Featured Technical No front brakes?

I had a early 70's T bucket for a while that had really really skinny tires and huge rears and frankly the front tires did not have enough traction in a hard stop to really matter and I honestly felt when they would lock up so easily I had less control as far as steering because one tire would lock up more like when slowing down to make a left turn onto a road . then flat spotting the tires were a thing to . Many of the old T buckets had little single position calipers about the size of a motor cycle caliper and did not do a whole lot in a hard panic stop but were plenty for basically a motor cycle tire.


Great brakes do not mean **** if the tires do not have enough traction . I saw a car last year that had some high dollar 6 piston stuff that were like 13" rotors and he had 4" wide front runners . A 8" disk and a single piston would have been as good .

so no brakes is unsafe but so is lots of braking and a tire to small to do what it needs to do because lock up can be worse .
On My 28 A PU I actually went a size wider on the tire so I can have more braking at the front I was always locking up one front coming off the highway fast on a side street. I then played with the valve so I had as much rear as I could get with out lock up . I had a lot of time in getting the best I could .

To be blunt the type of cars that guys would consider running no front brakes are the type of cars your at running 80 MPH in heavy freeway traffic . I cant even imagine drivng that 7o Fad type T on the free way this morning going to work on damp roads .
I was running 85 and getting p***ed in WI LOL

I have set of 12 spoke spindle mounts and they may see some street use but it will be back roads putting around or a Sunday cars and coffee type thing .

 

How much steering do you have with locked up skinny front runners ?
I'm all for front brakes but better have the tires to make them work .

The ideal solution would be a anti lock set up with skinny tires but that not going to happen on a HAMB car.

 

When I first built my Willys, I had '56 Olds drum brakes on the rear and in front, I had adapted junk yard slave cylinders to the old mechanical front brakes. Basically, dumb high school engineering yielding no front brakes, ok rear ones. It only took one event on rainy roads to convince me to get the front brakes working. I was coming to a stop light at modest speed when I applied the brakes. The rears locked up on the damp road with wide rear tires and the car instantly started going endo. It got perpendicular to the road when I was able to steer it straight just in time to save 2 or 3 surrounding cars. I'll NEVER ride in a rear-brakes-only car again. A disaster waiting to happen.

 

I was taught dry road one vehicle length for every 10 mph from bumper of vehicle in front of you unless racing

 

No. The law (federal and most states) allows cars built with only rear brakes to operate on public roads with only rear brakes, it doesn’t say anything about modifications. In the same way, cars built with only one taillight are allowed to operate with only one taillight. Doesn’t mean that it’s a good idea. Don’t give the bureaucrats any ideas.

 

To be able to go with the modern traffic it is a real good idea to be able to stop with the modern traffic.

 

You mentioned most the excuses drivers had for not running front brakes or backing the slack adjusters so they were ineffective. Another was the inability to steer if you locked up the front brakes. However, the truth is that the front brakes do a really large share of the work in sudden stops. I did a good bit of work with brake balancing on large trucks with air brakes. Even spent some time on the IH test track in Fort Wayne. I believe an IH engineer told me the front brakes contribute around 40% of the total stopping power. There is a whole lot of weight transfer to the front axle on a hard stop.

 

I hope you realize brakes on a race car is not for the purpose of slowing the car down. [A racer doesn't want to go slower]
The purpose of brakes on a race car is to transfer weight onto the front [where cornering forces, weight transfer, slip angle meet at a point of equilibrium]

@Olboy you haven't lived until you've jumped onto a purpose built racing machine that goes down a straight and turns in deep with no brakes


I had one of these 52 years ago

 

It took a second. Front brakes on the 2 front tires of an 18 wheeler are 40%.
For cars with reasonably close sized wheels and tires, the common figure is 60% or more.
https://engineerfix.com/what-percent-of-braking-is-done-by-the-front-brakes/

EDIT: @Kerrynzl and only one foot peg!

I don't think anyone here is saying it's the best, safest way to go. The examples are lightweight, vastly smaller front wheels and tires and edge cases, not anything common.

If safety is a major concern, nothing built pre-65 (You know, what this site is about) meets standards of even 30 years ago. Strap into your multi airbag and ABS equipped, tire pressure monitored, stability controlled, crumple zoned, blind spot monitoring and collapsible interior designed modern car.
Have fun with these folks.
https://www.consumerreports.org/car-safety/what-makes-a-safe-car-a6584555585/

 

18 wheelers have trailer brakes too.... bobtail of a cl*** 8 tractor is a totally different story with weight bias in braking because of the lack of weight on the rear axles...
I have an 18 percent grade in a section of my gravel driveway....I've had run-a-way events over the years where you just slide away with small tire contact area and rear brakes only
...plus I drive in the rain and rear brakes only on a wet surface....rear end may want to p*** the front end
silly me, I am an all axle have brakes guy....and I trailer my T with Nash Metropolitan rear wheel brakes only, down my driveway

 

Anti lock brakes is not going to happen on a HAMB car. But what could and should happen is adding an adjustable proportioning valve to the front brakes. You can dial down the front brake pressure as needed, to an appropriate level. Ideally, the rear tires should lock up slightly before the fronts.

