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1949 Ford Coupe RESURRECTION
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Discussion Starter #1
I've been on the earth 77 years so far, and have replaced quite a few pads/discs before, but never ran across this particular problem.. Sooo.. brake experts, chime in..

When I was building "The Judge", I bought some new front discs and pads to go on the S-10 front clip, and I don't remember the manufacturer, however, I do remember that the discs were green and the instructions said not to clean or remove the coating. I complied. After getting her on the road, I was alarmed at my lack of braking. So, since I was running only 12.5" vacuum on the power brakes, I installed a mid-80's GM vacuum booster pump and storage canister. That helped a little and was back in 2017. I now have about 4,000 miles on the car. Then I decided a couple of weeks ago to just get better pads, which are now Bosch high end pads. I can detect no difference.

The question is: When I disassembled the brakes to put the Bosch pads on, I noticed that the discs on both sides were VERY shiny, like a mirror. Just about as smooth as one could get on a Chip Foose paint job. The green is gone, except around the edges, which is what it's for, as I understand to limit rusting. I thought, well, let's knock off that shiny surface a little bit. So I broke out a 600 grit hand block sanding thing, and went to town. The surface is so hard that the 600 grit hardly made any affect on the surface.

So I said, well what the hell, and went ahead and put everything back together. Hardly any perseptible difference. And yes, I did the "break in procedure". Then on a lonely road, I attempted to lock up the brakes. No way in hell will they lock up.

I have googled and researched disc brake specifications and have read about such things as "proper roughness" expressed in "0.000 etc. mm" roughness, but these things are like a mirror. No, I don't know the diameter of the dual master cylinder, but I do have a "disc/disc" proportioning valve. Rears are Jaguar mid 80's XJS inboards..

And, what's ya'll opinions of used Bosch pads on either a "turned" disc or new discs? I have read conflicting opinions on that plan.

Just wondering, new discs and start over? (fastest fix), or take them off and have them turned (down for more than a day)... It's my daily driver and have no alternate transportation.. .. hate to ask any buddies to haul me around to a brake shop (15 miles away) to deliver and pick them up again... dang it...

Throw some opinions at me. ! ! !
 

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True Hotrodder
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New discs really should have a fine finish that is just enough to help the disc pads "break in". Most of the time when I see a mirror finish that indicates to me that it's over with and if a cut won't clean it up, then it's on to new ones. The other issue could be the master cylinder size - it's very important as is the pedal ratio. When we hot rodders start mixing and matching stuff, we can get ourselves into trouble real quick.
 

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Pads are in constant contact with the rotors , polishing is inevitable ! Some pads are so hard that it can lead to poor braking ,on the street . Lack of sufficient line pressure is the most likely reason for not being able to lock the wheels . Either wrong master bore or wrong pedal ratio , or both .
 

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If the pads are performance pads made for autocrossing and such street driving will never get them up to temp. that they work correctly.
Now the rotors, take them off, and have them turned(cut) And put on regular mid grade pads for a s-10.
Problem At first was most likely pads made for hard braking over and over again, auto crossing, road racing.
Now your problem is the glass like rotor surface.
Get the rotors turned and if you are lucky and they have not formed hard spots. you can reuse them.
I have no idea what pads you put on This time , but if you reuse them scuff them up with sand paper, as you most likely glazed them running them in those mirrored finish rotors.
Skip the fancy pads, and get mid grade pads from your favorite local autoparts store.
The s-10 brakes are nothing to write home about. So skip the fancy "performance pads"
 

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True Hotrodder
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The brake pad that Imsport suggested is actually a very good, all-around street and high-performance pad. I have a set on my JDM right now and they are far better than anything that I have gotten from an auto parts outlet. Your 7:1 ratio is perfect so I would suggest trying to verify the size of the master cylinder.
 

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The brake pad that Imsport suggested is actually a very good, all-around street and high-performance pad. I have a set on my JDM right now and they are far better than anything that I have gotten from an auto parts outlet. Your 7:1 ratio is perfect so I would suggest trying to verify the size of the master cylinder.
Oh I'm sure. BUT
his rotors are glazed and need to be turned/cut .
There is almost no point on putting great pads on the s-10 brakes. low mile vehicles that sit long enough to get rust on rotors, kill pads. the s-10 brakes were iffie in the truck.
 

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True Hotrodder
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I had already said that the rotors either needed a cut or to be replaced.

The S-10 brakes are not what I would call "iffie" in the S-10 truck or any number of other GM vehicles from that era, nor the number of disc brake conversion kits that use the same exact caliper. Heck I have a 1975 Monza that goes 5.60's in the 1/8 mile and just over 120 that has a set of these calipers on it. I have more than a few friends that race S-10s with rather stout power packages and power adders - they too have these calipers on their vehicles. Are they pretty - no, but they are effective. Are they as good as a set of Bremos or Wilwoods or Baer multi-puck calipers - of course not. But honestly with a decent set of Hawk pads or a similar performance compound, they perform well and for a guy sporting around in his clipped '49 Ford, they are an excellent compromise between cost, performance and service.
 

