Brakes and Braking distance

[chirstius]

Ok, help me out here...

I've had a debate with a friend a few times about brakes and upgrading brakes and the effect it would have on stopping distance. Now I'm not talking extended track use where heat dissapation becomes the most important factor I'm talking 70-0 stops.

My theory is that once you reach the point of having brakes on a vehicle that can lockup the tires it doesn't matter if they are drums or 6 piston BAER calipers it wouldn't affect your 70-0 stopping distance. The limiting factor in the braking distance has become the tires NOT the brakes. Would the super-duper track ready 6 piston calipers and cross-drilled and slotted rotors be easier to get consistent braking and better pedal feel out of? YES! But I don't see how that affects straight line stopping distance.

In order to stop in the shortest amount of distance you want to be RIGHT on the edge of locking up the tires and so long as the braking setup you have can reach that point it'll stop you the same right up until the tires break loose.

I think my buddy is confusing pedal pressure and travel with braking ability. When I drive my fiance's solara I always freak out cause it feels like there are NO brakes, the pedal feels like it travels forever until I actually feel something happen. On the G you need only to touch the pedal and the brakes are right there. Are the brakes on the G better? Well, hell yeah [] but if there were a way to improve the pedal feel on the solara without changing anything else on the braking system I would probably be fooled into thinking "wow the brakes are much better on this car now" when in reality they would not perform any differently in how fast or slow they could stop the car.

If I actually went and got a high end braking system for the solara but changed nothing else in the suspension, wheels or tires it might also give a much better pedal feel, and I might also think that the brakes were "better" but I say all I am doing is giving myself the ability to lockup the tires with less pedal travel and pressure, I won't be able to stop the vehicle in a shorter distance than I could before - assuming an "ideal" pass for both braking systems. If I wanted to actually take advantadge of the improved braking I'd need to (at the least) slap wider rims and tires on to provide more traction before lockup.

Am I totally wrong?

-Chuck

| 04 Black/Graphite 6MT | Premium | Nav | Aero w/ Spoiler | XM | Z Tube |

[GZire]

I think you are mostly right. When you can lock up your wheels then, yes the limiting factor is the contact patch (tire) on the pavement.

I had read about one person who had changed out his brakes and had about a 6 foot improvement versus stock. For a several thousand dollar modification it's not too good of an improvement for daily driving. While the total improvement was very slim, I believe what that person was looking for was on-track performance (reduction in brake fade), so the upgrade was right for his purposes.

Better brakes will definitely improve on the brake fade versus the stock and Brembos. One thing about better brakes is that they may apply pressure to the rotors better than the stock system enabling a more linear brake response (rather than the brakes going from slipping to sudden locking of the rotors).

The response from Q45Tech (from another forum) was that the stock systems on most vehicles are pretty close to the ultimate stopping potential for the cars for single stops (repeated stops such as under racing conditions are of course exempted from that response).

Now as far as your debate with your friend it would really depend upon what is put on. As with you I think increasing front tire width is a more effective way to increase stopping distances.

"you will rue this day....well go on start ru-ing" Stewie Griffin

[Kalmairn]

Outside the brakes themselves, tires play the major role in the braking power of a car - the total amount of grip limits the total amount of stopping power available to the vehicle in motion. They are the friction/rolling point between the moving object (car) and the non-moving object (ground).

That said, the brakes in a car can provide some improvement in total stopping distances for single-stop situations. The ability of the braking system to apply even pressure to a large surface area of brake can help generate additional friction without hitting the maximum on any given location on the rotor.

Additionally, the ability to apply even, solid pressure can overcome the generation of gasses created during hard braking. Although they play a greater role in repeat stops, brakes do heat up dramatically in the first hard stop, creating gasses that can push against the pads and reduce braking power.

Finally, some systems deal with heat, expansion, and other environmentals better. These systems can apply more consistent force to the rotors/drums and provide better stopping distances.

ABS brings a whole new set of concerns, but as I know even less about how ABS modulates, I'll skip that.

The majority, however, is in the tires. I considered on several occasions a post about how tires basically are the single best upgrade for most cars (not necessarily including the G or other true sports cars). The improvement in cornering and braking provided by high-performance tires and make all the difference in a panic situation.

Try an autocross on typical street tires (again, not in a true sports car, more like a stock Neon or Corolla), then put performance tires on the same car and try it again; you'll be amazed.

Kal.

'04 G35 Coupe 6MT, Black/Black, Premium Package, Aero Package w/Spoiler

[chirstius]

Thanks for the replies. GZire - You hit upon my point exactly - I would totally agree that a better braking system could (and probably would) show some improvement in slowing the vehicle (again excluding track or auto-x repeated heavy application) but for the cost it's just not worth it. The only way to see significant improvements is (as Kal said) to upgrade the contact patch (tires).

I am not discounting the many benefits of high performance braking systems - even in day to day driving. As has been stated the linear progression of braking force is essiental to being able to control a vehicle in performance and emergency situations but when it comes down to just sheer braking performance your money is better spent on a tire/wheel package than a new brake package - or at least get the tires and wheels first since they provide many other benefits besides improved braking.

This is good stuff to take back to work Monday...

-Chuck

| 04 Black/Graphite 6MT | Premium | Nav | Aero w/ Spoiler | XM | Z Tube |

[roneski]

I actually posted this on another thread, but it will apply well here too:

Here is some interesting reading for ya. Scroll down to where they are testing the 350Z performance brakes (non Brembo)vs. the track brakes (Brembo). Less than 2 feet of difference in stops below 80 mph and less than 5 feet of difference for all speeds above.

http://www.zeckhausen.com/testing_brakes.htm#

Oh look a chart... I like charts...

http://www.zeckhausen.com/testing_brakes.htm#Summary

The brembos don't significantly improve the braking coeffecient, the just dissapate heat better.

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