...I've seen plenty of articles, websites, etc... that show how to calculate braking distance from a speed down to zero. But what about trying to calculate braking speed down to another speed? For example, at a track, if you're at 150 MPH, and you want to get down to 60 MPH, how much braking distance will that take? To further this, we know, or it's been said, that the Z06's can brake 60-0 within 90 feet, so how many feet from 150 to 60, for example?

Anyone know of such a website / calculator for this?

 

The reason you see the data from 60 to zero is because that just a standardized test everyone uses. Like 0-60 or quarter mile acceleration times. Nobody bothers testing all the possible combinations.

On track just start with a conservative braking distance, worse case you will be too slow entering the turn. If that happens then extend the braking zone (go deeper) on the next lap. Repeat until you find the sweet spot. At some point you'll go too far and over cook it so make sure there is plenty of safe run off room.

 

https://www.random-science-tools.com...g-distance.htm

 

It depends on a lot of things that can't be easily thrown into an equation. If you do the procedure above and keep your speed constant driving into the corner, hit the brakes and repeat on the next lap 50 ft closer to the turn in point you will get some idea of how much distance it will take to brake from what ever speed you have set as your baseline. Factors to consider are whether or not you are braking up hill, down hill or on level ground. My experience is most tracks don't give you many level braking zones. Then you have to figure out whether or not there is sealer on the pavement, how old the pavement is, etc. Then which tires are you using and how many heat cycles are on them. Then of course how well you can control the braking to get the quickest slowing. The 60 - 0 is easy since it is a bury a foot on the brake pedal and see how fast the car stops.

Bill

 

Seen this website, again, only calculates from a speed to zero, with reaction times, not needed in a track scenario.

 

I don't think it matters, because every turn is different, every LAP is different. You can't assume that, say, braking from 120-60mph takes 150' in an ideal, controlled environment that next time coming up on a turn that requires a 120-60mph deceleration that the distance required to slow down is the same. Because if you NAILED the exit to the prior turn, you can be going 125mph instead of 120mph, and if you apply braking at exactly the same spot, you're probably going off track or into the wall because you just blew past your braking zone by 3 ft.

Here are all the factors that varies from turn to turn, lap to lap.

Camber
Elevation change
Surface conditions
- Temperature
- Precipitation
- Dirt
- Debris
Tire temp
Brake temp
Tire's age / numbers of heat cycles
...and a whole lot more.

Not to mention TRAFFIC. If you've got a car in front or behind you, the aerodynamic effects can have some effect on your braking performance. Not only that, if the car in front of you brake 2/10th of a second before you did, both of you will be taking a ride in the dirt or worse, parked into the tire-wall.

While I am ALL for data and scientific accuracy of driving, a friend of mine, who club races, and raced semi-professionally for a factory team, once told me that driving has as much to do with feel as it does the mechanical aspects. I once took a ride with him, and asked what he was looking at and for in a specific turn, and his answer was "I don't know. I just drive by feel and know what to do because I do this every other weekend." In fact, he commented that what we TEACH at our events, the looking ahead, vision skills, etc, they're fine for basics. But once you get into sharing a corner with 3 other cars, and when you're doing this more than 20 weekends in a year, you need to put all that together and that can only be accomplished by FEEL, because everything changes so rapidly on track that you never have the same turn conditions 2 laps in a row. And if you have to think about where and when to brake from a 120mph straight down for a 60mph turn, when there's a car in front, behind, and each side of you...Well, that 7/10th of a second for you to process, think, then execute will already all be TOO LATE.

 

I guess I should not had mentioned "track" in this post, as I am aware of all these variation possibilities, I'm not trying to get the best track time. I was just wondering if there was a calculation available that could compute 120-60, etc... rather then just 60-0.

 

Well...

You may have to do SOME work yourself, but it's not that hard to figure out. We have the 60-0 time and distance, so it's not hard to figure out the coefficient of friction. All these are simple, standard formula that will net you a pretty close approximation (since, well, you're not here for REAL WORLD results anyway).

http://www.softschools.com/formulas/...ce_formula/89/

This isn't a calculator, but explains how stopping distance work.



