Salt is a lubricant. As we all know it corrodes ferrous metals. Rust or blackened metal of a grey iron brake disc has a lower coefficient of friction than good shiny metal. That's why discs in good condition are so (and so massively under-appreciated) much more efficient at braking quickly. The MOT brake roller test is such a minimal standard for brakes and doesn't take into account the effect disc degradation has in a dynamic, high speed hard brake application. Not only is initial brake response delayed but so too is the maximum braking effect and the speed the brake reaches maximum retardation (which then needs ABS intervention) can be very much lower, or may simply not be reached at all.
If anyone cares to measure braking distance of corroded brake discs from highway speeds against that of bedded in new brakes, the result will evidence my point.
Unfortunately it is that same reason why many people often think the new brakes just fitted are an upgrade. Even rubbish quality new brakes will be far better than expensive old brakes which were in poor condition.
In short, don't necessarily go for expensive brakes. Being able to afford more regular disc changes will probably give more real life benefits. That said, more exotic brakes should give favourable results at high speed but lower speed stopping distances won't be much different.
That last point is something no one discusses and certainly not something a performance brake manufacturer or supplier of upgrade brakes which cost many times that of standard replacements will ever disclose. Finally, the main reason for a more expensive standard pad over a cheaper one is in the single pressing manufacture rather than batch manufacture. A pad formed in an individual pressing tends to be a much more consistent pad which has less performance variation. Obviously more expensive materials also play a significant part.
Last edited by Fruity; 14-06-19 at 02:33.