Disc brake conversion (70 Dart)

-
Are your Wilwoods (4) Piston calipers or just (2) piston like 72bluNblu mistakenly calculated?

LOL
Unfortunately, you both miscalculated. With the single floating caliper you have to double the normal force on the rotor, and multiply that times the surface area of the brake pads. Then the friction coefficient times the distance from the center of the caliper piston to the center of the hub to get the friction force on the rotor.

It's not a miscalculation in either case. The single piston force is not doubled, and the 4 piston calipers have 2 pistons per side of the caliper. Only one side is used for the calculation. This is explained earlier in the paper I linked in post #34 about how to do the brake force calculations, it's common practice for the calculation. Most of the available calculators for brake force include an explanation as well.

You could use the area of all 4 pistons for the fixed Wilwood calipers, but then you would also double the area for the single piston sliding calipers (opposite and equal reaction). Instead, one side of the caliper is used for the calculation so the results are easily compared and no doubling or halving needs to take place.

YOU are the one that claimed YOUR Brake Force Calculator was the best thing to use to evaluate a braking system. And you are also the one who claimed to be a Aerospace Engineer?

Now you have a problem with admitting you calculated the Wilwood calipers which are (4) piston and not (2) to get wrong info.

Just admit you were wrong and be done buddy!

i have tested almost all these brake systems on our brake dyno with brake pads and solid steel replacement pads. I work at an R&D OEM and everybody comes to us for evaluation. I don't have to look much further than your amateur numbers you came up with to know you had a mistake in obtaining your data. Your numbers weren't even close. But just using it to prove you didn't calculate your numbers right will never be enough for 72bluNblu will it.

Where is your data? As always, it's just you opinion and a Brake Force Calculator you screwed up and won't admit you calculated wrong. You yourself admit you have never taken any of your cars to a race track and claim to drive like a little old lady everywhere on the street, so where are you getting your testing results? And your correction numbers are wrong too. But I like the fact you took my reasons where multi-piston calipers benefit a braking system and retyped it on here like you discovered that info.

If your an Aerospace Engineer and machinist like you say you should be able to build your own brake force dyno on your lathe, then post REAL data here instead of your opinion that hurts our aftermarket. I'm sure it won't be up to SAE parameters for testing, but it would be real data, a big step for 72bluNblu!

Until I see REAL data you have collected, this is all just your opinion. As usual... So just suck it up like a big boy and admit you were blowing smoke out your ***.

Most of the people on this forum are happy with drum brakes or stock disc set ups. So that's really all they need here about.

I didn't do the calculation wrong as I explained above. The way I calculated it using a single side of the caliper is a common practice, that's why the calculators are set up that way. If you use both sides of the caliper for the fixed multi-piston calipers you must also double the area for the single piston sliders. There are plenty of examples of the calculations being done in that manner.

Your characterizations of my qualifications, and me personally, are inaccurate and not worth addressing further.

I will say this one time, and one time only, stop the bashing in this thread NOW !!

Thank you. Hopefully this post is straightforward enough not to be misconstrued as bashing.

I apologize for letting myself get dragged into the personal attacks.
 
It's not a miscalculation in either case. The single piston force is not doubled, and the 4 piston calipers have 2 pistons per side of the caliper. Only one side is used for the calculation. This is explained earlier in the paper I linked in post #34 about how to do the brake force calculations, it's common practice for the calculation. Most of the available calculators for brake force include an explanation as well.

You could use the area of all 4 pistons for the fixed Wilwood calipers, but then you would also double the area for the single piston sliding calipers (opposite and equal reaction). Instead, one side of the caliper is used for the calculation so the results are easily compared and no doubling or halving needs to take place.



I didn't do the calculation wrong as I explained above. The way I calculated it using a single side of the caliper is a common practice, that's why the calculators are set up that way. If you use both sides of the caliper for the fixed multi-piston calipers you must also double the area for the single piston sliders. There are plenty of examples of the calculations being done in that manner.

