Replacing rear control arms - lowers question. - Chevelle Tech
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post #1 of 17 (permalink) Old Jul 4th, 16, 1:50 PM Thread Starter
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Replacing rear control arms - lowers question.

Hey if you were replacing rear lower control arms which would you use if you had both available?

These seem to weight the same or close. Car will do some auto-x and HPDE

I also I have Umi adjustable for uppers.

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1969 Chevelle Malibu
73k miles
350/330 crate motor
5 spd - Legend 700
4.11 rear
Holley 4160 600cfm
Original console and bucket car
disc brakes
aluminum rad/elec fans
QA1 adjustable shock/new springs/new tubular control arms front and back / tall ball joints



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Last edited by Bullcrappy; Jul 4th, 16 at 2:24 PM.
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post #2 of 17 (permalink) Old Jul 4th, 16, 2:22 PM
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Re: Replacing rear control arms - lowers question.

The picture you show looks like lower arms not uppers. Also the tubular one looks shorter than the stock one. You won't be gaining anything by using the tube one over the stock one.
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post #3 of 17 (permalink) Old Jul 4th, 16, 2:25 PM Thread Starter
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Re: Replacing rear control arms - lowers question.

they are lowers.

they are same size.

neither are stock.


Quote:
Originally Posted by Bonkerman View Post
The picture you show looks like lower arms not uppers. Also the tubular one looks shorter than the stock one. You won't be gaining anything by using the tube one over the stock one.

1969 Chevelle Malibu
73k miles
350/330 crate motor
5 spd - Legend 700
4.11 rear
Holley 4160 600cfm
Original console and bucket car
disc brakes
aluminum rad/elec fans
QA1 adjustable shock/new springs/new tubular control arms front and back / tall ball joints



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post #4 of 17 (permalink) Old Jul 4th, 16, 3:56 PM
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Eugene
 
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Re: Replacing rear control arms - lowers question.

Sorry I misread your post. The bottom one in the picture looks like a stock lower arm but I can't tell if it is boxed in on the bottom or not. They will both do the same job so not much to gain either way.
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post #5 of 17 (permalink) Old Jul 4th, 16, 4:32 PM Thread Starter
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Re: Replacing rear control arms - lowers question.

Thanks Eugene that what I'm looking for... they are boxed. Both are an upgrade to stock unboxed.

wasn't sure if I should go with one over the other. sounds like no difference so no matter.

probably go with tubular as they are smaller and maybe hair lighter.


Quote:
Originally Posted by Bonkerman View Post
Sorry I misread your post. The bottom one in the picture looks like a stock lower arm but I can't tell if it is boxed in on the bottom or not. They will both do the same job so not much to gain either way.
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post #6 of 17 (permalink) Old Jul 4th, 16, 8:54 PM
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Re: Replacing rear control arms - lowers question.

I'd go with the tubular. They look like my UMI arms. I'm satisfied with them.
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post #7 of 17 (permalink) Old Jul 5th, 16, 1:17 AM
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Re: Replacing rear control arms - lowers question.

The stock looking arm looks stock.

I like the stock looking arm in that you are not relying on the weld that is in between the tube and the bushing housing.

The stock looking arm is boxed and that makes it very strong.

It looks like it has had a sway bar attached as I see a depression where the bolt has been.

What cannot be told from the picture is if there is support inside the arm to keep the arm from crushing when you tighten the sway bar bolts.

If you would post a picture of the bottom side so that I can see the weld job on the insert and whether there is support on the inside of the arm I can give you am much more informed opinion.

Glenn R. Lever
Rochester, New York 14617-2012
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post #8 of 17 (permalink) Old Jul 5th, 16, 8:28 AM
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Re: Replacing rear control arms - lowers question.

These are the UMI lower control arms I went with. They are very well constructed.


1964-1972 GM A-Body Rear Lower Control Arms, Fully Boxed, Premium [4021] - $269.99 : UMI Performance, Inc.
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71 Malibu, Cottonwood Green, 396 BBC, AutoGear M22W 4 speed, 12 bolt 3:55 posi.
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post #9 of 17 (permalink) Old Jul 5th, 16, 2:00 PM
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Re: Replacing rear control arms - lowers question.

Personally I would not use either one. The stock arms are designed to twist some, as the rubber bushings can only flex so much before they bind. By using poly bushings, you eliminate the bushing flex and rely on the arm to twist. If you box the stock arms or use solid arms (round or square tubing) you eliminate all twisting. Might be great for a drag only car but a street driven or one you want to handle well, this is the worst thing you can do.

What you need are arms with flex joints of some type. Many companies make this style (UMI, Global West, Speed Tech, etc.). This allows rotational motion without binding yet prevents side to side and up and down flex that the stock arms would have. They also prevent tearing out the stock frame/axle mounts due to binding. Yes they are more money but they will handle much better, ride better and put much less strain on all the parts.

Here is what I will be buying.
1968-1972 GM A-Body Pro-Touring Rear Suspension Kit [ABR824] - $674.99 : UMI Performance, Inc.
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1972 El Camino SS (clone), 350/350 combo, UMI upper and lower A arms, UMI 1" dropped springs, Bilstien shocks, Dakota Digital VHX gauges, Rev 17"x8" wheels, Nitto 555 tires.

Last edited by chevymike; Jul 5th, 16 at 2:08 PM. Reason: typo
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post #10 of 17 (permalink) Old Jul 5th, 16, 2:14 PM
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Re: Replacing rear control arms - lowers question.

