Boxed *UPPER* rear control arms
April 2nd, 2013, 02:25 PM
#1
72 Olds CS
Thread Starter
Join Date: Jun 2011
Posts: 6,657
Boxed *UPPER* rear control arms
I am redoing the rear suspension on my 72 CS that is only street driven. I have new boxed lower control arms w poly bushings, a 1" rear sway bar, factory frame braces, and new moog upper control arm rubber bushings.
I am wondering if I should box the upper control arms as seen on this site www.leverfamilysite.com/ (i cant post the direct link from work
)
I would 'upgrade' to tubular but I have read that the upper control arms need to flex or the ride can be very harsh plus the tubular UCAs are a bit spendy and if I can use that cash somewhere else I would rather do that.
I have read that to keep the ride from being harsh choose the rubber replacement bushings for the UCAs and poly for the LCAs.
I am thinking I can redo my stock UCAs and box them in as shown on the above link, but is there any reason I dont want to do this. I also saw at one point hotchkiss offered a boxed UCA like that but I couldnt find a sample image just now.
I am wondering if I should box the upper control arms as seen on this site www.leverfamilysite.com/ (i cant post the direct link from work
)I would 'upgrade' to tubular but I have read that the upper control arms need to flex or the ride can be very harsh plus the tubular UCAs are a bit spendy and if I can use that cash somewhere else I would rather do that.
I have read that to keep the ride from being harsh choose the rubber replacement bushings for the UCAs and poly for the LCAs.
I am thinking I can redo my stock UCAs and box them in as shown on the above link, but is there any reason I dont want to do this. I also saw at one point hotchkiss offered a boxed UCA like that but I couldnt find a sample image just now.
Last edited by RetroRanger; April 3rd, 2013 at 06:24 AM.
April 3rd, 2013, 06:23 AM
#2
72 Olds CS
Thread Starter
Join Date: Jun 2011
Posts: 6,657
Does any one think this is a bad idea?, good idea?
Here is the step by step to box the upper rear control arms
http://www.leverfamilysite.com/Boxin...ntrol_Arms.htm
http://www.leverfamilysite.com/image...ppers_0024.jpg
Here is the step by step to box the upper rear control arms
http://www.leverfamilysite.com/Boxin...ntrol_Arms.htm
http://www.leverfamilysite.com/image...ppers_0024.jpg
April 3rd, 2013, 06:52 AM
#3
Hot Rod Has Been
Join Date: Dec 2012
Location: Central Wisconsin
Posts: 339
Boxed arms are a bad idea for street cars... They all are designed to flex. A circle track car will rip the frame mounts out of the frame if boxed arms are used... We use SOFTER than stock bushings...
Poly bushings will also cause a harsh ride... Stock bushings are best.
Poly bushings will also cause a harsh ride... Stock bushings are best.
Last edited by krooser; April 3rd, 2013 at 06:55 AM.
April 3rd, 2013, 07:55 AM
#4
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 48,238
If you use a metal ball joint instead of a bushing at the front end of the arm where it attaches to the frame, the binding problem goes away. In this case, yes, make the arms as stiff as possible and let the ball joint do it's job. It's all about binding and metal fatigue, and the ball joint eliminates this.
April 3rd, 2013, 06:07 PM
#6
72 Olds CS
Thread Starter
Join Date: Jun 2011
Posts: 6,657
Thanks for the inputs guys
I guess for now I will run stock UCAs w rubber. Down the road I may upgrade to the UMIs they look like the only ones to offer the roto joint. I do wonder about the roto joint longevity tho ?
Joe I went to Jegs but I couldnt find any UCAs for 68-72 A bodys that looked like your image
Ziff how long have you had yours and how much and how do you drive ? I dont mind working pushing the limits of traction and w my new to me 3.42 posi rear I expect to do some more of that this year
I see there are 3 flavors to the UMI UCA roto joints, adj, non adj, and adj w poly which ones are you using ?
what was your setup before the UMIs ?
they do look pretty too
I guess for now I will run stock UCAs w rubber. Down the road I may upgrade to the UMIs they look like the only ones to offer the roto joint. I do wonder about the roto joint longevity tho ?
Joe I went to Jegs but I couldnt find any UCAs for 68-72 A bodys that looked like your image
Ziff how long have you had yours and how much and how do you drive ? I dont mind working pushing the limits of traction and w my new to me 3.42 posi rear I expect to do some more of that this year
I see there are 3 flavors to the UMI UCA roto joints, adj, non adj, and adj w poly which ones are you using ?
what was your setup before the UMIs ?
they do look pretty too
Last edited by RetroRanger; April 3rd, 2013 at 06:14 PM.
April 4th, 2013, 05:12 PM
#7
Registered User
Join Date: Jun 2008
Location: Near Muskegon Michigan
Posts: 1,015
Thanks for the inputs guys
I guess for now I will run stock UCAs w rubber. Down the road I may upgrade to the UMIs they look like the only ones to offer the roto joint. I do wonder about the roto joint longevity tho ?
