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TDCTDI
Samba Advocatus Diaboli
Joined: August 31, 2013
Posts: 12850
Location: North Carolina
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 Posted: Tue Apr 17, 2018 3:19 pm Post subject: Re: My 2 cents on disc brakes..... |
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And it gets worse with a Bus, every psychotic soccermom HAS to get in front of you to immediately hook a hard right to get into the gym after dropping the kid off at daycare. Some crazy bitch did that this morning as I was pondering the irony of the "baby on board" bumper sticker above the KIA logo.
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Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Tue Apr 17, 2018 5:07 pm Post subject: Re: My 2 cents on disc brakes..... |
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| Helfen wrote: |
Interesting to note here. A 2018 best
Dry Braking consumer report
Best models
Distance, ft.
Chevrolet Corvette Stingray 3LT
107
Porsche 911 Carrera S
108
Porsche 718 Boxster (base)
108
Chevrolet Camaro 2SS
112
BMW M235i
115
Maserati Ghibli S Q4
115
Chevrolet SS
118
Ford Fiesta ST
118
Tesla Model S P85D
118
Dodge Challenger
119
Take a guess what a 1971 U.S. spec. NON Super Beetle, all FOUR wheel DRUM brake, bias ply factory tires , standard Beetle did in Car and Drivers 60-0 braking test???????? 120 Ft!!!................My 2C |
Not really....and a BIG "but"....bear in mind...your 1971 spec beetle weighed about 2200 lbs with a driver and fuel. Almost no vehicles on that list....perhaps maybe the Ford Fiesta which can still weigh up to 2750.....weighs under 3000 lbs. Even the Corvette weighs 3500 lbs.
Corvette stingray: 3,298 to 3,362 lbs
Porsche 911 carrera s: 3,175 to 3,329 lbs
Boxster 718 base: 2,943 to 3,031 lbs
Camaro 2ss: 3,685 to 3,956 lbs
BMW 235i: 3,373 lbs
Maserati Ghibli S Q4: 4,123 lbs
Chevy SS: 3,997 lbs
Ford Fiesta ST: 2,720 lbs
Tesla model S P85D: 4,936 lbs
Dodge challanger: 3,894 to 4,448 lbs.
Braking is not JUST about tire width and swept area or drums and discs. Its about converting the WEIGHT and the forward enertia created by it....to heat...with frictioj and clamping force.
Your comparison is like comparing an apple to water melons! 
That is the reason for disc brakes. Ray |
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hitest
Samba Member
Joined: September 30, 2008
Posts: 10296
Location: Prime Meridian, ID
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| Posted: Tue Apr 17, 2018 8:59 pm Post subject: Re: My 2 cents on disc brakes..... |
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Newer cars also have safer brakes to compensate for increasingly more distracted drivers. Hence lane departure warnings, blind spot warnings, all the shit because makers cater to increasingly dumber drivers. Classic VW drivers are not in the same demographic and cannot be compared to the soccer mom's reaction time with her Brembos. I guarantee my defensive skills and reaction time has decades of evolution because of classic cars. Same with my 20 years or so driving service trucks with company logos on all sides. She (or albeit remotely, he) is already up the ass of the Honda ahead of her when she remembers she HAS and starts using her Wilwoods. Her brakes were tested by pros yet sold to the worst of distracted make up doing texting eating self-absorbed psychos Gen Y has to offer. Or He...
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| EverettB wrote: |
I wonder what the nut looks like.
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'62 L390 151, '62 L469 117, '63 L380 113, '64 L87 311, '65 L512 265, '65 L31 SO-42, '66 L360 251, '68 L30k 141, '71 L12 113, '74 ORG 181
FU#5 |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Wed Apr 18, 2018 4:20 am Post subject: Re: My 2 cents on disc brakes..... |
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I thought I killed the thread with my "everyone is on the power - nobody concerned about stopping" rant!
As far as what the other cars weigh out there in the traffic, I don't get to pick and choose the weight of the car I am following so it's really only their stopping distance that counts. For my part though weight reduction IS one of the modifications that can make a difference for sure and the only one in my favor at the moment. All else on this Buggy so far is stock.
