# SSBC front disc brake conversion problem!!!



## 66problem (Oct 25, 2010)

I have a 1967 gto in our shop that came in for a front power disc brake conversion. Was manual drums to start. SSBC kit part number A123-23. After installing the kit and going to a test drive the car would not stop itself. I contacted ssbc and they said to go with a smaller bore master cylinder to increase line pressure. I now have 1300 psi at the front brakes and 600psi at the rear brakes numbers that ssbc is happy with. The car still will not stop like it should. Every brake part on the car is new from the booster to the pads and shoes. Have tried three different types of pads and got the rotors cut and still the same thing car slows down but doesnt stop like it should. if anybody has any helpful information please share. this car is going to be the end of me!!!!


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## 05GTO (Oct 6, 2004)

What is your vacuum source for the booster?


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## 66problem (Oct 25, 2010)

not sure i understand your question my vacuum source comes from the intake manifold and i have enough vacuum


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## Eric Animal (Oct 28, 2007)

Did you add/change the proportioning valve? A friend of mine just did a disc brake upgrade and got 2, yes 2, bad ones in a row!!!!!!!!!!!!!!!!!!!


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## Rukee (Feb 8, 2007)

:agree worth checking out.


The only time I've seen this issue is if the rotors are turned too smoothly.


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## Backup (Oct 16, 2010)

66problem said:


> I now have 1300 psi at the front brakes and 600psi at the rear brakes numbers that ssbc is happy with.


Where are you getting these numbers from? Inline pressure gauge? If so, where in the lines are you reading the pressures? Did you bench bleed the components before you installed and re-bleed the entire system after installation? Are you getting a parking brake light at any point when you apply pedal pressure? From time to time, I've seen systems that are not completely bled (bench bled first) have air pockets in them that cause the brakes to have problems without a spongy pedal. If you're getting good readings with a direct pressure gauge right before the calipers, then your prop valve should be good. Might be in the calipers. If you're not getting good readings at the calipers then it has to be the prop valve. Also, what kit is this? Standard disc or "big" brakes? I know you said they told you that was a good pressure, but maybe they were thinkin of the wrong kit. I know what kit you have (rotor size and caliper type) has a lot to do with pressure required. It's possible that your using the wrong prop valve as well. The standard gm disc/drum prop valve doesn't allow the right pressure to the front for some of these disc conversion kits. I would suggest running a good adjustable prop valve from wilwood or something. They'll save you a little dough as well cause they're about half the cost of the fixed pressure repro's. I wish you the best of luck with this one. Brakes can be tough to diagnose sometimes because they're not so complicated and people tend to overcontemplate. Remember that the first rule of hydraulic troubleshooting is that the first component that can be the problem usually is the problem


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## 66problem (Oct 25, 2010)

im taking my readings right at the calipers and drums. the kit uses a 11 inch rotor and gm single piston calipers. it is the only kit that will fit on the stock 14inch wheels. and for now i took out the prob valve from the system and have full preasure running to the front and rear brakes. the car stops a lot better. im going to try to put a new set of rotors on it because it is the only parts that i have not replaced yet. im keeping my fingers crossed and loosing sleep over this car.


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## jetstang (Nov 5, 2008)

I had rebuilt the brakes on my 70, new calipers, slotted/drilled rotors, new lines and all. It pulled hard right and didn't stop-heavy pedal. Then I swapped out the master cylinder and booster with new AC Delco products, now the brakes will put you on your head! I also thought it was pad compound that was the issue. I also had swapped calipers thinking they were sticking. I would bleed the brakes again and check/swap the brake booster, also may be a defective master cylinder.


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## 66tempestGT (Nov 28, 2009)

when you are checking the pressure are you lightly touching the pedal like you would while driving or are you standing on it harder. ordinary driving you dont apply much pressure to the pedal.


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## Backup (Oct 16, 2010)

66problem said:


> im taking my readings right at the calipers and drums. the kit uses a 11 inch rotor and gm single piston calipers. it is the only kit that will fit on the stock 14inch wheels. and for now i took out the prob valve from the system and have full preasure running to the front and rear brakes. the car stops a lot better. im going to try to put a new set of rotors on it because it is the only parts that i have not replaced yet. im keeping my fingers crossed and loosing sleep over this car.