 

I agree with that 100%.
Many drivers out there do not, unfortunately.

 

I started performance vehicle brake testing in the early '70s that included some tractor trailers, and learned that erratic steering control during hard braking is why some drivers/companies dis-connected/removed front tractor brakes, giving up the small percentage of braking they provided. The main issues were no power steering, and drum front brakes.

Trucks in this era were pretty basic by today's standards, but as driver comfort and strict mid-'70s FMVSS braking standards became law that required front wheels to have brakes, power steering and eventually front air discs became standard, drastically reduced any steering control issues during hard braking.

 

I have never built any vehicle driven on the streets that didn't have sufficient front tires, wheels, or suspension to operate without front brakes. I don't need the addition liability attached to such a thing.

Any locked tires reduces braking effect, front or rear. Any time the tires on either axle lock up, vehicle control becomes very limited. When the fronts lock up, you loose steering, but the rear brakes are still functioning, so you have all 4 tires stopping your car. When the backs lock up, the back wants to p*** the front, but if you have no front brakes, those locked up rear tires are all the braking power you have.

A proper anti lock system requires a lot of engineering based on each vehicle it is installed in. Moving an anti lock system from one vehicle into a different one may make things worse. An adjustable proportioning valve can be adjusted to accomplish a good balance between the front and rear brakes. Then its just a matter of the driver being capable of not lock up all 4 wheels in an emergency situation.

The only excuse for poor brakes these days is negligence. Negligence is liability. If you choose to run your ride without front brakes, be prepared to be responsible for any bad outcome that may happen because of your choice. The repair cost of anything you may hit, and the ticket for "Failure to reduce speed to avoid an accident." and probably more tickets, won't care what excuse you have.

 

I've built [from scratch] many brake systems ,and use measurements like wheelbase and CGH etc to anticipate weight transfer calculations.
It is a complex process and something I don't recommend to those that are mathematically challenged.

For those that cant do the math, one thing I recommend is to test the system in a controlled environment [but almost nobody does this]
You need some method to adjust the front / rear brake bias [fluid mechanics] This can be either a balance bar pedal box , different wheel cylinders or different bore calipers .AND not an adjustable proportioning valve [YET!]

You need a straight piece of road with damp /wet surface and you go out and slam the brakes on observing which end locks up first [without the proportioning valve]
You make adjustments to the bias via balance bar or wheels cylinders until it is close enough to even.

The wet conditions will require more rear brake bias due to less weight transfer.
Once this is sorted you then do the test again in dry conditions with the bias untouched.

In the dry there is more weight transfer so you should get more rear lock up.
This is when the adjustable proportioning valve is used [to limit maximum rear line pressure for the dry]
All road cars are set with a slightly rearward bias for wet conditions and a proportioning valve for those "Oh ****" moments.
Also one last thing about this whole thread that people are starting to understand. Brakes don't stop the car ....The tires do.
You start at the tire footprint and work backwards up the system to the driver's foot.


And the absolute best ABS system is driver skill. This takes years to develop [trail braking into corners etc]
But to develop this skill you need to "push your luck" to the threshold of traction which is not recommended in daily traffic. [foot, hand, seat coordination needs to be sharp]
I've had p***engers think my old '84 Mazda pickup had ABS because of this reactive skill.

This ^^^ is a road racing thing

 

If you cant steer then you have no control.
With something like a t bucket like I had that ran skinny front runners ot was way to easy to lock up a front wheel .
You can screw around with the brake bias all you want but guys running little skinny front tires only have so much traction , add in a solid axle and hair pins were body roll will take pressure of a wheel and it gets dicey turning off a highway going very fast .

Im not condoning running no front brakes im pointing out that if you have some light car with a 4" wide tire brakes or no brakes there not going to do a lot at higher speed or on a wet road .

In the T bucket at times I felt the brakes were a detriment in a turn or trying to maneuver and brake hard . The thing on a wet road trying turn off the highway fast would push in a straight line if the brakes locked up.
That was a vehicle with a 4" frint and a 12" wide rear tire . Honestly it wasent what most would call safe in traffic brakes or not.
You cpuld screw with the rear brake valve all you want but that dosent change the front brakes . At one point I considered putting the valve on the front brakes so I could dial frint brakes away so I cpuld not lock them up.

