New brakes , still have poor braking power

[jacksonfdny]

I've had almost everything replaced but still have poor braking power and not able to lock up brakes on my 67.5
New Nissan pistons ( all 4 ) along with new pads . Rotor's are in good shape with no glazing
Rear shoes replaced with new Nissan shoes , drums are good with no glazing . Brake cylinders work as they should
Brake fluid competently drained and replaced with new fluid . Bled all brakes numerous times . Brake pedal nice and firm and correct height
All work done by a Master Mechanic at his shop that does a lot of work on high performance cars both race and vintage cars . This is also a car that was built by Mike Young so i believe all work was done correctly .
Should i be able to lock up my brakes ? i do have brand new tires all around I've read about different size master cylinders , would having the wrong size master cylinder give me blemished braking power

[Gregs672000]

I'm not an expert on brakes, but while it is not good to lock them up, you probably should be able to. What kind of thickness is there on the rotors? I believe part of my braking problems long ago was the rotor was just too thin to work well. Also, are the rears fully adjusted? If they are way out, that can cause problems. The should drag some (not a lot, but some). Does the car stop quickly?

[fj20spl311]

Do you have a firewall brace?
Can you see the cylinder move when applying the brakes?
Brake pad compound is very important to how much "bite" the brakes have.
Have you bedded the brake pads?
Rear brake adjustment is very important.

Better braking come from higher Cf pads, which can be hard to find for stock brakes.

[greydog]

I was thinking brace too as it seems like you've done everything else "right".
Braking on the roadsters has been often discussed. There's no power assist so it takes much more force than most are used to.
For example, my 300zx brakes are well modulated, a little pressure slows the car, more slows faster. It'll stand on it's nose before the ABS kicks in.
The VW's take less pressure and are not as easy to modulate.
I find both our roadsters to take much more pressure to stop quickly but with enough force, both will "brake skid".
Dan

[redroadster]

Newly turned rotors will not stop well
If the pads are free in the caliper
No hose problems , and sure there is no air in the cly ,do you get a good squirt of b fluid when bleeding or a weak squirt
Best to bench bleed the master again

[fj20spl311]

In EBC pads you can get yellowstuff pads for a 59 Jag XK150 that should be the correct pad.
Do your own research.

[jacksonfdny]

Thanks to all for your input . I will check to see if there is any movement of master cylinder when i apply the brake , i know there are no cracks in the firewall around the MC. Rear brakes have been adjusted and readjusted many times just to make sure .Rotors are within specs and are not newly turned . My mechanic says most of the vintage cars he has worked on with non assisted brakes are pretty much like my car . i think my brakes are pretty weak and have heard other members say you should be able to lock up your brakes and i can not . I've also read about different size MC being used and that can cause less braking power . How do i check to see if my MC is correct for my car ? I hope i can fix this so i can feel safe driving my car
Thanks again

[Alvin]

You should definitely be able to lock up the brakes with the stock setup. I would ping "bikermike" on the forum his spl has a well-sorted stock braking system and he might have a few suggestions

[bikermike]

In addition to the suggestions above...

Have you followed the bed-in procedure for the front pads?

Confirm the dimensions of the front pads. I have found new ones are often over spec and need to be sanded down around the periphery to fit the calipers. If not you have the likelihood that they get wedged and braking power may be diminished.
http://www.311s.org/phpBB3/viewtopic.ph ... ns#p255069

Front brake pad dimensions
47.5 x 16.7 x 53.98 mm (1.87 x 0.66 x 2.125 in.)

Was brake bleeding done in the correct sequence?
http://www.311s.org/phpBB3/viewtopic.ph ... ed#p214849

On LHD car:
1 rear driver
2 rear pass
3 front driver
4 front pass

This sequence is not intuitive for someone without specific experience on these cars.

What is the age of your hoses? Could they we swelling under pressure?

Hope that helps...

[Gregs672000]

I don't know of any other smaller masters that fit. I currently use the 510 master with larger front calipers (Toyota 4runner 4 piston) and RX7 rear discs without any problem (I had changed out the brake lines years ago so it fits without adapters). I had read that the 280z master was larger and might give a bit more pedal pressure so I bought one but will not install it until this winters overhaul.

Agree with proper bedding suggestions. If you want to, you can switch to the 280z master if you use adapters (in the wiki) and that should give you more pedal pressure. The masters are not expensive, might have the bleeders on the opposite side but if you're not worried about being ABSOLUTELY stock, that may be better for you.

[jacksonfdny]

Brake pads were worked to fit calipers correctly , these were Nissan pads . I assume there are better pads that i could use ???
There is no movement of MC when brake pressure applied
Will have car on a lift in a few days and i will check condition of my hoses for swelling
Bedding front pads was not done and car has been driven maybe 50 miles since then . After 50 miles did the adjust themselves ?
After rear shoes were replaced my car would pull to the right , we corrected this buy readjusting rear brakes a few times ( two more clicks on one side and backing off 1 click on the other side to make car stop in a straight line with out pulling . Weak braking before and after this readjusting of rear breaks

[FergO2k]

Sorry, missed this:
<< How do i check to see if my MC is correct for my car ? >>
The size of the bore (7/8 vs 15/16) is cast into the side of the master cylinder. From memory.... the 280Z is 7/8 and the roadster is.... 13/16? (slightly smaller) There is a relationship between volume of fluid displaced per stroke and the pedal vs shoe pressure. I have never been able to explain it clearly, but Phil Erickson has....
Since you had a reputable shop do the brakes change, I assume they got all the air out using some sort of pressure bleeder. When home bleeding (horrible term), lifting the back end helps a bit. (and Andy Cost recommendation. But what the hell, who has been able to bleed the brakes without jacking up the car anyway? If you re-bleed and air comes out, then there is a leak somewhere.

