MT brakes

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Model T Ford Forum: Forum 2012: MT brakes
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Saturday, March 31, 2012 - 11:01 pm:

Has anyone installed these and what is your feeling on installation and performance?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Monday, April 02, 2012 - 11:53 pm:

not a soul out there has tried these?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Tuesday, April 03, 2012 - 12:04 am:

Dave,
Do you mean Rocky Mountain Brakes?
Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Tuesday, April 03, 2012 - 12:19 am:

Sorry Dave, I saw the ad in classifieds after I posted:

"Information: Disc brakes from MTbrakes; new product announcement! www.MTbrakes.com offers disc brake kits for all years and wheel varieties. Working with Wilwood� disc brakes, we have recently upgraded our kits with a newly produced 2 piston caliper and improved mounting brackets. Unobtrusive and easy to install email enquiries @ anclark03(fronty)atshaw.ca. Please remove (fronty)at, and exchange at =@ to reply.
Allan Clark 250-752-8178"

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve McClelland on Tuesday, April 03, 2012 - 12:33 am:

$2500 worth of brakes on a ( in most cases ) $4000 to $8000 dollar car, I'd have to weigh that one for a long time unless I lived in the mountains or maybe if I had an 80mph T


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Tuesday, April 03, 2012 - 10:09 am:

The brakes look like they are less noticible than Texas T brakes and more effective than Rocky Mountain brakes. They make brakes for the front as well, but I don't think the Model T front axle is designed for brakes.

MT brakes has a few pictures, but they do not clearly show what is available or how they are installed. Maybe that is so someone won't steal the idea.

I would like to be able to switch out the wooden and the wire wheels on my speedster depending on how I feel that day and wonder if this can be done on Allan's design.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Tuesday, April 03, 2012 - 10:27 am:

Steve,

$2500???

The website says $1050 for small drum type rear ends. Maybe you're thinking of the 4 wheel brake option but, for most cars, this is overkill, (in my opinion).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, April 03, 2012 - 02:56 pm:

Even the most best brakes you can put on a T are barely good enough.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Tuesday, April 03, 2012 - 03:11 pm:

Disconnect the front brakes on your daily driver modern car and drive around a few days and see how well you do.
I don't care if you have power disc brakes in the back with drilled & grooved rotors and ceramic pads it aint gonna stop worth a darn.

Wait until you are going about 20 MPH on a freshly paved street and you have to do a panic stop. ZZZZZZZ crash.

Remember, 70% of the stopping power of the average old rear wheel drive car is on the front.

Pedal a bicycle as fast as you can and lock up the rear brake. slide, slide slide...
Now do it with only the front.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve McClelland on Tuesday, April 03, 2012 - 04:30 pm:

I agree Jerry, my T isn't fast enough for disc brakes although it's what ever a fellow wants for his car, if you like to tinker around and change stuff I say go for it.... But I would be real concerned about the 4 wheel brake option that's a lot of stress on front axle components, that are already week to start with. I just don't like the thoughts of wood wheels and hydraulic brakes we have that set up on a 1928 Dodge right now but this one was factory built not an add on kit, we're currently in the process of changing out the wood wheels for wire spokes on it for added safety 55-65 mph on wood spokes isn't a good combination .


Top of pagePrevious messageNext messageBottom of page Link to this message  By Walt Berdan, Bellevue, WA on Tuesday, April 03, 2012 - 05:29 pm:

Front brakes on a T would require beefing up the front suspension. It's not that terribly hard to do.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, April 03, 2012 - 05:48 pm:

It takes less to put drum front brakes on a T than small drum rear hyd brakes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Tuesday, April 03, 2012 - 06:24 pm:

If you use only the front brake on your bicycle, your nose will likely be on the pavement or in the dirt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Tuesday, April 03, 2012 - 07:50 pm:

Aaron,

Comparing two wheel brakes on a Model T versus a modern car is not relevant. The T was designed for two wheel brakes and is driven nowhere near the same way nor is it nearly as heavy as a modern car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Tuesday, April 03, 2012 - 08:31 pm:

Come on Jerry, a T was built that way because in 1908 few if any cars had front brakes.
Are you saying a T will stop just as good without them???? Have you ever drven one?
Why do you think every car since has had 4 wheel brakes?
It is relevant.
What do you think the stopping distance of a T is compared to a T with four wheel brakes?
I would say a T would stop in 1/3 the distance with 4 wheel brakes.
I have a touring with hydraulic brakes on the rear. It is dangerous at any speed.
I was wondering, how would you design a car to stop well with only rear brakes?
The T was designed to be driven without a heater too, but most of us still freeze our asses when we ride in one on a cold day.
By the way, bicycles were designed with only a rear brake. I guess the front one is not needed?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, April 03, 2012 - 09:21 pm:

SUE SAID motorcycles stop with 80% on front brake.

BTW, traffic reporters have commented on sharp rise in motorcycle accidents on the freeways, obviously due to pain at the pump.

One of my favorite rants:

Cycle goes down; traffic tied up = wasted (other peoples') fuel.

Fatal cycle accident = massive tie up while coroner called out.

Hence, motorcycle riders are selfish and inconsiderate... :-(

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Tuesday, April 03, 2012 - 11:56 pm:

I have the Texas T hydraulic brakes on my 25 coupe. I actually bought them from Bill Tharp, when they were called Colorado Brakes, but they are the same thing.

I have asked several questions here on the forum over the last several years, and searched previous posts for answers to other questions I have had, and really appreciated the answers that other members have offered. I respect all of the opinions offered, and realize that some issues really do come down to personal preferences.

But when it comes down to the topic of hydraulic disc brakes on a Model T, the issue gets a little more clear cut for me. Those people that express opinions that indicate they do not believe that hydraulic disc brakes are a good idea, should probably try a set on their car before they expect the rest of us to give their opinion much credit.

I have asked every person I ever met that have installed a set of hydraulic disc brakes, either a set that they designed and built, or a set like the Texas T Brakes, and not one person is willing to take them off.

I am willing to concede that you can have an opinion that you don't like the looks, or they are not period correct, or anything about the way they look. But, maybe you should refrain from commenting about how they work, until you've tried them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Harrison,Norco Ca on Wednesday, April 04, 2012 - 12:14 am:

Michael,I just finished installing a set of the Texas T discs on my 27 Tudor and I couldn't agree more.It is nice to know you can safely stop.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernard from San Buenaventura, Calif on Wednesday, April 04, 2012 - 02:14 am:

I would like to install a set of 4-wheel disc brakes with brake power booster and ABS feature on my T. And dual air bags. And air conditioning.
Please do not tell me that's not a good idea. Like Michael Thomas I think you are not qualified to comment unless you tried all of those things yourself.

Anyone?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, April 04, 2012 - 07:32 am:

I have been driving on 4-wheel hyd drum brakes on my Ts for the most of 50-100K miles. Rear drum brakes are a giant effort for little gain. The fronts are the best thing you can do for a T you drive.

Rear disc brakes appear to be as easy to install as RM, and far safer when wet or holding when pointed uphill. Two serious rollover accidents happened on recent national tours due to aux brakes not holding when driver missed a shift or had drivetrain failure going uphill.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Wednesday, April 04, 2012 - 08:43 am:

Of course a T with both front and rear brakes will stop better than one with only rear brakes.

But that's not the point here. A T with disc rears will stop better (much better) than one with stock brakes. Its the improvement that counts.

None of us has the best brakes that are available on our personal cars, if we did a new chevy would cost $50K.

So you do what you can with the resources you've got, or you keep it stock and drive very carefully!

(Well...better drive that way anyways ;o) )

Cheers
schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, April 04, 2012 - 09:15 am:

Chevys must be getting close to $50K, Bud. I heard the average new car is $30K. That's what a house should cost..

I believe my 8 year old Monterey with ABS and stability control is the best braking available, but I haven't kept up with the news on that. I will be putting on better tires when these are gone, however.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Wednesday, April 04, 2012 - 11:47 am:

Come on yourself Aaron. I never said a T wouldn't stop better with 4 wheel brakes. Of course it would. I just said it's pointless to compare it to a modern car in any way. Apples and oranges.

