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04-26-2021, 09:55 AM | #1 |
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Stopping Distances
This topic comes up often, and it is mostly as an excuse by some to avoid touring on main roads.
Is there a table of stopping distances for a stock Model A? The only person I have seen test stopping distances is Flathead Ted.
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Bob Bidonde |
04-26-2021, 10:00 AM | #2 |
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Re: Stopping Distances
Such a weird rationale – as if dump trucks and logging trucks weren't out on these same roads. The only way I see it making sense is if you as a driver don't know your own stopping distance and thus don't feel safe, but it seems that you could establish this empirically pretty easily.
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04-26-2021, 10:21 AM | #3 |
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Re: Stopping Distances
Bob, what a great idea. Car owners testing their stopping distance and reporting back to the Barn. I will do this when I get home in May. How do you propose doing the test? 25 mph, level dry asphalt road? Anything faster may be a safety hazard. And I would propose reporting the conditions and status of brakes, like stock, juice, FHT modified, etc.
Many year ago my uncle participated in a braking test. I don't know who sponsored it. A device was mounted to the car that fired a mark on the pavement. The driver would respond when they heard the bang. Another mark would be placed when the driver hit the brakes. That way the reaction time could be measured as well as the total stopping distance. I can see a paint ball gun being used today.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
04-26-2021, 10:52 AM | #4 |
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Re: Stopping Distances
I would do it in a big empty parking lot. Also if there's a good free GPS speed recording app out there that folks could use, that would probably be a more reliable baseline than trying to get a timely read on a speedo that may or may not be accurate.
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04-26-2021, 11:19 AM | #5 |
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Re: Stopping Distances
Such a stopping needs to start with a common base line and the GPS for measuring speed is perfect.
It should be limited to stock Model A mechanical brakes using correct size tires, with the notation of either cast iron brake drums or original pressed steel, woven or bonded linings. ('Cheating' could happen with bonded linings as there are various hardness available.) 'Gentlemen, Start Squealing Your Brakes !' |
04-26-2021, 07:51 PM | #6 |
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Re: Stopping Distances
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I'm part of the only ever generation with an analogue childhood and a digital adulthood. |
04-26-2021, 08:04 PM | #7 |
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Re: Stopping Distances
A shopping plaza is under ideal conditions which rarely ever exist. Too many variables to compile meaningful results. JMO
Last edited by McMimmcs; 04-26-2021 at 09:03 PM. |
04-26-2021, 08:11 PM | #8 |
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Re: Stopping Distances
Synchro, Best was 19 feet but what was the range? Was the best newly rebuilt stock brakes with cast iron drums, or what? Inquiring minds want to know.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
04-26-2021, 09:18 PM | #9 | |
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Re: Stopping Distances
Quote:
The front brakes were fitted with those floating pin wedges, cast iron drums and woven linings rivetted on. The back ones were stock standard - woven linings rivetted on and steel drums. I had done it that way un an effort to get something like the correct front/rear balance right. The back ones still locked too early so I have replaced the front actuating levers with a pair of the longer ones from the back. I don't think that has improved the stopping distance much, is any but it takes less pedal pressure and I don't have near as much brake fade. My brother in law has Flat Head Ted brakes on the front and I would rate them as about the same. Dammit! There goes another secret. I also like to use a cross shaft from a LHD car. I drill out the rivet holding the arm for the rod from the pedal and move it over to the right side. When it is lined up with the pedal, it is nearly out of that dip it has in it so it goes under the gearbox By then, the clevis eye is further from the axis of the shaft and I have more leverage I know, I know. That's cheating. Tell the hand! Safety come first. As they say, it is not only cars that are recalled by their maker!.
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I'm part of the only ever generation with an analogue childhood and a digital adulthood. Last edited by Synchro909; 04-26-2021 at 09:24 PM. |
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04-27-2021, 12:03 AM | #10 | |
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Re: Stopping Distances
Quote:
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04-27-2021, 05:13 PM | #11 |
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Re: Stopping Distances
No, they are not a direct fit. The shaft on the rear brakes is bigger than the front actuating shaft so I made a sleeve. After removing the original arm, I put the sleeved rear arm on (oriented so the clevis is facing the wheel) and secured it with a rivet I also made. Be prepared to have to grind down the rivet at the back or it will hit the spring perch. The fact that the clevis is now higher than it was means the anti rattle springs have to be modified a little to keep the brake rod straight and that's about it. You will also have to twist the lever to get it lined up with the direction of pull on the front rods. I have a Philips head screw driver with just the right diameter shank to fit the clevis. I mount the lever on the actuating shaft and hold it in the vice while I give it a good nudge till the screw driver and shaft are parallel.
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I'm part of the only ever generation with an analogue childhood and a digital adulthood. Last edited by Synchro909; 05-02-2021 at 01:15 AM. |
04-27-2021, 06:56 PM | #12 | |
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Re: Stopping Distances
Quote:
Thanks Synchro. Sound like something I want to investigate further. Always willing to learn something new. |
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04-26-2021, 09:14 PM | #13 |
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Re: Stopping Distances
As part of a reliability check a couple years ago The Beaver Chapter MAFCA set up a special run to test braking power and stopping distance. I wasn’t on that committee, so I don’t know if the data was saved or, if so, by whom. But it was a worthwhile event and I encourage every club to do it, along with a regular pre-tour season reliability check: lights, horn, braking power, wipers, seat belts, tire wear, etc.
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Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole. |
04-26-2021, 10:09 PM | #14 |
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Re: Stopping Distances
That's interesting because I find the need to stop quickly much more in city traffic than out on the roads. and highways. I do like the state highways and county roads better than driving the Interstates, but not for the fear of stopping as much as holding up 80 mph traffic. Drive defensively in any case!
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04-27-2021, 04:13 AM | #15 |
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Re: Stopping Distances
I set my brakes up with the fronts working first and the rears last. Big difference. Back in the day on gravel roads you wanted the rears to work first. All cars now the fronts work first.
Something to think about. |
04-27-2021, 08:41 AM | #16 |
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Re: Stopping Distances
Wick, I AGREE! But try convincing some old(er) and not so old "Model A Mechanics" that insist on setting up brakes "as Henry did" or using the Brake Board.
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04-28-2021, 02:03 AM | #17 |
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Re: Stopping Distances
Agreed. That's why so many vehicles have disc brakes up front and drums out back and not vice-versa. Something like 70% of the stopping power comes from the front brakes.
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04-27-2021, 12:43 PM | #18 |
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Re: Stopping Distances
I agree with Wick. My brakes are set up with more braking in the front. The "weight transfer" is towards the front when braking. By the way, the only time when locking up the brakes will result in shorter stopping distance is on gravel or dirt roads where the tires act as plows.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
04-27-2021, 05:43 PM | #19 |
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Re: Stopping Distances
Brake testing by humans, especialy old type humans will seldom yield results even close to the way they were when fresh out of the factory. While locking them up and skidding to a stop can be repeated many times close enough for every day use, a professional driver can normally shorten the stopping distance by at least 5% by pulsing. A lot of bent fenders and dead people could have been saved if they taught that in driver education 101.
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04-27-2021, 08:39 PM | #20 |
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Re: Stopping Distances
Yeah, mine should be set up with more front bias. I can grab a hand full of E Brake if things get too serious to balance the rears.
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