Hey, can anyone give me an example of their car with comment about the driveability of the car, brake feel and how hard it needs to be pushed to lock tires up. Must be without power assist system! Manual only! Caliper diameter and piston count. Master cyl. diameter Pedal ratio.
and rotor diameter and tire diameter and tire tread compound and vehicle weight and.................??? Ray
On my 27 I am running 40 Ford brakes up front with Buick drums. On the rear I have a 9 inch 68 Mercury Montego rear axle with stock Mercury brakes (whatever diameter those are). My master cylinder is a 66 Chevy pickup dual chamber with one half running my clutch. I am not using any proportioning valve or residual valves and braking is fine. I don't think I have ever had to lock up the brakes, but it will stop as quickly as my daily driver that has abs and discs all around. Tires are 5.60 x 15 front and L78 x 15 rear (bias plies), car weighs probably in the 2,000 pound range. Only downside I have ever found is that when the front brakes get wet, like in a hard rain or if I just washed the car, the first few stops are a little dicey. Once the water is dried out from stepping on the pedal a few times the braking returns to normal. I did notice when I ran at the Billetproof drags that I had to use the second turn off lane to bring it down from speed, but that was driving over 90 mph, which is faster than I ever push it. Don
about 75% of this question depends on what you want for a car. are you building a traditional rod with bias plys?? if so it doesn't really matter what you run. I've got a 28 roadster with 42-48 ford brakes all the way around and a 39 ford master cylinder. brakes are great and I can lock up the bias plys pretty easily. don't need much more than that. if you are wanting to run radials and disk brakes.... I can't help you as that is post 1964
The brake system required to stop a T bucket is a lot different then the brake system required to stop a 59 Cady. Without more information about you ride, we can only guess. On top of that, locking up the tires is not the fastest way to stop a car.
It is a Model A PU with V8. Locking up is the max. that brakes need to achieve, more from that is pointless.
Its more about pedal feel and the degree of modulation you can achieve just prior to lock up. Two different cars with the same tyres and wieghts and suspension design will lock the brakes, but one may come to a stop much quicker by being able to modulate the pressure on the pedal to keep it just below locking up, and therefore maximising the decelerative grip of the tyres.. this stuff is a world of variables, and any opinion on a car by the owner of that car car, on here, isnt really worth anything to you. Despite that gloomy outlook.. I run 39 hydraulic Ford 12" lockheed brakes all round, 6.5 to 1 pedal ratio, 1" bore dual chamber master, in a 1000kg 32 Roadster. it stops pretty good. but I highly doubt it would outperform anything modern in terms of minimum stopping distances from a certain speed.. the 5.50 x 16 bias plys on the front would see to that!! My experience with brakes , after building quite a lot of hotrod chassis, is the further you deviate from a factory combination of parts and master to slave bore ratios ,pedal ratios etc.. the worst a car stops. Pick an OEM system that should adequately stop your car, and stick as closely to that in terms of specs and parts as is practical.
I think it's a very useful question. It would be very interesting to get a whole lot of qualified data on the table and see if we can draw any general conclusions from it. The idea isn't to get definite answers but a spread of diverse examples to get an idea from. It would be very informative.
I'll fill in some of the ???'s Add to that...... Coefficient of friction, Pedal pressure , Clamping pressure, Wheelbase, Centre of Gravity height, Rear Caliper piston area, Rear disc diameter Play with Road Racing cars and you'll discover the Calculations are "endless" The math is simple but there is a shitload to calculate. Most fabricators simply fit an adjustable "Twin Master Cylinder" pedal box then use "applied research and development" [ try it an see ] The human input responds better to pressure than distance, so it is easier for the driver to modulate a firm pedal than a soft spongy pedal [ poor mans ABS brakes ] When I mean soft spongy, I am referring to "too much mechanical / hydraulic leverage" and softish friction materials
Finally someone understands my goals. There are books, forums, sites about the science and math, but it is impossible to aquire some real life numbers and little 'hands on' experience notes? I am not trying to take someone's setup, put it straight into my machine and then get killed with it. I would like to see other examples for doing the brake math. Because there are many variables, it would be good to have some real life reference points. Let me get to it another way, Chevy Vega has caliper diameter of 48mm and MC 3/4" = 19mm, Ford Pinto has caliper diameter of 66mm and MC 15/16" = 23,8mm, can anyone name their pedal ratio?
