I thought breaking is limited by the tire/street contact, not by the break?
Or at least it should be. That's why there is a v_max that a car is not allowed to exceed and a faster or heavier car will have better breaks.
And 70 km/h as here should be far away from v_max.
It's a combination, but any modern (disc) brake can block a wheel so in practice this should not be an issue. The only time it might be a problem is after dragging the brakes on a long downslope (which is why you shouldn't do that, the hydraulic oil will boil and your brakes will stop working).
Or at least it should be. That's why there is a v_max that a car is not allowed to exceed and a faster or heavier car will have better breaks. And 70 km/h as here should be far away from v_max.