Disc brake conversion (70 Dart)
You can't calculate brake force from your excel format.
Nice try though. Most calculators I see are wrong.
Of course you can calculate brake force, and that's exactly what that excel spreadsheet does.
Now, the
calculated force will be different from the
actual force applied in a real world scenario, but since there isn't any real world data available the calculated force is the best comparison that can be made with the information we have.
It's the same calculator posted on other sites. It doesn't work, it doesn't address plateau, the friction coefficient is a middle of the road number, and it doesn't calculate based off each individual caliper piston or vehicle weight or address static axle load distribution and assumes clamping load is always equal on all friction surfaces. There is also a factor that can be added for heat and kinetic energy, inertia changes when different size wheels are used. A correct calculator would have my numbers lower, but the old +73 you are always assuming in a perfect working model. They won't be. And your braking force on your +73 (if you want to accept those numbers as golden) can only be generated if the wheel does not lock up. Your numbers have it locking up long before reaching your maximum clamping force. So that alone reduces the braking force because it's sliding the tire. Cold drum brakes can stop better than disc brakes that are cold. And if you are using a .45 for friction, those pads will have to have a little heat to work properly.
40 year old technology? Caliper style disc brakes where invented in the 1890's. Our modern hydraulic disc set ups all have roots to early 1950's designs. It's just a piston with fluid pushing it, I'm not getting where you think nothing has improved over the years or are you expecting some new way of clamping a brake pad?. Your floating calipers are prone to stick and are way more common in producing uneven pad wear, your single piston footprint produces pad flex and doesn't grip the rotor evenly, so throw out your .5 friction coefficient of you Hawk pads. It's also the reason why Neon's got recalled for the brake pads coming off the backer plates. They flexed too much.
I'm sure the OP just wants to get a little more updated braking than drums and should be fine rebuilding what he has. He really doesn't need to know much more.
There are similar calculators posted all over the place. I picked one that included as many variables as we have information for. They work fine as long as they're used properly, but like any calculation they make some assumptions. That's the nature of engineering, the mathematics can only be done with so many variables, so you have to make some assumptions. How accurate those assumptions are will determine how closely the calculations match the real world results.
The calculator I used allows you to change the friction coefficient, you can enter whatever number you want there. But since this is a comparison between different calipers the actual value for the friction coefficient isn't that important, all the matters is that you're using the same coefficient for all the brakes you're comparing. The actual number you get is less important than the difference between the numbers for each caliper. So you can change the friction coefficient to whatever you like, the end number will change, but the % difference between the calipers that are being compared will be the same.
As for the rest of the variables you mentioned, lets take a look:
Vehicle weight, axle load distribution, and inertia changes with wheel size- these are all basically irrelevant here. We're assuming that the calipers we're comparing are going on the same car, so, all of those numbers will be the same. Those numbers do effect the actual stopping distance of the vehicle, but the force applied by the caliper isn't changed by any of those variables.
Heat and kinetic energy- These are primarily effected by the weight of the car and the coefficient of friction of the pads. We're holding those to be the same, so, the difference in heat generated will primarily come down to the braking force applied, which is what we're comparing. The wildcard is heat dissipation, because the calipers/rotors that dissipate heat faster will be less likely to overheat. But those heat dissipation numbers are information we don't have, and if you use the same estimate for both brake systems then it's going to be cancelled out anyway, so you're just back to comparing braking force.
Clamping load- The calculations assume perfect clamp force distribution and that all of the clamping load turns into braking force. This is the biggest shortfall of the calculations for this comparison, because we aren't comparing the same style of caliper. Fixed calipers should have better clamp force distribution than sliding calipers. They should also lose less force to binding and flex. That means the fixed calipers will be more efficient and their real world brake force number should be closer to the calculated number than the slider calipers will be, which is what I have said from the very beginning. But that's where the % difference comes into play. Based on the calculations, the difference in efficiency can be 24% before the real world brake forces would be equal. That's a big number. If it were 10%, it would be pretty easy to say the fixed calipers would provide better real world results. But it's 24%, so, that's not a good assumption based on the information we have.
Locking the brakes/sliding the wheels- Both brake systems have this issue. Again, this will effect the stopping distance of the car, but for comparing the calipers and finding which one generates the most brake force it's irrelevant. You can argue that you don't need to use the calipers with the most braking force because of this, but that doesn't change which calipers can provide the most braking force. Tire compound also has a big part in this, so you can certainly argue that if you're running skinny drag race front runners you don't need the best brakes, because you won't be able to put that force to the ground. But that's an argument against upgrading your brakes and spending a ton of money, and the Wilwoods are the most expensive option being compared.
I'm pretty sure the OP disappeared a long time ago. But having more information to make a better informed decision is never a bad thing.