I get a chuckle out of guys with a light roadster with a narrow front tire running 11" rotors made to stop a 3800 pound car .


Never had a issue woth back brakes looking up trying to p*** the front wheel .
Usually pulls the vehicle straight. Learned driving carts and dune buggy and atvs ice racing.

Im currently dealing with a situation were I have to much brake on my Model A PU .
It's got non Hamb front and rear independent suspension and I do not have enough rear brake as far a piston area so even with the proportion valve wide open im not applying enough brake and the 12in rotors with Willwood multipiston front calipers are way to touchy and ill lock up the fronts before I can get enough line pressure to the rear . I need more caliper in the rear .

Ideally you want the rear to come on and lock just slightly before the front . I cant get that on my truck currently . Not enough surface area on the rear calipers vs the front. This is a suspension that will out handel my Vette .

 

Are you sure this is correct...???

 

I suppose it could be in the mind of a guy that is used to only having rear brakes.
All this is coming from a guy that has a model A pickup with "suspension that will out handle his Vette." but can't figure out how to keep high performance front brakes from locking up the front tires. The expectation is that high performance brakes are coupled with high performance tires. If your not going to use high performance tires, why spend the extra money for high performance brakes? Who wants to bet against my thought that the model A pickup probably has skinny little front tires on it that were bought to "look cool," rather then larger, wider, performance tires designed to match the performance of the front brakes?

I don't ever want the rear wheels to lock up before the front, but then again, I don't really want the front tires to lock up either. I know that still rolling tires under heavy braking function much better then locked up tires do.

 

Yes without a "proportioning valve" There should be slightly more rear bias [needed for slippery conditions]

But his wording is incorrect . All brakes react at exactly the same time. It is weight transfer and rear brake bias that causes rear lockup. [before the front]
When I refer to rear brake bias it is not More brakes than the Front , it is more than normal bias.
So if in the dry a car requires 60% front and 40% rear we would dial it in for the wet at eg: 55% front 45% rear

This ^^^ is because brake torque and weight transfer is a lot less in poor traction situations.
But when you really stand on the brakes in the dry the line pressures will increase, so the ideal situation is all the extra pressure goes to the front only.
The 45% rear bias in the rear could have the same line pressure as 40% rear brake bias in the dry [because the proportioning valve blocks the extra pressure p***ing]

When we race cars in the rain we always adjust the brake bias more rearward

All wheel brakes are better than only rear wheel brakes
The issue is the front rear brake bias

Racing Motorcycles are lightweight and have skinny tire yet they can really haul up.
Early sports cars and Formula Fords are similar.
The problem is heavy cars with skinny tires asking too much of the traction available.
So the fix is more rear brake bias. [definitely not "no front brakes"]

I know a young guy who put huge rotors and 6 pot Brembos on his BMW E30 .
This thing could just about stand the car on the headlights.

The very first day he drove it in the wet, he "rear ended" a car in front [we call this a Liberace ]
Just a slight press on the pedal was enough to lock the front in the wet without having rear brakes having enough brake torque.
The lesson was "Tires stop the car" brakes only "remove kinetic energy"

If you get "out of your depth" with brake bias , simply install a pedal box/ balance bar with twin MC's [And TEST it]

 

Good question. As a former stock car racer, I prefer it that way. But production cars were usually designed the other way, so that the fronts locked up before the rears, prior to the invention of anti lock brakes. This lowered the liability of the manufacturer, and is safer for the “average” driver.

But my point is, you want the front and rear tires on a hot rod to lock up at “close” to the same time, as you are steadily increasing the brake pedal pressure. Of course, this will vary depending on the surface you are on. Wet pavement vs dry pavement vs a dirt road, etc.

Having no front brakes is a terrible idea, in my book. It’s ok for a “show” car, but not so good for driving to the show.

 

Front vs Rear brake 'power' is difficult to properly design, especially if one (me) isn't an engineer. But, I tried. Way back when disk brakes were a rarity I had a 58 Ford PU with a 354 and push ****on Chrysler trans. Pulled them out of a car at Dad's salvage and did the transplant. Really successful in getting a great running truck. But like all pickups of the time it would swap ends under hard braking especially in the wet/damp when empty.

After one spooky panic stop in traffic I 'engineered' a fix, And it worked, pure luck.

I adapted 56 New Yorker 12" front brakes to the Ford axle. Turned the inner bearing seat on the spindle down to fit the Mopar inner bearing. I think .062. Outer fit as did the bearing to bearing length. Made some spacers to get the backing plates on the spindle and now I had more front brakes and no less rear.

