Electroweak Symmetry Breaking and Precision Tests with a Fifth Dimension

We perform a complete study of flavour and CP conserving electroweak observables in a slight refinement of a recently proposed five--dimensional model on $R^4\times S^1/\Z_2$, where the Higgs is the internal component of a gauge field and the Lorentz symmetry is broken in the fifth dimension. Interestingly enough, the relevant corrections to the electroweak observables turn out to be of universal type and essentially depend only on the value of the Higgs mass and on the scale of new physics, in our case the compactification scale $1/R$. The model passes all constraints for $1/R\geq 4.7$ TeV at 90$\%$ C.L., with a moderate fine--tuning in the parameters. The Higgs mass turns out to be always smaller than 200 GeV although higher values would be allowed, due to a large correction to the $T$ parameter. The lightest non-SM states in the model are typically colored fermions with a mass of order $1-2$ TeV.