Car tires are supposed to be constructed for safe,

economical, pleasant and environmentally friendly

driving. Three performance measures that would quite

well represent the major operational characteristics of

tires within the mentioned topics would be

noise emission, wet friction and rolling resitance.

Since the latter affects fuel consumption it also

affects economy and exhaust emissions.

It is sometimes claimed that when trying to reduce

exterior noise emission, there is a conflict with

friction and perhaps also with rolling resistance. The

implication would be that one could not reduce

tire/road noise any further without sacrificing

safety or economy. A European Union directive with

noise emission limits for tires is underway. It has

been suggested that tires should meet certain limits

also

with regard to friction; assuming a conflict between

requirements for low noise and high friction.

Consequently, it is important to study this matter

further.

Earlier studies have indicated that there is no

consistent conflict between friction and noise

characteristics with respect to road surfaces. For

12 tires tested on 5 surfaces Denker found no

significant noise-friction correlation, until he

normalized friction values in an unusual way, in which

case

he found weak conflicts between noise and friction.

Tests in 1992 by Nelson for 16 car and 9 truck

tires indicated weak noise-safety correlations,

suggesting a conflict between the parameters, but this

could well have been biased by the inclusion of a wide

range of tire widths. According to Ejsmont, a

general conflict between noise and rolling resistance

properties could not be found. A recent and

quite comprehensive study in Germany, made on 48

car tires, concluded that neither was there any

correlation between noise and rolling resistance, nor

between noise and "wet braking". The same was

found between noise and aquaplaning speed.

These authors conducted a pilot study in 1997 with the

purpose to establish relations between

exterior tire/road noise, wet friction and rolling

resistance of current car tires. The first

conclusions

suggested that there is no significant conflict

between friction and noise or between rolling

resistance and

noise. This study was limited to 28 tires so it was

decided to continue with testing in order to get

higher

confidence of the results and to examine altogether

about 100 modern car tires of similar size. The

results

of this study, which is believed to be the most

comprehensive study of these relations so far, are

presented here.