 Judging by this info, it sounds like a pad and disc problem. If you took the prop valve out and it stopped better its most likely because you're getting a higher pressure to the drums and they're doing more of the work, as long as you're getting the same readings at the calipers now as you did before you took out the prop valve. If you're getting higher pressure now, then the prop valve was the problem (not set right). 
You said you're getting good pressure all the way down at the calipers so the system should be working fine to that point. Even if they're new calipers the pad friction may not be high enough. I believe you said you had the rotors cut, so there shouldn't be any issues with some type of compound on the surface. It sounds like a different pad compound would help, but I still think the main problem was with the prop valve.


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## Wob (Dec 2, 2010)

Did you ever figure out the problem?


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## Chris Holabaugh (Jan 18, 2009)

I put SSBC power brakes on the front of my 65 GTO and we are having problems with them also. The power side is not working at all, the peddle is hard as a rock. I have a large cam so I am only putting out 15 inches of vacuum and when we talk to them they said you need 18 inches, but the 15 should produce enough to make them work. The whole system was completely redone this past summer. The last thing we tired was to manually pump up the brakes and the system would not hold vacuum, so the next thing we are looking at is the vacuum canister. I had to use the small canister because of the size of my value covers.


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## 646904GTO (Feb 10, 2008)

I have SSBC disc brakes on all four corners of my '64. My pedal is hard and the car is very hard to stop. I thought it was a vacuum issue at first, then proportioning valve. I replaced the valve twice, last one coming off another system that worked. I had similar pressure readings at the gauge on the valve. I also installed a vacuum pump. You know what? I have a new set of GM stockers and am going to swap them out. At least it will stop, after all these cars have no anti-lock brakes so if you get on them hard enough they just gotta lock up..nope won't do it and they don't STOP THE CAR! I have had enough, they are coming off! 
BTW when one contacts SSBC about issues; instantly you are wrong and you must be doing something wrong..isn't the customer always right? enough!


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## 66tempestGT (Nov 28, 2009)

ive seen similar issues on other sights. i would be interested to know if anybody has solved them.


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## Eric Animal (Oct 28, 2007)

I was told to go with Wilwood. So I am. I'm not bad mouthing anyone....just saying......PLEASE post the cure when you find it so we have it for the "data bank"........:confused


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## BearGFR (Aug 25, 2008)

Could it possibly be an issue with the bedding procedure for the pads/rotors? I'm going with Wilwood too, and they came with a documented process for bedding that I intend to follow religiously once I get the car driveable.

Bear


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## Instg8ter (Sep 28, 2010)

would be interested in seeing the braking comparison of the aftermarket conversions vs. 68-72 GM stock w/ceramic pads and drilled rotors (both working correctly of course), wondering if the few extra feet is worth the extra 1200-1500 dollars? GM calipers look nice painted up too


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## jetstang (Nov 5, 2008)

I did the brakes on my Astro van today. No issues with bad rotors or drums. I replaced the front brakes, test drive, no better. Inspected the rears, getting close, so replaced the shoes. BACKED off the ebrake cable to ensure I got all adjustment in the drums. Replaced shoes, hardware kit, and greased everything, adjusted brakes, then tensioned E brake to get 5 clicks or so. One wheel was locked up, readjusted both rears so they both had slight drag. Test drove, and the brakes are incredible, first time the thing stops since I've owned it, over a year:cheers.. I thought I had a bad hydroboost, but it was just worn, improperly adjusted brakes and E brake..
Just an example of attention to detail..


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## Jeff's Classics (Feb 24, 2010)

Instg8ter said:


> would be interested in seeing the braking comparison of the aftermarket conversions vs. 68-72 GM stock w/ceramic pads and drilled rotors (both working correctly of course), wondering if the few extra feet is worth the extra 1200-1500 dollars? GM calipers look nice painted up too


