# Brake Question

Given the expertise of some of the participants in this group I have a question.
Approaching a stop sign at 60 mph is it better for the brakes if I
A) Slow at a steady rate over a period of say 15 seconds or B) Brake at a higher rate of deceleration so that I come to a stop in say 4 seconds?
Any opinions would be appreciated as I have had this discussion and there seems to be no "right" answer.
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My primary thought is that if you stop slow and steady, it gives the heat more time to dissipate. That will help protect your rotors and drums. This method (at least on level ground or uphill) will also allow drag to slow the vehicle a little, saving fuel and brake wear (although probably not much).
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I agree with that. As for wear, it takes a given amount of friction to stop the moving mass. The brakes will generate approximately the same amount of heat, but the curve in temperature rise will be considerably different. The fast heating is more likely to induce rotor warp.
The smart thing to do to minimize brake wear and possible rotor warp is to coast down a bit and then drop back a gear.
An even smarter thing would be to drive closer to the speed limit in the first place. :)
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That comment is certainly reasonable with the given example...... I don't know of many stop signs in 60 mph zones. Of course, if you were approaching a red traffic light at 65 mph, that would change everything.
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Bob wrote:

FWIW, I've driven on some rural highways with high speed limits that actually have traffic lights every few miles. IIRC, they were in Delaware and the Carolinas.
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Around here there are lots of stop signs in 55mph zones - not so far from the 60mph the OP referenced.
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Around here, we have a sense of humor about such comments. When I was 17 or so, it was not uncommon to see how fast I could go and still make the stop sign on the corner. And I could not understand why the insurance company would charge me more than some 30 year old.
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Damn that sense of humor thing. It's so easy to miss sometimes...
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Edwin Pawlowski wrote:

I would rather replace pads and rotors than clutches or add stress to an automatic.

Exiting the freeway (speed limit 70) there is a short ramp (angled down) approaching a T, light controlled intersection. With traffic on my bumper I don't have the option to slow down prior to getting off. Well I do, I suppose, but then I would be one of those people that I occasionally talk about slowing down on the freeway :) .
My point of inquiry was whether a slow application of friction/build up of heat was better than a quicker one. Rather than the dissipation of heat it is a question of a slow or rapid build up of heat, if one method produces more heat than another and whether the slow process wears the pads more than a more rapid approach.
I think you are right about the lower curve of heat build up.
Thanks for the responses.
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Here's the deal. Except for nearly negligible wind drag/rolling resistance losses, you're generating the same amount of heat either way. Brakes are nearly 100% efficient in their conversion of your vehicle's kinetic energy to heat energy. The more quickly you add heat, the higher the rotor temperature will become, because it dissipates the heat at a slower rate than it is absorbed when braking. In fact, the heat dissipation is indeed the important factor for this reason.
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jp103 wrote:

It depends somewhat on how you define better, but if I assume that by better you mean less wear and lower brake peak temperatures and less thermal strain to the brake components, then a long and gradual stop is better than a rapid stop.
Matt
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