Brake caliper bore sizes - Page 3 - Chevelle Tech
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post #31 of 46 (permalink) Old May 23rd, 16, 8:53 PM
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Denny
 
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Re: Brake caliper bore sizes

Are sure are you that your parking is correctly adjusted? A lot of people have problems doing it correctly. If the parking brake is not correctly adjusted, the piston retracts too far from the disc, creating a large gap that needs a long pedal travel to compensate.

I've seen a post on the web where a guy put a 2 lb RPV and said that his problem was solved that way. With the 2 lb RPV, he probably created a force that counteracted this piston retraction (like the brake is always applied) and so you have no gap anymore. It probably works, but it's not the proper solution to the problem: The parking brake needs to be adjusted properly.

Changing the mechanical advantage of your brake pedal would be a bad solution too. Even a worst one, if your problem is only pushing more fluid to fill a gap. Yes, you will need less pedal travel to fill the gap (probably still too much anyway), but once the gap filled, your brakes will be more sensitive than they're supposed to. Remember that your front brakes will be affected as well.

You have the correct m/c bore for the 1970 Chevelle front calipers you have and I would even tend to suggest a larger one like the stock 1-1/8" (but that is more of a preference), so going smaller (or decreasing pedal ratio) doesn't sound like a good idea.

If the rear calipers weren't correctly matched to the front ones, you will still get a good pedal and you wouldn't even feel the difference in braking performance, except in emergency braking situations.

If you are sure that your parking brake is well adjusted and that the system is well bled (it sounds like it is), there is basically only one reason for a low pedal; a bad m/c. If you try another m/c and you got the same pedal, you can bet that it is your parking brake adjustment.


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post #32 of 46 (permalink) Old May 23rd, 16, 9:45 PM Thread Starter
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BILL
 
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Jeff and Jack, you are both right about the larger bore size according to Wildwood. I also talked with them several days ago after lots of frustration because I have their master cylinder and proportioning valve. I didn't know my bore sizes, but i guess they did and also recommended a larger 1 1/8 bore. If this is answer, then I wasted more money on the wrong master cylinder. I really think my parking brake arms are right, but could be adjusted just a touch more off the stops. They're set about a 1/16 off the stops now, is that not enough??????
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post #33 of 46 (permalink) Old May 24th, 16, 6:45 AM Thread Starter
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BILL
 
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Re: Brake caliper bore sizes

On my parking brake, I went through the steps just like the instructions said and if I work the lever by hand or with a wrench, it hardly moves at all before engaging the caliper. I even had a bad caliper in the kit, which I had to eat the cost of because of the time frame between purchase and installation, that I had to replace because you could pump the lever and it would touch the pads and keep moving. Like I said, after adjusting the parking brake, mine is set about a 1/16 off the stops on both sides. Should it be set a little more???? Also had one of the cable housings come out of the hole in the baracket on the caliper and got stuck and may have hot spotted the rotor while driving to test the brakes.

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post #34 of 46 (permalink) Old May 24th, 16, 8:56 AM
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Re: Brake caliper bore sizes

sounds like you have it adjusted fine.
Time to change things up now and re test.
Like pedal ratio and possibly removing proportioning valve.
I would have to try that before getting a different mastercylinder.

But know this a master cylinder too small will sometimes fail in a bad situation. I call it driving through the mastercylinder.
My 1/2 ton ford van was subjected to a lot of heavy loads and I put the brakes through some hard times.. many times all the pressure applied to the master cylinder was too much and the thing would let the pedal go to the floor and you got minimal brakes if any.

I had a friend that had the same issues and he went with a 1 ton master cylinder with a larger bore.. said it stopped his truck way better.
Weak links will be found.. but you are not trying to stop 16,000 lbs either.

just more food for thought
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post #35 of 46 (permalink) Old May 24th, 16, 10:28 AM Thread Starter
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Re: Brake caliper bore sizes

Hey, i didn't want you guys to think i went over you're head in talking with Wilwood. I had talked to them first and to be honest, sometimes i doubt some things those tech guys tell me, i just wanted input from you guys before i spent more money for nothing. I've wasted enough cash already on brakes and i am NOT happy at all with my current system. In my opinion, i don't have air in the system, i just have a master that has a bore that is actually to small and would take another quick pump to move enough fluid to the calipers (like a bottle jack) or the pedal will travel much further. I also feel that i could add a 2 lb residual valve to compensate some of that, but i really don't like the thought of my calipers dragging. I guess if i adjust the parking brake more it would kind of have the same effect, but drag there too. This is all just my opinion, but just look what i have now, a bunch of NEW parts the don't play well together. What do i know about it!!!!!!!!!!
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post #36 of 46 (permalink) Old May 24th, 16, 10:37 AM
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Re: Brake caliper bore sizes

No you did the right thing and all this adds up to knowledge in the long run.
Not everything you or I will do to a vehicle will pan out on the first try every time.

The longer you play with stuff the more you learn.
I try and offer advice from my experiences ..Heck by the time i was 24 I had owned over 250 vehicles. Now a bunch of those were doner vehicles.
1/2 of those were drivers and all needed something fixed on them.

I asked all kinds of people for advice.. and the library was a big help and old car magazines with do it and fix it articles helped.

Get the knowledge wherever you can and let it sink in.

I actually prefer to buy projects like shells of a vehicle and make them my super reliable daily drivers.
Helps to have a bunch of parts leftover from all those doner vehicles.
Then you can mix and match and see what does and does not work together.
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post #37 of 46 (permalink) Old May 24th, 16, 4:01 PM Thread Starter
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BILL
 
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Re: Brake caliper bore sizes

Hey Denny, sorry about calling you Jack. I didn't pay enough attention i guess. My Daddy has told me that my whole life. Thanks for the info about my brakes.
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post #38 of 46 (permalink) Old May 24th, 16, 6:00 PM
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Denny
 
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Re: Brake caliper bore sizes

You should apply the brakes and release them, check how far are the rear pads from the disc (both side). Both pads should be touching the disc. If not, something is wrong with the caliper.

If the calipers are OK, check the m/c. Simplest check to do would be to block the m/c's outlets and apply the brakes. If you still have a long pedal travel, then you are sure that it is the m/c.

Otherwise, I can't really think of anything else but air bubbles.


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post #39 of 46 (permalink) Old May 24th, 16, 11:12 PM
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Re: Brake caliper bore sizes

I have those rear calipers. You probably heard all this already, but the caliper has to be shimmed just right to center it on the rotor and the parking brake cables have to be adjusted tight enough so the pads touch but don't drag with the ebrake off or the pedal will be low. I had to pump the crap out of the ebrake probably 20 times to get the self adjusters kicked in then go back and readjust the cables, then bleed the brakes. I can bleed mine with caliper bolted on vertical and the ebrake off, it was easy to bleed them really.

I don't know if it's feasible for you or what you want to do, but I would suggest you put a standard GM 4 wheel disc master and booster on it with no proportioning valve and 3/16" rear line. This setup works well for me and lots of other people. Sometimes it's not worth it to try and reinvent the wheel.
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post #40 of 46 (permalink) Old May 25th, 16, 11:58 AM Thread Starter
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Re: Brake caliper bore sizes

Tom, how do you bleed you calipers when they are installed??? The bleeders have to be horizontal when bleeding or there will be air left in them. I did not know this in the beginning, so i called the company i purchased them from and they explained how they are made and how i needed to bleed them. I have tried to do it like you said but i couldn't get it, so i made some blocks to put in them. Also, i did shim the calipers to center them in the beginning. I hear what you are saying about the GM master and booster, but i have a pretty healthy solid roller cam with low vacuum. I know it sounds like i am making excuses, but i am still keeping an open mind, because i know these are just parts that i need to get to work together. I do know there is a reason my stuff isn't working and i want to find it.
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post #41 of 46 (permalink) Old May 25th, 16, 1:49 PM
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Re: Brake caliper bore sizes

Quote:
Originally Posted by BSONGER View Post
Tom, how do you bleed you calipers when they are installed??? The bleeders have to be horizontal when bleeding or there will be air left in them. I did not know this in the beginning, so i called the company i purchased them from and they explained how they are made and how i needed to bleed them. I have tried to do it like you said but i couldn't get it, so i made some blocks to put in them. Also, i did shim the calipers to center them in the beginning. I hear what you are saying about the GM master and booster, but i have a pretty healthy solid roller cam with low vacuum. I know it sounds like i am making excuses, but i am still keeping an open mind, because i know these are just parts that i need to get to work together. I do know there is a reason my stuff isn't working and i want to find it.
I was just able to bleed them normally. I left them open until they dripped. Then closed them and did it the normal pump and hold way with somebody in the car. Mine also had the thing in the directions about unbolting them and turning them to bleed them, but I didn't have to do it.

I really think these brakes need power to stop well. It just requires too much pedal effort to stop quickly. Even in the top hole there isn't enough ratio IMO. GM didn't make many manual disc cars for a reason. Maybe hydraboost if you can't use vacuum.
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post #42 of 46 (permalink) Old May 25th, 16, 10:00 PM Thread Starter
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As bad as I hate to spend more money on this system, I'll probably end up buying another master cylinder and adding some sort of power to it. I have new stainless quarter inch lines to the rear that I'll have to think about before I replace them with 3/16 lines though. As of now, I'm going to do more inspecting of what I have and how it's working.
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post #43 of 46 (permalink) Old May 25th, 16, 10:04 PM Thread Starter
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Sorry, that is (a) 1/4" line to the axle and then 3/16 after the flex line.
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post #44 of 46 (permalink) Old May 26th, 16, 2:01 AM
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Re: Brake caliper bore sizes

1/4 to the axle is fine if it's a hard line.

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post #45 of 46 (permalink) Old May 26th, 16, 6:32 AM Thread Starter
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Re: Brake caliper bore sizes

Yes, it's a hard line. Thanks for all the help and suggestions from everyone.

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