I can post regarding Baer Brakes...I installed their SS4 front disk brake kit and just did the first drive last week. It uses 11" rotors and fits under my 15" Cragar mags. Planning to test-fit some 15" Pontiac Rally IIs in the near future. Left the stock rear drums because I don't think rear disks are necessary or worth the cost/effort.
The Baer kit installs quickly and easily, and has everything needed, including good instructions. Their recommendation is to drive ~300 miles easy to break in the rotors/pads before bedding them, and I've only got ~100 miles. Car stops straight as an arrow with no hands on the wheel (big improvement over drums). I would like to use less pedal effort, but the smaller diameter master cylinder on my car is supposed to provide better "feel". I may swap out the old booster and/or MC to be sure both are fully operational, the booster looks really old.
I will report back on performance once the kit is broken in and pads bedded. So far it's better than the drums, but I would like to see shorter stopping distances once broken in.
Jeff


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## Wob (Dec 2, 2010)

Does anyone make a conversion for drum wheels other than SSBC though? I have a new set of 15" drum steelies with dog dishes and I would hate to have to get rid of them to upgrade.



BearGFR said:


> Could it possibly be an issue with the bedding procedure for the pads/rotors? I'm going with Wilwood too, and they came with a documented process for bedding that I intend to follow religiously once I get the car driveable.
> 
> Bear


Pads make a huge difference in braking ability, but it would not explain the heavy pedal effort, only elongated distances in stopping. This sounds like engineering problems in the booster and proportioning. 



Instg8ter said:


> would be interested in seeing the braking comparison of the aftermarket conversions vs. 68-72 GM stock w/ceramic pads and drilled rotors (both working correctly of course), wondering if the few extra feet is worth the extra 1200-1500 dollars? GM calipers look nice painted up too


Here is something to keep in mind with brakes.
Not necessarily does...
1 - Bigger equal better braking
2 - Cross Drilled or slotted equal better braking
3 - Carbon ceramic, exotic alloys etc equal better braking
(outside of racing...)

Now its not to say they can not influence, but standalone, not necessarily. 
Pads can certainly influence pedal feel and braking distances though. Compounds can influence cold and hot braking temps for sure. The average driver (both in car terms and the individual) will never utilize the true braking abilities of even stock setups. Tires in fact play a much bigger role in braking distance than rotor size, # of pistons and pad compounds. This is why you often don't see big differences in distances in the aftermarket vs. stock comparisons. 

Let's break it down. Braking systems simply dissipate friction in exchange for heat. Brakes ability to scrub heat very much influences braking distances. But most stock brakes do not generate the heat in regular use to start overheat. Now, coming back to that in moment, let's review the different type of rotors. Solid steel brakes are often used on low heat applications. I.E., rear brakes on a small car. Vented steel is more than substantial standard for most cars front and back. Steel slotted rotors are designed to literally scrap clean the pads on an application which will play in areas of very high heat which could compromise the pad surface. These heat levels are generally MUCH higher than any reasonable driver will see. And due to the design a slotted rotor will wear through pads at an accelerated pace. The other potential benefits of a slotted rotor are in some braking applications the pads can outgas, in which a slotted rotor can help (a rare occurrence), they can channel some water away from the pad and rotor (helpful is VERY wet conditions, but generally overkill since brake heat itself is often enough to keep the brakes reasonably dry). Steel cross drilled were introduced as a different means of dissipating heat. However they have a few problems: 1) cross drilling naturally weakens the rotor 2) cross drilling accelerates pad wear. Cross drilled are often little more than a "gotta-have it" marketing maneuver. The disc undrilled is usually _oversized_ for the application since the drilling weakens the disc. It is not uncommon to create fractures alongside the holes in race conditions. Beneficially, they can lower unsprung rotating mass (less unsprung weight, the better the shocks can control the suspension. Also easier on bumps due to this and can marginally help acceleration and braking.) Often the liveliness of a sports car can restored or slightly gained with a lighter setup. In a relatively stock form A-body, it would likely go unnoticed. Now conversely, in sports cars lighter is better and better heat dissipation is as well. Carbon/Carbon (supppper rare) and carbon composites (getting less rare) are fantastic heat sinks, but again, generally MASSIVE overkill for anything that does not see dedicated track service. 

So pads play a role in the heat dissipation as well. Some pads require more heat to "bite". Others less. Race pads are often pretty scary on the street as their operating temperature is considerably higher than a cruiser will ever see. Stock replacement heat range pads (organic, semi-met, etc do quite a good job for non-racing applications. Higher friction pads _can_ grip a rotor with more "bite". For example: an organic pad can bite hard with low effort, but dont dissipate heat well. A semi-met can dissipate higher heat well but have higher pedal effort and have less "bite". Other compounds can change "bite", wear, noise, dust, heat characteristics, etc. This is one of the biggest areas if you want to shorten braking distances to spend time experimenting. Thankfully its the cheapest too.

