Originally Posted By: JHZR2
Is there a difference?
It seems like no matter where I go, no matter how careful, shops do at least some damage on the rear of the wheel...
Yet new from the factory is pristine.
What gives? Is there some difference in equipment?
Yup! The machines are completely different.
I tried to find a video of a set up but was unable to do so - so allow me to describe the procedure.
The tires are sequenced by vehicle - 4 tires plus the spare. The wheels are also sequenced 4 wheels plus the spare wheel. The wheels are placed on a conveyor. The wheels are spray lubed and the tires drop down from above so the tire is canted in front of the wheel. The conveyor moves forward into a set of shoes that engage the rim and push the beads over the rim edge and onto the rim. Sometimes the next station aligns the marks on the wheel with the marks on the tire - and sometimes those marks are aligned by how the wheels and tires are placed on the conveyor. Next station has a cylinder that comes down and pushes the bottom bead into the bottom rim flange, adds air pressure then lifts up. As it lifts up, the top bead is seated. Followed by the balancer - followed by a guy who applies the balance weights. Up until this point nobody has touched either the tire or the wheel or the assembly since the tires and wheels were loaded onto the conveyor - It's completely automated. The conveyor moves at about one assembly every 5 seconds - so a whole vehicle pops out every 30 seconds or so. From end to end, the process takes about 5 minutes or so.
Needless to say this process and the machinery have been refined so it doesn't mess up the tire or the wheel. It also has been set up to accommodate a wide variety of tires and wheels - even different diameters and widths. The real trick is sequencing the wheels and tires to the vehicle - which is obviously done by computer. Remember the Phrase *Quality is Job 1*? At Ford, each vehicle is given a job number starting with the first vehicle of the model year (Job 1!). All the parts for this vehicle are sequenced using that job number. Other car manufacturers use a slightly different phrase, but they use a similar system. The vehicles don't have to be built in order, but usually it's pretty close.
Also needless to say, the equipment is fairly expensive - way, way, way beyond what a tire shop could afford. On the other hand, what tire shop do you know that does 20 to 30 vehicles an hour?