Wheel Alignment and Laser Wheel Alignment Systems – Questions and Answers

Further elaborating on the topic of wheel alignment, here we have assembled some of the most commonly asked questions, the answers to which you might find helpful!

What are master chassis points in wheel alignment?

Master chassis points are two places on your chassis that we use to align your wheels to. Master points can be any two points; still, it is best for the points to be square with your suspension hook-up points. The reason these are used in wheel alignment is because the wheels have to remain square to the suspension, while the chassis remains in a consistent location within the four contact patches. Without chassis points, you can achieve accurate wheel alignment, but the chassis can be completely out of square with the wheels.

Why measure at the contact patch?

Traditional wheel alignment methods measure the wheel (tire) location at the wheel centerline. Real Square Laser Wheel Alignment Systems measure the wheel location at the bottom of the tire. Why?

Because the chassis only knows where the contact patches are. Imagine a table with four legs. Now image the legs are on scales. The weights only change if you move the location of the bottom of the legs. The leg could be straight or bent in a loop. The table top is your chassis, the bottom of the legs are your contact patches. The chassis does not know where the wheel centerline is, it only knows where the contact patches are.

Consequently, with our laser wheel alignment systems, we measure at the contact patch as that is the most relevant location. Traditional wheel alignment methods used the centerline because that was the widest point of the tire, and thus, the most accurate measuring location. Modern wheel fixtures solve this problem.

Automotive wheel alignment machines continue to use the wheel centerline, because they’re only concerned with wheel alignment, not rear end lateral placement or wheel weights. To achieve maximum consistency, we measure at the contact patch.

Should I align the right side contact patches?

This question does not have a straight-forward answer. Aligning the right side contact patches is a set-up decision and not a rule or law. The chassis only knows where the contact patches are.

The Real Square Laser Wheel Alignment systems use the contact patch as the measurement reference point, because that is the most relevant and consistent location. We do not suggest that wheel alignment should happen at the right side contact patches, but we absolutely suggest that the contact patch is the best place to reference your rear end location. The recommended procedure is to set the rear end placement, using your traditional method and then log the measurements using your Real Square wheel alignment fixtures. This is your baseline. You can now accurately maintain the rear end location regardless of camber changes.

Always remember to check driveline alignment using your centerline laser as you move the rear left to right!

Hopefully, this has given you an introductory overview that will assist your knowledge in wheel alignment as well as the Real Square Laser Wheel Alignment systems. We will keep posting more Q&A materials on this topic, so keep checking us out!