Adjusting rear control arms?

[UC645]

Does anyone how to properly adjust a full set (upper and lower) rear control arms to make sure the rear end is centered from left to right?
I’ve been messing with this for a couple of hours and can’t seem to get it all right.

 

[mccormack944]

Make sure you’re measuring from the frame or other chassis hard points never the body. Ideal way to adjust them would be match them up in length to your originals, adjust the wheelbase so it sits square front and back sometimes called checking rear steer or thrust angle after that is set using primarily the lowers, lock the lowers down and use the uppers to square left and tight, then set your pinion angle. After that you could make subtle adjustments to change things such as preload rear steer etc if you’re racing but that should get you where you want for a start

 

[UC645]

Adjustable rear control arms aren’t for squaring it left and right, they should have a very minuscule effect on left right centering. Also make sure you’re measuring from the frame or other chassis hard points never the body. Ideal way to adjust them would be match them up in length to your originals, adjust the wheelbase so it sits square front and back sometimes called checking rear steer or thrust angle after that is set using primarily the lowers, lock the lowers down and use the uppers to set your pinion angle. After that you could make subtle adjustments to change things such as preload rear steer etc if you’re racing but that should get you where you want for a start

Checked the length on all 4 arms just to be sure, turns out I had the lower left a quarter of an inch longer than the right, and somehow had the right upper nearly a quarter inch longer than the left.
Got those squared up and the rear looks like it’s now straight. I’m just mocking up the rear to weld spring perches on.

 

[gnvair]

This video is very informative on how to properly adjust rear control arms.

 

[Rt Jam]

Whether you are adjusting pinion angle or wheelbase or some other unknown reason. The 2 uppers should be the same length as each other. Same with the lowers, same as each other.

 

[gnvair]

Whether you are adjusting pinion angle or wheelbase or some other unknown reason. The 2 uppers should be the same length as each other. Same with the lowers, same as each other.

Watch the video I posted. That is one of best explanations and demonstrations.

 

[Rt Jam]

Watch the video I posted. That is one of best explanations and demonstrations.

It's a great video explaining how to do it wrong. Upper control arms that are not equal in length to each other is not correct. Everything else he explains is solid.

 

[mccormack944]

It's a great video explaining how to do it wrong. Upper control arms that are not equal in length to each other is not correct. Everything else he explains is solid.

Do you have a reason why they need to be same length? Adjusting the different arms to different lengths is all part of his you take an ok car and dial it in. The adjustments are to take into account any inconsistencies, do you really think every single metric frame has all 4 control arm brackets welded and drilled in the exact same spot, and every single rear end housing has all 4 brackets welded and drilled in exactly the same spot? If that was the truth no one would make adjustable arms. Also have you ever heard terms such as rear steer or preload? Those are adjustments used on both circle track and straight line cars to dial in their setup. The only reason I can come up with for you saying equal length is to prevent bind but sorry to tell you these things are nothing but bind. The only way to stop the bind is with heim joints, and if that’s the case the indifferent bar angles aren’t a concern but it still goes back to these cars are imperfect in the first place

 

[gnvair]

It's a great video explaining how to do it wrong. Upper control arms that are not equal in length to each other is not correct. Everything else he explains is solid.

Ok dude. We will take you seriously when you build as many successful 7 second race cars as he has. http://www.teamzmotorsports.net/Default.asp

 

[bracketchev1221]

Like was said. Start by setting the lowers equal. This will get the rear perpendicular to the frame and set the tires equal front to back. The uppers, will move the rear left and right if the are not correct so adjust those. Unfortunately, the cars are not perfect from the factory, so they may require some offset and tweaking to get it right. For the most part like was also said, in these cars if you set the bars equal to what you had, it SHOULD be really close to start with. For this reason I tend to stick to solid lower bars and only adjustable uppers.