Curious about Bendix Brake Booster "pedal feel"

[c9zx]

I hope it helps a bit. The gauge can be fabricated from sheet metal and some metal work. I've made several over the years. Kind of a PITA but, it shortens the process of getting the pushrod length right. Chuck

 

[Stanglover]

I hope it helps a bit. The gauge can be fabricated from sheet metal and some metal work. I've made several over the years. Kind of a PITA but, it shortens the process of getting the pushrod length right. Chuck

I had planned on trying it out today, but it's pissing with rain here today, but tomorrow for sure. To be honest, I'm not too worried about the -.015" I seem to have mistakenly put in to the push rod length. If it were a 1/16" I'd be much more concerned and redo the job correctly. I'll let you know if it has made any difference.

Actually, now I'm curious. I may still have the instruction sheet I got with the booster, m/c and SSBC brake kit. I tend to keep that stuff....., but not always.

Well, no cigar! found everything else, but not the instruction sheets for the booster or m/c.  Oh well. anybody reading this will now know to set the push rod to m/c between zero clearance to NO MORE THAN .015" movement on the m/c piston as the  '71 Ford manual describes. Section 12-01-04, subsection 3, Adjustments.

 

[Stanglover]

Update. So, I adjusted the push rod length slightly as mentioned before and noticed no difference. The brakes are adequate, but that's about all. The booster holds vacuum and the check valve works with the 'suck/blow' test, so I guess it's good, just not what I'd originally hoped for when I added it.

The end.

 

[73pony]

I guess it kind of depends on what you are comparing it to. My pedal feel is harder for sure than my wife's Volvo, but it very similar in feel to my Audi. It is firm but stops great. It is an original front disc brake care running original master (rebuilt) and original booster. Front Discs have been upgraded to 4 piston wilwoods with drums still out back. That upgrade did not effect pedal feel only how well it stopped. 

 

[Bill73Ragtop]

I installed the SSBC front drum to disc on my 69 vert back in 2005.  It has never performed or felt close to what the stock 73 disc system provided.

I did all that you have done in the past decade - changed all flex lines to braided stainless, changed booster, rebuilt distribution block,  changed MC and it still has a hard pedal which feels more like manual than power.  All vacuum tests indicate everything working as it should.  Brake line pressure is over 1500 psi at the calipers and 800 psi at the rear drums.  Tried a new set of SSBC brake pads (which are organic)  and a new set of LEED semi -metallic pads - neither provided any kind of bite that felt adequate.   Last month I installed EBC green pads which improved the stopping enough to justify the cost.  I only have 20 miles on the EBC pads, so as they continue to bed in for the next 100 or so miles they might provide a bit more bite.

At this point I have thoughts that maybe the pedal that came with the SSBC kit had the fulcrum point a bit off but that's a issue for another day.   With SSBC gone, not much recourse available there.   LEED will work with you, but they will want brake line pressure data before anything else.

I use a small BB size ball of plumber's putty and a strip of saran wrap to measure the air gap at the adjusting rod and MC piston.  Insert the 3/8" wide strip of saran wrap (cut to fit into the bore with ends hanging out), drop in the putty and fit the MC to the booster. It's a pain, but I will  run down & lightly snug the nuts to ensure the MC is solidly in place.  Remove, pull out the squished ball of putty and measure the thickness.  I usually cut it in half with razor blade to get a better profile measurement.  As mentioned, you want the tiny bit of air gap so system is not under pressure when pedal is released.

Wish I could tell you the solution, but in my experience, most SSBC systems in vintage mustangs had the same issue of not feeling like power assisted systems should.  My local shop guy installed  four of these SSBC setups on 65, 67, 69 and 70 cars with similar results....somewhat adequate, but not what you wish.   I would love to try Wilwood or similar, but cost to replace all stock wheels/ tires puts that on the 'if I win the lottery' shelf.

 

[Stanglover]

I installed the SSBC front drum to disc on my 69 vert back in 2005.  It has never performed or felt close to what the stock 73 disc system provided.