In fact it was a weight increase that brought me to thinking that I need to upgrade the brakes. I thought my brakes were just fine until last summer we were on a holiday, pulling a little trailer with a canoe and luggage in it (maybe 500lbs) in heavy traffic going down a mountain pass and someone a mile or so up ahead jumped on the binders. Suddenly I was very aware that the old drum brakes were not up to modern standards!
As hitest eludes to I used to think I was a superior driver too but with 40 years of driving, about 80K/year behind me and having driven several million miles I have come to the conclusion the I am really not that special. Not sure if it is wisdom that has taught me that or old age is catching up but it is fact!
We seemed to have switched to measuring stopping power in feet rather than seconds. All good but as I now have my Buggy down for an engine change I cannot redo my test. I'm sure there is a formula for calculating decelleration that would convert my stats to feet... |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9145
Location: Canada
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| Posted: Wed Apr 18, 2018 9:38 am Post subject: Re: My 2 cents on disc brakes..... |
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The problem with real world stopping distances and the ones you posted is that the brake tests are done with cold brakes and it is one time not repeatedly. In the real world brakes get hot from stop and go traffic and repeated stops. Chances are the modern cars with 4 wheel disks will not have their stopping distances affected that much as disks and their pads cool themselves FAR better than drums and shoes which are trapped in an enclosed area with no airflow. Drums also expand with heat meaning the shoes have to travel farther. So repeat those tests after driving the cars around town for half an hour and then measure distances. I'll bet the beetle adds another 30 feet to its stopping distance.
I've done 3 buggies and 2 beetles with 4 wheel disks and I'll never go back. After they are broken in disks stop all the cars far straighter, far sooner and with better control. I drove a friends car last year a while after he got it on the road with all new brakes (everything was new). compared to my 57 with 4 wheel disks and about the same suspension and tire setups, the disks were hands down far better than drums. I found a night and day difference.
brad |
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hitest
Samba Member
Joined: September 30, 2008
Posts: 10296
Location: Prime Meridian, ID
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| Posted: Wed Apr 18, 2018 7:07 pm Post subject: Re: My 2 cents on disc brakes..... |
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From Brad to another- you do bring up a fact I seldom remember: Holding a straight line. It's such a habit with drums to jam that steering wheel straight the second you heave on the brakes- since they rarely track true. It's such a muscle memory event I hadn't even thought of it.
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| EverettB wrote: |
I wonder what the nut looks like.
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'62 L390 151, '62 L469 117, '63 L380 113, '64 L87 311, '65 L512 265, '65 L31 SO-42, '66 L360 251, '68 L30k 141, '71 L12 113, '74 ORG 181
FU#5 |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9145
Location: Canada
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| Posted: Thu Apr 19, 2018 8:19 am Post subject: Re: My 2 cents on disc brakes..... |
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| hitest wrote: |
| From Brad to another- you do bring up a fact I seldom remember: Holding a straight line. It's such a habit with drums to jam that steering wheel straight the second you heave on the brakes- since they rarely track true. It's such a muscle memory event I hadn't even thought of it. |
No matter how carefully I set up my brakes or machined my drums I could never get my autocross cars to not pull one way or the other with drum brakes. And large sticky slicks only made the problem worse....way worse.
I came into the stop box once, threw out the anchor and the car pivoted on the left front wheel and did a 180 and the car only traveled another 10 feet. I went into the box backwards without hitting cones or the timing gear. That was the most violent end swap I ever experienced.
brad |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Thu Apr 19, 2018 10:23 pm Post subject: Re: My 2 cents on disc brakes..... |
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| slalombuggy wrote: |
| hitest wrote: |
| From Brad to another- you do bring up a fact I seldom remember: Holding a straight line. It's such a habit with drums to jam that steering wheel straight the second you heave on the brakes- since they rarely track true. It's such a muscle memory event I hadn't even thought of it. |
No matter how carefully I set up my brakes or machined my drums I could never get my autocross cars to not pull one way or the other with drum brakes. And large sticky slicks only made the problem worse....way worse.
I came into the stop box once, threw out the anchor and the car pivoted on the left front wheel and did a 180 and the car only traveled another 10 feet. I went into the box backwards without hitting cones or the timing gear. That was the most violent end swap I ever experienced.
brad |
Thats not really because of whdther its disk or drum....its because of brake bias and balance. You have to tune for that.
The first VW to have REALLY good brakes and active tuning to keep the car on a a straight line during high speed braking was the VW 411 sedan....which had a fairly advanced for its time.....rear brake pressure regulation and limiting system. You can buy a HUGE range of aftermarket systems to do this on "built" cars.....but its tedious work to get it set up. Ray |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Fri Apr 20, 2018 4:50 am Post subject: Re: My 2 cents on disc brakes..... |
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| Sounds like the rear brakes locked up first. Worst possible imbalance! |
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slave1pilot
Samba Member
Joined: February 22, 2010
Posts: 943
Location: Tehachapi CA
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| Posted: Fri Apr 20, 2018 6:58 am Post subject: Re: My 2 cents on disc brakes..... |
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| TDCTDI wrote: |
| Some crazy bitch did that this morning as I was pondering the irony of the "baby on board" bumper sticker above the KIA logo. |
Is the irony that she is driving erratically with a "Baby ob Board" sticker, or the Kia logo?
I was talking with our lead brake development guy (we work for Hyundai/Kia at the test track) about this disc vs drum brakes topic. I tried to relay some of the comments stated and he got a really good laugh out of them.
I'm going to send him the link so he can read over it.
Maybe I can get his professional input.
_________________
My Photobucket for my Herbie Project - http://s1288.photobucket.com/user/TK-439/library/Herbie?sort=3&page=1
Currently:
1963 Ragtop Beetle
Previously:
1967 Beetle
1968 Beetle
1970 Beetle |
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Fri Apr 20, 2018 8:03 am Post subject: Re: My 2 cents on disc brakes..... |
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| oprn wrote: |
| Sounds like the rear brakes locked up first. Worst possible imbalance! |
In a imbalance situation the brakes that steer the car are the ones you want to lock up the LAST. If the fronts lock up first there is no steering control.
Even the old time manufacturers knew this and that is why the old cars of the early 1900's had only rear brakes. |
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TDCTDI
Samba Advocatus Diaboli
Joined: August 31, 2013
Posts: 12850
Location: North Carolina
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| Posted: Fri Apr 20, 2018 10:39 am Post subject: Re: My 2 cents on disc brakes..... |
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| slave1pilot wrote: |
| TDCTDI wrote: |
| Some crazy bitch did that this morning as I was pondering the irony of the "baby on board" bumper sticker above the KIA logo. |
Is the irony that she is driving erratically with a "Baby ob Board" sticker, or the Kia logo?
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Her driving erratically, combined with “baby on board”, “Killed In Action” acronym.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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slave1pilot
Samba Member
Joined: February 22, 2010
Posts: 943
Location: Tehachapi CA
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Fri Apr 20, 2018 1:20 pm Post subject: Re: My 2 cents on disc brakes..... |
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| Helfen wrote: |
| oprn wrote: |
| Sounds like the rear brakes locked up first. Worst possible imbalance! |
In a imbalance situation the brakes that steer the car are the ones you want to lock up the LAST. If the fronts lock up first there is no steering control.
Even the old time manufacturers knew this and that is why the old cars of the early 1900's had only rear brakes. |
I am not sure how to say this without offending you but that is just so - so - so wrong! This is not the first time I have seen this myth stated here on this site and it just is not correct!
When the fronts lock first you loose adhesion to the road and therefore the tires have no ability to control the direction of the car. Momentum dictates it will go in the direction you were traveling before the brakes locked - straight ahead. The rears are still adhered to the road and follow the front - straight ahead. That is the safest in the majority of cases.
When the rears lock first the loss of traction means the rears no longer have any directional reference to the road and less adhesion than the fronts and any attempt at changing direction by the front tires will now result in the rear of the car trying to pass the front. If you hold the car straight all may end ok but any attempt to change direction WILL result in an immediate and violent spin out. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Fri Apr 20, 2018 1:48 pm Post subject: Re: My 2 cents on disc brakes..... |
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| oprn wrote: |
| Helfen wrote: |
| oprn wrote: |
| Sounds like the rear brakes locked up first. Worst possible imbalance! |
In a imbalance situation the brakes that steer the car are the ones you want to lock up the LAST. If the fronts lock up first there is no steering control.
Even the old time manufacturers knew this and that is why the old cars of the early 1900's had only rear brakes. |
I am not sure how to say this without offending you but that is just so - so - so wrong! This is not the first time I have seen this myth stated here on this site and it just is not correct!
