Meaning behind marked tires and check engine light importance

I was washing myca rand noticed there are little red and yellow dots onmy new tires. I remember reading quite awhile back that one of them is supposed to line up with the filler? I thought I’d ask before saying something to the tire store. — Jen

Some/ many tire manufacturers mark their tires with small colored paint dots to aid in the best installation/balancing process. As well made as tires and wheels may be, there can be minor variations in tire weight around its circumference, tire rolling resistance, and wheel weight, and radial run-out.

Yellow and red dots allow two differing methods of-match-mounting the new tire to a wheel. A yellow dot indicates the point of lightest weight of the tire. When there are no manufacturer marks on the wheel indicating the point of minimum radial run-out, the yellow dot should be aligned with the wheel’s valve stem, the wheel’s heaviest point. This is referred to as the weight method.

If awheel is marked as described above, with perhaps a dimple or dot, the red tire dot should be aligned with it. This matches the tire’s greatest radial run-out with the wheel’s least radial run-out. This is called the uniformity method, and is preferred, if possible.

There are a few flies in the ointment with this process. The valve stem of an aluminum wheel isn’t necessarily the wheel’s heaviest point (as it was on steel wheels). Additionally, as a wheel bumps and thumps along throughout it’s life, its point of radial run-out may change. These canmake the position of the dots perhaps of little or no consequence.

There is a tire balancing process many shops employ using a Hunter Road Force Balancer where the machine feels the tire using a loaded roller as it is spun. This senses variations in tire rolling resistance and uniformity. These are factored into the balancing and tire/wheel matching processes, resulting in the smoothest possible ride. In some cases the tire may be dismounted and rotated on the wheel for the best match, again making the position of the colored dots moot.

A competent tire installer should also; check for damage to or a possible bent wheel, dirt buildup on the tire/ wheel sealing surface, use proper lubrication on the tire bead prior to installation, insure the bead seats fully and uniformly, the wheel seats correctly on the hub, and the lug nuts are correctly tightened.

When a check engine light comes on, how serious can this be? Should I stop driving, or get it fixed the next day, or when it’s good for me? Everyone tells me something different! — Ken

There can be literally a hundred possible reasons for an illuminated check engine/service engine soon light. This indicates a fault has been recognized that will likely increase exhaust or fuel tank emissions beyond an allowable point. Some faults are more serious than others. If the engine runs smoothly with no noticeable issues, and the transmission shifts correctly, this is probably a check it within a week or less situation. If noticeable engine or transmission issues are present, look into it today or tomorrowmorning, especially if there is thumping/power loss! And if the lamp flashes, try to stop driving right away or change the driving type so the flashing changes back to steady. Continuing to drive will possibly trash the expensive catalytic converter!