Choosing between rear lower and upper control arms for camber adjustment

[Big Smurf]

Why do most people replace the rear lower control arm (RLCA) to adjust camber? Wouldn't using an adjustable upper control arm (RUCA) avoid messing with suspension motion ratio or anti-roll bar mounting? Thoughts?

 

[NYPizzaPie]

Why do most people replace the rear lower control arm (RLCA) to adjust camber? Wouldn't using an adjustable upper control arm (RUCA) avoid messing with suspension motion ratio or anti-roll bar mounting? Thoughts?

You're spot on about motion ratio and antiroll bar mounting, these can be affected!
But good aftermarket RLCAs are designed to keep those changes minimal for typical camber adjustments. It's all about finding the simplest way to get that camber dialed in without over complicating the whole setup.

 

[thatsjamesali]

Why do most people replace the rear lower control arm (RLCA) to adjust camber? Wouldn't using an adjustable upper control arm (RUCA) avoid messing with suspension motion ratio or anti-roll bar mounting? Thoughts?

Just adding to what @NYPizzaPie said. Most folks go with adjustable RLCAs for camber on many platforms because it's often simpler to package and offers a wider range of adjustment without fouling other components. While a RUCA could theoretically work, it often runs into clearance issues with the chassis or even the spring or shock assembly. Finding one with adequate strength and adjustability can be harder. Plus, for many McPherson strut setups, the lower arm dictates more of the effective pivot point. While you bring up valid points about motion ratio and sway bar mounting, in practice, the RLCA tends to be the more straightforward and widely available solution!

 

[Jo.or.nathan]

Why do most people replace the rear lower control arm (RLCA) to adjust camber? Wouldn't using an adjustable upper control arm (RUCA) avoid messing with suspension motion ratio or anti-roll bar mounting? Thoughts?

Adjustable RUCAs can help, and yeah, they're less likely to mess with suspension geometry or anti roll bar mounts since they sit higher up, but their camber adjustment range tends to be smaller, also, RUCA is more complex or expensive to swap on some cars

 

[TunedToy86]

Had this debate when setting up my old track car. I considered using RUCAs for camber adjustments but the clearance issues near the chassis and shock made it really tricky. In the end I opted for adjustable RLCAs because they were much easier to install, provided a greater range of adjustments, and didn't need me to modify other components. Sure you do adjust the motion ratio slightly, but for mild camber changes, it really didn't make much difference. Overall it turned out to be a simpler solution for most setups

 

[Big Smurf]

You're spot on about motion ratio and antiroll bar mounting, these can be affected!
But good aftermarket RLCAs are designed to keep those changes minimal for typical camber adjustments. It's all about finding the simplest way to get that camber dialed in without over complicating the whole setup.

I guess I was overthinking it. If decent RLCAs keep geometry changes minimal, I might go that route. Simpler sounds better than reworking the whole suspension just for camber tweaks

 

[Big Smurf]

Just adding to what @NYPizzaPie said. Most folks go with adjustable RLCAs for camber on many platforms because it's often simpler to package and offers a wider range of adjustment without fouling other components. While a RUCA could theoretically work, it often runs into clearance issues with the chassis or even the spring or shock assembly. Finding one with adequate strength and adjustability can be harder. Plus, for many McPherson strut setups, the lower arm dictates more of the effective pivot point. While you bring up valid points about motion ratio and sway bar mounting, in practice, the RLCA tends to be the more straightforward and widely available solution!

I hadn't considered the clearance issues with RUCAs or how the RLCA affects the pivot point more, it sounds like going RLCA is just more practical for my setup after all

 

[Big Smurf]

Adjustable RUCAs can help, and yeah, they're less likely to mess with suspension geometry or anti roll bar mounts since they sit higher up, but their camber adjustment range tends to be smaller, also, RUCA is more complex or expensive to swap on some cars

I didn't realize RUCAs usually offer less adjustment range and could be pricier to swap. That definitely makes RLCAs seem like the more practical choice, even if they slightly affect geometry

 

[Big Smurf]

Had this debate when setting up my old track car. I considered using RUCAs for camber adjustments but the clearance issues near the chassis and shock made it really tricky. In the end I opted for adjustable RLCAs because they were much easier to install, provided a greater range of adjustments, and didn't need me to modify other components. Sure you do adjust the motion ratio slightly, but for mild camber changes, it really didn't make much difference. Overall it turned out to be a simpler solution for most setups

It sounds like the real-world tradeoff favors RLCAs especially if the motion ratio impact is minor for modest camber tweaks. I'm leaning that way now too, just to keep things simple