The caliper: Lighter is great similarly in rationale to the rotor (although unsprung, it is not rotating - duh). BUT, will would at best effect braking or acceleration in the lowww %'s. It could improve some handling characteristics from a drastic lose in weight in some (not stock or mild A-body applications). Aluminum calipers can help dissipate heat better and multiple pistons can help better spread pad pressure and alleviate hot spots and cope with some rotor/pad imperfections. Again, really only relevant in race applications or aggressive motorsports. 

Brake fluid is often overlooked factor by racers, but since the fluid is hygroscopic, over time, boiling point is lower by its absorption of water in the air. Its why you see wet and dry boiling point on fluid. Now again, a wet point is still WAY less than a driver will see on the street. Old fluid can lead to a less confident pedal as well.

So getting back to my point about heat a while back. You will not see the temps on the street that will warrant 90% of the "high end" braking systems. Pads are the key in combination with tires. The things I look for are how does the pad bite? Is it linear? Does it maintain its integrity over time? Over repeated hard stops? Next I look at wear and noise. And all of the friction in the world is not helpful if you can just locking up brakes and sliding. GOOD tires not only improve braking distance, but they improve ride, handling, comfort, noise and wet handling. The "idiots" guide to brakes IMO? If you can't lock your wheels up, play around with your pad compounds. If you aren't seeing high speeds and are a cruiser, play around with some organics. If you are a high way cruiser, maybe a semi-met. Find something that feels good and can lock it up. Then play with your tires, find something that fits the characteristics you want. Grip is your friend. Now this is a simplified version, but locking up brakes doesnt mean you are braking well as mentioned. And high grip doesnt mean it either. You need to find the right balance. So in my humble opinion, Wilwoods for your stock to even low-medium tune GTO is likely massive overkill. There are LOADS of people that will swear that they switched and its light years better, etc. And it probably is (although often its lightened wallet syndrome), but its likely from fresh good pads, new fluid and sometimes a better proportioning setup. Remember manufacs tend highly bias to the front to avoid some sketchy emergency braking from their avg drivers. Playing with bias as well as suspension settings can yield gains too (exchanging weight transfer, etc). 

This is from my 10+ years in racing. I'm not an expert by any means, so if there are any brake engineers, please jump in and feel to correct any of my ramble! I stand by my rulings as do many other racers which seeing braking systems the same way. My 2200lb turbo MX-5 with 350hp runs little more than stock steel rotors and a set of race pads and high temp fluid. I have yet to overheat them. Enough to put more than a few trophies in my case too. Even the engineers I have spoken to at Lamborghini over the years have admit that the stock steel setup on their Gallardos is more than adequate for even heavy track use (in comparison to the carbon setup). 

Tires and pads my friends, save your money on anything less than a semi+ dedicated road course car. 

Whew, sorry for the new member ramble. Hopefully helpful though. 

Rob


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## Jeff's Classics (Feb 24, 2010)

Wob said:


> Does anyone make a conversion for drum wheels other than SSBC though? I have a new set of 15" drum steelies with dog dishes and I would hate to have to get rid of them to upgrade.
> 
> 
> Rob


Baer Brakes and Wilwood make kits, and also there are several kits available based on stock-style systems, some of which include new spindles. The Baer kit used the stock drum spindles. You may need to run thin wheel spacers if your wheels were originally designed for use with drums only, and you go with Baer or stock-style 4-piston calipers.

Jeff


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## Instg8ter (Sep 28, 2010)

Wob said:


> Does anyone make a conversion for drum wheels other than SSBC though? I have a new set of 15" drum steelies with dog dishes and I would hate to have to get rid of them to upgrade.
> 
> 
> 
> ...