Your characterizations of my qualifications, and me personally, are inaccurate and not worth addressing further.



Thank you. Hopefully this post is straightforward enough not to be misconstrued as bashing.

I apologize for letting myself get dragged into the personal attacks.

WILWOODS!!!!
 
I hate to break it to you but Willwoods are basically an aluminum version of the OEM Kelsey Hays 4 piston design? No big deal???


LMFAO...oem is no where close to the quality or performance of WILWOODS!!
 
It's not a miscalculation in either case. The single piston force is not doubled, and the 4 piston calipers have 2 pistons per side of the caliper. Only one side is used for the calculation. This is explained earlier in the paper I linked in post #34 about how to do the brake force calculations, it's common practice for the calculation. Most of the available calculators for brake force include an explanation as well.

You could use the area of all 4 pistons for the fixed Wilwood calipers, but then you would also double the area for the single piston sliding calipers (opposite and equal reaction). Instead, one side of the caliper is used for the calculation so the results are easily compared and no doubling or halving needs to take place.



I didn't do the calculation wrong as I explained above. The way I calculated it using a single side of the caliper is a common practice, that's why the calculators are set up that way. If you use both sides of the caliper for the fixed multi-piston calipers you must also double the area for the single piston sliders. There are plenty of examples of the calculations being done in that manner.

Your characterizations of my qualifications, and me personally, are inaccurate and not worth addressing further.



Thank you. Hopefully this post is straightforward enough not to be misconstrued as bashing.

I apologize for letting myself get dragged into the personal attacks.

I stand corrected. I knew you had the right numbers, I just could not see where the friction of the opposite pad was accounted for in the sliding caliper. I see it now. Thanks.
 
Dream on. The numbers don't lie...


Dream On..thats a song by Aerosmith..Wilwoods are on my car so I know firsthand how well perform..theres those that have them and those that wish they had them,if your happy with that 50 year old technology good for you!!
 
It's not a miscalculation in either case. The single piston force is not doubled, and the 4 piston calipers have 2 pistons per side of the caliper. Only one side is used for the calculation. This is explained earlier in the paper I linked in post #34 about how to do the brake force calculations, it's common practice for the calculation. Most of the available calculators for brake force include an explanation as well.

You could use the area of all 4 pistons for the fixed Wilwood calipers, but then you would also double the area for the single piston sliding calipers (opposite and equal reaction). Instead, one side of the caliper is used for the calculation so the results are easily compared and no doubling or halving needs to take place.



I didn't do the calculation wrong as I explained above. The way I calculated it using a single side of the caliper is a common practice, that's why the calculators are set up that way. If you use both sides of the caliper for the fixed multi-piston calipers you must also double the area for the single piston sliders. There are plenty of examples of the calculations being done in that manner.

Your characterizations of my qualifications, and me personally, are inaccurate and not worth addressing further.



Thank you. Hopefully this post is straightforward enough not to be misconstrued as bashing.

I apologize for letting myself get dragged into the personal attacks.

You can't calculate brake force from your excel format.
Nice try though. Most calculators I see are wrong.
 
Last edited:
Dream On..thats a song by Aerosmith..Wilwoods are on my car so I know firsthand how well perform..theres those that have them and those that wish they had them,if your happy with that 50 year old technology good for you!!

You keep believing. You are using the same technology. Your pistons are .11 inches larger. Yes, my calipers were rebuilt 30 years ago and my car will stop as well as yours. DOT 5 fluid, Hawk HPS pads, new rotors. Good luck with your New 50 year old technology. Not even close to the sliding single caliper with 11.75 rotors. I have both, and can buy whatever I want.
 
You can't calculate brake force from your excel format.
Nice try though. Most calculators I see are wrong.

However it is an acceptable way to compare brake systems at a simplified theoretical level. 72bluNblu calculations are more accurate than yours. Your swept diameters are off and you neglect the friction on the second brake pad on a floating caliper in your calculations.
 
However it is an acceptable way to compare brake systems at a simplified theoretical level. 72bluNblu calculations are more accurate than yours. Your swept diameters are off and you neglect the friction on the second brake pad on a floating caliper in your calculations.

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.
 
I know most of what you say, and agree with what you are saying, the problem I have is in your calculations on the spread sheets. 1. You do not account for the friction from the opposite pad in a floating caliper. 2. The braking diameters are incorrect unless I am missing something. I have been driving fast A Bodies for 45 years and unless the is a failure, stuck pistons, calipers frozen, glazed pads or rotors, all of the OEM disc systems work fine. To me the refinements are in the different diameter pistons to evenly apply pressure to the pads, higher friction materials, larger OD rotors to get a better moment arm, thicker rotors and pad materials to dissipate the heat better. Not raelly new technology I can't just upgrade to ant system I have. As for the floating calipers, I'm sure they are not optimum but can really get the job done. I have not seen pad wear problems in any of my cars, including an 96 ACR Neon with 250,000 street miles. I do not road race, so I am not standing on my brakes and trashing a set of pads, rotors, and at least 1 set of race tires every weekend. I usually replace pads every 100,000 miles and Rotors every 200,000 miles.
 
I know most of what you say, and agree with what you are saying, the problem I have is in your calculations on the spread sheets. 1. You do not account for the friction from the opposite pad in a floating caliper. 2. The braking diameters are incorrect unless I am missing something. I have been driving fast A Bodies for 45 years and unless the is a failure, stuck pistons, calipers frozen, glazed pads or rotors, all of the OEM disc systems work fine. To me the refinements are in the different diameter pistons to evenly apply pressure to the pads, higher friction materials, larger OD rotors to get a better moment arm, thicker rotors and pad materials to dissipate the heat better. Not raelly new technology I can't just upgrade to ant system I have. As for the floating calipers, I'm sure they are not optimum but can really get the job done. I have not seen pad wear problems in any of my cars, including an 96 ACR Neon with 250,000 street miles. I do not road race, so I am not standing on my brakes and trashing a set of pads, rotors, and at least 1 set of race tires every weekend. I usually replace pads every 100,000 miles and Rotors every 200,000 miles.

I did road race a 400 HP Forward Motion 2.2 Shelby Charger in the late 80’s early 90’s and later a Neon, the stock brakes sucked after both cars had marginal upgrades and weren’t on the either car very long. Pads even disintegrated outside the piston diameter due to flex/heat on several manufacturer brands. You can’t put the heat into the metal backers on the pads without them bending under a single piston. And there was a lot of tapered worn pads and shuddering. And with race pads that produce high dust, the floating calipers stop floating. On street cars the old single pistons work for most people just fine. I doubt many people push their old floaters very hard.

Sounds like you are pretty easy on your brakes. Most people here are. I doubt mine last 1/4 of those miles on any car I have.

I did have a rare thing happen once. I had a cast iron rear caliper brake in half and the piston fell out approaching a turn at about 90 mph. Most likely though that came from a few months earlier when the car was pulled out of a trap backwards with a strap and maybe a poor casting.
 
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.
 
The calculator being used is for brake bias, not clamping force. Clamping force would use all the piston to calcutate. Brake Bias (front to rear) is where you use 1/2 a multi piston caliper to do calcs. True clamping force isn't calculated that way. When calculating bias a single piston gets to include the outer pad area when it's pulled to the rotor, or you just cancel out 1/2 of a multi piston caliper to balance out your calcs for bias. These calcs always assume that a multi piston caliper is doing more work on one side of the caliper than the other and the piston aren't floating in the caliper. Which can be true for people that don't shim out their multi piston fixed calipers to begin with. Usually the car will pull slightly to one side under braking in that case.
 
-
Back
Top