Car is not braking to its full potential - CorvetteForum - Chevrolet Corvette Forum Discussion

Notices
C3 General General C3 Corvette Discussion not covered in Tech
Sponsored by:
Sponsored by:

Car is not braking to its full potential

Old 09-23-2018, 10:04 PM
  #1  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default Car is not braking to its full potential

So I have been struggling with my '75 brake system for a bit. First I thought it was only the bleeding problems, so I did that, while doing that, I found a leak in brake-line. I fixed that. Brakes were still not really stopping the car well. Brakes are not powered by the way, no brake booster.

Next I took off front brake pads, they looked like they were worn funny. Got new brake pads for front axle, while changing brake pads, I found out one of the brake caliper was leaking. Sooo went ahead and replaced that too. Brakes got better but no were close to their full potential.

Rear brake pad seemed fine, but i was like why not. So I ended up changing the rear brake pads as well, found rust and gunk and leaks in the rear calipers too. Replaced them both. put new brake pads.

Bleed the who system. Brakes are still crappy. I am not sure what else I can try. I have checked all calipers for leaks all lines for leaks. Calipers are new, brake pads are new. System is bled, with no bubbles.

The car does stop, but its a slower stop then it should be able to stop. If I stomp the brake peddle, it should lock the wheels. Currently, it does not . Any help will be appreciated.
skhan is offline  
Old 09-23-2018, 10:44 PM
  #2  
maj75
CF Senior Member
 
Member Since: Jan 2007
Location: Lighthouse Point FL
Posts: 802
Thanked 69 Times in 58 Posts
Default

Master cylinder is the only component left. Assuming all the rebuild calipers are good, (I’ve had a bad rebuilt caliper) the master might be leaking internally and not generating the correct pressure.
maj75 is offline  
Old 09-23-2018, 10:50 PM
  #3  
Strokemyaxe
CF Senior Member
 
Strokemyaxe's Avatar
 
Member Since: Jul 2014
Location: Arlington TX
Posts: 582
Thanked 22 Times in 21 Posts
Default

Many questions.

1. What makes you think it’s still not braking to its full potential.

2. Pads are worn “funny”? What do the rotors look like? Grooved? replace them.

3. How did you bleed the brakes? Which wheel first, second, third, fourth? What is the total amount of fluid you bled out?

4. What dot fluid? Synthetic? What was in it before?

-Stroke

Last edited by Strokemyaxe; 09-23-2018 at 10:51 PM.
Strokemyaxe is offline  
Old 09-23-2018, 10:56 PM
  #4  
jsbwac
CF Senior Member
Support Corvetteforum!
 
jsbwac's Avatar
 
Member Since: Jan 2009
Location: New Jersey
Posts: 1,018
Thanked 6 Times in 6 Posts
Default

I would also check the master cylinder. Did the fluid run down in it? Maybe try bleeding that quick, and if not, replace.
jsbwac is offline  
Old 09-23-2018, 11:56 PM
  #5  
cagotzmann
CF Senior Member
 
cagotzmann's Avatar
 
Member Since: Jun 2011
Location: Sherwood Park Alberta
Posts: 2,055
Thanked 173 Times in 137 Posts
Default

Originally Posted by skhan View Post
So I have been struggling with my '75 brake system for a bit. First I thought it was only the bleeding problems, so I did that, while doing that, I found a leak in brake-line. I fixed that. Brakes were still not really stopping the car well. Brakes are not powered by the way, no brake booster.

Next I took off front brake pads, they looked like they were worn funny. Got new brake pads for front axle, while changing brake pads, I found out one of the brake caliper was leaking. Sooo went ahead and replaced that too. Brakes got better but no were close to their full potential.

Rear brake pad seemed fine, but i was like why not. So I ended up changing the rear brake pads as well, found rust and gunk and leaks in the rear calipers too. Replaced them both. put new brake pads.

Bleed the who system. Brakes are still crappy. I am not sure what else I can try. I have checked all calipers for leaks all lines for leaks. Calipers are new, brake pads are new. System is bled, with no bubbles.

The car does stop, but its a slower stop then it should be able to stop. If I stomp the brake peddle, it should lock the wheels. Currently, it does not . Any help will be appreciated.
So what brake pads did you select. Most OEM replacements that are metallic based last long, but don't stop with any kind of G forces. The best pads for stopping power for my C3 has been the Raybestos ST47 Pads.