You can plug in the 60-0 distance of 92ft into this calculator to get the coefficient of friction (again, ideal world conditions):

http://www.csgnetwork.com/stopdistcalc.html

I went ahead and did the "math" (or some computer server somewhere did), the for said distance is ~3.387(this is a static value).

Plugging theof 3.387, but changing the value from 60mph to 120mph, it gives me a theoretical stopping distance of 368 ft. So we can infer from the difference that to slow down from 120mph to 60, then from 60 to 0, is 368 - 92 = 276 feet.

Give or take a few, theoretically speaking. Or just a first down shy of a FOOTBALL FIELD.

 

Hmmm.... interesting, I'll have to check these sites out. I do think, at least with my car, 120mph to 60mph can happen in a lot faster than 276 feet, heck to me, even 60mph to 0 seems like it can happen in a lot shorter than 90 feet, but that just might be "seat of the pants" measurements, as these ceramic brakes are something else!

 

Well...

If we do not take into consideration other variables, this is the "theoretical" stopping distance based on the 92" of stopping distance as tested by instruments. You have to take real world conditions into account for say, a 120mph to 60mph test, that stuff is out the window.

Remember, at 120mph you're traveling a little over HALF a football field per SECOND. At that speed, even slowing down from 120mph, let's say it takes you 2 seconds to slow it down to 60, in that span of time you've already traveled a full football field. Perspective in a high speed car is much, MUCH different than reality when you're going at speed, IMO.


Fast forward to about 2:05. This is a HEAVY braking zone, going from 120mph down to about 60mph for the turn in. Took a total of 5 seconds and from in-car it certainly didn't look or feel like that was a full football field, but I can assure you, it IS and then some.

 

Yeah, I think I'll have to practice more at the track to try and find what my car can do, and come up with some calculations myself.

 

Thanks for finding the distance calculator formula. I went on the internet and tried to find it but couldn't so you post was extremely important.

The key number that is needed in the formula is coefficient of friction, ug. Since the ZO6 has a published 60-0 mph braking distance of 99 feet I plugged in these two known numbers and got a ug of 1.2. Once this is known then plugging in the speed quickly gave the breaking distance. If you are familiar with the Texas Mile (if not, look it up on You Tube), done at the Victoria, TX, airport every year, they show the 1 mile top speed or many cars. The world record for a C7 ZO6 is 184 mph. However, most of the ZO6 cars turned in speeds around 170 mph. This gives a braking distance of 805 ft. Our club is considering doing our own version of the Texas mile at a local airport but I had to know the stopping distance after reaching 170 mph to calculate how long a runway is needed. The minimum would be 5,280+805=6,085 ft. but that gives no room for error if you had braking problems so I believe that we would need a runway of at least 7,000 ft. for safety. Luckily I found a local airport that has two 7,300 ft. runways so that should be sufficient.

You may have to do SOME work yourself, but it's not that hard to figure out. We have the 60-0 time and distance, so it's not hard to figure out the coefficient of friction. All these are simple, standard formula that will net you a pretty close approximation (since, well, you're not here for REAL WORLD results anyway).

http://www.softschools.com/formulas/...ce_formula/89/

This isn't a calculator, but explains how stopping distance work.



You can plug in the 60-0 distance of 92ft into this calculator to get the coefficient of friction (again, ideal world conditions):

http://www.csgnetwork.com/stopdistcalc.html

I went ahead and did the "math" (or some computer server somewhere did), the for said distance is ~3.387(this is a static value).

Plugging theof 3.387, but changing the value from 60mph to 120mph, it gives me a theoretical stopping distance of 368 ft. So we can infer from the difference that to slow down from 120mph to 60, then from 60 to 0, is 368 - 92 = 276 feet.

Give or take a few, theoretically speaking. Or just a first down shy of a FOOTBALL FIELD.[/QUOTE]

 

Nice exercise, but FWIW, raced motorcycles from 1977 to 1982 and cars with SCCA from 1984 to 2011. You find a marker and brake. Have more room after apex, find a new marker and brake there. I raced open wheel Vees and Formula Fords a few years. Brake later and later into a corner till I saw a whiff of smoke off inside wheel. Next lap, brake 5 feet earlier. Tire temps, track surface, even morning to afternoon sessions make a difference. Had braking point go to sh*t more than once when I watched for fender next to me dip, then I'd brake. Usually worked... usually.