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Old 07-19-2013, 11:12 PM   #1
Slowered318
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E30 Brake Adjustment

Calling out for someone with brake system expertise.

I made up a diagram explaining my planned setup. I have all new parts so I can't really turn back now. My rotors and callipers are stock size, I installed new pads last year, master cylinder is almost shot and I need a complete brake fluid flush. The car has stock wheels with good rubber.

What prompted me to do this. My pedal is soft and not very responsive, stopping distance is rather poor. When my ABS kicks in (only wet roads) I can hardly force the car into a skid and the pedal sometimes sinks almost to the floor. Also when threshold braking I think the fronts are locking up before the rears. I think the stock bias is a little too idiot proof for me as I know how to drive this cars at the limit.

My question is that if I remove the stock pressure regulator and install an adjustable one will it give me better control over my brake bias and help me to use all 4 wheels to stop? Also if the master cylinder is 25/25mm bore compared to the stock 22/17mm, will this cause any problems because of the ABS like excessive sensitivity? Will having a restriction on the rear line cause any problems to the master cylinder, blow by or rupture the seals somewhere?

Sorry so many questions, I've searched for hours and can find a strait answer. Is this all a really bad idea? I don't want to spend thousands on a big brake kit and new wheels/tires.
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The major difference between my 318is and an e30 M3 is that the noises come from the engine and not the passengers

Last edited by Slowered318; 07-19-2013 at 11:45 PM.
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Old 07-26-2013, 05:02 PM   #2
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My question is that if I remove the stock pressure regulator and install an adjustable one will it give me better control over my brake bias and help me to use all 4 wheels to stop?
Better control? Yes. Before you had 0 control over your bias. Now you will have some. This qualifies as better.

Will it help you brake with all 4 wheels? That is the theory. I have an adjustable proportioning valve installed in my Miata. I have not driven it as of yet though so I can not tell you how much it helped. The vast majority of the braking power comes from the front. I do not know if increasing the amount of brake pressure to the rear wheels helps with braking distances or will just cause them to lock up sooner.

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Originally Posted by Slowered318 View Post
Also if the master cylinder is 25/25mm bore compared to the stock 22/17mm, will this cause any problems because of the ABS like excessive sensitivity? Will having a restriction on the rear line cause any problems to the master cylinder, blow by or rupture the seals somewhere?
I do not know the answer to this. But if you are so super at braking you feel you should increase rear brake pressures why don't you just rip the ABS out? Theoretically an increase in braking effort in the rear should take some load off the front, reducing the need for ABS in the first place.
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Old 07-26-2013, 05:33 PM   #3
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Why don't you flush the fluid and see where that leaves you? The bias valve will of course help adjustment, if that will help you stop sooner I couldn't say...

Why do you want to restrict the read line?
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Old 07-26-2013, 06:58 PM   #4
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I've heard people installing a larger master cyl. Also start with clean fluid, also bleed the ABS system. Sometimes dirt or old fluid will reduce effective braking. the e30's braking system is pretty balanced to begin with. Obviously more braking required to the front due to the weight of the engine etc. The only solution I have heard about improving stopping distance is bigger brakes. more surface area faster stopping but as mentioned who is to stay with any of these mods you just won't end up locking up and skidding?
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Old 07-27-2013, 08:37 AM   #5
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Quote:
Originally Posted by food View Post
Better control? Yes. Before you had 0 control over your bias. Now you will have some. This qualifies as better.

Will it help you brake with all 4 wheels? That is the theory. I have an adjustable proportioning valve installed in my Miata. I have not driven it as of yet though so I can not tell you how much it helped. The vast majority of the braking power comes from the front. I do not know if increasing the amount of brake pressure to the rear wheels helps with braking distances or will just cause them to lock up sooner.



I do not know the answer to this. But if you are so super at braking you feel you should increase rear brake pressures why don't you just rip the ABS out? Theoretically an increase in braking effort in the rear should take some load off the front, reducing the need for ABS in the first place.
Well my goal is not to drastically increase the rear brake pressure. When going to the 25/25mm master cylinder you have a lot more fluid going to the rear brakes, I just want to tone that down with the adjustable valve to give me a "close to stock" brake bias. I'm doing this in a way that I can revert to the factory specifications if it ends up being dangerous or unsatisfactory.

I would only remove the ABS if it was faulty beyond repair. Regardless of how aware or competent my braking is, if someone else were to drive the car or I was in a panic situation the results could be disastrous.
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The major difference between my 318is and an e30 M3 is that the noises come from the engine and not the passengers
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Old 07-27-2013, 08:41 AM   #6
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Originally Posted by cormier View Post
Why don't you flush the fluid and see where that leaves you? The bias valve will of course help adjustment, if that will help you stop sooner I couldn't say...