Tried many brands from OEM Metalic's , organic , Hawk, Wilwood , Carbotech , Raybestos etc. Carbotech have also been a good. Also my BF Radial TA's could lock with any Pad, My Michelin Sport Sports required Hawk, Wilwood, Carbotech, Raybestos, to lock the tires. The nitto NT01's required Carbotech & Raybestos to lock the tires. But if you cannot lock tires like GF Radial TA's then you have air in the system trapped somewhere. Most common area's are.

So did you bleed the Master Cylinder while on the car ?
How did you bleed the calipers ? Is the pedal nice and firm (manual brakes)
cagotzmann is offline  
Old 09-24-2018, 07:56 AM
  #6  
bashcraft
CF Senior Member
 
bashcraft's Avatar
 
Member Since: Jan 2006
Location: Butler Pa
Posts: 6,037
Thanks: 0
Thanked 57 Times in 45 Posts
Default

It's possible that you have a master cylinder for power brakes instead of manual brakes. A manual brake master cylinder has a 1" piston and a power brake master has a 1-1/8" piston which will require much more pedal force to achieve the same fluid pressure.
bashcraft is offline  
The Following User Says Thank You to bashcraft For This Useful Post:
Syl1953 (09-25-2018)
Old 09-24-2018, 08:17 AM
  #7  
terrys6t8roadster
CF Senior Member
 
terrys6t8roadster's Avatar
 
Member Since: May 2012
Location: Allenton Wisconsin
Posts: 1,666
Thanked 156 Times in 153 Posts
Default

Is the brake pedal mushy, low, requiring numerous pumps to get pedal pressure, hard with no stopping? Glazed rotors from having brake fluid on them will cause good pedal and hard to stop condition. Any pulling under hard braking? T
terrys6t8roadster is offline  
Old 09-24-2018, 09:05 AM
  #8  
Rodnok1
CF Senior Member
 
Rodnok1's Avatar
 
Member Since: Sep 2016
Location: NC
Posts: 2,029
Thanked 75 Times in 66 Posts
Default

Originally Posted by bashcraft View Post
It's possible that you have a master cylinder for power brakes instead of manual brakes. A manual brake master cylinder has a 1" piston and a power brake master has a 1-1/8" piston which will require much more pedal force to achieve the same fluid pressure.
Very possible or brake rod in wrong hole in brake pedal if it has two on your year, I fought that issue before on other vehicles.
Rodnok1 is offline  
Old 09-24-2018, 09:26 AM
  #9  
69Vett
CF Senior Member
 
69Vett's Avatar
 
Member Since: Oct 2007
Location: Austin Texas
Posts: 3,590
Thanked 208 Times in 195 Posts
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
Default

a corvette is very difficult to bled completely, I thought I did mine right 4-5 times.
until finally got them completely bleed.
my very last trick, was tapping calipers with rubber hammer, during bleed process.
this dislodges the air bubbles clinging to the inside of the calipers.
good luck
69Vett is offline  
Old 09-24-2018, 10:17 AM
  #10  
kansas123
CF Senior Member
 
kansas123's Avatar
 
Member Since: Sep 2006
Location: Wichita Kansas
Posts: 1,095
Thanked 41 Times in 40 Posts
Default

Not sure I read that you replaced the brake hoses, could be the rubber is now weakened and or collapsed, causing poor brake performance.
kansas123 is offline  
Old 09-25-2018, 10:18 AM
  #11  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by maj75 View Post
Master cylinder is the only component left. Assuming all the rebuild calipers are good, (I’ve had a bad rebuilt caliper) the master might be leaking internally and not generating the correct pressure.
How would I test that?
Bleed the master cylinder? is it possible to bleed the master cylinder while on the car.
skhan is offline  
Old 09-25-2018, 10:25 AM
  #12  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by Strokemyaxe View Post
Many questions.

1. What makes you think it’s still not braking to its full potential.

2. Pads are worn “funny”? What do the rotors look like? Grooved? replace them.

3. How did you bleed the brakes? Which wheel first, second, third, fourth? What is the total amount of fluid you bled out?

4. What dot fluid? Synthetic? What was in it before?

-Stroke
1. The car does not lock the wheels. if the brake are fully engaged, the wheels should lock. Plus the car stops too slow.
2. Pads were worn slanted, not equally.
3. Bled the break by pumping the peddle and opening and closing the bleeder valve.
4. I used dot 3 and 4. I am not sure what it was before. Didnt think it needs anything special.
skhan is offline  
Old 09-25-2018, 11:01 AM
  #13  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by cagotzmann View Post
So what brake pads did you select. Most OEM replacements that are metallic based last long, but don't stop with any kind of G forces. The best pads for stopping power for my C3 has been the Raybestos ST47 Pads.