I did all that you have done in the past decade - changed all flex lines to braided stainless, changed booster, rebuilt distribution block,  changed MC and it still has a hard pedal which feels more like manual than power.  All vacuum tests indicate everything working as it should.  Brake line pressure is over 1500 psi at the calipers and 800 psi at the rear drums.  Tried a new set of SSBC brake pads (which are organic)  and a new set of LEED semi -metallic pads - neither provided any kind of bite that felt adequate.   Last month I installed EBC green pads which improved the stopping enough to justify the cost.  I only have 20 miles on the EBC pads, so as they continue to bed in for the next 100 or so miles they might provide a bit more bite.

At this point I have thoughts that maybe the pedal that came with the SSBC kit had the fulcrum point a bit off but that's a issue for another day.   With SSBC gone, not much recourse available there.   LEED will work with you, but they will want brake line pressure data before anything else.

I use a small BB size ball of plumber's putty and a strip of saran wrap to measure the air gap at the adjusting rod and MC piston.  Insert the 3/8" wide strip of saran wrap (cut to fit into the bore with ends hanging out), drop in the putty and fit the MC to the booster. It's a pain, but I will  run down & lightly snug the nuts to ensure the MC is solidly in place.  Remove, pull out the squished ball of putty and measure the thickness.  I usually cut it in half with razor blade to get a better profile measurement.  As mentioned, you want the tiny bit of air gap so system is not under pressure when pedal is released.

Wish I could tell you the solution, but in my experience, most SSBC systems in vintage mustangs had the same issue of not feeling like power assisted systems should.  My local shop guy installed  four of these SSBC setups on 65, 67, 69 and 70 cars with similar results....somewhat adequate, but not what you wish.   I would love to try Wilwood or similar, but cost to replace all stock wheels/ tires puts that on the 'if I win the lottery' shelf.

Bill, that was a very useful reply, thanks. 

1) Brake pressure, how do you measure that, is there a gauge I can buy to test? I'm sure there pressure will be good, but well worth checking.

2) Pads, interesting. My pads have been on the car for 12 years now and likely due for a change anyway. I'll check out the EBC pads that you used.

3) Air gap on the  push rod-m/c , so I'm not wrong as I did the same thing. This is despite the Ford manual clearly stating zero gap to a max of  +.015"  on the m/c piston.

4) The SSBC brakes were really a remake of the Kelsey-Hayes brakes from years earlier. They may simply have duplicated bad performance problems, hence the bad feel on the pedal. I too chose these because of wheel size, 14", and the fact they were a direct replacement as well as being cost effective. I did not know SSBC were gone, surprising!

5) Pedal pin location. In my case, I also bought Mustang Steve's clutch bearing kit, which also contained the push rod pin and location dimensions. I checked this alignment before welding the pin in to the original pedal arm, pic posted earlier. 

So, it seems to be typical of these brakes, hard pedal feel and only just adequate braking. I guess the easiest fix is to allow waaay more room for stopping and just hope never to have to panic stop.

Thanks,

Geoff.

EDIT: which pads did you get and am I right in thinking they were for the SSBC same as mine? That's the way I read it, but may have misunderstood. 

 

[c9zx]

As Bill73ragtop mentioned, changing to a semi-metallic pad may improve initial bite and be more fade resistant. I don't know who makes them for the calipers you have but you might check APC/Centric/C Tek, Performance Friction, Raybestos. Chuck

 

[Stanglover]

As Bill73ragtop mentioned, changing to a semi-metallic pad may improve initial bite and be more fade resistant. I don't know who makes them for the calipers you have but you might check APC/Centric/C Tek, Performance Friction, Raybestos. Chuck

 Thanks Chuck,  I'll check into suppliers. As the original SSBC pads are getting down, I certainly do need to be looking to possibly better pads in the near future.

 

[mjlan]

Geoff-

Can you elaborate on the 'pedal feel' complaint?

