Braking power?

[sabrie]

I am getting my '73 back on the road and just replaced most of the brake system: Front rotors, calipers, pads, master cylinder and booster, and all the brake lines. Bled the brakes, brakes work, victory! Pedal feels good, but when I got out for a drive it seems like it should brake harder. I have disc up front and drums in back, should I be able to lock the wheels up when stopping? I may bleed the lines more, but looking to see if I should be able to get that kind grip or if I'm expecting more than I should from a 50 year old machine.

 

[tony-muscle]

You may have to press the pedal harder. It will also depend on the surface you are testing on. On the other hand, it may be good that you can't lock up the tires.

 

[Doug's 73 Mach1]

These cars were long before ABS to prevent lock up. You should be able to lock them up if you push hard enough. Ideally you don't want to lock them up when stopping on dry, wet or slippery conditions which is a matter of how hard you press on the brake pedal.

 

[giantpune]

Yes, with factory power discs and factory width tires, it should be no problem to lock up the brakes and leave some skid marks on the road. I have locked them up doing 35mph on asphalt. FWIW, even cars with 4 wheel manual drums should be able to lock up at least a couple of the wheels.

Do you have the correct style master cylinder and proportioning valve for disc brakes?
Did you bench bleed the master?
Do you have the front calipers on the correct side? If you mix them up, you cant get all the air out of them.

 

[Bentworker]

I am getting my '73 back on the road and just replaced most of the brake system: Front rotors, calipers, pads, master cylinder and booster, and all the brake lines. Bled the brakes, brakes work, victory! Pedal feels good, but when I got out for a drive it seems like it should brake harder. I have disc up front and drums in back, should I be able to lock the wheels up when stopping? I may bleed the lines more, but looking to see if I should be able to get that kind grip or if I'm expecting more than I should from a 50 year old machine.

What kind of pads / shoes did you use? Also, did you bed them in? Pad compound plays a lot into how they grab. Also properly bedding in the pads by doing several aggressive stops from 40-50mph to 0 will make a big difference.

Make sure the drum brakes are properly adjusted, that the shoe radius matches the drum radius and that all hoses / lines/ cylinders/ calipers are in tip top shape and bled.

 

[AcesArneson]

Don’t forget to adjust the rear brakes while driving to tighten them up. Drive backwards and brake aggressively to get the auto adjuster set.

 

[c9zx]

+1 on what kind of pads were used. Ceramic pads don't dust much but do not "bite" as well as a semi-metallic pad. Semi-metallic also has more fade resistance and dust more. I have semi-metallic pads on all my vehicles. PQ Pro by Centric are good value fro Rock-Auto. Chuck

 

[sabrie]

You may have to press the pedal harder. It will also depend on the surface you are testing on. On the other hand, it may be good that you can't lock up the tires.

Thanks, just trying to figure out if it working correctly, or not.

 

[sabrie]

These cars were long before ABS to prevent lock up. You should be able to lock them up if you push hard enough. Ideally you don't want to lock them up when stopping on dry, wet or slippery conditions which is a matter of how hard you press on the brake pedal.

Understood, just wondering if they should, in which case I have not adequately bled the system or something else is keeping them from working correctly.

 

[sabrie]

Yes, with factory power discs and factory width tires, it should be no problem to lock up the brakes and leave some skid marks on the road. I have locked them up doing 35mph on asphalt. FWIW, even cars with 4 wheel manual drums should be able to lock up at least a couple of the wheels.

Do you have the correct style master cylinder and proportioning valve for disc brakes?
Did you bench bleed the master?
Do you have the front calipers on the correct side? If you mix them up, you cant get all the air out of them.

Master cylinder is correct for disc front/drum rear, and bench bled so I think I am good to go there. Will try bleeding the lines more and see if I missed some air there. Calipers are on the correct sides and the bleeders point up. Think if I have an issue its residual air in the line or something in the distribution block.

 

[c9zx]

You may want to check the master cylinder pushrod length, probably a long shot. Chuck