Tried many brands from OEM Metalic's , organic , Hawk, Wilwood , Carbotech , Raybestos etc. Carbotech have also been a good. Also my BF Radial TA's could lock with any Pad, My Michelin Sport Sports required Hawk, Wilwood, Carbotech, Raybestos, to lock the tires. The nitto NT01's required Carbotech & Raybestos to lock the tires. But if you cannot lock tires like GF Radial TA's then you have air in the system trapped somewhere. Most common area's are.

So did you bleed the Master Cylinder while on the car ?
How did you bleed the calipers ? Is the pedal nice and firm (manual brakes)
I am using Hawk performance pads.
I did not bleed the master cylinder, didnt know I need to.
Bled the calipers by pumping the brake and opening and closing of valve technique. the pedle is nice and firm.
skhan is offline  
Old 09-25-2018, 11:02 AM
  #14  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by bashcraft View Post
It's possible that you have a master cylinder for power brakes instead of manual brakes. A manual brake master cylinder has a 1" piston and a power brake master has a 1-1/8" piston which will require much more pedal force to achieve the same fluid pressure.

How do I tell if this is the case?What do I need to measure? Or are there any indications on the cylinder like tag or writing which will tell me this?
skhan is offline  
Old 09-25-2018, 11:04 AM
  #15  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by Rodnok1 View Post
Very possible or brake rod in wrong hole in brake pedal if it has two on your year, I fought that issue before on other vehicles.
mmm. So I need to look at the Pedal? Could you explain this a bit more please.
skhan is offline  
Old 09-25-2018, 11:05 AM
  #16  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by kansas123 View Post
Not sure I read that you replaced the brake hoses, could be the rubber is now weakened and or collapsed, causing poor brake performance.
I did not change the rubber hoses. They seem to have been put on by the previous owner. They look like in good conditions. Clean and solid.
Not sure if that is the issue. How could I test that?
skhan is offline  
Old 09-25-2018, 11:14 AM
  #17  
Fredtoo
CF Senior Member
 
Member Since: Jun 2014
Posts: 145
Thanked 24 Times in 21 Posts
Default

Originally Posted by skhan View Post
I am using Hawk performance pads.
I did not bleed the master cylinder, didnt know I need to.
Bled the calipers by pumping the brake and opening and closing of valve technique. the pedle is nice and firm.
Some race pads need heat in them to work right.
How fast are you going when you do the panic stop?
Fredtoo is offline  
Old 09-25-2018, 11:30 AM
  #18  
bashcraft
CF Senior Member
 
bashcraft's Avatar
 
Member Since: Jan 2006
Location: Butler Pa
Posts: 6,037
Thanks: 0
Thanked 57 Times in 45 Posts
Default

Originally Posted by skhan View Post
How do I tell if this is the case?What do I need to measure? Or are there any indications on the cylinder like tag or writing which will tell me this?
You'll need to remove the master cylinder and measure the bore diameter from the back.
bashcraft is offline  
Old 09-25-2018, 11:47 AM
  #19  
skhan
Junior Member
Thread Starter
 
Member Since: Aug 2018
Posts: 30
Thanked 1 Time in 1 Post
Default

Originally Posted by Fredtoo View Post
Some race pads need heat in them to work right.
How fast are you going when you do the panic stop?
I have tried them up to 45mph.
skhan is offline  
Old 09-25-2018, 12:04 PM
  #20  
Fredtoo
CF Senior Member
 
Member Since: Jun 2014
Posts: 145
Thanked 24 Times in 21 Posts
Default

How many miles on the pads?
They do take some time to bed in, especially on used rotors.

And

Do you have one of those IR heat guns? It is a good tool to see all your calipers are working (getting hot)

After you are sure the pads are bedded, try a few stops from highway speed. That should get the brakes up to operating temperature.
If it makes a big difference, you may need a pad that works at lower temps.
I put some Raybestos pads in my car, and they made a big improvement over the 20 year old brand X pads that were in there.
RAYBESTOS SP8XP Street Performance; Metallic (from Rock Auto)
Fredtoo is offline  

Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: