Hard brake pedal solution, finally!!
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
I was reading that electric cars use electric vacuum pumps as the source of vacuum for their brakes. That sounds interesting.
But i was also thinking that if low vacuum was the problem, then it should be at all times, since engine startup.
But it is worth giving some consideration.
But i was also thinking that if low vacuum was the problem, then it should be at all times, since engine startup.
But it is worth giving some consideration.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
I was reading that electric cars use electric vacuum pumps as the source of vacuum for their brakes. That sounds interesting.
But i was also thinking that if low vacuum was the problem, then it should be at all times, since engine startup.
But it is worth giving some consideration.
But i was also thinking that if low vacuum was the problem, then it should be at all times, since engine startup.
But it is worth giving some consideration.
Summit racing sells them and they only come on when vacuum is low - we ran one on the chevelle - but it was loud when on and only lasted about 3/4 of one season on a car that sees virtually no mileage
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Guys your starting to cut straws with your analysis of altitudes.
That is why your brakes work so good when you are decelerating from a 60mph roll, especially if you have a manual and you are using the gears to slow you down. You are creating a TON of vacuum, and essentually trying to pull the pistons off the rods when there is that much vacuum. Hence the reason you will hear of guys throwing their cars into neutral as they cross the finish line while drag racing or shut off their cars all together and coast. (neither is advisable for other reasons).
That is why your brakes work so good when you are decelerating from a 60mph roll, especially if you have a manual and you are using the gears to slow you down. You are creating a TON of vacuum, and essentually trying to pull the pistons off the rods when there is that much vacuum. Hence the reason you will hear of guys throwing their cars into neutral as they cross the finish line while drag racing or shut off their cars all together and coast. (neither is advisable for other reasons).
Been following your posts on the new master. Its apparent that replacing good parts with more of the same good parts is not getting the job done. I went about the same route as you and did the ABS also with no real change.
When I installed a different part mainly the J55s, there was a marked improvement in brake performance which got me into the “normal” area. You might have the right idea on a beefed up master. Just wondering how you picked it. If it has a larger piston area, it seems like it can deliver more fluid per distance of movement of piston.
They say the J55s are the “big brakes”. I always wondered what was big about them other then the housing maybe. They use the same pads as the 12” system. But just found out today from GM that they both use the same rebuild kit hence same size pistons. So I got to figure they work better only because they are a 13” system.
Last edited by pcolt94; Aug 30, 2007 at 09:47 PM.
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
Ok, so I took a shot. I knew it all didn’t feel right and I was hanging it out there, but got to try. Glad you came I with the info.
Been following your posts on the new master. Its apparent that replacing good parts with more of the same good parts is not getting the job done it. I went about the same route as you and did the ABS also with no real change.
When I installed a different part mainly the J55s, there was a marked improvement in brake performance which got me into the “normal” area. You might have the right idea on a beefed up master. Just wondering how you picked it. If it has a larger piston area, it seems like it can deliver more fluid per distance of movement of piston.
They say the J55s are the “big brakes”. I always wondered what was big about them other then the housing maybe. They use the same pads as the 12” system. But just found out today from GM that they both use the same rebuild kit hence same size pistons. So I got to figure they work better only because they are a 13” system.
Been following your posts on the new master. Its apparent that replacing good parts with more of the same good parts is not getting the job done it. I went about the same route as you and did the ABS also with no real change.
When I installed a different part mainly the J55s, there was a marked improvement in brake performance which got me into the “normal” area. You might have the right idea on a beefed up master. Just wondering how you picked it. If it has a larger piston area, it seems like it can deliver more fluid per distance of movement of piston.
They say the J55s are the “big brakes”. I always wondered what was big about them other then the housing maybe. They use the same pads as the 12” system. But just found out today from GM that they both use the same rebuild kit hence same size pistons. So I got to figure they work better only because they are a 13” system.
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 800
Likes: 3
From: Port Orange FL
Roy
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
My 94 sits at about 49-52 KPa at idle, i have JL9 12 inch brakes, and the car stops fine.
When i got it, it wasnt real good, i got rid of the pads that were on it and put on a set of Genuine PBR pads (which is what they left the factory with) and f**k me dead if im lying, but the brakes started working alot better.
Im not sure what the "stock replacement" pads are over there or where they are made, but if they are not PBR and not made in Australia, they are NOT what it left the factory with.
When i got it, it wasnt real good, i got rid of the pads that were on it and put on a set of Genuine PBR pads (which is what they left the factory with) and f**k me dead if im lying, but the brakes started working alot better.
Im not sure what the "stock replacement" pads are over there or where they are made, but if they are not PBR and not made in Australia, they are NOT what it left the factory with.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Hydraulics 101:
Smaller the pistion the more PSI it will deliver but less volume. If you have a very stiff feeling pedal, a smaller piston will soften the pedal.
A larger piston will deliver more fluid over a given movement, but will require more peddle force to do so, and not as much pressure for a given movement.
For my replacement I went to a 1.031 piston, which is slightly larger than what stock is - but the reason I did this is with my peddle pivot point changed due to no booster, I have a TON of leverage and my peddle moves a ton now. Therefore I am hoping I can deliver more fluid to the show; and retain more pressure than before (stock) due to my peddel pivot point change.
Time will tell - I am not holding my breath.
And I have EBC greenstuff pads on all 4 tire - and they did make a BIG difference before - but the brakes are still shabby in my opinion.
Was the hydroboost system brought up in this discussion? Wilwood gave me the name of an outfit that builds custom brake setups for cars - to accomidate the need to keep my 15" racing wheels.......I did not call - but would imagine you will have well over 1000 beans invested to get a set. Stopping is not THAT big of a concern to me; if he would have told me it would gpick me up .1sec in the 1/4 then I might be interested
Smaller the pistion the more PSI it will deliver but less volume. If you have a very stiff feeling pedal, a smaller piston will soften the pedal.
A larger piston will deliver more fluid over a given movement, but will require more peddle force to do so, and not as much pressure for a given movement.
For my replacement I went to a 1.031 piston, which is slightly larger than what stock is - but the reason I did this is with my peddle pivot point changed due to no booster, I have a TON of leverage and my peddle moves a ton now. Therefore I am hoping I can deliver more fluid to the show; and retain more pressure than before (stock) due to my peddel pivot point change.
Time will tell - I am not holding my breath.
And I have EBC greenstuff pads on all 4 tire - and they did make a BIG difference before - but the brakes are still shabby in my opinion.
Was the hydroboost system brought up in this discussion? Wilwood gave me the name of an outfit that builds custom brake setups for cars - to accomidate the need to keep my 15" racing wheels.......I did not call - but would imagine you will have well over 1000 beans invested to get a set. Stopping is not THAT big of a concern to me; if he would have told me it would gpick me up .1sec in the 1/4 then I might be interested
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Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Not going to dispute your findings. But you got to know there are a ton of people who have tried all different kinds of pads with no dramatic change in performance including me. Its hard to believe there could be such a difference in these OEM pads.
When you say the “the brakes started working allot better” I’ll accept that. But what I think the people here including myself are looking for is when the brakes are applied hard, it will launch the passenger if seat belt is not on, all the krap in the back of the car is now in the front and the tires are squealing. I use to kinda c-o-a-s-t to a stop….scary.
I have used the very basic pad, from your basic auto part supply store on ever one of my current cars, and all I have owned and never had a problem as being discussed. I broke the glaze on my rotors, changed them, used different pads and did see small differences. A coupe times I thought I was close but after things smoothed out and broke in, I realized I was basically back to where I started.
I am willing to meet with anyone in Orlando who is willing to take the Pepsi challenge & compare brakes.
So I guess what we need to do is get someone with the 12” system to invest in buying pads from a GM dealer.
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
Not going to dispute your findings. But you got to know there are a ton of people who have tried all different kinds of pads with no dramatic change in performance including me. Its hard to believe there could be such a difference in these OEM pads.
When you say the “the brakes started working allot better” I’ll accept that. But what I think the people here including myself are looking for is when the brakes are applied hard, it will launch the passenger if seat belt is not on, all the krap in the back of the car is now in the front and the tires are squealing. I use to kinda c-o-a-s-t to a stop….scary.
I have used the very basic pad, from your basic auto part supply store on ever one of my current cars, and all I have owned and never had a problem as being discussed. I broke the glaze on my rotors, changed them, used different pads and did see small differences. A coupe times I thought I was close but after things smoothed out and broke in, I realized I was basically back to where I started.
I am willing to meet with anyone in Orlando who is willing to take the Pepsi challenge & compare brakes.
So I guess what we need to do is get someone with the 12” system to invest in buying pads from a GM dealer.
When you say the “the brakes started working allot better” I’ll accept that. But what I think the people here including myself are looking for is when the brakes are applied hard, it will launch the passenger if seat belt is not on, all the krap in the back of the car is now in the front and the tires are squealing. I use to kinda c-o-a-s-t to a stop….scary.
I have used the very basic pad, from your basic auto part supply store on ever one of my current cars, and all I have owned and never had a problem as being discussed. I broke the glaze on my rotors, changed them, used different pads and did see small differences. A coupe times I thought I was close but after things smoothed out and broke in, I realized I was basically back to where I started.
I am willing to meet with anyone in Orlando who is willing to take the Pepsi challenge & compare brakes.
So I guess what we need to do is get someone with the 12” system to invest in buying pads from a GM dealer.
Heel & Toe
Joined: Aug 2007
Posts: 15
Likes: 0
Thats exactly right, but that is going to have the opposite effect from what you are trying to accomplish. A master cylinder with a smaller bore will give you more movement on the pedal, and greater leverage on the calipers, resulting in more distance to push, but less effort required to stop the car. A larger master is going to result in full engagement of the brakes after a very short movement of the pedal, less leverage against the calipers and a wooden feel to the system requiring a lot of effort.
Roy
Roy
Your statement is correct. I have experienced the problem of too large of a piston size on the master cylinder first hand. It was on an off-road racer..... a VW convertible based Class 5 car...I added a custom master cylinder setup with 2 side-by-side master cylinders as is commonly used on racers to allow a balance adjustment for front to rear braking bias. The first set of master cylinders I used had 1" piston diameter and the car would not stop AT ALL. The pedal was extremely hard, and it just wouldn't generate enough pressure at the wheel cylinders. I changed to 3/4 inch master cylinders and it worked like a champ with great pedal feel.
Yes, my '91 with a hard pedal feels just a little like that first attempt I made on the VW, but I've hesitated to suggest this as a problem for the Vette, as I assumed that the factory has enough resources to engineer it correctly - unlike my first seat of the pants attempt.
This thread started with the re-setting of some codes in the ABS as a solution, and that was very encouraging, but it doesn't sound like all believe that this could be the universal solution.
Drifting
Joined: Mar 2004
Posts: 1,500
Likes: 1
From: Mauldin sc
St. Jude Donor '05
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Seems like this post would be in a better place for people who are trying to gain more power.
The people here are trying to STOP and trying to pick up information on brakes.
Case...man, I would like to come to Australia anyway, brakes or not.
A lot of good information in these posts on braking design and characteristics. Things that most of us did not think about when doing normal brake work on other vehicles that act as expected.
The people here are trying to STOP and trying to pick up information on brakes.
Case...man, I would like to come to Australia anyway, brakes or not.
A lot of good information in these posts on braking design and characteristics. Things that most of us did not think about when doing normal brake work on other vehicles that act as expected.
Last edited by pcolt94; Sep 1, 2007 at 03:18 PM.
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
Seems like this post would be in a better place for people who are trying to gain more power.
The people here are trying to STOP and trying to pick up information on brakes.
Case...man, I would like to come to Australia anyway, brakes or not.
A lot of good information in these posts on braking design and characteristics. Things that most of us did not think about when doing normal brake work on other vehicles that act as expected.
The people here are trying to STOP and trying to pick up information on brakes.
Case...man, I would like to come to Australia anyway, brakes or not.
A lot of good information in these posts on braking design and characteristics. Things that most of us did not think about when doing normal brake work on other vehicles that act as expected.
QUOTE=pcolt94;1561748842]Seems like this post would be in a better place for people who are trying to gain more power.
The people here are trying to STOP and trying to pick up information on brakes.
....
seems more like a post to sell something or to divert to another business entity because of the tag line link!.....
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Intermediate
Joined: Jun 2003
Posts: 43
Likes: 1
From: Morris Plains NJ
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
I'd like to try a 84-87 master cylinder on one of your cars.
The piston is considerably smaller, so you'd get more pressure to the brakes at the expense of longer pedal travel.
It's got enough fluid for my 6 piston wilwoods so surely it'll work with the stock 88-96 brakes.
It looks like it'll bolt right up for 88-89, I can't speak for any years after that.
The piston is considerably smaller, so you'd get more pressure to the brakes at the expense of longer pedal travel.
It's got enough fluid for my 6 piston wilwoods so surely it'll work with the stock 88-96 brakes.
It looks like it'll bolt right up for 88-89, I can't speak for any years after that.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Should work, hard to say i guess. It will need a different reservior on the later models for the connection of the ABS prime pipe. Front cover of boosters are the same part (or extremely close to it) from start to finish, except ZR1s.
Nice avitar by the way
Nice avitar by the way