My question is essentially a variation of the Ehrenfest paradox in SR. But hopefully with some experimental data. In the LHC, for example, a fixed number of particle bunches with some length are injected into the main ring. Now, as the velocity of the particles increases, the bunches would be expected to Lorentz contract to smaller length (for a stationary outside observer). However, at the same time the distance between successive bunches should also decrease. This seems paradoxical, since the circumference of the accelerator remains constant. What actually happens in the accelerator to the bunch lengths and distances between bunches? My understanding is that the bunches do Lorentz contract, but is there any explanation for the paradox? There has been some discussion of this in the forum before, but I was unable to find any satisfactory answer. Born rigidity, which is often evoked in the context of the Ehrenfest paradox, does not play a role here.