Should you upgrade brakes when you upgrade power

[Zuban]

Sorry this is a bit random but today i was involved in a discussion on another forum where the reasoning given that when a cars power is upgraded, engine transplant in this case, that the brakes dont need upgraded because the stopping distance between the car pre and post upgrade is the same as the weight hasnt changed, which in this instance it hasnt. And that only if its going to be used on track they should be upgraded. so both cars travelling at 100mph take the same time to stop, so therefore the brakes dont need upgraded.

now personally, i'd have thought it depends on so many factors, what the stock brakes were like, how much power is being added, where and how its going to be driven that to make a statement like that is pretty ludicrous, i can think of a few reasons why i think its a pretty stupid thing to say but would like to see what others think as i seem to be the only one that thinks its a bit short sighted!.

 

[Zuban]

well i agreed it isnt actualy needed, it was the reasoning i had a problem with, it seems a very simplistic point of view, and one that really only applies to one set of circumstances, and makes too many assumptions.

 

[Zuban]

really depends on the car in question

some cars are woefully underbraked as standard.

well I've cooked the brakes on 2 models of the cars in question, although the statement didn't seem limited to just those cars but any, one with uprated pads in which case I think it was the fluid that became the issue, which according to the same person doesn't happen and will only happen on track with or without increased power lol. I managed it on the backroads near my house... but never managed to cook those same brakes going round castle combe!

 

[Zuban]

so i'm guessing from the varied responses here that to say that because the weight of the car hasnt changed everything will be fine, is well, a bit silly? as there is clearly a lot more to it

 

[Zuban]

If your car didn't need bigger brakes before the upgrade, and you don't put it on a track now, it doesn't need bigger brakes after. Brakes absorb and dissipate kinetic energy, which is a function solely of speed - the fact you can accelerate faster does not increase the energy to be got rid of. If you drive at the same speed (and you probably will - the speed you drive at is only minimally related to what the car is capable of for most people). Unless you have feet on both pedals at once, all that matters is the speed that you are doing when you brake, which is unrelated to power in road driving.

Thus, driving on a public road, it's hard to see how the extra performance will need bigger brakes unless you are using it to go a LOT faster than you did before. Bearing mind that big power upgrades result in small increases in top speed (as an example, I have about 65% extra power to get a 12% increase in top speed), then your road speeds will probably not change much anyway, so this still doesn't need bigger/better braking. ONLY a change in driving style needs bigger brakes, and then really only if you go on a track now, but didn't before. And it's the track use that matters, not the extra power. The kind of roads where you can get brake fade are few and far between, and again, your speed on them probably isn't much higher now.

the thing i wondered though was what about the fact that ok your not always going to be going significantly faster when you reach a corner, but greater acceleration surely means your covering the same distance in less time, so the potential for the brakes to have to dissapate a similar amount, probably more, heat, but in less time, it maybe isnt a huge difference but surely a consideration?.

surely the equation johnnycoupe posted regarding kinect energy and heat, would be followed by another equation showing how fast that heat is dissapated, and a factor of that would be time?

 

[Zuban]

Exactly, you have a way of increasing the heat into the brakes over same time period, ie work done. Yet there is nothing to improve the rate at which heat is rejected from the brake or the heat capacity of the brakes.

Work done is what matters and is why torque is useless unless you can apply it at a decent rate, work done, power.

thanks, see this is where the reasoning given, as in both cars still stop in the same distance, fell flat on its face for me, its not that the statement is incorrect, it just makes too many assumptions, whether these differences are enough to manifest themselves as a problem, who knows that surely depends on a bunch of other variables, but to come out with a blanket statement like that seems shortsighted.