The left side and right side brake chambers on an axle must match; vehicle handling can be negatively affected if they are different. However, mismatched brake chambers on a steering axle is an out-of-service condition that must be corrected before a truck is driven.
The reason why mismatched brake chambers are a problem is that brake chambers of different sizes create different pushrod forces. This is because the diaphragm inside the chambers applies force to the pushrod, and the larger the diaphragm is for a certain air pressure, the greater the force on the pushrod.
So if a truck has mismatched brake chambers on a steer axle, one side of the truck will brake harder than the other and this will cause the vehicle to pull to one side when braking. This is a serious safety hazard! Also, mismatched chambers don’t just happen; this is a result of a mistake during the chamber(s) installation.