Joe I went to Jegs but I couldnt find any UCAs for 68-72 A bodys that looked like your image
Ziff how long have you had yours and how much and how do you drive ? I dont mind working pushing the limits of traction and w my new to me 3.42 posi rear I expect to do some more of that this year
I see there are 3 flavors to the UMI UCA roto joints, adj, non adj, and adj w poly which ones are you using ?
what was your setup before the UMIs ?
they do look pretty too
The pair that you have pictured are the one's that I am running. The non adjust with the roto joint. I run about 1000 miles a year on weekends and do drive her hard at times. Originally I had the stock upper arms with the boxed lowers with poly, and the factory braces or so called traction bars. The rear was really stiff and bounced. I added these and it did make quite a difference for the ride and handeling. I also run 3.42 gears and there is no hop at launch if you do that. Anyways, I am happy with my choice.
I guess for now I will run stock UCAs w rubber. Down the road I may upgrade to the UMIs they look like the only ones to offer the roto joint. I do wonder about the roto joint longevity tho ?
Joe I went to Jegs but I couldnt find any UCAs for 68-72 A bodys that looked like your image
Ziff how long have you had yours and how much and how do you drive ? I dont mind working pushing the limits of traction and w my new to me 3.42 posi rear I expect to do some more of that this year
I see there are 3 flavors to the UMI UCA roto joints, adj, non adj, and adj w poly which ones are you using ?
what was your setup before the UMIs ?
they do look pretty too
The pair that you have pictured are the one's that I am running. The non adjust with the roto joint. I run about 1000 miles a year on weekends and do drive her hard at times. Originally I had the stock upper arms with the boxed lowers with poly, and the factory braces or so called traction bars. The rear was really stiff and bounced. I added these and it did make quite a difference for the ride and handeling. I also run 3.42 gears and there is no hop at launch if you do that. Anyways, I am happy with my choice.
April 4th, 2013, 07:36 PM
#8
Registered User
Join Date: Jan 2009
Location: Maryville, Illinois
Posts: 82
After some lengthy conversations with Mark at SC&C, I have put the UMI uppers and lowers in my current build. They have roto joints in the lowers also to help eliminate the binding. I also went with the Hellwig rear sway that mounts to the axle tube and then to the the frame. This should be more effective and is along the same lines as modern cars use.
April 5th, 2013, 07:10 AM
#10
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 48,238
http://www.jegs.com/i/Ridetech/029/1...Fcud4AodMX4A3A
Note that those ARE adjustable - the rod end is threaded into the body of the arm.
Whatever you do, do NOT get something that looks like the ones below, with the adjuster in the middle of the arm:
Whoever designed that is NOT a structural engineer. The bending moment is highest at the midpoint, which is exactly where the smallest section is located for that threaded adjustment. Sorry, but this is a stupid design. Yeah, it makes adjustment easier, but it also significantly increases the flexibility of the arm, negating the whole reason for buying them in the first place!
April 5th, 2013, 08:11 AM
#11
Registered User
Join Date: Mar 2008
Posts: 3,883
Under acceleration, the pinion tries to climb the ring gear, so the front of the diff tries to tilt up. This compresses the lower arms and stretches the upper arms. Hence the need for boxing the lower arms. I have boxed upper arms for general strength, and other situations like strong braking. I don't know at what point (power, road racing, etc.) stronger arms are needed. I think a lot of people who would be well served by stock arms get the aftermarket stuff because of inventive marketing.
April 5th, 2013, 08:41 AM
#12
72 Olds CS
Thread Starter
Join Date: Jun 2011
Posts: 6,657
Thanks Joe
I did a drill down search for control arm for a 71 cutlass but those don't show up, now I saw the name/manufacturer and redid the search they still don't show up lol?
Rund I agree stuff IDK about I ask here and I am happy to get people's ideas an reasoning, stuff like JOes insight on the spohn arm being weak where it needs strength ....very good to know !
I did a drill down search for control arm for a 71 cutlass but those don't show up, now I saw the name/manufacturer and redid the search they still don't show up lol?
Rund I agree stuff IDK about I ask here and I am happy to get people's ideas an reasoning, stuff like JOes insight on the spohn arm being weak where it needs strength ....very good to know !
April 5th, 2013, 10:23 AM
#13
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 48,238
Thanks Joe
I did a drill down search for control arm for a 71 cutlass but those don't show up, now I saw the name/manufacturer and redid the search they still don't show up lol?
Rund I agree stuff IDK about I ask here and I am happy to get people's ideas an reasoning, stuff like JOes insight on the spohn arm being weak where it needs strength ....very good to know !
I did a drill down search for control arm for a 71 cutlass but those don't show up, now I saw the name/manufacturer and redid the search they still don't show up lol?
Rund I agree stuff IDK about I ask here and I am happy to get people's ideas an reasoning, stuff like JOes insight on the spohn arm being weak where it needs strength ....very good to know !
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