Adjusting UCA/LCA

[o2sys]

I know probably get for this...but I've searched and just don't understand the adjustments of the UCA and LCA.

I know how they can improve that handling and wheels hop and all the other stuff I can read but I have no idea what it means to adjust them and what does what.

For example making the UCA does what? What are you looking to achieve by extending or shortening? Too long does what too short does what?

Same for the LCA, adjusting it does what to the axles? What are you looking to achieve by extending or shortening? Too long does what too short does what?

Can someone help me out to understand in very simple terms?

 

[Sky Render]

Adjusting the UCA allows you to set pinion angle.

You should never adjust the lengths of the LCAs, as that would affect your wheelbase. The exceptions are for circle track use (to add some "default" steering to the car), or a ludicrously-overpowered drag car that needs to preload one side of the suspension for hard launches.

 

[o2sys]

So the average person who buys adjustable lca don't really adjust them? So no point in buying a adjustable one over a none adjustable unless of the two scenarios you mentioned above.

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[BMR Tech]

Adjustable Control Arms are a great choice, for users who's best interest, is the performance of the suspension system.

Adjustable LCA provide several advantages, over non-adjustable pieces.

-They allow you to "dial-in" your alignment. So, for example, instead of running whatever thrust angle the fixed length LCA provide, you can adjust the thrust angle to "0". Zeroing out your thrust angle is always a very good idea. This will ensure the rear axle wheels are squared up to the front. It typically also results in better toe readings. Like Thrust, I am a fan of toe settings being as close to zero as possible. It is often impossible, so setting thrust to zero is my recommendation.

-They allow for wheelbase adjustment. This can be beneficial, for select/certain applications. Often times, my customers have issues with tire clearance, which an adjustable LCA can help with. You can also lengthen your wheelbase just slightly, which can lead to enhanced performance. The longer the LCA, the more stable the rear axle. The longer the wheelbase, without getting "too" technical, can and will enhance stability - while, the shorter wheelbase enhances agility - per say. For example, very general, an autocross car may benefit from the shorter wheel base, and a road course may benefit from a longer wheelbase. In drag racing, the longer wheelbase is typically always better - unless wheelies are more important than ET.

Adjustable UCA can also provide advantages!

-If you are upgrading the UCA on your car - I always recommend an adjustable piece. The PRIMARY purpose for the adjustment, on the cars that I support....is simply to adjust drivel-line angles. (AKA: Adjusting Pinion Angle)

-There is also benefit to lengthening the UCA. Like the LCA, lengthening the UCA will add stability to the rear axle. This is why you will find people upgrading to 11+ UCa in their 05-10 Mustangs, because the 11+ UCA is 1" longer. A more stable axle, leads to better performance anywhere, in any driving form. The catch is, you have to watch your pinion angle when lengthening the UCA. If you keep the stock 18.5" length on the LCA, but lengthen the UCA too much....your drive-line angles will hate you - I promise.

I hope that helps.

 

[o2sys]

Ok but according to this link:

http://www.cherod.com/mustang/HowTo/LCA _adj.htm

Its says to adjust LCA for the pinion angle?!

 

[BMR Tech]

So what happens if you buy a fixed length LCA and later decide to drop your car? Not to worry, you don't need to change your LCAs; instead you can adjust the pinion angle by replacing the upper control arm (UCA) with an adjustable one. Ideally it is desirable to make the adjustments on the LCAs instead of the UCAs because the LCAs are easier to access and thus much easier to adjust.!

Well - I agree with the part in bold.

In Red - that is simply not true. Well, it is - as the LCA are easier to get to....but, adjusting the LCA for pinion angle is just not what you do on these cars.

What ends up happening is, you change your wheelbase drastically. I do not recommend altering wheelbase, as a by-product of changing something else.

 

[Sky Render]

Sure, the LCAs are easier to access. Definitely. But it alters your wheelbase, just like Kelly and I both said. It's furthermore a PAIN IN THE BUTT to get them both the same length, with zero thrust angle, and the correct pinion angle! The UCA is the preferable method of doing this, and while more difficult, the adjustment only needs to be done once! So who cares if it's a little more difficult to access, especially considering how difficult it is to get both your LCAs the EXACT SAME length?!

 

[SoundGuyDave]

+1 to both of the above... Setting up the rear is honestly best done on an alignment rack, where you can see (instantly!) how changes to one component will affect another. Generally speaking, set the LCA to center the axle in the wheel openings, and adjust so that the wheelbase is identical side-to-side. Next, adjust the UCA for proper pinion angle, the go back and touch-up the LCAs to ensure thrust angle is as close to 0* as you can get it. Finally, adjust the PHB to center the axle in the car, and re-check everything. I did it on a shop floor, with plumb-bobs, chalk-marks and a tape measure and it took me nearly 4 hours. After I replaced my axle assembly (wreck damage), it took me about 30 minutes on a computerized alignment rack. MUCH easier!

 

[Sky Render]

I just used my stock LCAs as a "jig" and put the bolts through them and the adjustable BMR control arms at the same time to make them both the same length. Seemed to work pretty well.

EDIT:
Make sure you use blue LocTite on the jam nuts!!!

 

[o2sys]

Can I use those magnetic camber degree tools to measure the pinion angle?

 

[jayel579]

https://www.youtube.com/watch?v=oe-GXr9yeCA

Adjusting UCA