Tyre contact patch is defined into defaultbikemotogp.bml under the section "front" and "rear".
The string is fTrack (default is 0.14 front and 0.2 rear): by lowering it, the bike leans in a lower position giving an increased tyre section on the groud.
Lean angle is not determined by the leanlimit string into defaultbikemotogp.bml, but it's limited turn by turn based on tyre grip, speed and other parameters.
So if you limit the lean angle, to say.. 50°, the bike can't lean more than that even if the tyres have more to give, but if you limit it to a proper higher value (let's say 64) the bike can lean as much as the tyres can without crashing: it could be 54°, 59° or even more. By doing so I can find the optimum tyre grip values by looking at the lean angle:
grip = tan(lean angle) ex: tan(59°) = 1.66