[fj20spl311]

There is a relationship between volume of fluid displaced per stroke and the pedal vs shoe pressure. I have never been able to explain it clearly, but Phil Erickson has....

Thanks for the kind words.
There are lots of things to improve the braking.
After getting the system working correctly: I assume that has been completed.

MOST important is Cf of the pads......JUNK those Nissan pads, things have come a long way since 1967.
Get some high friction pads. EBC Yellowstuff ~ $100 add 30-40% braking power. They also make Redstuff ~ $80 that is not quite as aggressive. There are also other brands
If you want to do it on the cheap RockAuto has metallic pads for less than $20 that might be better.

Once you get the braking power, you might want to work on pedal pressure.
Small Master Cylinder 510 is 3/4. You can also change the pedal ratio.
Both of these ideas may not be appropriate for a 67.5 2L as the are not stock
Getting SS flex lines are a good idea, IMHO.

[fj20spl311]

PS: You might try sanding the pads and rotors and follow the bedding process.
Here are some from tirerack.

ATE
400 to 500 miles of moderate driving is recommended. Consumer should avoid heavy braking during this period.

BREMBO GRAN TURISMO
In a safe area, apply brakes moderately from 60mph to 30mph and then drive approximately 1/2 mile to allow the brakes to cool. Repeat this procedure approximately 30 times.

HAWK
After installing new pads make 6 to 10 stops from approximately 35 mph with moderate pressure. Make an additional two to three hard stops from approximately 40 to 45 mph. Do not allow the vehicle to come to a complete stop.When completed with this process, park the vehicle and allow the brakes to cool completely before driving on them again. Do not engage the parking brake until after this cooling process is compete.
Note: Hawk racing pads (Blue, Black, HT-10, HT-12) may require a different bed-in procedure. Contact your sales specialists at the Tire Rack for racing application information.

POWER SLOT
Follow the brake pad manufacturer's recommended break-in procedure taking care not to produce excessive heat in the system. Avoid heavy braking for the first 400-500 miles.

STOPTECH

When a system has both new rotors and pads, there are two different objectives for bedding-in a performance brake system: heating up the brake rotors and pads in a prescribed manner, so as to transfer pad material evenly onto the rotors; and maturing the pad material, so that resins which are used to bind and form it are ‘cooked' out of the pad.
The first objective is achieved by performing a series of stops, so that the brake rotor and pad material are heated steadily to a temperature that promotes the transfer of pad material onto the brake rotor friction surface. There is one pitfall in this process, however, which must be avoided. The rotor and, therefore, the vehicle should not be brought to a complete stop, with the brakes still applied, as this risks the non-uniform transfer of pad material onto the friction surface.
The second objective of the bedding-in process is achieved by performing another set of stops, in order to mature the pad itself. This ensures that resins which are used to bind and form the pad material are ‘cooked' out of the pad, at the point where the pad meets the rotor's friction surface.
The bed-in process is not complete until both sets of stops have been performed.

Bedding-in Street Performance Pads

For a typical performance brake system using street-performance pads, a series of ten partial braking events, from 60mph down to 10mph, will typically raise the temperature of the brake components sufficiently to be considered one bed-in set. Each of the ten partial braking events should achieve moderate-to-high deceleration (about 80 to 90% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat by around the fifth stop (also about the time that a friction smell will be detectable in the passenger compartment). This does not indicate that the brakes are bedded-in. This phenomenon is known as a green fade, as it is characteristic of immature or ‘green' pads, in which the resins still need to be driven out of the pad material, at the point where the pads meet the rotors. In this circumstance, the upper temperature limit of the friction material will not yet have been reached.
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when all ten stops have been performed - not before. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied. After cooling the vehicle, a second set of ten partial braking events should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.

Bedding-in Club Race or Full Race Pads

For a typical performance brake system using race pads, the bed-in procedure must be somewhat more aggressive, as higher temperatures need to be reached, in order to bring certain brands of pad material up to their full race potential.
We typically recommend a set of ten partial braking events, from 60mph down to 10mph, followed immediately by three or four partial braking events, from 80mph down to 10mph. Alternately, a set of eleven stops, from 80mph to 40mph, or a set of seven stops, from 100mph to 50mph, would be approximately the same. As with street pads, each of the partial braking events should achieve moderate-to-high deceleration (about 80% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Again, depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat about halfway through the first set of stops. This does not indicate that the brakes are bedded-in, except where race-ready pads are being used. This phenomenon is the same as that which occurs with high-performance or street pads (except that, when race-ready pads are used, they do not exhibit green fade, and they will be bedded-in after just one complete set of stops).
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when the recommended number of stops has been performed - not before. As a general rule, it would be better to perform additional stops, than not enough. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied.
After cooling the vehicle, a second set of the recommended number of stops should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.
Racers will note that, when a pad is bedded-in properly, there will be approximately 2mm (0.1 inch) of the pad edge near the rotor, on which the paint will have turned to ash, or the color of the pad will have changed to look as though it has been overheated.
In summary, the key to successfully bedding-in performance brakes is to bring the pads up to their operating temperature range, in a controlled manner, and to keep them there long enough to start the pad material transfer process. Different brake system designs, pad types, and driving conditions require different procedures to achieve a successful bed-in. The procedures recommended above should provide a useful starting point for developing bed-in procedures appropriate to individual applications. 

[Gregs672000]

Glad you posted the proper bedding techniques for the various pads, as that typically makes a big difference. I experienced this several years ago doing brakes on my stepson's car. He was in a hurry so we did not follow proper bedding procedures and the car did not stop as well as before we did the brakes (doh!). A few days later we pulled the pads, sanded them and the rotors, then followed the instructions for bedding and they then worked correctly.