If I had to guess I would start playing with your pedal ratio. The conversion to vacuum assist should have increased the MC bore dia. in concert with a move to the pin on the pedal to take advantage of the vacuum assist to the pressure from your foot.

Sorry if I missed this in the above posts!

-Matt

 

[Carolina_Mountain_Mustangs]

Just found this topic and can add a couple things. For some reason the 1971 master cylinder is different from 72 & 73. It is 1" dia. and 72 & 73 is 15/16" for power disc brakes. The 72 & 73 with drum brakes have a 1" dia. piston. 
BTW Booster Dewey does not exist anymore. He retired and on of his employees took over the business. I sent them a booster last year to rebuild and the cost to ship out and back plus the rebuild was crazy. If you go to parts house they list having them but if you try to order they are always out of stock. 
So I decided I would figure out a way to take the crimps out of the booster can and open one up to see what was inside. I made a fixture to hold the can and I pry the crimps open. Some will always break the material was stretched. Some broke on the one Booster Dewey did. 
Inside the booster not much to see. You have a huge cone shaped spring the rubber diaphragm and a Bakelite molded disc that holds the center of the rubber. There is a seal for the rod and also a dust filter of sorts, felt.
Since it was so simple inside I decided to go looking for a rebuild kit and soon found out that all the Mustang and Ford supply houses stop at 1970. I kept digging and took about a year and half and I located all of the components and ordered some, pic attached. 
So for me to be able to rebuild them I will need to add to my fixture some so that i can add a screw press to hold the can together while the crimps are pushed back in. I have too many projects going right now with mowing grass, garden and working on my 72 Q vert trying to get into paint before cold weather. So booster rebuild I have put on the back burner. 
I did pick up one core from one of the members and will tear down and put in molasses tank to take the rust off. One of the things I do not like is pretty much every booster is really rusty especially on the bottom half due to leaking brake fluid from the master cylinder. That is also what takes out the booster the brake fluid going into the booster. I do have a blast cabinet but I hate standing there. Once the molasses has taken the rust off I would phosphate then fill the rust pits in and sand smooth. That will be the big time consuming part. 
So for someone to do their own you have to invest some time and money into making a fixture to take them apart and also put them back together. I was going to test using my AC vacuum pump. I tried using a brake bleeder hand pump on the one booster Dewey did but could not get a vacuum at all. I called them and expressed concern and he assured me it had been tested and was good.

I have been driving my 73 vert with a bad booster for years, lol. You can slide the tires but you do have to stand on the pedal. It is like stated a real pain to take the booster off. I put my 73 Mach 1 on the two post lift and raised it up some and stood on the floor outside the car. With the crushed disc in my neck I cannot get under the dash so good.

 

[mjlan]

Geoff-

I forgot you asked about brake pressure:

https://www.summitracing.com/parts/leb-bpg001?rrec=true

Threads into the bleeder port, may need a hose to allow the gauge to clear things.

This would give you some insight into what the calipers and wheel cylinders (still rear drums?) are seeing for pressure.

-Matt

 

[Stanglover]

Geoff-

I forgot you asked about brake pressure:

https://www.summitracing.com/parts/leb-bpg001?rrec=true

Threads into the bleeder port, may need a hose to allow the gauge to clear things.

This would give you some insight into what the calipers and wheel cylinders (still rear drums?) are seeing for pressure.

-Matt

Thanks, I'll check that out for sure.  

While I don't think that I'll improve pedal feel with the set up I currently have, I may be able to improve braking quality. Stopping is more important than "feel' !

Again many thanks to all who have supplied valuable input. I'm sure it will serve to help others.

Geoff.

 

[Bill73Ragtop]

Bill, that was a very useful reply, thanks. 

1) Brake pressure, how do you measure that, is there a gauge I can buy to test? I'm sure there pressure will be good, but well worth checking.

2) Pads, interesting. My pads have been on the car for 12 years now and likely due for a change anyway. I'll check out the EBC pads that you used.

3) Air gap on the  push rod-m/c , so I'm not wrong as I did the same thing. This is despite the Ford manual clearly stating zero gap to a max of  +.015"  on the m/c piston.

4) The SSBC brakes were really a remake of the Kelsey-Hayes brakes from years earlier. They may simply have duplicated bad performance problems, hence the bad feel on the pedal. I too chose these because of wheel size, 14", and the fact they were a direct replacement as well as being cost effective. I did not know SSBC were gone, surprising!

5) Pedal pin location. In my case, I also bought Mustang Steve's clutch bearing kit, which also contained the push rod pin and location dimensions. I checked this alignment before welding the pin in to the original pedal arm, pic posted earlier. 

So, it seems to be typical of these brakes, hard pedal feel and only just adequate braking. I guess the easiest fix is to allow waaay more room for stopping and just hope never to have to panic stop.

Thanks,

Geoff.

EDIT: which pads did you get and am I right in thinking they were for the SSBC same as mine? That's the way I read it, but may have misunderstood. 

Hi Geoff:

1) LEED sells a brake line pressure gauge set, pretty much the same as what Summit sells  https://leedbrakes.com/i-23439488-brake-pressure-gauge-kit.html

It measures up to 3000psi so it's kinda of a 'one-time' use and into the drawer thing.

2)I got the semi-metallic pads from LEED back in April.  Did not make much difference from the barely used SSBC organic pads.  My rotors are still in very good condition (machine marks still evident) so I scuffed them with red prep pads to remove any light glaze that may have been present to ensure I was not having issues due to glaze.

EBC 'Green Stuff' pads are from Summit. https://www.summitracing.com/parts/ebc-dp21157/year/1967/make/ford/model/mustang

Use 1967 FORD MUSTANG EBC Greenstuff 2000 Series Passenger Car Organic Brake Pads DP21157.  They fit perfectly in the calipers.  I also used the EBC Green pads in my 1973 mustang convertible for years and they were worth the cost for the increase performance in braking.

3) .015" is just a sliver of space. I've always been schooled that unless you can measure zero pressure for zero gap, a tiny space is the way to go.  I'm probably at .010.  Pedal travel is maybe 1/2" before you can feel system engaging.  Zero brake drag after driving / engaging brakes (car rolls easily)

4) SSBC (they were local for me) closed up shop last year without much notice.  LEED (also local for me) seems to have taken up the business SSBC used to have.  Actually LEED used to supply SSBC with most of their stock.

If I ever figure out how to make them feel and perform as well as the factory, I'll post it.  If I stand on the brake pedal, the car stops well, but its more pressure than what I would normally expect with power assist booster.

Bill

 

[Stanglover]

Hi Geoff:

1) LEED sells a brake line pressure gauge set, pretty much the same as what Summit sells  https://leedbrakes.com/i-23439488-brake-pressure-gauge-kit.html

It measures up to 3000psi so it's kinda of a 'one-time' use and into the drawer thing.

2)I got the semi-metallic pads from LEED back in April.  Did not make much difference from the barely used SSBC organic pads.  My rotors are still in very good condition (machine marks still evident) so I scuffed them with red prep pads to remove any light glaze that may have been present to ensure I was not having issues due to glaze.

EBC 'Green Stuff' pads are from Summit. https://www.summitracing.com/parts/ebc-dp21157/year/1967/make/ford/model/mustang

Use 1967 FORD MUSTANG EBC Greenstuff 2000 Series Passenger Car Organic Brake Pads DP21157.  They fit perfectly in the calipers.  I also used the EBC Green pads in my 1973 mustang convertible for years and they were worth the cost for the increase performance in braking.

3) .015" is just a sliver of space. I've always been schooled that unless you can measure zero pressure for zero gap, a tiny space is the way to go.  I'm probably at .010.  Pedal travel is maybe 1/2" before you can feel system engaging.  Zero brake drag after driving / engaging brakes (car rolls easily)

4) SSBC (they were local for me) closed up shop last year without much notice.  LEED (also local for me) seems to have taken up the business SSBC used to have.  Actually LEED used to supply SSBC with most of their stock.

If I ever figure out how to make them feel and perform as well as the factory, I'll post it.  If I stand on the brake pedal, the car stops well, but its more pressure than what I would normally expect with power assist booster.

Bill

Hi Bill. Thanks for that valuable info. On the space between the push rod and m/c piston, I'm totally in agreement with you. I'm positive I read that there was a recommended space of .015", so I guess my mind isn't as bad as I was starting to wonder. In my years of prototyping, I used the plasticine 'trick' a million times to gauges clearances (well, maybe not a million, but....).

As for the pressure gauge and pads, I would like to find a Canadian supplier as exchange and international shipping are a killer right now, so I may have to wait for a while. 

Again many thanks, I really appreciate your experience and input.

Geoff.

I would definitely say my brakes are about the same as yours with maybe a tad less travel before engagement. 

 

[Bentworker]

I’m curious how much of the “take up” travel has to do with the master cylinder itself.

There might be something to the Mustang Steve modern master cylinder swap.

http://www.mustangandfords.com/features/1906-vintage-mustang-tech-questions-answers

 

[Stanglover]

I’m curious how much of the “take up” travel has to do with the master cylinder itself.

There might be something to the Mustang Steve modern master cylinder swap.

http://www.mustangandfords.com/features/1906-vintage-mustang-tech-questions-answers

Thanks, I just saw this post today, I didn't see it in "Content". I may contact Mustang Steve and ask for advice or tips, but I would absolutely like to keep the stock appearing m/c. Maybe I need to switch to a 1" bore instead of the 15/16" I know is on there.

 

[Stanglover]

For us Canadians, I found a supplier of Leed Brakes and EBC brake pads in London Ontario. I followed up on a reply from Bill73ragtop and contacted Leed Brakes about the pressure gauge kit. They refered me to [email protected]. or http://www.performanceunlimited.ca/

Currently the EBC pads are out of stock, but they do have the pressure gauge it listed under an SSBC number, A1704 at $58.99 + shipping.

The Green Stuff pads are $196.00 cad.

Hope that may help someone else.

 

[Stanglover]

Hi Geoff:

EBC 'Green Stuff' pads are from Summit. https://www.summitracing.com/parts/ebc-dp21157/year/1967/make/ford/model/mustang

Use 1967 FORD MUSTANG EBC Greenstuff 2000 Series Passenger Car Organic Brake Pads DP21157.  They fit perfectly in the calipers.  I also used the EBC Green pads in my 1973 mustang convertible for years and they were worth the cost for the increase performance in braking.

 Hi Bill, Just to confirm we are talking apples to apples, I took a pad out of an SSBC 4 piston caliper to measure and photograph it. From your memory, do these equate to the EBC DP21157 you bought? At 196 bucks (Cad) as set, I'd hate to find they don't fit my calipers.

Thanks in advance.

Geoff.

 

[Bill73Ragtop]

Geoff:  The EBC pads were a perfect match to the SSBC (and LEED semi-met) pads. They are a precise fit into the calipers.  That's quite the markup in price from here in the states.   Base cost here is $124 plus tax to +/- $130 US.

I'll  send you a PM, but I could ship you the LEED s-m pads if you want to try them.  Since its across the boarder it may take some time to get to you.

 

[Stanglover]

Geoff:  The EBC pads were a perfect match to the SSBC (and LEED semi-met) pads. They are a precise fit into the calipers.  That's quite the markup in price from here in the states.   Base cost here is $124 plus tax to +/- $130 US.

I'll  send you a PM, but I could ship you the LEED s-m pads if you want to try them.  Since its across the boarder it may take some time to get to you.

Bill, thanks. I did get and reply to the PM.

As I said in the PM, good to know EBC and Leed are the same as SSBC pads. That may be very useful info for others with the same brakes.

As for mark up, at the approx current exchange rate, they would be about $175 Cad plus 13% tax and shipping, so blows a hole in 250 bucks, but I'm willing to give them a try. Heck, I've dropped more in a bar before.... (strip bar)!!