picture of one in a test, from Trailmaster (low buck), and a trashed stocker. Even for those stock/low-buck parts, the Jeeps were getting pounded pre-runner style with absolutely no mercy. Does it really matter if one is 20% stronger when control arms failures to your average wheeled (or even hard rock crawler) Jeep are almost non-existent to begin with - especially if it comes at a weight penalty?

And aluminum? Why bother? These are layman wheeler's rigs for the most part, not circuit racers. I could lose an equivalent amount of weight from my Jeep by eating a few less chimichangas per week. Seems like bringing a SCUD to a knife fight. The fact that RK is considering this for public JK kits just tells me that JK owners at large just have WAY too much money to burn. Not that I can blame RK for that - if I was in their shoes I'd do the same thing.

I think a well-designed kit with corrected geometry and maximized articulation capabilities makes the utmost sense. RK and Poly (and a number of others) already offer this. Four-wheeling, anyone?

It's interesting information, sure. But for a lot of people this whole wheelin' thing seems to have moved from 'Hey, let's go hit the trails with what we've got!' to complete and total obsession over inconsequential minutia that make no real-world difference.


Totally agree with this.


I asked earlier if anyone knew how much force a JK could generate falling onto or impacting a control arm? Knowing the bending strength of something has no relevance if we don't know how much force we are trying to counter.

If the JK can only generate 10K lbs of force, then ANY of the quoted arms (and maybe even the stock arms) are sufficient.



Quote:
Originally Posted by Rock Krawler Suspension View Post
Wow, the educational post has now turned into the same old BS which is not what it was intended to be at all!

.....
Sorry for all of those who are actually triing to learn something and educate themselves on the basics of materials, process, etc. We hope you can read through alot of the BS, take in the facts, and think for yourself. We truely started this post to help educate and help out the entire JK Community.

Rock Krawler

I would love to have an open discussion on suspension here. I think it would be great for the community.

Unfortunately there are too many children in this forum stuck on name calling and bashing.

Let's put all the brand names and BS aside and actually have an educational discussion.

__________
Cole Ford
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