Tire RED DOT Question

Uniformity Method



When performing uniformity match-mounting, the red mark on the tire, indicating the point of maximum radial force variation, should be aligned with the wheel assembly's point of minimum radial run-out, which is generally indicated by a colored dot or a notch somewhere on the wheel assembly (consult manufacturer for details). Radial force variation is the fluctuation in the force that appears in the rotating axis of a tire when a specific load is applied and the tire rotated at a specific speed. It is necessary to minimize radial force variation to ensure trouble-free installation and operation. Not all wheel assemblies indicate the point of minimum radial run-out, rendering uniformity match-mounting sometimes impossible. If the point of minimum radial run-out is not indicated on a wheel assembly, the weight method of match-mounting should be used instead.

Weight Method

When performing weight match-mounting, the yellow mark on the tire, indicating the point of lightest weight, should be aligned with the valve stem on the wheel assembly, which represents the heaviest weight point of the wheel assembly. After match-mounting by either of the above methods, the tire/wheel assembly can be balanced.

Click to expand...

Tire and wheel manufacturers continually develop new manufacturing methods to enhance the uniformity of their products because radial runout, lateral runout, force variation and imbalance can affect a vehicle's ride quality.

Match mounting tires on wheels is a process where a tire's installed position on the wheel is specifically selected to help minimize the final combination's force variation and/or imbalance. One match mounting procedure aligns the tire's measured high point of radial force variation with the measured low point of the wheel's radial runout. The other simply aligns the tire's lightest spot with the wheel's heaviest spot.

Original Equipment (OE) tire suppliers are required to mark the tire's "high point" while OE wheel manufacturers mark the wheel's "low point." This helps the vehicle manufacturer match mount combinations that maximize new car ride quality while reducing the amount of balancing weight.

photoToday, many vehicle manufacturers specify the use of a temporary tag applied to tires and wheels that are removed before the vehicle is put into service. Unfortunately, this means that there are no permanent marks to reference later.

There was a time when the valve stem hole on standard wheels indicated the optimum place to which the tire should be match mounted. However, with the advent of styled, steel wheels and aluminum alloy wheels, the stem position evolved into an aesthetic issue rather than being a uniformity indicator. Add to this the probability of wheels retaining their original runout after thousands of miles of use and you can understand that simply mounting the tire so the colored dot is at the valve stem is no longer required practice.

We have found that the only way to accurately match mount replacement tires on used original or new aftermarket wheels is to use Hunter tire balancers which have the ability to measure wheel runout and tire force variations under load before the tire and wheel are installed on the vehicle. Using these machines, a colored dot might be positioned anywhere on the wheel relative to each wheel's runout measurement. In the end, the markers have little, if any, relevance when replacement tires are installed.

Click to expand...