Don't get so worked up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Wednesday, April 04, 2012 - 07:50 pm:

I'm still waiting to see if anyone can keep on topic and tell me something about MT brakes. The drums appear to be of a smaller diameter than the Texas T brakes, so they would be less noticible.

Has anyone had any experience with them or know someone who has?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Wednesday, April 04, 2012 - 09:07 pm:

Dave -- Give me a couple of weeks and I'll have a report for you. I have a set on the "new" driver I'm building, but I haven't driven it yet. I am very close to doing that, but my progress will be held up by our club's tour next weekend. I organized the tour, so it has been taking up a lot of my time.

I can also give you a comparison opinion with the ones TX T Parts offers, as I bought a set of those from Bill Tharp and installed them on my previous driver, a '15 Touring. I can tell you that those work GREAT!, but I don't yet know how the MT's will compare. Stay tuned.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Wednesday, April 04, 2012 - 11:29 pm:

Jerry, my modern car is lighter than my T. What's that got to do with anything?
It isn't pointless to compare it with anything else. What else can you do to prove how much better four wheel brakes are than two? It sure is easier than putting front brakes on a T to test the effectiveness.
Anything with wheels can be used to compare the effectiveness of front wheel brakes with just rear. Even and airplane or a farm tractor.
I can't think of anything that would stop the same with just rear brakes.
If it makes such a difference on a modern car it will make just as big of a difference on a T, within a few % depending on the modern car's front to rear weight ratio.
The first time I drove my '29 Nash I thought it would be just fine to run around with only rear brakes. It had too many parts missing so I put juice brakes on the rear.
I drove about 3 miles on level ground on the streets in San Francisco and never drove it again until I had front brakes too.
It stops almost as well as a modern car, if not just as well. It has Pinto rear brakes and Ford F1 pickup brakes in front.
I've put several thousand miles on it with never a close call. I cruise about 50 MPH, can go faster.
My T has hydraulic rear brakes and I have had too many close calls while driving in town at speeds below 30 MPH. I never drive it any more and probably won't until I get some front brakes.
It does stop pretty well with four or more people in it though. But the wheels slide too easily even then.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Thursday, April 05, 2012 - 02:54 am:

The T benefits far more with front brakes than any modern car, due to extreme weight shift with its high CG and short wheelbase.



Per the above, you can get only .35G braking before skidding with rear only brake.

I was hoping someone would take these illustrations and run with them. Some real calculations need to be done before installing a front brake. "That looks weak, let's beef it up," is scary, but I've seen that from some erstwhile mechanics who want to sell front brakes. We deserve better.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Thursday, April 05, 2012 - 03:15 am:

I'm not a purist, but improvements should either be almost invisible or should add a significant improvement.
As Rick just demonstrates above, you get skidding at the rear wheels at a relatively low retarding. Disc brakes does not change that regardless of how many pistons the calibers have! You MAY obtain a lower pedal pressure to obtain the skidding with discs and the over all performance may be more consistent.
To get the T to brake significantly better, frontbrakes is the only way forward and that will require very visible changes to the front.
Over here the whole setup will require technical documentation approved by an independent technological institute (like the German based TÜV) so that is not a way to go.
And again - the Model T wheel are so narrow so the upper limit for braking are not high. Yes, I know the theory says that the friction are independent on the friction area, but that is not quite true with rubber and tarmac. Why do you think they have those wide wheels on high performance cars?
It may make some sleep better and that's good.
As several had said - everyone have their opinion and act accordingly.

All I can say is: Drive carefully and to your cars abilities.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Derek Kiefer - Dexter, MN on Thursday, April 05, 2012 - 10:33 am:

Ricks, what are those brakes from, and how far do they move the wheels outboard?

If it moved the wheels outboard so the tire patch is entirely outboard from the king pin centerline, have you noticed the car wandering from side to side as it hits bumps, increasing steering effort, or pulling to one side under heavy braking if one wheel has more or less grip than the other?

Also, did you make any changes to the wishbone?

I've been considering building a front-brake setup, but the above are my biggest concerns. I like the way yours look, as they're small enough to not be very noticeable.

