How far does the typical wheel cylinder travel on a drum set up? On a properly adjusted system. Sorry I’ve searched and can’t find an answer. Trying to figure the amount of volume needed in the system. Thanks. one guy said .20 inches. That’s the only answer I found.
It would depend on the diameter of the piston and how big the area behind the pistons is, plus the travel to find the volume. Then add the brake lines and hose volume plus the master cylinder. Then there is the loss when bleeding the system. Or you could just add brake fluid until the system is full.
There are too many variables for a definitive answer. If the relaxed circle of the shoes are close to the inside circle of the drum, .20-inch sounds about right. Typically though, the two diameters differ and although the "adjusted" shoe slightly drags at the bottom, the wheel cylinder piston travels further for contact. Cylinder diameter also has to figure in.
measure the travel of the master cylinder to figure out the total volume of fluid, and do some math....having to do with bore sizes, and number of cylinders. My guess is between 0.05 and 0.20"
The..."wheel cylinder"...doesn't go anyplace, that the car doesn't go. You push the brake pedal, the cylinder, just sits there, as attached to the axle or spindle ! But...when you push the pedal, the "pistons" DO...move. Depends on the cylinder size, and if the brakes are manual adjusted, or automatically adjusted. Without seeing what you are working with (my crystal ball isn't working today), I'd say with a single push of the pedal, the answer above is close, probably, .180"/.200". Mike
Ok thanks. Problem is my pedal is going almost to the floor. No air. All new system. My 7/8 bore is giving me .66 cubic inches of volume. I’m just thinking that isn’t enough for some reason. I was wondering if there was a magical number the wheel cylinders Normally travel. if my wheel cylinders do travel .2 let’s say, they need .654 cubic inches. Maxing out the 7/8 bore.
Thanks Mike. Was it you that had a badass write up on brake hydraulics? I can’t find it. if calculating the volume a master cylinder puts out, do you double the number for a dual master or not. like my 7/8 dual. Travel is 1.10 inch. Volume is .66inches. Do you double this number?
You are asking a tiny part of the entire developed and engineered system. Then you provide some other measurements and ask how the whole system is sized, along with the actual complaint. If you want to do all the math, there are a hundred websites to get into all the numbers. https://brakepower.com/brake-calculator-instructions.htm http://www.how-to-build-hotrods.com/brake-system.html https://thebrakereport.com/tbr-tech...-a-parametric-1d-brake-model-part-1-out-of-3/ However, you are trying to find the solution to the issue. Block off the rear brake circuit. How does this affect pedal travel? Then block off the front brake circuit and try the pedal again. This will narrow the diagnosis. Remember, a properly operating system will have built in safety, meaning that when working properly, the pedal will only travel roughly half it's travel. This allows for air, wear and other factors to still provide braking when the system is compromised.
Are you sure the master cylinder piston is getting it's full stroke when the pedal is fully depressed? Could be a linkage issue and not a hydraulic one. Is the free play correct?
Any chance of posting exactly what it is that you are working on and if there has been any modifications?
I know you asked your question, mentioning a properly adjusted system, but just reinforcing that the shoes should be adjusted right up, including parking brake system, for best results.
Good idea on isolating the front and rear. We blocked off rear and had a great pedal then. Thanks. Helps me to talk these things out. I’ll report back when we find the issue with the rears honestly I’ve read so many damn brake articles my head spins. I’ve never had an issue on the last 5 custom set ups. Reason why this one has gotten to me.
Treadlevac gone. Made a bracket. Got rid of the 2:1 pedal ratio and made a 6:1. Would like to had a 5:1 but i would need a different pedal for that.
There's your problem - The 'KIT' ... ... you bought, did you mention to the seller your were removing an OEM INSTALLED TREADLE-VAC SYSTEM and going with a regular vacuum booster? Who is the seller of the kit? Can you show a photo of the pedal and linkages under the instrument panel you have on it now? Is the car still four wheel drum or have you done a front disc upgrade? Is the high dollar MC four wheel drum or DISC/DRUM? You did save all of the take-off parts hopefully?
As a start a manual brake car would have had a 1" master cylinder so who ever came up with the 7/8" master missed something.
If all drum, were residual pressure valves used? This should identify the problem(s) - https://www.jalopyjournal.com/forum/threads/1954-lincoln-brake-swap-question.1271208/
You start here to correct your present situation. All TREADLE-VAC related parts must be removed and then start with the non-power brake pedal design for the car ...