When the fronts lock first you loose adhesion to the road and therefore the tires have no ability to control the direction of the car. Momentum dictates it will go in the direction you were traveling before the brakes locked - straight ahead. The rears are still adhered to the road and follow the front - straight ahead. That is the safest in the majority of cases.
When the rears lock first the loss of traction means the rears no longer have any directional reference to the road and less adhesion than the fronts and any attempt at changing direction by the front tires will now result in the rear of the car trying to pass the front. If you hold the car straight all may end ok but any attempt to change direction WILL result in an immediate and violent spin out. |
Yes....in theory...but not quite correct...in a rear weight bias car. It is absolutely correct that you DO NOT want the fronts to lock up as you noted. But....you also do not want the rears to lock up first...again as you noted...and preferably not at all.
The rears should NEVER lock on a rear weight bias car. Because...the only reason they lock is rear to front inertial weight transfer....and if the rears lock during inertial transfer...its because the rear is lifting.
And if the rear lifts...virtually any movement in the front end at all can cause the rear end to pivot around the front end as it reaches the end of its lifting ability. This IS the 911 syndrome.
Oddly...I found that the 411 and 412 have the "911 syndrome" almost as bad as the early 911's...IF you do not have the brake pressure regulator or if yours is malfunctioning.
Types 3's can do this too most especially on wet pavement. I think the beetles are a little less prone due to shorter wheel base and weight distribution.
You can fix that on any car for pretty cheap these days. You can buy an adjustable aftermarket rear brake pressure regulator that installs in line and adjust it.
Here is a link to a whats inside of teh 411/412 rear brake pressure regulator (same one for Porsche 914, and some BMW and Mercedes of the era)
https://www.thesamba.com/vw/forum/viewtopic.php?t=664753
It was kind of an early anti-lock brake type thing. It allows pressure to go to the rear brakes until it reaches a pre set 530 lbs of force.....then it keeps that force level as long as you keep your foot on the pedal....but does not allow it to increase or decrease. Ray |
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TDCTDI
Samba Advocatus Diaboli
Joined: August 31, 2013
Posts: 12850
Location: North Carolina
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| Posted: Fri Apr 20, 2018 2:48 pm Post subject: Re: My 2 cents on disc brakes..... |
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| slave1pilot wrote: |
ohhhhh...
I didnt think of that. |
And now, you'll never look at a KIA again without thinking that. BWAHAHAHAH! 
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Fri Apr 20, 2018 3:44 pm Post subject: Re: My 2 cents on disc brakes..... |
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| oprn wrote: |
| Helfen wrote: |
| oprn wrote: |
| Sounds like the rear brakes locked up first. Worst possible imbalance! |
In a imbalance situation the brakes that steer the car are the ones you want to lock up the LAST. If the fronts lock up first there is no steering control.
Even the old time manufacturers knew this and that is why the old cars of the early 1900's had only rear brakes. |
I am not sure how to say this without offending you but that is just so - so - so wrong! This is not the first time I have seen this myth stated here on this site and it just is not correct!
When the fronts lock first you loose adhesion to the road and therefore the tires have no ability to control the direction of the car. Momentum dictates it will go in the direction you were traveling before the brakes locked - straight ahead. The rears are still adhered to the road and follow the front - straight ahead. That is the safest in the majority of cases.
When the rears lock first the loss of traction means the rears no longer have any directional reference to the road and less adhesion than the fronts and any attempt at changing direction by the front tires will now result in the rear of the car trying to pass the front. If you hold the car straight all may end ok but any attempt to change direction WILL result in an immediate and violent spin out. |
Read what I said; the LAST to lock up. Steering control is paramount.
I have a couple of cars that I use in grand touring and they both have adjustable proportioning valves. Before the car goes out on the track the car is adjusted so that all braking forces are equal, then in final adjustment I slightly adjust the rears to lock first. If you loose the front steering because of a skid you loose all control. Tail wag can be controlled to a degree while front tires skidding cannot. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Fri Apr 20, 2018 3:51 pm Post subject: Re: My 2 cents on disc brakes..... |
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| raygreenwood wrote: |
Yes....in theory...but not quite correct...in a rear weight bias car. It is absolutely correct that you DO NOT want the fronts to lock up as you noted. But....you also do not want the rears to lock up first...again as you noted...and preferably not at all.