Thanks Wob, very informative and it's consistent with what i have been told by a few engineers. i have better ways to spend the extra grand (motor), beside brakes just slow you down


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## 66tempestGT (Nov 28, 2009)

:agree :cheers


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## jetstang (Nov 5, 2008)

jetstang said:


> I did the brakes on my Astro van today. No issues with bad rotors or drums. I replaced the front brakes, test drive, no better. Inspected the rears, getting close, so replaced the shoes. BACKED off the ebrake cable to ensure I got all adjustment in the drums. Replaced shoes, hardware kit, and greased everything, adjusted brakes, then tensioned E brake to get 5 clicks or so. One wheel was locked up, readjusted both rears so they both had slight drag. Test drove, and the brakes are incredible, first time the thing stops since I've owned it, over a year:cheers.. I thought I had a bad hydroboost, but it was just worn, improperly adjusted brakes and E brake..
> Just an example of attention to detail..


And the next morning, 10 miles out of town and my left rear was ROLLING smoke! I adjusted the rears tight, instead of letting the self adjusters take care of business. I backed off the adjustment and the ebrake and brakes are fine.. Then backed it around a parking lot to get the adjustment back and all is good. I haven't readjusted the parking brake as I'm still a little gun shy, lol..:rofl::rofl:

Very well put Wob, I replaced everything on my 70 with stock new components with slotted rotors for bling and the brakes will put you on your head.


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## Wob (Dec 2, 2010)

Jeff's Classics said:


> Baer Brakes and Wilwood make kits, and also there are several kits available based on stock-style systems, some of which include new spindles. The Baer kit used the stock drum spindles. You may need to run thin wheel spacers if your wheels were originally designed for use with drums only, and you go with Baer or stock-style 4-piston calipers.
> 
> Jeff


Thanks Jeff. I looked at the Serious Street setup from Baer, but its more brake than I need. If its just a caliper issue, I could be persuaded to get just calipers and brackets, but I dont think Baer splits up their packages. 

The Wilwood Forged Dynalite Pro Series Front Brake Kit isnt a bad setup although again a little over kill and a bit cheaper. Seems like you need to mod the spindles and I still will need to get MC, booster and lines. 

What are other "stock-style" setups you mentioned? I was perfectly happy going with an OPGI setup with spindles, booster, MC, plain discs, brackets etc if it would fit my wheels. I have a lot of tire on my car now (really for style only - just a 46 year old daily driver lol) so spacing it would be interesting. Some SMALL spacers maybe. 



Instg8ter said:


> Thanks Wob, very informative and it's consistent with what i have been told by a few engineers. i have better ways to spend the extra grand (motor), beside brakes just slow you down





66tempestGT said:


> :agree :cheers





jetstang said:


> And the next morning, 10 miles out of town and my left rear was ROLLING smoke! I adjusted the rears tight, instead of letting the self adjusters take care of business. I backed off the adjustment and the ebrake and brakes are fine.. Then backed it around a parking lot to get the adjustment back and all is good. I haven't readjusted the parking brake as I'm still a little gun shy, lol..:rofl::rofl:
> 
> Very well put Wob, I replaced everything on my 70 with stock new components with slotted rotors for bling and the brakes will put you on your head.


:cool


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## xkeots (May 16, 2009)

66problem said:


> I have a 1967 gto in our shop that came in for a front power disc brake conversion. Was manual drums to start. SSBC kit part number A123-23. After installing the kit and going to a test drive the car would not stop itself. I contacted ssbc and they said to go with a smaller bore master cylinder to increase line pressure. I now have 1300 psi at the front brakes and 600psi at the rear brakes numbers that ssbc is happy with. The car still will not stop like it should. Every brake part on the car is new from the booster to the pads and shoes. Have tried three different types of pads and got the rotors cut and still the same thing car slows down but doesnt stop like it should. if anybody has any helpful information please share. this car is going to be the end of me!!!!


I have the same kit that I bought from OPGI to fit in my stock 14" rally rims. It came with a CCP proportioning valve. I have re bled the system, took the master out again as SSBC recommended and re bench bled it. I bought the centering tool from CCP for the proportioning valve to keep it centered while bleeding and after I sent the car out to a shop last week. They can't get the brakes to stop correctly either. I am getting 19 lbs of vacuum to the booster. Has anyone come up with a fix for this system? I call SSBC and I keep getting the same BS answers but they give the wrong answer over and over. I spent a lot of money for this and I want it to work correctly.
Thanks
Jax
67 GTO


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