Good call, Moonrnr. I posted this about 6 mouths back, time to roll it out again... Generic Upgrade Install Guide 1. Research before buying. 2. Know that the company provides instructions and/or has a tech line if you do not have the knowledge and experience to install and diagnose the component/system. If you rely on someone else, make sure they are available and know what to do. They are not your 24/7 warranty call unless this has already been worked out. 3. Buy from a reputable seller if you don't have the knowledge and experience to deal with a bad seller and don't want to waste your time. 4. Read and understand the instructions before install, and ensure all parts are included and they fit your application. Gather necessary tools and any additional parts. 5. If there are any questions, ask before install. Often there is no returns for installed or partially installed items, especially electrical. Also note any steps that would make it difficult to revert back to original. 6. Now install, noting any variances and fixing any issues found during install. 7. Understand that very few parts operate completely independent of any other parts. Make sure that other parts the new component relies on are operating properly. Make sure the new parts are not subjected to extreme pressures, temperatures, vibrations, voltages or fluids they are not designed to handle. Many of us have just grabbed the box, gone out and started ripping things out and slapping the new part on. This is often successful, but when it isn't it falls on the person doing the work to diagnose why. These forums are full of people who do fit the profile described in step 2, but if you come on here and ask for help, please include as much info as possible about steps 4-7 in the first post and understand that it's like walking into a bar full of regulars who have had this question asked by a dozen new patrons before. There will be banter, there will be opinions and there will be questions about what you did. We all start somewhere and nobody knows everything. Just try to figure it out before just asking for the answer when it could easily be one of a dozen things, most of which are at least inspected by following the guide.
You are one brave man, sir. You have opened yourself to flying food particles from the entrenched PASCALS RASCALS RAIDERS that seem to be entrenched here. So grab your head bucket and hold on as it is surely due to start flying. Any who, my main interests are with FLM. I have no EDSEL CATALOGING (which I should) but I can see by the rocker cover it is a 410CI E-475 MEL that will make his 1958 EDSEL MERC body based. He just needs to find the take-out parts from a similar manual brake MERC. There are honest quality kit makers out there, the trouble is in finding them. Might be wise to stay away from EvilBay.
Bore on the wheel cylinders is 29/32. That cute and very spendy master cylinder has as you said a 7/8 bore. Even with the rear brakes quite a bit out of adjustment you should have enough volume in the master cylinder to stop if that is the only issue. Not well and not with a lot of pedal but it should stop. Snooping Rock Auto a Drum Drum 68 Ford Galaxy has 29/32 rear wheel cylinders and a 15/16 bore master cylinder. The also have 1.031 front wheel cylinders. Those late 60's Drum/drum dual master cylinders are what most of us use to go to dual master cylinders on older rides. Not fancy or pretty but they worked fine on big sedans and full size pickups in the late 60's and early 70's. Do you have 10 lb residual valves or Check valves? You have to maintain pressure in the lines on drum brakes or air can get in past the cups, especially if the brakes aren't adjusted right. Again, rear brakes adjusted correctly? Meaning tightened up until you cannot turn the wheel and backed off eleven clicks. It is still will and is supposed to have a fair amount of drag. If you can't feel that drag that is part of the problem. That I would check and correct before I did anything else, crank them down so that you cannot turn the tire by hand and back them off 11 clicks, That is the way I was taught in 1962, that is the way I have adjusted brakes that run in the thousands and the way I taught my students Id you don't feel or hear a drag your brakes aren't adjusted correctly. The only other thing I have is that I have seen too many guys who are clueless as to how to correctly bleed brakes. If you have a helper pumping the pedal, they have to pump SLOWLY so fluid has time to get from the reservouir to the bore of the cylinder. Then they have to hold the pedal down until you open the bleeder, let air and fluid out and close the bleeder and tell them to pump it again. I've had too many helpers who thought that as soon as the pedal hit the floor after I opened the bleeder they could let off the pedal and that doesn't work.
- WE NOW RETURN YOU TO REGULAR PROGRAMING - What you have posted makes no sense. The problem is PEDAL RATIO and incorrect MC APPLICATION/SIZING (well that and a general misunderstanding of brake theory).
I was going to add front discs to my 56 Ford. Before I did it I changed the complete rear end to an 8.8 with F-150 11” drum brakes, 3/8” wider than the stock 56 Fords. During the installation and while I still had drums in front I checked the rear wheel cylinders. They were 1-1/8” since the truck had power brakes so I changed them to 15/16”. I was planning on using Wilwood’s front disc system with no booster and during a discussion with one of their techs about M/C diameter he asked about the rear wheel cylinders. I told him what I did, he said “perfect”. The M/C is 7/8” and the system works great.
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