  The high-precision HERA data allow searches for up to TeV scales "Beyond the
Standard Model" contributions to electron-quark scattering. Combined H1 and
ZEUS measurements of inclusive deep inelastic cross sections in neutral and
charged current ep scattering are considered, corresponding to a luminosity of
around 1 fb$^{-1}$. A new approach to the beyond the Standard Model analysis of
the inclusive $ep$ data is presented; simultaneous fits of parton distribution
functions and contributions of "new physics" processes are performed.
Considered are possible deviations from the Standard Model due to a finite
radius of quarks, described within the quark form-factor model, and due to new
electron-quark interactions in the framework of $eeqq$ contact interactions
(CI). The resulting 95% C.L. upper limit on the effective quark radius is
$0.43\cdot 10^{-16}$ cm. The limits on the CI mass scale extend up to 10 TeV
depending on the CI scenario.