The rears should NEVER lock on a rear weight bias car. Because...the only reason they lock is rear to front inertial weight transfer....and if the rears lock during inertial transfer...its because the rear is lifting.
And if the rear lifts...virtually any movement in the front end at all can cause the rear end to pivot around the front end as it reaches the end of its lifting ability. This IS the 911 syndrome.
Oddly...I found that the 411 and 412 have the "911 syndrome" almost as bad as the early 911's...IF you do not have the brake pressure regulator or if yours is malfunctioning.
Types 3's can do this too most especially on wet pavement. I think the beetles are a little less prone due to shorter wheel base and weight distribution.
You can fix that on any car for pretty cheap these days. You can buy an adjustable aftermarket rear brake pressure regulator that installs in line and adjust it.
Here is a link to a whats inside of teh 411/412 rear brake pressure regulator (same one for Porsche 914, and some BMW and Mercedes of the era)
https://www.thesamba.com/vw/forum/viewtopic.php?t=664753
It was kind of an early anti-lock brake type thing. It allows pressure to go to the rear brakes until it reaches a pre set 530 lbs of force.....then it keeps that force level as long as you keep your foot on the pedal....but does not allow it to increase or decrease. Ray |
The theory is correct for all cars Ray. The difference with VWs, the 911 series Porsche and Corvair by the way, is that the problem is exaggerated by the rear weight bias of the cars. It gives them a polar moment of inertia that is unfavorable in the situation we are discussing. Due to the rearward center of gravity of these cars they tend to oversteer badly which translates into easy and violent spin outs on hard braking when the back wheels lock. The same thing happens in a hard corner under power when the back wheels lose adhesion. That and the lifting you mentioned are the whole premise of the book Ralph Nader wrote "Unsafe at any speed!"
My VW Rabbit and Jettas will do it too under the same braking conditions but with the forward center of gravity it is much much milder and much easier to control.
And that is one of the major reasons for the move away from rear engine/rear drive to the front engine/front drive cars we have today. More predictability for the inexperienced masses! |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Fri Apr 20, 2018 4:06 pm Post subject: Re: My 2 cents on disc brakes..... |
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| Helfen wrote: |
Read what I said; the LAST to lock up. Steering control is paramount.
I have a couple of cars that I use in grand touring and they both have adjustable proportioning valves. Before the car goes out on the track the car is adjusted so that all braking forces are equal, then in final adjustment I slightly adjust the rears to lock first. If you loose the front steering because of a skid you loose all control. Tail wag can be controlled to a degree while front tires skidding cannot. |
Stopping in a safe and PREDICTABLE manor is paramount. That is rarely possible with the rear locked up and wagging all over Hades half acre!
How you set your race car up for the track should NOT be confused with how a car needs to be set up for the street. Race cars are often set up that way to initiate a skid going into a corner so that on application of power it translates into a drift. That is light years away from what happens on the street in an emergency braking situation!
Well Ok, I used to drive like that on the street when I was young and foolish!!  |
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Helfen
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Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Fri Apr 20, 2018 7:55 pm Post subject: Re: My 2 cents on disc brakes..... |
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| oprn wrote: |
| Helfen wrote: |
Read what I said; the LAST to lock up. Steering control is paramount.
I have a couple of cars that I use in grand touring and they both have adjustable proportioning valves. Before the car goes out on the track the car is adjusted so that all braking forces are equal, then in final adjustment I slightly adjust the rears to lock first. If you loose the front steering because of a skid you loose all control. Tail wag can be controlled to a degree while front tires skidding cannot. |
Stopping in a safe and PREDICTABLE manor is paramount. That is rarely possible with the rear locked up and wagging all over Hades half acre!
How you set your race car up for the track should NOT be confused with how a car needs to be set up for the street. Race cars are often set up that way to initiate a skid going into a corner so that on application of power it translates into a drift. That is light years away from what happens on the street in an emergency braking situation!
Well Ok, I used to drive like that on the street when I was young and foolish!! |
I know, I know. I was in automotive engineering for 34 years. Thank goodness someone came up with the idea of ABS for the likes of the wannabe. The only known devise that lets the driver have his cake and eat it too, meaning he gets control of his steering without loosing his rear end even though he might still meet his end. Unfortunately, no one has a kit for ABS in a A/C bug to my knowledge. It would be quite good for empowering the uninitiated though. |
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