Thanks,
Derek


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Thursday, April 05, 2012 - 11:40 am:

I installed a double wishbone, which is a late wishbone welded to an early one at the apex, with the late ball removed.

Nash Metropolitan 8" x 1 1/4"

Wood wheels are pushed outboard hardly at all; just the thickness of the drum face.

Model T kingpins are vertical, putting them inside the tire track. My car has always been a stable driver at all speeds. Regardless, I always had a death grip on the wheel at speeds above 50, until I installed a modren, '37-48 Ford, steering gear with 10:1 ratio.

Inclining the kingpins like cars with factory front brakes would help in case of uneven braking, but that is not easy to accomplish. Braking with a front wheel off the pavement will cause the wheel with greater traction to pull the wayward wheel back onto the pavement. Even with kingpins inclined, there will always be pull toward the wheel with greater traction. I've experienced that too often in my modern cars.

Foreign material such as brake fluid or grease on the shoe/drum is a worst case. I have driven in extremely heavy rain, and not had more than a momentary reduction of braking.

Michael, race cars put as much rubber on the road as possible, so the super soft high traction compound will last the race, or a good portion of it.

I couldn't get Coker to tell us whether their balloon tires are softer compound than their clinchers, but my limited testing has found their clinchers to have pretty darn good traction. Fresh clinchers are not the limiting factor in stopping a T. Putting your passenger into the windshield is - - even with a seatbelt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernard from San Buenaventura, Calif on Thursday, April 05, 2012 - 12:44 pm:

Michael,
your post makes me wonder: what are the requirements in Denmark and Germany in regard to brake equipment when it comes to registering a car. I know you guys need turn signals, flashers, dual taillights, but what are the requirements when it comes to brakes?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Thursday, April 05, 2012 - 10:59 pm:

I am reviewing the calculations for the shift in braking force. I wonder if the center of gravity would really be 40 inches above the ground? That seems high to me. The engine and transmission are probably the heaviest items on the car and I think they would probably be below 40 inches, and there is not much above 40 inches, as far as weight is concerned. Lowering the center of gravity in the calculations would lessen the weight shift, thus leaving more braking force on the rear wheels. I guess I am still pondering the situation because my real life experience with my car and my "seat of the pants" feel, just doesn't reflect what the numbers show...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Friday, April 06, 2012 - 12:37 am:

If you can come up with a better number, Michael, go for it, and tailor it to your car. 40 inches was an easy to divide number, and just a starting point. Please share your numbers. I've been disappointed in the response so far.

I think you can figure the CG of a typical person is at about the belly button, maybe the bottom of the sternum. For worst case, you have to figure every seat is occupied. An FAA standard person has been 170 lbs for the last 60 years, and their formula had no room for growth. :-)

Dense things above 40 inches besides the salt water bags include the glass and glass frame.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Friday, April 06, 2012 - 06:00 pm:

Bernard, you basically list all the exceptions. The rules in Denmark is, that the rules that was in power when the car was new is the requirements today. And we have effective lobby organizations on national and EU level to keep it that way. The authorities are empowered to put limitations so if your car do not have headlights at all you may be banned from the streets from 1/2 hour after sunset to 1/2 hour before sunrise for example.
Flashers was demanded on all cars back in the 1950's and all traficators where banned. On VW type 1 (Beetle) workshops put a plate on the build-in traficator (in the B column) and a flasher on the plate. !0 years ago the lobby organisation have got the traficators back IF the lamp flashes. This is a very easy modification to the traficators.
I am not sure when symmetric rearlamps came, but sometime after WWII. This is no big deal either and do make sense.
Apart from this - no requirements regarding emission, 1/4 tax when over 24 years, inspection every 8th year (modern daily cars every second), whatever technical specs required back then is the same.
Apart from the tax, I think this is much the same in the other EU countries including Germany, though UK are considering dropping the inspection for old cars.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug - Glow in the dark, IL on Friday, April 06, 2012 - 06:43 pm:

Not that I care who does what to their cars. Has anyone spoken to their insurance company to see if the modified brakes will be covered. Also has anyone gotten the advice of a lawyer on the possible outcome of a personal injury accident with modified brakes? Would it make any difference? Just a thought.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rick Goelz-Knoxville,TN on Friday, April 06, 2012 - 07:37 pm:

All this and Dave still doesn't have an answer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Friday, April 06, 2012 - 09:54 pm:

Doug, the answer to Texas T brakes is, the original brakes are still hooked up. I just backed them off a little so that the hydraulic pick up the braking first. If, for some reason, the hydraulic fail, I still have plenty of pedal left to use the standard brakes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Harrison,Norco Ca on Friday, April 06, 2012 - 10:54 pm:

Ditto


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Saturday, April 07, 2012 - 12:52 am:

Rick

At least Mike Walker has an answer. It might be a couple of weeks before we receive it, but it is worth the wait.

Never would of thought I would generate this much discussion about brakes, but this is how the forum works.

Now if it would only warm up so I can put my Speedster back together.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug - Glow in the dark, IL on Saturday, April 07, 2012 - 02:48 am:

Michael, I understand and don't disagree. I am speaking of liability.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Saturday, April 07, 2012 - 10:55 pm:

If I were to set up a test, to see which system stops faster, Texas T brakes vs. standard T brakes, how would I do it? I have a stock 1925 Couple. I can disconnect the hydraulic brakes and adjust the standard brake to work as usual, run the test, then back off the standard brake and hook up the hydraulic brakes, and run it again. I have a nice new, level, asphalt street in front of my house, I can use.

So how would you set it up?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Sunday, April 08, 2012 - 02:05 am:

I would find a paved dead end road that wasn't used much.
Then I would put a line across the road and get back about a 1/4 mile and take a run toward the line with the throttle set against a small pair of vise grips used as a throttle stop. set the grips so the car would go about 37 MPH for a some distance before crossing the line. When I crossed the line I'd cut the throttle and hit the brakes at the same time.
Each test should be repeated three times to get an average stopping distance for each brake configuration.
When you push the throttle up and slam on the brakes you must stay where the car stops and measure how far the car went after crossing the line.
I would do each type of brakes three times with just the driver in the car and then I'd do it three more times with the same brakes but with 150 lbs. of weight in the front passenger's seat and 150 lbs. in the rear seat or in the trunk.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, April 08, 2012 - 08:20 am:

I have the full powerpoint the above slides were taken from, if anyone is interested. It's too big to post here.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, April 08, 2012 - 08:22 am:

Here's the whole physics of braking thing I posted last year:

7:47 AM 7/28/2011

http://phors.locost7.info/phors01.htm

The first law: a car in straight-line motion at a constant speed will keep such motion until acted on by an external force. The only reason a car in neutral will not coast forever is that friction, an external force, gradually slows the car down. Friction comes from the tyres on the ground and the air flowing over the car. The tendency of a car to keep moving the way it is moving is the inertia of the car, and this tendency is concentrated at the CG point.

The second law: When a force is applied to a car, the change in motion is proportional to the force divided by the mass of the car. This law is expressed by the famous equation F = ma, where F is a force, m is the mass of the car, and a is the acceleration, or change in motion, of the car. A larger force causes quicker changes in motion, and a heavier car reacts more slowly to forces. Newton's second law explains why quick cars are powerful and lightweight. The more F and the less m you have, the more a you can get.

The third law: Every force on a car by another object, such as the ground, is matched by an equal and opposite force on the object by the car. When you apply the brakes, you cause the tyres to push forward against the ground, and the ground pushes back. As long as the tyres stay on the car, the ground pushing on them slows the car down.

Let us continue analysing braking. Weight transfer during accelerating and cornering are mere variations on the theme. We won't consider subtleties such as suspension and tyre deflection yet. These effects are very important, but secondary. The figure shows a car and the forces on it during a "one g" braking manoeuvre. One g means that the total braking force equals the weight of the car, say, in pounds.



In this figure, the black and white "pie plate" in the centre is the CG. G is the force of gravity that pulls the car toward the centre of the Earth. This is the weight of the car; weight is just another word for the force of gravity. It is a fact of Nature, only fully explained by Albert Einstein, that gravitational forces act through the CG of an object, just like inertia. This fact can be explained at deeper levels, but such an explanation would take us too far off the subject of weight transfer.

