The Jalopy Journal
Discussion in 'The Antiquated' started by LWEL9226, Mar 11, 2020.
What problems will there be with disc brakes on the rear and drum brakes on the front???
Instantaneous direction change on hard braking, without warning, and quickly enough that you will not have time to react.
Nothing at all.
The problem is, the odds reset, every time you regain forward momentum.
Can you afford that gamble?
Ever pull the console mounted e-brake handle on a rent-a-stang at 60? Sure you have, we all have.
Did you ever see a factory produced auto with that setup? I think that I'd follow those engineers lead if at all possible. Is there a compelling reason to consider using rear only discs ?
Go for it!! I think you’re far enough away from me and all my relatives have moved out of Oregon
Disc in the front drums in the back is the factory style. This is because they like having a greater bias in the front than the rear. Generally there is a greater stopping capability with discs. Then again the fronts are usually larger than the rears so it factors out well. If you choose to do as you suggest, i would install an adjustable proportioning valve, just to get the bias right, and adjust it so the fronts come on first, or before the rears. You will most likely need a different master cyl set for your application as well.
If you can get the braking force divided properly between front/rear it could work just fine. If you get too much braking force at the rear, as you are likely to get, the rear wheels will become the front wheels any time you brake hard while turning, i.e. the rear wheels lock up long before the front wheels and from there you're probably just along for the ride until the car has stopped somewhere.
Don’t do it, There’s a reason from the factory the discs are on the front. They want most of the braking power in the front and not the rear
In other words... the OP found a deal on a disc brake rear for his build...
What’s the rear out of?
was there an option in the vehicle for rear drums ?
Drums can be easily adapted to an axle.
or convert your fronts to disc as well.
a drum front/ disc rear sounds silly and dangerous
The hardest part will be driving backwards everywhere.
You building a funny car....?
I had a straight front axle drag car back in the day that only had 12x3 drum brakes on the rear. No front brakes at all. Stopped just fine at 100 mph
The topic of disc brakes is not HAMB friendly, but if you have the choice, get discs for all around, with larger ones on the front. The stopping power is at least 70-75% for the front. Look at some of the custom builds, the bigger discs and pads are in the front. The rears can be large, too, but the stopping power comes from the front.
My brother had a 1000cc Kawasaki road bike and his front brakes made the rear ones look tiny. He said the stopping power for bikes is about the same, maybe more, since the rider is also leaning forward, too. It is standard in the industry. (cars and bikes...)
When disc brake applications came out for custom motorcycles and hot rods, there were standards sizes and people tried all combinations. (Airhearts) Then the designers and engineers took over and the math told them the stopping power is in the front and larger discs were necessary.
Don't get fooled again... Stay with discs for pure stopping power, but traditionally, drums in the front and rear are HAMB appropriate. (or at least don't show your disc brakes in photos.)
Lots of really wild misinformation in this thread. Assuming the rear disks under consideration are on a rear end that is from a vehicle that's similar in size/weight to the vehicle that's being built, and the front drums are also appropriate size, then the main effect is probably that the rear brakes are less likely to "go away" under conditions that might cause fade on the front brakes.
Rear disc brakes are not the same as front disc brakes, guys. They have smaller pistons, etc. The braking proportion thing still applies with 4 wheel disk brakes.
But it's all speculation, because we don't have enough information.
I think it'll work just fine but you may have to turn your master cylinder
180 degrees and rig up some sort of linkage;
let me know how it turns out...
Thank everyone that answered my question... Most of the answers are about what I expected, I just wanted confirmation....
A friend wants me to help him put a newer rear end from an F-350 under his 1950 F-5....
I will recommend him to return the disc brake rear and trade it for one with drums....
Thanx.... Lynn W
Oh...it's a big truck. That makes a difference.
It is always the rest of the story ......
What is he planning on doing with the big F-5??? Towing a trailer much? PACCAR (Peterbuilt / Kenworth) built many a tractor with rear brakes only, and nothing on the front axle. The concern with big trucks, especially ones that pull a trailer most of the time is if too much brake bias is to the front, it unloads the rear suspension under braking, locks/skids the rear tires and quickly leads to a jack-knife condition.
And many truck drivers had the front brakes removed from their rigs. The concern wasn't as much with the rears sliding as it was with not being able to steer if you locked the front brakes. Bottom line is that they were all wrong. A heavy truck will stop the best with brakes on all the wheel ends as long as they are proportioned correctly. It's more of a moot point since the advent of anti-lock braking.
Agreed. Getting the bias is critical. My point was with the OP asking about putting a disc rear on an old F-5 sized truck, especially if it pulls a trailer or is loaded most of the time, it probably won't be a problem, but attention needs to be paid to the brake bias and front suspension geometry to minimize nose dive.
Jim, that is old school I don’t think that’s been done in more than 30 plus years and not legal any how
Yup. Totally illegal now.
Plus, an ever increasing number of semi trucks have discs, in all positions.
Haven't seen one with drums at our loading dock, in about a year.
I think the problem with disc on rear is they always self adjust and drums only self if they working properly
I see ADJUSTABLE proportioning valves and check valves in your future!
Just buy the front axle from whatever donated the rear axle. Get the rest of the brake system, too.
The truck will probably not ever be used very hard.... Big trailer not very likely....
It was originally a flat-head 6 cyl….. Plan is to put in a small block Ford (302)….
Already looking for a drum brake rear end….
Thanx to everyone....
One ton drum brakes are a pain in the A$$ to work on. I’d keep the disc brake rear end and up grade the fronts.. A couple years ago we did a front disc brake swap on my uncles 3/4 ton Chevy and it stops with confidence now.. It was vacuum boosted power drums before.. It was basically a spindle swap from an 80 C20 chassis on to his 69 C20.
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