Contour Enthusiasts Group Archives Forums Modifications Brakes stopping diastance.........

assuming nothing else changes, say you stop from 60 to 0 in 130 feet with a disc/drum set-up, then you change to a disc/disc set-up, how much shorter distance are we talking?

"assuming nothing else changes" in this case probably very little.

The issue here simply becomes how many times this set up can do this without fade.

Add to this some "changes" such as pads, hoses, calipers, rotors etc etc and then you'll see a change. This is because the brake torque values have changed. Not so in the first instance. Also keep in mind that under hard conditions like this that the fronts will be doing most of the work unless you make other changes to bias the rear more, being careful to not lock up of course.

I changed the springs and the car doesn't have as much nose dive now. I haven't tested the car on a track but it seems to stop a little faster now that the weight seems to stay over the rear tire better.

The only thing that will shorten your stopping distance is stickier tires.

Everything else is just braking feel and heat management (fade resistance.)

Feel factors:

Initial bite
Modulation

For more info, check out This GRM article, and "Braking Systems in Plain English"

Originally posted by RogerB:

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The only thing that will shorten your stopping distance is stickier tires.

Everything else is just braking feel and heat management (fade resistance.)

Feel factors:

Initial bite
Modulation

For more info, check out This GRM article, and "Braking Systems in Plain English"

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Close, but not completely true, at least for anyhting other than low speed stops. Not all brake systems, in a decent traction situtaion, can apply enough brake torque from high speeds to lock the wheels. In these situations, larger rotors, or higher friction pads, or anyhting to increase brake tq will decrease stopping distances.

Basically, your statement is true, but not an absolute.

Originally posted by Rara:

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Originally posted by RogerB:

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The only thing that will shorten your stopping distance is stickier tires.

Everything else is just braking feel and heat management (fade resistance.)

Feel factors:

Initial bite
Modulation

For more info, check out This GRM article, and "Braking Systems in Plain English"

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Close, but not completely true, at least for anyhting other than low speed stops. Not all brake systems, in a decent traction situtaion, can apply enough brake torque from high speeds to lock the wheels. In these situations, larger rotors, or higher friction pads, or anyhting to increase brake tq will decrease stopping distances.

Basically, your statement is true, but not an absolute.

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I guess I should say, "assuming that you can lock up the tires..." I thought of this after I wrote that, but felt it was a non-player, and here's where MHO comes in.

I would say that any of the stock braking systems on any Contour are good enough, stock, to lock up the tires at any speed that that particular Contour is capable of in a one-time stop (i.e., street use).

Originally posted by RogerB:

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I would say that any of the stock braking systems on any Contour are good enough, stock, to lock up the tires at any speed that that particular Contour is capable of in a one-time stop (i.e., street use).

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Well, here that really depends on the tires and the road conditions. Also keep in mind it takes much less brake torque to maintain a locked condition than to get to the locked condition, so a momentary loss of traction can lock a wheel at almost any speed. Again, I guess my point is, its still a bit more complex an issue than your statements let on.

Originally posted by Rara:

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...Its still a bit more complex an issue than your statements let on.

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Understood, and I would answer that most things are more complex than a) there's room or time to discuss here and b) I am capable of understanding or explaining. (I'm just an enthusiast, not an engineer.) Basically, I feel that I have answered his question accurately with the facts relevant to his particular situation. For further detail I referred him to two articles that have been very helpful to me in my own understanding of the situation.

Now, for the sake of discussion, I would say that you and I are saying mostly the same thing, except that I am accepting a certain baseline assumption (that we can outbrake our street tires, which I believe) for the sake of simplifying the argument. Now, if I mounted R-compound tires and ran on dry, young concrete, would my baseline still be satisfied? I don't know. Would changing rear drums to discs shorten my stopping distance in this case? Probably not. Would brake modifications that allow me to generate more torque at the front wheels for a given pedal effort shorten my stopping distance? To the point that I can generate enough torque to lock up the front, yes, but no further. As quoted in the second article, above, once the tires start sliding, more force is just more force.

Analogy: Aerodynamic flow is a lot more complex than Bernoulli's equation, but the equation still works. Likewise, braking may be a lot more complex than I let on, but it doesn't change the fact that your interface with the road surface, whatever it is, is the limiting factor in braking performance. What good is generated torque once the tires' ability to absorb it is saturated?

Originally posted by contourlover:

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I changed the springs and the car doesn't have as much nose dive now. I haven't tested the car on a track but it seems to stop a little faster now that the weight seems to stay over the rear tire better.

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FWIW, the lack of dive doesn't affect weight transfer. In fact, the faster you stop, the more weight transfer occurs. On the other hand, the change in springs do affect the way the tires hold to the road which could help reduce braking distance.