After trying it out, I became a believer in front brakes! Not the same as what's being discussed but the principles appl

 

Yes, but you talk about your racing background and how you upgrade brakes before you upgrade horsepower. So, I gave examples of racecars that don't use brakes around.

 

The truck has independent front and rear suspension , coil overs and handling wise its pretty well sorted out . It will out handel my Vette and has 51%f - 49%r weight ratio at about 2800 pounds.

My front tires are not particularly narrow and not particularly wide .
Lot of HAMB and or street rods run them.

There a 195 60 15. I can maybe go to a 205 and keep it in the fender well. There not some 4" wide front runners .
I can not go inward with the rim as the custom built 7" rims are back spaced to just clear the control arm. The tire is fine for daily driving

If you knew anything about setting a adjustable proportioning valve you would know you set it to were the rear brakes will just lock up before the fronts then you back it off untill the fronts lock up slightly before and then further pedal pressure would then lock the rears. Thats how I set up my old auto crossing car ( sbc powered 240 z ) and every performance street car I have built .
On the Z when competing id set the valve to give the rear lock up a fraction before the front so I had steering at just under max .
On the street back to front lock up first

As I stated before you started talking and speculating , was CURRENTLY I do not have enough piston surface area in the rear calipers to make a adjustable porportioning valve usable because even wide open I can't get lock up on the rears before the fronts to be able to adjust it back . Even if I had a much wider tire on the front im not going to get maximum rear braking ever how it CURRENTLY is. And as I stated the problem is the multi 6 piston Willwoods are much more surface area ( pad area as well) then the SMALL single pistion rear calipers has .
I know what the issue is . I need more pistion area on the rear so I can get close to the same pas pressures front and rear.
Im running a 12.5" rear rotor and currently a calipers that clears the 5.5" back space 15" rim is not easy with the current mounts and parking brake in the calipers.
The fix is either a smaller rotor were i can fit a larger piston caliper OR a second small caliper like a drift car but only in line with the current caliper ( no hand operated drift brake)

My point was that in my current situation my large calper front brakes are way to much for my current tire when I cant get to max or even decent rear brakes with out front brake lock up. Another words how it is currently it has little rear braking when the very easy fronts lock up .
I mentioned it because its a lot like when I had the T bucket with very narrow front fronts that that would lock up to easy and you had no steering .
On a T like that with 14" wide rears and 4" fronts the rears did more stopping and frankly if you were trying to turn off a highway at a decent speed yoi had a good chance of locking up a front and not being able to turn and not really gaining much as a 4" tire is not going to do much in that situation .

Stock p***enger cars send brake pressure to the slightly to the rear first especially with drums with a residual valve generaly ( 10 lb for drums this helps prevent nose dive and a front pulling to one side under light braking then as more pressure is applied the fronts become on more .

The plan is this summer after fixing the rear brakes is a low profile tires on a 17" and 18" rim off the Mustang and to go auto cross it .
Its currently a 275 60 15 rear 195 60 15.

Any way my point was on something like a 70's style T bucket with great big and really littles that the front brakes do very little and in some cases are a detriment when there doing very little stopping but locked up loosing steering .

Looks can be deceiving. It will out handel most gen 1 and 2 Camaros and will out handel my Vette . Front tires on it being a limiting factor .
Not Hamb . But you cant tell in this pic.

 

I had twin master cylinders and a adjustable balance bar in a stock car.
It worked well when track conditions changed .

In the Tbucket I had , yes front brakes were better in a straight line when I had it dialed in so all 4 wheels were balanced at the lock up point but braking into a sharp turn I frequently had brake lock up and the front pushing. I played with it a lot but the fact is little tires only do so much .

This is were I chuckle when I see giant rotors and big calipers on a muscle car or drag car and they have narrow front runner unless there doing a 100 panic stops in a row its likely hurting performance.

I see a lot of T bucket type cars built now with a 11.5 rotor and a GM caliper and pretty small tire width and while they stop fine there over kill and add a lot of unsprung weight and rotating m*** for a very light car .
A current 27 T project I have came with the same set up . Its got the same brakes as a 4000 pound station wagon would have in the 70's . Hopefully it can get a lighter set up on it when done.

On my A pu Unless I change my entire parking brake set
There is no current dual piston or larger piston single caliper that will clear my current rims . It runs a Nissan caliper to get 15" the rims on. The C4 vette caliper is had planned on hits.

Non HAMB stuff that should go into the non hamb area to keep discussing it.

 

My friend bought a street rod with 12 spoke spindle mount wheels on the front. It had a dual master cyl and two front GM brake calipers per side on the rear. It stopped ok, just different seeing 4 calipers on the rear.