The behaviour of a motorcycle on the road is largely governed by tyre properties. This paper presents experimental and numerical analyses dealing with the influence of tyre properties on the stability of weave and wobble in straight running. The final goal is to find optimal sets of tyre properties that improve the stability of a motorcycle. The investigation is based on road tests carried out on a sport-touring motorcycle equipped with sensors. Three sets of tyres are tested at different speeds in the presence of weave and wobble. The analysis of telemetry data highlights significant differences in the trends of frequency and damping of weave and wobble against speed. The experimental analysis is integrated by a parametric numerical analysis. Tyre properties are varied according to the design of experiments method, in order to highlight the single effects on stability of lateral and cornering coefficient of front and rear tyres. An extended series of road tests made it possible to analyse the influence of the tyre set on the stability characteristics of the same sport-touring motorcycle. The substitution of the tyres may lead to variation up to 14% in weave natural frequency and 47% in weave damping ratio at high speed. The effect of tyres on wobble stability is a bit smaller, with maximum variations of 10% in natural frequency and of 30% in damping ratio. It is difficult to analyse by means of road tests the influence of the individual tyre parameters on stability, but by means of the special tyre test machine of DIMEG; it is possible to measure the tyre properties needed for numeric simulation. For this reason, a parametric numerical analysis based on DOE method was carried out to highlight the effect of tyre properties. When a comparison between numerical and road test results was possible, a satisfactory agreement was found. Parametric analysis showed that rear and front cornering coefficient by far have the largest influence on weave and wobble natural frequency, respectively. Damping ratios are influenced in different ways by several parameters, only front and rear lateral stiffness have a negligible influence on weave and wobble, respectively.