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1949 Ford Coupe RESURRECTION
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737 Posts
Discussion Starter #13 (Edited)
Ok, thanks guys....now we are getting somewhere...maybe. so the next question is (since I sometimes hear it in discussions about brakes)...and a lot of guys have opinions about it..so, what IS the correct diameter master for S-10 calipers? And for 85 Jag xjs calipers??

As a reminder, brakes feel perfectly fine in a "normal" stop. Both the pressure on the pedal and distance of pedal movement. And at about 10 mph, a sudden hard push on the pedal and you might fly through the windshield, but at 40 or 50 or higher and some idiot in front of me does something stupid, I have felt a number of times that I was in big trouble.

By the way, the discs are drilled and slotted..

And why, at such low mileage would they be/get glazed?
 

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I had already said that the rotors either needed a cut or to be replaced.

The S-10 brakes are not what I would call "iffie" in the S-10 truck or any number of other GM vehicles from that era, nor the number of disc brake conversion kits that use the same exact caliper. Heck I have a 1975 Monza that goes 5.60's in the 1/8 mile and just over 120 that has a set of these calipers on it. I have more than a few friends that race S-10s with rather stout power packages and power adders - they too have these calipers on their vehicles. Are they pretty - no, but they are effective. Are they as good as a set of Bremos or Wilwoods or Baer multi-puck calipers - of course not. But honestly with a decent set of Hawk pads or a similar performance compound, they perform well and for a guy sporting around in his clipped '49 Ford, they are an excellent compromise between cost, performance and service.
Whatever you say. One stop then a cool down till the next round. That is what you are hanging your hat on?
Ya, tell me more.
First thng tossed on g bodys that see any type of autox, is the oem brakes.
Street driving is more than one stop every 20+ minutes.
They are fine for a swap to a rod. but don't expect much more out of them, and why standard parts store pads are just fine. The swept area is small, and the clapper flex is bad. Hard pads just turn the rotors to mirrors. as the rotor material is soft. Some need the brakes to stop 20k miles on the same rotor/pads. not have the pads make a mirror out of the rotors before the next service.
I have been down this road with g body's. performance pads are great if you are willing to pull the rotors every 4 thousand miles and turn them to get the rotor face finish back, as the like glass finish doesn't help stopping.
This is my opinion and you know what they say about opinions.
Difference is. I have owned vehicles with these part #'s 82g body/86 g body, 85s-10 2wd, 87s-10 2wd. and gone down this road.
 

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1949 Ford Coupe RESURRECTION
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737 Posts
Discussion Starter #15
And by the way, I NEVER "ride the brakes" ...there is a long and fairly steep hill (nearly a mile) between my place and town where I see at least half of the cars riding the brakes alllll the way down ..I scream more there than anywhere else.
 

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Slow but willing learner
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Have you put a vacuum gauge on your pump to make sure you have proper vacuum to your booster?

John
 

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Brake pads can make a huge difference.
My first oval race car(25+ years ago now) had Big Gm calipers that were aluminum and had two pistons. With parts store pads you could not lock up the wheels, ever. During a race they did OK but at the time I didn't know how much GOOD brakes would help the car go faster. I put on those same Hawk black pads and the difference was huge. The Hawk pads will chew up your rotors if you do alot of heavy braking.
 

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1949 Ford Coupe RESURRECTION
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737 Posts
Discussion Starter #18
Have you put a vacuum gauge on your pump to make sure you have proper vacuum to your booster?

John
I set the vacuum control switch to 20" when I installed the booster, and when I turn on the ignition switch, I can hear it run, then cycle off, so I'm sure I'm good there. Here's what I did:
 

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True Hotrodder
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Brake pads can make a huge difference.
My first oval race car(25+ years ago now) had Big Gm calipers that were aluminum and had two pistons. With parts store pads you could not lock up the wheels, ever. During a race they did OK but at the time I didn't know how much GOOD brakes would help the car go faster. I put on those same Hawk black pads and the difference was huge. The Hawk pads will chew up your rotors if you do alot of heavy braking.
I just checked my records, Hawk pads on my JDM for just over 7 years and 37k miles. I am sure there is some wear on the rotors (new when the Hawks were installed) but they still feel great, stop well and I expect I will get more time out of them.

I would say that autox certainly puts more pressure on brakes and the attending system but that's not street driving either.
 

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1949 Ford Coupe RESURRECTION
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737 Posts
Discussion Starter #20
Ok, guys... I surely hate to even say this, but my Jag IRS rear brakes just started making that familiar grinding sound. Uh OHHHH.. So I just pulled the removable panel in the trunk and guess what... ONE of the F'ING pads has ground into the disc. ... deductive reasoning tells me the following: The rear brakes have been doing all the work, AND, one of the calipers probably has a stuck piston, since I can see that it appears to have very little wear on the inboard pad, and the other disk and from what I can see, (can't see the outboard pads from the top), the inboard pad also looks like it's still quite thick.. Hell, I have been stopping on just one pad all this time, on the rear????.... ain't no way a pad goes out in 4,000 miles unless it's doing all the work... holy CRAP.. and those that are familiar with JAG IRS inboard brakes, the only way to replace or even work on the brakes is to drop the entire rear end, out of the car, and then take it apart. Pray for me...........I'm not going to worry about the front brakes for now.. I'll be "down" for a few days on this issue... and a LOT of money....Thanks, everybody..
 
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