I think Don's Hot Rods has provided the type of info asked for with a fairly detailed example of his brake component combination. As Ned Ludd has said a good cross section of folks posting what they run with and how they see the combination working is about as good as us mere mortals would hope for and leave the maths to others...
I run Speedway's kit with 11 inch rotors, single piston midsize early 80's gm calipers on the front. Stock 10x2 53 ford drums on the rear. Wilwood dual manual master under the floor with adjustable proportioning valve. Works good.
80s midsize = G-body, front callipers are 63,5mm. 53 ford rear wheel cylinder should be 7/8"=22,23mm sedan and 15/16"=23,8mm wagon. Wilwood has many different MCs, which one do you have? http://www.wilwood.com/m/MasterCylinders/MasterCylinderLanding.aspx?app=Master Cylinder What is your pedal ratio to master cylinder, Steves29 ?
I've got 11 inch gm disc in front s-10 drum in back 1" master power brake romote fill master cyl with the stock studebaker pedal on my stude and it will put it on its nose with just moderate pedal pressure. very happy with my brakes and I was worried they would suck. I had just got done doing the same car for my uncle with the corvette small power booster and the brakes sucked on that car.
My 32 is setup like this: 32 ford chassis, 4" dropped front axle, 42 ford front spindles, 48 ford cross steering, 46 ford split wishbones, panhard bar. Rear is triangulated four bar, coilovers. No sway bars. Vehicle weight is 2310lbs with full fuel. I think weight distribution is nearly 50/50 but might be more biased to the front - I need to borrow some scales. 6.5:1 ratio hanging pedal from a Jeep CJ, modified for a round ford pedal pad, 1" Corvette style master cylinder, no booster, no residual valves 11" GM rotors, 69-77 style large GM calipers, stock pads Stock non-adjustable GM proportioning valve Stock S10 rear brakes Pedal travel is fairly short, effort is light to moderate. Effort is comparable to my Mazda CX7 or perhaps a bit heavier. The front discs will lock up before the rears and hard braking is very stable and straight.
69-77 large GM = fullsize, like Caprice maybe? then it has 75mm callipers. S10 rear wheel cyl 3/4", = 19,05mm If I find a ratio between caliper diam. / MC diam. then you, Mustangsix, have the strongest braking combo out of these front disc cars mentioned this far in this thread.
Hey mate! You’ve got it wrong here. The power of the brakes [ as in clamping pressure ] starts with the driver’s foot. It is easy to increase the clamping pressure! All you do is increase the pedal ratio and use the smallest diameter master cylinder and largest diameter pistons in the callipers. The problem with doing that is excessive pedal travel and poor feel in the brakes. Now go back to your original questions. What you really should be asking is the ratio of piston diameters [ clamping pressures ] between the front and rear brakes ,this is far more important . My background is road racing , where we use the maximum braking at the absolute last possible moment without one end locking up [ if you don't drive like this another driver will ,and pass you under braking ] Under extreme braking there is a lot of weight transfer onto the front so the rears have a tendency to lock up more [ In less braking situations this not an issue as traction required is also less ] When traction conditions are reduced [ wet weather ] the car will not get enough weight transfer before the tyres exceed traction so the front wheels will lock up. In wet conditions we always dial in more rear brake bias. If you have a hotrod with small front wheels [ T buckets , Hi-boys etc ] you will also need more rear brake bias. The master cylinder in most situations controls all for wheels, so if you increase calliper piston area on the front the rears also need increasing. [ that's why it is easier to reduce M/C diameter ] With a single master cylinder [ tandem but not twin ] the line pressures are the same at all 4 corners, so the front and rear bias is normally adjusted with wheel cylinder or piston diameters If if can’t do the math, my advice is to try and find a similar wheelbase/ weight performance road car and copy the front and rear brakes. [ clamping pressures can be adjusted with M/C and pedal ratios ] Most car manufacturers have got their calculations quite close for a mass produced / everyday situations so don’t try and re-invent the wheel unless you really know what you’re doing. And please be careful when taking advice from some “Parts Jockey” counter jumper. [ all they want to do is sell you their shit ]
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