Brake issues continued

Topic: Brake issues continued (Read 5843 times) previous topic - next topic

Brake issues continued

January 30, 2014, 09:29:07 PM

I have an 88 LX that I have performed a 5 lug conversion on the front. Conversion was done with 95 Mustang parts. Not much of a difference from the original. I decided to go further. I replaced the calipers with new ones and pads as well. Replaced the rotors with drilled and slotted. I put on a MC for a 95 Mustang GT. From there, the brakes were not even safe. I decided to put on a brake booster for a 93 Cobra Mustang. It is now safe to drive. Still seems to be lacking. Did I pick the wrong MC? Open for suggestions. Still waiting for the TC parts car for the rear diff. After that, I will Convert the rear to 5 lug with the parts I have.

Thank U Darren. 93 Cobra booster was a good choice. It helped the braking tremedously. All I had to do to put it in was make the holes a little bigger. Just needed that to give a little wiggle room. Otherwise, could not get it past the strut tower.

Brake issues continued

Reply #1 – January 31, 2014, 01:25:07 PM

Define "still seems to be lacking."

Soft pedal? You mention only the front for the conversion......Rear is still 4 lug or previously done?

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Reply #2 – January 31, 2014, 03:27:54 PM

Yes, rear is still 4 lug with drums. Pedal not soft at all. It takes excessive pressure to get the car to stop. I suppose it could be the bias, but kind of silly to change the prop valve until I do the rear conversion.

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Reply #3 – January 31, 2014, 09:20:39 PM

Truthfully, sounds like its booster related. Check the vac line and the plastic fitting. Before i hooked my booster up it was hellaciously stiff but still stopped.

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Reply #4 – February 01, 2014, 02:47:43 AM

That master cylinder you installed has a 1-1/16" bore which is way too big for your setup.

When you change to disk brakes on the rear the pedal should feel softer and the brakes should work better, until then, a smaller MC will fix your prob.

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Reply #5 – February 01, 2014, 09:09:37 AM

So should he have kept the original MC and just added the 93 Cobra booster?

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Reply #6 – February 01, 2014, 05:21:56 PM

Well the stock MC is 21mm which comes right around 13/16"
Thats a pretty large jump in size
So the stock MC could be too small or it could be just right
The only way to know is for him to try it or if somebody has tried out this exact combo

If the sn95 front calipers have a close enough bore size to the stock calipers then the stock MC might do the trick

On my TC I'm going to sn95 brakes on the front as well, rear is already disc, and I will be using a 93 cobra booster with a 93 cobra MC which has a 1" bore

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Reply #7 – February 02, 2014, 11:25:17 PM

When I changed the MC is when things headed south. It felt as though I had the booster disconnected. Huge change when I changed the booster. As big of change as it was, I feel the original MC would be a little too much. When my next paycheck comes in I will order a 93 Cobra MC. Perhaps that will put me where I need to be. Upgraded braking is the whole point in swapping to 95 Stang parts, so I must get this right.

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Reply #8 – February 15, 2014, 07:27:53 PM

You will have to install the manual proportioning valve anyhow so why not do it now? Gut the proportioning valve side of the stock combination valve and install a manual proportioning valve like a Wilwood with a twist . You are all out of whack with your bias.

If you are going to stay with the 11.65" front rotors then switch to the '99+ dual caliper PBR calipers. Huge improvement over the single piston units you have now. You will have to massage the spindles a little (knock some casting flash off basically) to get them to fit. Do a search on this and several sites will pop up showing what has to be done. I ran this setup with the stock SN 95 rear disc brakes and it was 10 times the brakes than the stock garbage Ford put on these cars.

I have the GT master cylinder on both of my cars with the full Cobra brake setup and the pedal effort is perfect. It might be a smidge better with a 1" bore MC but I'm not willing to change it out.

Darren

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Reply #9 – February 16, 2014, 08:22:16 AM

Still beating this to DEATH. A master that is over 1" in diameter is to big. We have covered this numerous times. I have posted pedal ratios of all the pedal assemblies and have instructed the procedure. Ditch all the stock valves including the differential and install an adjustable proportional valve in the rear system. Use a cylinder between 7/8 and 1 " MAX!!! Use a 2 port cylinder of your choice for diameter and do not over build it with all the old obsolete . Another words ditch all the stock valves and use only one valve to the rear brakes. Simple clean and it works.

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Reply #10 – February 16, 2014, 08:35:44 AM

Here we go a cylinder of 7/8 and a dual area booster This is a good setup for a small caliper 4 wheel disc setup. You will need a slightly larger piston diameter with more pistons per caliper.

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Reply #11 – February 16, 2014, 11:24:24 AM

Chrome,
This is not meant to be a hijack but I think we need to invest some time here so that those that read this thread are well informed on the subject.

While I do respect Tom's knowledge and years of experience I would like for some clarification on his statement in post #10. I would like to know what setup he is referring to when suggesting that only a 7/8" or 1" bore MC be used? I'm not worried about the pedal ratio as that has been covered so it is a constant in this equation so we can ignore it for the sake of keeping the discussion less confusing.