Lf is the lift force exerted by the ground on the front tyre, and Lr is the lift force on the rear tyre. These lift forces are as real as the ones that keep an airplane in the air, and they keep the car from falling through the ground to the centre of the Earth.

We don't often notice the forces that the ground exerts on objects because they are so ordinary, but they are at the essence of car dynamics. The reason is that the magnitude of these forces determine the ability of a tyre to stick, and imbalances between the front and rear lift forces account for understeer and oversteer. The figure only shows forces on the car, not forces on the ground and the CG of the Earth. Newton's third law requires that these equal and opposite forces exist, but we are only concerned about how the ground and the Earth's gravity affect the car.

If the car were standing still or coasting, and its weight distribution were 50-50, then Lf would be the same as Lr. It is always the case that Lf plus Lr equals G, the weight of the car. Why? Because of Newton's first law. The car is not changing its motion in the vertical direction, at least as long as it doesn't get airborne, so the total sum of all forces in the vertical direction must be zero. G points down and counteracts the sum of Lf and Lr, which point up.

Braking causes Lf to be greater than Lr. Literally, the "rear end gets light," as one often hears racers say. Consider the front and rear braking forces, Bf and Br, in the diagram. They push backwards on the tyres, which push on the wheels, which push on the suspension parts, which push on the rest of the car, slowing it down. But these forces are acting at ground level, not at the level of the CG. The braking forces are indirectly slowing down the car by pushing at ground level, while the inertia of the car is 'trying' to keep it moving forward as a unit at the CG level.

The braking forces create a rotating tendency, or torque, about the CG. Imagine pulling a table cloth out from under some glasses and candelabra. These objects would have a tendency to tip or rotate over, and the tendency is greater for taller objects and is greater the harder you pull on the cloth. The rotational tendency of a car under braking is due to identical physics.

The braking torque acts in such a way as to put the car up on its nose. Since the car does not actually go up on its nose (we hope), some other forces must be counteracting that tendency, by Newton's first law. G cannot be doing it since it passes right through the centre of gravity. The only forces that can counteract that tendency are the lift forces, and the only way they can do so is for Lf to become greater than Lr. Literally, the ground pushes up harder on the front tyres during braking to try to keep the car from tipping forward.

By how much does Lf exceed Lr? The braking torque is proportional to the sum of the braking forces and to the height of the CG. Let's say that height is 20 inches. The counterbalancing torque resisting the braking torque is proportional to Lf and half the wheelbase (in a car with 50-50 weight distribution), minus Lr times half the wheelbase since Lr is helping the braking forces upend the car. Lf has a lot of work to do: it must resist the torques of both the braking forces and the lift on the rear tyres. Let's say the wheelbase is 100 inches. Since we are braking at one g, the braking forces equal G, say, 3200 pounds. All this is summarized in the following equations:

3200 lbs times 20 inches = Lf times 50 inches - Lr times 50 inches

Lf + Lr = 3200 lbs (this is always true)

With the help of a little algebra, we can find out that

Lf = 1600 + 3200 / 5 = 2240 lbs, Lr = 1600 - 3200 / 5 = 960 lbs

Thus, by braking at one g in our example car, we add 640 pounds of load to the front tyres and take 640 pounds off the rears! This is very pronounced weight transfer.

By doing a similar analysis for a more general car with CG height of h, wheelbase w, weight G, static weight distribution d expressed as a fraction of weight in the front, and braking with force B, we can show that

Lf = dG + Bh / w, Lr = (1 - d)G - Bh / w

These equations can be used to calculate weight transfer during acceleration by treating acceleration force as negative braking force. If you have acceleration figures in gees, say from a G-analyst or other device, just multiply them by the weight of the car to get acceleration forces (Newton's second law!). Weight transfer during cornering can be analysed in a similar way, where the track of the car replaces the wheelbase and d is always 50% (unless you account for the weight of the driver). Those of you with science or engineering backgrounds may enjoy deriving these equations for yourselves. The equations for a car doing a combination of braking and cornering, as in a trail braking manoeuvre, are much more complicated and require some mathematical tricks to derive.

