Front/rear brake bias

[Synchro909]

We all know that Henry designed the Model A braking system with a strong bias towards the rear. On one of my cars, I have moved the bias towards the front a little by installing cast drums and the floating wedge adaption that has been around for quite a while. The rear brakes are standard. Bonded linings all round.
At a recent workshop held by our club, mine performed fairly well in a crash stop from 20mph. (0.75g and stop in 18 feet). During that test, the rear wheels still locked up so I'm certain that I could improve things further by adding still more braking to the front. I regard safety as more important than originality, after all, what's the point of having a nicely restored original car you hate driving in modern traffic. Here is my idea. I don't expect I am the first to come up with this but I would like to know whether anybody else has tried it or knows somebody who has.
Part of the reason the rear brakes work better than the front is the longer actuating arms. I am thinking of putting a pair of the rear levers on the front. Simple solution if it works and hardly noticeable.
If I replaced the bonded linings with woven ones, I realise I would get an all round improvement but the bias wouldn't be changed. Woven linings on the front only might help.
Your collective input appreciated.

[Bill G]

What about backing off the rear adjusting wedge one or two clicks and making sure the fronts hold and grab with the setting on the adjusting board as the rear would normally be? I think there would inherently be an extra half inch of pedal travel, but in my thinking it would bias the fronts without changing the leverages of the arms. Something I have wondered about....

[kimlinh]

I also was thinking of making longer arms for the front however I was concerned because the greater leverage will put more stress on the front brake parts and the front does not look as strong as the back. The lever, shaft, rod arrangement that actuates the front shoes is nor very robust. I'd like to know if anybody has tried this and how it worked?

[wmws]

I agree with Magicbox51. That is what I have done and now the fronts and backs lock up at the same time. Easy to do.

[larrys40]

I have done over the years and do a good number of Model A brake jobs and have a reputation for doing them with great results. I understand the conversation but here is my thoughts based on Edsel and Henry's design.

You really don't want the front brakes to lock up totally as it encumbers your effort to steer the car. Rear brakes, yes with more emphasis to them. The rear arms are longer for the advantage of the effort in movement of the rods and mechanical advantage to the rears. The original system design works well when properly restored and adjusted. In my opinion that's the key. Not brake floaters, not longer arms on the front, but a properly restored system and 4-wheel brake adjustment.
Other than that the best thing you can do is to use the cast iron drums. Randy Gross's, snyders, or Brattons, whatever your personal choice. I've used them all with excellent results from all. I do favor the softer molded linings as I've had issue the last few years with some of the wovens. One of the lining manufactures tells me it's the resin used in the wovens that causes some noise now and then.

If you did decide to change and put longer arms on the front it isn't without possible issue. You may need longer brake rods, it also puts the rod in the direct proximity of the shock which might not be favorable, and you would have to shorten the return/anti-rattler which isn't a big deal.

If you do a proper individual wheel and then 4 wheel brake rod adjust even with the fronts locking when doing the adjust ( 4 wheels off ground) the fronts can be locked on the adjust but when braking on the road they will be tight but not lock like the rears. If all 4 wheels locked up and your steering is encumbered by that who knows what direction you may go.

Having said all that all the cars I've done stop well. So fully restored properly and adjusted I believe is the key. Many of the modifications over the years are what fails. I do respect the fact that there are some improvements on certain components and some excellent ideas out there, but I prefer the original system in itself done and lubricated as should be can be very optimal.

Larry Shepard

[Frank Miller]

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Why would longer arms give bias to the rear? With everything being equal, a longer arm on the rear means less application of the brakes. So once the fronts make contact which should happen first with the shorter arms the rears are now being applied at a lesser rate with less force being required. Like I said all things being equal with no play or variations.

[MickeyT]

Sorry wrong thread.

[Dick Carne]

"If I replaced the bonded linings with woven ones, I realise I would get an all round improvement but the bias wouldn't be changed. Woven linings on the front only might help."

I might encourage using bonded linings with cast iron drums, rather than switching to woven linings with cast drums. I had always been of the opinion that woven linings would provide more "grab" regardless of their application, but from personal experience, I will assure you that is certainly not the case, and in fact, quite the contrary (when using steel drums, there is no doubt but that the woven linings are a better alternative). Having used Flathead Ted's floaters, I will also offer that I have not been able to determine any real benefit from having made this transition over a properly restored original brake system. Properly maintained, the original brake system as designed should provide more than ample stopping capability - just my opinion, for what its worth.

[daren007]

Keep in mind the weight on the rear wheels is much less then the front thus making it easier to lock the rears. Also under braking the weight shifts to the front adding to the problem.

[CWPASADENA]

Henry designed the Model A with a 40/60 front to rear brake bias.

By the end of the 1930's, Fords were designed with a 60/40 bias. Most front engine cars will have somewhere between 60/40 and 70/30 bias.

Adding more bias to the front will definitely improve the braking of a Model A.

What I did when I restored my Tudor was to use cast iron drums and woven linings.

I have floating wedges on the front and I LINGTHENED THE FRONT LEVERS BY 50%.

This results in a bias of 50/50 or may be even a little more to the front because of the use of the floating front wedges.

I use the car for touring and often drive it on the freeways at 55 MPH or more.