From my experience as stated above I have had zero issues with either setup on my Coupe (stock SN95 brakes with the +99 PBR calipers & the current full Cobra setup) while utilizing a stock 95 GT 1-1/16" bore MC. The 94/95 GT's and 94-98 V6 cars came factory with a 1-1/16" bore MC and both had the exact same brake setup while the 94/95 Cobra came factory with a 15/16" bore MC (after '96 the GT's and Cobras were switched to hydroboost). I looked this up on a couple of good brake conversion sites and here is the rundown of MC's and cars:

'85 Towncar - (SAE Threads) 1" bore, old style aluminum reservoir unit, no low fluid sensor
'93 Cobra - (metric threads) 1.00" bore
'94-95 GT/V6 - (metric threads) 1 1/16" bore, stock plug in for the low fluid sensor
'94-98 V6 - (metric threads) 1 1/16" bore, stock plug in for the low fluid sensor
'94-95 Cobra - (metric threads) 15/16" bore, stock plug in for low fluid sensor, ports are reversed thread sizes from 87-95 LX/V6/GT
'99 V6 - (metric threads) 1.000" and 1.006" bore, can be converted to work for the low fluid sensor on the Fox3 cars although the general consensus is to stay away from these units
'96+ V8 Units - These are hydroboosted and the mounted is vertically vs horizontal required for a vacuum booster

I do agree that keeping a braking system a simple as possible is key however in most cases it is just simpler to removed the proportioning valve out of the combination valve and install the manual proportioning valve. It keeps a person from having to bend, cut, and double flare brake lines when the majority of us are not that good at it. For someone who works on cars for a living especially the older ones or building customs and hot rods building brake lines and having a really good double flare tool is part of the tool box. So for the majority of the guys on this board the less they have to mess with the system the better which is why I try and recommend the '85 Towncar MC even though is has what some consider to be an outdated look, it is a bolt in. Once that is done a person only has to worry about two double flares to install the manual proportioning valve which is pretty good if you ask me.

The reason the combination valve modification and installation of the manual proportioning valve is so common on the Mustangs is that there is a brake line union just above the heater core tubes on the fire wall for the rear brakes. You simply remove this and install the proportioning valve and change the MC and you are done. No flaring, no cussing, not a thing to worry about unless you are swapping boosters and then there is a little cussing. With our cars the union does not exist so its a little more complicated. If a person is wanting the more updated look of the 93 Cobra or 94 and up MC then you can always buy the installation kit for one of these here:

http://www.maximummotorsports.com/Power-assisted-Brakes-C517.aspx

You just pick your year of car & type of master cylinder that you are installing. They even have the SAE to metric adapters to keep you from having to flare anything.

Anyhow, I just thought I would post this up for anyone that is considering this swap so you know what is available and that it is not that big of a deal just a little time consuming but the results are worth every penny and all the cuts and cussing.

Darren

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Reply #12 – February 16, 2014, 04:57:57 PM

Ok simply put the ratios are constant and can be fudged around with some fancy mods but lets not go there. And if a person does not feel conferrable with cutting and flaring that is a good point. But there are latterly thousand of adapters available to do this swap easily. Now when picking a master one has to determine how many pistons said system has to activate and achieve a pedal ratio that will suffice a normal pedal feel. Normally that is somewhere around 100 PSI at then pedal for normal feel. It also determines the pedal travel. So a smaller piston diameter will travel more but apply more pressure with a less applied pedal pressure. As a bigger piston will travel less and require more pedal pressure. Normally a 4 wheel single piston caliper setup will work with a 1 1/8 master with a 3-1 pedal ratio with power assist. But our cars do not have a 3-1 ratio so a smaller piston diameter is necessary in my thinking. With more pistons per caliper you need more volume. So a diameter at or around 1 " is about max for this application. As far as removing all the stock JUNK in my view it is mandatory because it does ABSOLUTELY NOTHING with a 4 wheel disc system. It also makes the instillation clean and leak free. Less connections less chances for leaks. Normally we very rarely use a master larger than 1" and this is confirmed with the wellwood engineers we deal with when designing systems. THE ABOVE cylinder specks is great but means nothing without PEDAL RATIOS!!!! What is the PEDAL ratio of the TOWN CAR or the COBRA ETC!!!!!

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Reply #13 – February 16, 2014, 08:15:06 PM

Tom,

I get what you are saying with pedal ratios, MC bores, number and diameter of pistons in the caliper, and the weight of the car and how that is distributed front to back. The majority of the people here have street cars and may not have the math background to lay out a full on brake system. I understand it and can do the math but I also understand the 1-1/16" bore MC has worked on my cars for years now and believe me the brakes will put you through the windshield and the pedal effort is what would consider a very boosted feel not hard at all. The pedal ratio in both of my cars is a 3:1 as the pedal assembly in the Bird is a Fox Mustang assembly. All of the above MC's work well with this pedal ratio with the 1" bore being the optimum one but the 15/16" and 1-1/16" working well as well. I'm 6-2' and 200 so having a little more pedal effort is not a huge deal to me. Now if a person was 5'6" and a buck forty then the smaller MC bore may be the way to go unless they are a power lifter.

Anyhow, I've said all I can about this as I am just posting up what I have installed and works and have installed on several other cars and it works. I think what you are saying works as well as you have obviously been there and done that so its just two schools of thought that solve the same problem.

Darren

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Reply #14 – February 17, 2014, 11:31:56 AM

Quote from: TOM Renzo;428965

Still beating this to DEATH. A master that is over 1" in diameter is to big. We have covered this numerous times. I have posted pedal ratios of all the pedal assemblies and have instructed the procedure. Ditch all the stock valves including the differential and install an adjustable proportional valve in the rear system. Use a cylinder between 7/8 and 1 " MAX!!! Use a 2 port cylinder of your choice for diameter and do not over build it with all the old obsolete . Another words ditch all the stock valves and use only one valve to the rear brakes. Simple clean and it works.

Tom, ur responce to one of my previous posts is the reason I felt I had the wrong MC. Telling my the size of bore on the MCs tells me nothing without telling me which cars they come from. Once I get this functional with the stock prop valve, I will look into changing it to an adjustable one. For now, I still have FACTORY rear drums on 4 lug. I am waiting on a parts car so I can get some deeper gears and an 8.8.