Now you know why weight transfer happens. The next topic that comes to mind is the physics of tyre adhesion, which explains how weight transfer can lead to understeer and oversteer conditions.
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rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Friday, May 04, 2012 - 12:30 am:

Just went to their website again. The brakes are advertised for $1050 USD, and when you go to order them the price is $1200 CAN. Quite a difference since the US and CAN $ are pretty much equal value at this point.

Wonder if Mr Walker has his setup working as of yet.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Kable on Friday, May 04, 2012 - 02:29 am:

Like most people I have my own take on what I would like to have on my cars, as has been said it is a personal decision but I would like to know what situation people are anticipating that would require them to have to add disc brakes?

Having traveled across the USA and back through large cities such as San Francisco and LA as well as the Rockies and down the west coast as well as here in Sydney which has traffic as bad or worse than any city you are likely to go to. I'm yet to find that Rocky Mountain brakes or the transmission brake are not capable of stopping the car when its driven to traffic conditions. As I"m traveling at the same or slower speed normally around 40 mph or less anywhere I can usually stop the T easily, wet road dry road whatever.

Sure I could be caught out if suddenly someone rapidly stops in front of me, that happens to lots of people every day in modern cars but from my point of view its not worth the expense or the look of disc brakes itself to ever go that far.

Obviously this is a confidence thing, some of us don't have much confidence in driving a T as they are so used to modern cars, there have even been people who have decided to sell there car because they deem its unsafe to drive. Luckily a good proportion of owners know their car and its limitations and drive it quite successfully year in year out without any need for disc brakes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes, Men Falls, WI on Friday, May 04, 2012 - 10:39 am:

Peter

I have a speedster and my 17 year old likes to drive it. Have you ever ridden with a teenager in a speedster? My car will go over 60, but I don't drive it that fast.

I don't plan on putting any in my touring.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Friday, May 04, 2012 - 09:31 pm:

I finally got to drive my chassis. The brakes didn't work as well as I expected, so I called Allan to discuss the situation. He said that some of the earliest of his kits (mine was one of the first 4 kits) were sent out with a master cylinder that was not sized properly for two-wheel operation. He's having Wilwood send me a different master cylinder.

So you'll have to stay tuned a little longer. :-)

By the way, I think I see now why folks like T speedsters. They really scoot when they aren't hauling a body around!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve in Tennessee on Friday, May 04, 2012 - 11:25 pm:

Not to argue with anyone, but the braking in this video is pretty effective and its rear brakes only.

http://www.youtube.com/watch?v=Ny2uOFIZQlQ


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Kable on Friday, May 04, 2012 - 11:38 pm:

Dave, I would think giving a 17 year old a speedster with disc brakes would implant in his mind "I have 2012 brakes " One year in a normal T first would teach him a lot about not having brakes.

Steve what type of lining do you think the horses have on their shoes?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug - Braidwood (glow in the dark), IL on Saturday, May 05, 2012 - 06:22 am:

But Steve, that's the all wheel (or hoof) drive model. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Saturday, May 05, 2012 - 09:02 am:

I always wonder about those who claim that the effectivness of their stock rear drum brakes really helps in an emergency situation. I'm talking here about the stock setup NOT the setup with the stock rear brakes linked to the brake pedal.

If its truly an emergency situation based on reaction time (for example someone pulling out in front of you unexpectedly) I just don't think anyone has the ability to yank on that brake lever as quick or as naturally as he can get a foot on the brake.

If you agree, then isn't any type of brake that's linked to the wheel brakes (whether they're drums, discs, RM's, rear wheel, front wheel or all wheel) much better than the stock system alone ?

Or do you think that the transmission brake alone is adequate ?

I'm a bit of a newbie at this (only about 300 miles of T driving) and interested in your opinion.

Cheers
schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Saturday, May 05, 2012 - 09:27 am:

Bud, if the car has a Ruckstell or aux tranny that can possibly go into neutral, you GOTTA' have wheel brakes. Some people survive those neutral events without wheel brakes.