The brakes are phenomenal, the best of any Model A I have ever driven.

After heavy brake usage the front drums are a little hotter than the rears, this means the fronts are doing more braking than the rears which is what you want.

Brake application is easy with good modulation with a firm pedal when fully applied.

I have had to make 2 panic stops from "speed" and all 4 wheels will lock up.

I have over 12,000 miles on the car. I just adjusted the brakes for the first time sense
I restored the car. I had to take 1 click on the rears and 2 on the fronts.

Woven linings work just fine with cast iron drums. Ford used woven linings on late '31 cast iron drums and an 32-34 fords which all had cast iron drums.

Currently available bonded linings are hard with a lower coefficient of friction than woven linings.

The brake rods are long enough and the anti rattle springs are easily adjusted so the rods are straight.

I offset the modified levers slightly to clear the shocks. Note, the 30-31 levers were offset to clear the shocks.

A properly restored and adjusted Model A brake system will work very well.

A properly restored and adjusted Model A brake system with longer front levers and floating wedges will work so much better.

This is my experience.

Chris W.

[updraught]

I thought this was a good explanation of why it is not good for the back to lose it:

"In an oversteer, turning more and braking harder will shift the weight even more to the front and the back will spin even faster. It is possible to have the car turn completely round the other way or even flip over. Whereas in understeer, braking harder and turning more will not fix the loss of control, but the car will simply continue straight until it stops. It will not spin and shouldn't flip."

https://www.quora.com/Why-is-underst...into-road-cars

[Curtis in MA]

If you lengthen your actuating lever you have less travel from fully released to fully actuated. Is this still enough?

[Railcarmover]

Self centering brake shoes is a definite improvement over fixed centering.The shoes ability to follow the drum on application greatly increases braking effect. Brake 'floaters' are common today,all drum type braking systems self center.

I second the coefficient of friction improvement with woven over bonded,couple that with the reduced application force of mechanical vs hydraulics,higher brake lining friction coefficient is critical to maximize braking effort.

[Railcarmover]

The reason roller tracks on mechanically centered systems wear out is they take the pull of the shoe when it contacts the spinning drum. With a floating shoe the 'pull' is used to increase braking effect,the drum 'grabs' the shoe,and the rotational force,instead of working against the roller track,aids the brake application.

[Dick Steinkamp]

If you compare a properly rebuilt and lubricated, adjusted to stock spec stock Model A brake set up to a worn out one, certainly the rebuilt one will stop the car better than the worn out one.

If you take that rebuilt system and adjust the brakes so that the brake bias is to the front (like most every other car that followed the Model A) the car will stop better than the one adjusted to stock spec.

If you take the rebuilt system with the front brake bias and add Ted's floater kit (front and rear), that essentially turns the brakes into self energizing as was done in the 1950s braking systems, the car will stop even better.

[Kevin in NJ]

I am still waiting for someone to prove that the mechanical brakes as provided by Ford were actually 60/40 breaking as most assume.

I have yet to find actual data to show the rate of application of the brakes as set up by Factory specs yields any bias. All I have seen is peoples assumptions that is the case.

In reality I have not seen the prints showing the application rate at the shoes. This is relationship between the angular movement at the lever translating to wedge movement on the shoes.

That is how much angular movement on each lever creates how much physical spreading of the brake shoes. The data exists in a pile of factory drawings. I know this because I someone was nice enough to look up a detail about the brake drums for me. He was surprised to find drawing after drawing showing the brake operation with .001" accuracy in operation.

Please understand I am only pointing out everyone is guessing as to the operation of the brakes and what comes on first. Most assume that the rears come on first, but no one knows for sure base on factual data. My research and talking to people who know a lot more than me is inconclusive. I have found comments going both ways in technical documents.

One idea that was forwarded to me by a very very knowledgeable A person was that the rears are brought on faster because they have a lower rate of application so you need to start then sooner for proper braking equalization. Documentation from Barrett brake manuals indicates otherwise. The A person has factory prints, but did not reference them to me on this subject.

So I would like to see some factual data.

Who is going to Benson Research and can page through the prints to see if they can find the answer real quick??

Please keep in mind I am not saying anyone is wrong at this point. I just know I can not tell you what is correct with respect to braking application rate for the front and rear.

[Curtis in MA]

If you get that technical it could be 38/62 or 42/58 when built. As soon as there is some wear, oil or water on the pads, etc it would change slightly.
In the Service Bulletins it tells dealers how to adjust the brakes, back engage first.

[100IH]

What might be the cats meow is a mechanical proportioning valve. Picture the brake cross shaft at the center of the car and think about the vertical ends. If the end was able to slide up or down, it would alter the leverage bias similar to changing the lever length at the axle ends of the brake rods. Can't get away from timing of application being changed along with applied forces changing.

[Railcarmover]

Given the narrow footprint of the tires for safety you want bias to the rear,regardless of braking efficiency a skidding tire does not react to steering input. Run 16's? Bias to the front,stock bias to the rear....in the end bias is a.matter of broke adjustment

[BILL WILLIAMSON]

I just TOTALLY SYNCHRONIZE all my adjustments & rods, and it works just FINE for me.
Bill Screechtoahalt