Quote:
Originally Posted by chevymike View Post
Personally I would not use either one. The stock arms are designed to twist some, as the rubber bushings can only flex so much before they bind. By using poly bushings, you eliminate the bushing flex and rely on the arm to twist. If you box the stock arms or use solid arms (round or square tubing) you eliminate all twisting. Might be great for a drag only car but a street driven or one you want to handle well, this is the worst thing you can do.

What you need are arms with flex joints of some type. Many companies make this style (UMI, Global West, Speed Tech, etc.). This allows rotational motion without binding yet prevents side to side and up and down flex that the stock arms would have. They also prevent tearing out the stock frame/axle mounts due to binding. Yes they are more money but they will handle much better, ride better and put much less strain on all the parts.
I agree, EXCEPT it probably doesn't make a huge difference on the lower arms, as they are "nearly" parallel... There may be some bind...

For upper arms, I completely agree, go with rubber or swivels on both ends...

As for the lowers, I chose the Global West (TCA-4?) as they have the swivel at one end...


As for this post, I think I'd use the tubulars. I have run a similar set of stock arms, boxed with 3/16" plate, and they worked well, but I still wonder about the thinner material of the original box...

Once you go RAT, you never go back...
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post #11 of 17 (permalink) Old Jul 5th, 16, 2:36 PM
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Re: Replacing rear control arms - lowers question.

Quote:
Originally Posted by 1966_L78 View Post
I agree, EXCEPT it probably doesn't make a huge difference on the lower arms, as they are "nearly" parallel... There may be some bind...

For upper arms, I completely agree, go with rubber or swivels on both ends...

As for the lowers, I chose the Global West (TCA-4?) as they have the swivel at one end...


As for this post, I think I'd use the tubulars. I have run a similar set of stock arms, boxed with 3/16" plate, and they worked well, but I still wonder about the thinner material of the original box...
Even parallel, the rear axle twists and in turn uses the bushing to allow rotational twist. Take your springs out start jacking up one side and I think you'll be surprised at the amount of twist there is. Poly bushing allow almost zero rotational flex. Again, straight line not an issue but street/corner carving/auto-x there is a lot of bind. I would rather use stock bushings than poly. Too often suspension bind is confused for "stiffer" suspension.

1972 El Camino SS (clone), 350/350 combo, UMI upper and lower A arms, UMI 1" dropped springs, Bilstien shocks, Dakota Digital VHX gauges, Rev 17"x8" wheels, Nitto 555 tires.
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post #12 of 17 (permalink) Old Jul 5th, 16, 2:41 PM Thread Starter
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Re: Replacing rear control arms - lowers question.

My uppers are swivel...

here is kit I have basically purchased although separately purchased.

68-72 GM A-Body Upper & Lower Control Arm Kit [ABR801] - $314.99 : UMI Performance, Inc.

I could have stepped up to the roto joint on lowers... not sure how much gain there would be. I don't think enough for me to sell these two sets and buy a third.

I also have larger then stock sway bars front ant rear.
Front 1 1/4" or 1 /3/8 up front forget which and 1" rear...




Quote:
Originally Posted by chevymike View Post
Personally I would not use either one. The stock arms are designed to twist some, as the rubber bushings can only flex so much before they bind. By using poly bushings, you eliminate the bushing flex and rely on the arm to twist. If you box the stock arms or use solid arms (round or square tubing) you eliminate all twisting. Might be great for a drag only car but a street driven or one you want to handle well, this is the worst thing you can do.

What you need are arms with flex joints of some type. Many companies make this style (UMI, Global West, Speed Tech, etc.). This allows rotational motion without binding yet prevents side to side and up and down flex that the stock arms would have. They also prevent tearing out the stock frame/axle mounts due to binding. Yes they are more money but they will handle much better, ride better and put much less strain on all the parts.

Here is what I will be buying.
1968-1972 GM A-Body Pro-Touring Rear Suspension Kit [ABR824] - $674.99 : UMI Performance, Inc.

1969 Chevelle Malibu
73k miles
350/330 crate motor
5 spd - Legend 700
4.11 rear
Holley 4160 600cfm
Original console and bucket car
disc brakes
aluminum rad/elec fans
QA1 adjustable shock/new springs/new tubular control arms front and back / tall ball joints



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post #13 of 17 (permalink) Old Jul 5th, 16, 9:08 PM
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Re: Replacing rear control arms - lowers question.

I'd buy a set of these:

box plates for rear lower control arms
https://www.summitracing.com/parts/o...SJYaAh0Z8P8HAQ

not hard to weld.

Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #14 of 17 (permalink) Old Jul 5th, 16, 9:36 PM Thread Starter
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Re: Replacing rear control arms - lowers question.

Tom. agreed welding is not tough but neither is looking at a picture

The square set IS boxed and the tubular are well tubular.

I have both in my possession now just wanted opinions between those two that i have already.

no need to weld or box...all done already.




Quote:
Originally Posted by Tom Mobley View Post
I'd buy a set of these:

box plates for rear lower control arms
https://www.summitracing.com/parts/o...SJYaAh0Z8P8HAQ

not hard to weld.

1969 Chevelle Malibu
73k miles
350/330 crate motor
5 spd - Legend 700
4.11 rear
Holley 4160 600cfm
Original console and bucket car
disc brakes
aluminum rad/elec fans
QA1 adjustable shock/new springs/new tubular control arms front and back / tall ball joints



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post #15 of 17 (permalink) Old Jul 5th, 16, 11:31 PM
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Re: Replacing rear control arms - lowers question.

I see the pic of your rectangular arm. It appears to be collapsed around the bolt hole as if it were boxed with a piece of flat strap. don't see anything that looks like a internal support to keep from collapsing the arm when tightening up the stabilizer bar bolts, which is why I posted the link to the real part.
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