Without wheel brakes you have to be absolutely sure the rearend doesn't have babbit spacers, or any other weak link.

Whether wheel brakes are an advantage was well discussed on another recent thread.

Pick your poison...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel D. Chicoine, MD, Pierre, SD on Saturday, May 05, 2012 - 10:55 am:

Ken Meeks and I were comparing/discussing his disk brakes vs my Rocky's that I was adjusting alongside a waterfall the day before his accident. I know there were a lot of factors potentially involved in the accident, and I await a final analysis, but I wonder if they had anything to do with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Saturday, May 05, 2012 - 01:19 pm:

I dropped off the McNerny front brake backing plate patterns and also the first lever patterns. I was told to expect the castings (two sets for 25 and older and two sets for 26-7) mid week. Talk about good service!!
For those who don't know this a reproduction of a original era accessory. There are a few more patterns to make but I wanted to get some of these parts in metal as it will help to figure out the original parts that I don't have to copy.

I put a different design of cable operated mechanical front drum brake (that works with the stock T transmission brake) on my '27 roadster last year. I made a bolt on front wish bone "doubler". I spent a LOT of time on this set up and the results where truly rewarding from a drivability and safety point of view. The car now handles and stops like a new car in both forward and reverse. You can back up and steer with two fingers. You can do a panic stop with one side on wet grass and the other side on pavement with no hands on the wheel and stop smoothly and straight. It was however a significant amount of work and the T market place would never pay to have this done.

So I decided to reproduce a few sets of the McNerny and see. They will not give you the superior handling but they will at least stop the car when some dufus pulls in front of you and slams on his brakes in his modern car. Your car, your life, your money, you make your own decisions.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Keith Gumbinger, Kenosha, WI on Saturday, May 05, 2012 - 01:21 pm:

Noel - I agree with you whole - heartedly on this. Could his rear disc brakes locked up so quickly that it hastened the car to skid sideways and then roll over?

I guess we'll never know for sure, but it made me wonder.

Keith


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Saturday, May 05, 2012 - 06:22 pm:

The transmission brake is capable of locking up the rear wheels so I don't see how disc brakes can lock them any quicker causing an accident. I see the advantage of having wheel brakes, especially with a Ruckstell or Warford. I can even see the advantage in the case of a failed pinion. However, I can also see the advantage of power brakes, antilock brakes, power steering, and air bags, but I don't want any of that on my T. I may install RM's or similar one day, but they are period correct. I just can't get past the 'ugly' factor of disc brakes and frankly, I guess I'm just willing to accept the risk.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Saturday, May 05, 2012 - 07:36 pm:

The Ken Meeks accident has been throroughly investigated and disc brakes had nothing to do with it. Those of us on the Model T Tour in Florida this March heard the complete report. The report is rather exhaustive and thorough, and is supposed to be available at some time, but I do not have the particulars on the release.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas on Saturday, May 05, 2012 - 07:46 pm:

As a further note, as I made a post earlier in this thread, I would re-state that, braking is not just "locking up the brakes". A good braking system allows for a controlled slow down or stop. It is my opinion, after using both, that I have better, smoother, controlled braking with my disc brakes. Yes they can be considered "ugly", but I would rather have "ugly brakes" than be back in those "ugly situations" with modern drivers who pulled out in front of me or stopped quickly, all the while just not realizing that a Model T can't stop as fast as they can. Even the best defensive driving will not get you out of every situation.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel D. Chicoine, MD, Pierre, SD on Saturday, May 05, 2012 - 09:42 pm:

Thank you Michael. I have not heard or seen the report, but would like to. As a "participant" in the accident, and a bit more than an acquaintance of Ken's, I have been awaiting further information on the possible causes. Keith and I have discussed concerns that the brakes might have contributed with the high humidity, heat, and road surface to cause the accident. I'm glad to hear that is not the case.
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Danuser on Saturday, May 05, 2012 - 11:25 pm:

Guys Meeks sale is next Sat, preview Friday afternoon, thought you'd like to know, the reprod. parts have been sold as well as the wrecked car


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