Stopping distance of a 911

[BeyGon]

How many feet should it take, more or less, for an 89 911 with pretty new Bridgstones on it to stop from 65-70 mph? Full lock, no ABS. Dry grooved concrete.

[sailchef]

Two, applied firmly to the break pedal!

[old man neri]

Originally Posted by sailchef

Two, applied firmly to the break pedal!

Haha, nice one.

To answer your question...who knows. Too many variables.

What exact kind of pavement? What temperature of pavement? How old is the pavement? What kind of bridgestones? How many miles on them (new ones still have mold release compounds on them). What psi? What temperature are the tires? What is the size of the tires? What kind of brake pads? Are the pads cool or hot? What type kind of rotors? How old are the brakes?...etc

That being said, locking up your tires like that isn't the best of ideas.

[GH85Carrera]

It will take a lot longer to stop with the tires locked up that it would with proper brake modulation. Lockup is a bad idea.

[BeyGon]

I guess I will have to find an old Road and Track article.

[Cooper911SC]

1982 R&T article.

Min. Stopping distance from 60MPH 146ft 80 MPH 266ft

Control in panic stop, Excellent

Pedal effort required for 0.5G stop 18lbs.

Hope this helps.

Coop

[Zeke]

Dean, curious that you are asking the question. The real answer is how many feet it takes the driver to respond to the situation. IIRC, you reported that you looked away from the road for an instant and the next thing you saw was what you hit. I was really sorry to see the damage to your car, but I trust it's fixed perfectly now.

So, you tell us!

[Jack Olsen]

Originally Posted by Cooper911SC

Min. Stopping distance from 60MPH 146ft 80 MPH 266ft

Control in panic stop, Excellent

Shorter still if there's a wall to help you slow down.

[BeyGon]

Originally Posted by milt

Dean, curious that you are asking the question. The real answer is how many feet it takes the driver to respond to the situation. IIRC, you reported that you looked away from the road for an instant and the next thing you saw was what you hit. I was really sorry to see the damage to your car, but I trust it's fixed perfectly now.

So, you tell us!

I slid a long way, I hit the brakes at about 65ish. I drove down the freeway the next day to look at the marks before they went away. But, couldn't really tell how far because of traffic, didn't get out to pace them. I had new Bridgstones on it, not as sticky as the old ones, more miliage and so on. I just wondered if I had the sticky tires if it would have made a real difference. These tires got flat spots from the slide. They had maybe 2000 miles on them.
The car is supposed to be done tomorrow, we will see.

[BeyGon]

Originally Posted by Cooper911SC

1982 R&T article.

Min. Stopping distance from 60MPH 146ft 80 MPH 266ft

Control in panic stop, Excellent

Pedal effort required for 0.5G stop 18lbs.

Hope this helps.

Coop

Thanks, that's what I was looking for.

[RSTarga]

Jack, I love your theory, and Dean forget about last time, next time leave more room between you and the car in front.

[old man neri]

Originally Posted by Jack Olsen

Shorter still if there's a wall to help you slow down.

OUCH! I feel bad for you.

[RSTarga]

Jack, now I see why the factory RSR's had 4 tabs to keep the windshield attached to the car. I always wondered what they were for.

[GrantG]

Originally Posted by Cooper911SC

1982 R&T article.

Min. Stopping distance from 60MPH 146ft 80 MPH 266ft

Control in panic stop, Excellent

Pedal effort required for 0.5G stop 18lbs.

Hope this helps.

Coop

Those numbers aren't very good. I think a short stopping distance for a modern sportscar from 60mph is around 110ft. Very tire dependent...

[bonkers]

Originally Posted by BeyGon

I slid a long way, I hit the brakes at about 65ish. I drove down the freeway the next day to look at the marks before they went away. But, couldn't really tell how far because of traffic, didn't get out to pace them. I had new Bridgstones on it, not as sticky as the old ones, more miliage and so on. I just wondered if I had the sticky tires if it would have made a real difference. These tires got flat spots from the slide. They had maybe 2000 miles on them.
The car is supposed to be done tomorrow, we will see.

If the tires flat-spotted then the brakes were locked up and all bets were off.

Theoretical stopping distances wont help you in a situation like that, only improving your situational awareness and your reactions will.

[emcon5]

Originally Posted by GrantG

Those numbers aren't very good. I think a short stopping distance for a modern sportscar from 60mph is around 110ft. Very tire dependent...

I would be really interested to see how improved this number is with modern tires. Tire technology has come a long way in the past ~25 years.

Tom

[Reaper930]

Its not only about tire tech as it is having enough tire to brake so that the braking limit is close to the traction limit of the tires. I know from my experiences that a car that will lock them up easily can use some more rubber to combat and delay until more pedal pressure is applied to achieve lock up.

[Zeke]

There are too many variables, as mentioned. The freeway where Dean was most likely was heavily grooved and somewhat uneven, as most are in CA. In addition, it could very well have been concrete as opposed to asphalt. Furthermore, it could have been recently machined and regrooved as they are doing that all over the place. I haven't gotten out to look closely, but the newly surfaced and regrooved roads look slick to me.

Regarding the comment about flat spots and lock up, when you are looking up the ass of a monster SUV with its tail hiked up because he is panic stopping, I doubt you will be able to modulate your brakes as you might entering a corner at the track.

Nope, you're gonna stand on them and clinch your fists, if not something else.

[Superman]

Originally Posted by Cooper911SC

1982 R&T article.

Min. Stopping distance from 60MPH 146ft 80 MPH 266ft

Control in panic stop, Excellent

Pedal effort required for 0.5G stop 18lbs.

Hope this helps.

Coop

This was with tire technology from the 1980's. Today's tires are way beyond that. When I was setting up my insurance policy the woman asked if my SC has antilock brakes. Of course, it does not. Afterward, I chuckled to myself that I'd be happy to have a braking contest with any of today's antilock brake cars. My car weighed 2450 with about 1/3 tank of gas and the Bilstein shocks were fresh.

BTW, 60 mph is 80 feet per second. Stopping in 145 feet is.....violent.

[Zeke]

Originally Posted by Superman

.

BTW, 60 mph is 80 feet per second. Stopping in 145 feet is.....violent.

Especially when there's 130 feet between you and a stationary object.