Upper control arms, Adjustable or fixed?

[Space Dynamics]

Take note; I plan to take my car to the autocross and latter to some HPDE sessions. It is also my daily driver.



I've read many topics regarding upper control arms, most of them are friends having trouble choosing what brand to purchase. Brand aside, why would I choose fixed upper control arms over Adjustable?

[ford396]

In my opinion: fixed control arms are great for most people who want to bolt a part on to their car with minimal modifications. Adjustable control arms offer the advantage of being able to tweak length; thus changing camber gain slightly. They also allow for caster and camber adjustments that may be beyond where your upper mounts are designed to allow these settings, or you may decide to try a different spindle with different king pin inclination. This can be a two edged sword, as it is easy to make things worse if not aware of the effects that each change may bring about. This is where we get back to the fixed arms.

Bob

[Space Dynamics]

Thank you very much for the information!

Another question: My front springs currently have rubber separators in them ( I suppose they collapsed a bit) Would purchasing new (stiffer) springs be unwise without a matching set of leafs for the rear? Since I am replacing my upper control arms this would be a perfect time to put new springs in.

[Rod]

you will probably get 10 people and ten answers.....adjustable arms are cool but once you set the adjustment...you will probably never reset them, sorta like coil overs once you set the ride-height you wont change that either...

I use solid structured arms...

[TheJDMan]

It might help if you identify what car you are working on.

[BMR Sales]

you will probably get 10 people and ten answers.....adjustable arms are cool but once you set the adjustment...you will probably never reset them, sorta like coil overs once you set the ride-height you wont change that either...

I use solid structured arms...

I Agree!

[a67]

Whether to run adjustable upper A-arms also depends upon which vehicle they are being bolted to. Many of the GM cars use shims between the upper arm and chassis to set the camber & caster. In this case an adjustable arm eliminates the shims and allows the camber & caster to be set via adjusting the a-arm itself.

No issues here with tweaking lengths and such, the proper adjustment is the one that gives the proper camber and caster angles.

Bob., running adjustable uppers on the '87 Regal...

[Gratefuldiver]

I have adjustable. In theory you can adjust them for great street handling and then install a shim pack for really aggressive handling when you want to go to the track, then simply remove them when done. That's what Ive been doing but have had a few small issues with my A-Arm bolts. Anymore I will just install new nylon insert nuts when I remove the shims. I think most of the issue was not using anti seize along with not using grade 8 nuts with the grade 8 bolts.

[Josh@Ridetech]

you will probably get 10 people and ten answers.....adjustable arms are cool but once you set the adjustment...you will probably never reset them, sorta like coil overs once you set the ride-height you wont change that either...

I use solid structured arms...

Exactly, this. Also, bushings in a fixed arm don't allow as much noise transfer as an adjustable heim does. Adjustable arms require quite a bit more maintenance.

[RobNoLimit]

I'll be #10. We make suspension systems and A-arms both ways. Most are fixed, but our all out performance minded systems use adjustable arms. Some, like SPC, use delron lined bushing adjusters with grease zerks for smoother operation and lower noise/maintenance. We use these type.
On an accurately designed IFS, the location of the pivot centerline of the A-arms is pretty important. With an adjustable arm, the pivot shaft can be set fixed, and only the ball joint moves around during adjustment. While this can/does change the effective length of the arm, and can change the camber gain rate, these are the trade-offs.
I like adjustable arms made with indexed hex stock adjuster sleeves. We engrave numbers on the flats of the sleeves, #1 - #6, so that it is easy to identify locations. Strength and durability is not an issue, you just neeed to decide what fits your plan the best.

[Gratefuldiver]

I like the idea of the sleeves being numbered

[Marcus SC&C]

We work with both types of arms everyday at the shop, all different brands and on many types of cars. Fixed arms great for applications where you know exactly what ride height, rake, static alignment settings, etc. you`ll be using and the fixed arms are designed for exactly that format. In other words they`re ideal for factory built cars that are carbon copies of each other. Things get a little more sketchy when you start dealing with hot rods and race cars where no two are exactly the same. Adjustable arms usually have a much wider adjustment range than fixed arms and often retain the ability to use shims as well. They are sometimes even modular so that they can be easily reconfigured for special applications. If your car requires geometry modification/correction to achieve best performance (as most vintage muscle cars do) then the upper A arms need to be made to match the new geometry or safe travel and the ability to achieve an acceptable static alignment may be compromised. In this role adjustable A arms can be a real problem solver. We work with and sell both types of arms but honestly once you`ve worked with adjustable arms for awhile you feel a little handicapped with fixed ones. In either case it`s critical that the A arms match the exact application. Here`s a link to a short additional article on A arms. http://scandc.com/new/node/944 Mark SC&C

[Space Dynamics]

Thank you very much for the valuable information my friends. The opinions and experiences I read are a big help!

[Rod]

Making adjustment to those adjustable arms is cool and most times you will need to recheck and adjust your alignment also....I use the solid arms because the arm is only affected by shims and the wanted movements is easily repeatable with shim stacks, and the shims in my arms are zip tied together and when I auto cross I simply slip in a few extra shims (a pre-determined set) to make the car have 2.5 degrees of camber...and after an event I just remove those extra shims and that puts me back to my 1 degree of daily driver camber and of course, these changes also affect the toe in and toe out...by adding camber that increases the toe out which is the wanted desirable affect for autocross....ok..I cant give away all my secrets but that is how I use my solid control arms

[Nicks67GTO]

One of the reasons I chose the SPC arms was for Pontiac header clearance. I had a moderate size stack of shims on my old frame and my stock upper control arms almost punched a hole in my hooker super comps on the passenger side, right in the rear upper a arm mount. I filed the stock arms down but I was concerned that I might have clearance issues with fixed arms if I had too much shim in there so I picked the SC&C chassis with the SPC adjustable uppers to avoid any shims. I have tons of clearance now. I'm not sure if my concern was warranted but I'm pretty happy with my purchase and Marc has been a ton of help.

[Marcus SC&C]

Rod, we`ve been recommend doing exactly the same thing with the SPC adjustable A arms for years. They say great minds think alike! Once the adj. arms are locked down they become fixed arms and shims work exactly the same. Mark SC&C