Why do you want to restrict the read line?
I'm doing a mini overhaul of the brake system, new flexible lines and master cylinder. I guess now is a good time to experiment with it and see if I can improve the pedal feel and stopping distance.
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Old 07-27-2013, 08:51 AM   #7
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Originally Posted by Ceeker View Post
I've heard people installing a larger master cyl. Also start with clean fluid, also bleed the ABS system. Sometimes dirt or old fluid will reduce effective braking. the e30's braking system is pretty balanced to begin with. Obviously more braking required to the front due to the weight of the engine etc. The only solution I have heard about improving stopping distance is bigger brakes. more surface area faster stopping but as mentioned who is to stay with any of these mods you just won't end up locking up and skidding?
Any pointers on bleeding the ABS unit, do I have to go to the dealership or can it be done with a little finesse?

I really don't think my brake pads and callipers are lacking the power to lock up my tires if I push hard enough. Something else is reducing my braking power, in the 12 years i've had this car I have not been able to get the brakes to where I want them. Even after replacing all 4 rotors, pads and rebuilding the callipers the braking still felt quite lazy compared to other cars. I even replaced the booster hose with a 300psi air line and installed a new check valve. Maybe it's time to go to extremes but I don't see the point to larger rotors and multi piston callipers if the problem is in the master or ABS system.
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The major difference between my 318is and an e30 M3 is that the noises come from the engine and not the passengers

Last edited by Slowered318; 07-27-2013 at 09:18 AM.
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Old 07-27-2013, 09:22 PM   #8
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Quote:
Originally Posted by Slowered318 View Post
Calling out for someone with brake system expertise.

I made up a diagram explaining my planned setup. I have all new parts so I can't really turn back now. My rotors and callipers are stock size, I installed new pads last year, master cylinder is almost shot and I need a complete brake fluid flush. Take care of that first. The car has stock wheels with good rubber.

What prompted me to do this. My pedal is soft and not very responsive, stopping distance is rather poor. When my ABS kicks in (only wet roads) I can hardly force the car into a skid WHAT? and the pedal sometimes sinks almost to the floor. Also when threshold braking I think the fronts are locking up before the rears. As they should I think the stock bias is a little too idiot proof for me as I know how to drive this cars at the limit. No offense, but you don't.

My question is that if I remove the stock pressure regulator and install an adjustable one will it give me better control over my brake bias and help me to use all 4 wheels to stop? Also if the master cylinder is 25/25mm bore compared to the stock 22/17mm, will this cause any problems because of the ABS like excessive sensitivity? Will having a restriction on the rear line cause any problems to the master cylinder, blow by or rupture the seals somewhere? Don't do any of that.

Sorry so many questions, I've searched for hours and can find a strait answer. Is this all a really bad idea? I don't want to spend thousands on a big brake kit and new wheels/tires.
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Originally Posted by food View Post
Better control? Yes. IF you know what you're doing. Before you had 0 control over your bias. Now you will have some. This qualifies as better.

Will it help you brake with all 4 wheels? That is the theory. I have an adjustable proportioning valve installed in my Miata. I have not driven it as of yet though so I can not tell you how much it helped. The vast majority of the braking power comes from the front. I do not know if increasing the amount of brake pressure to the rear wheels helps with braking distancesNo, it does not. or will just cause them to lock up sooner.



I do not know the answer to this. But if you are so super at braking you feel you should increase rear brake pressures why don't you just rip the ABS out? No point, if it's a street car, just get a new/rebuilt one IF needed. Theoretically an increase in braking effort in the rear should take some load off the front, reducing the need for ABS in the first place.
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Originally Posted by cormier View Post
Why don't you flush the fluid and see where that leaves you?That. The bias valve will of course help adjustment, if that will help you stop sooner I couldn't say...
No, it would not.
Why do you want to restrict the read line?
Quote:
Originally Posted by Ceeker View Post
I've heard people installing a larger master cyl. It will just FEEL stiffer, will not really help. Also start with clean fluid, also bleed the ABS system. Sometimes dirt or old fluid will reduce effective braking. the e30's braking system is pretty balanced to begin with. Obviously more braking required to the front due to the weight of the engine etc. Has nothing to do with the weight of the engine.The only solution I have heard about improving stopping distance is bigger brakes. more surface area faster stopping That is so not true. but as mentioned who is to stay with any of these mods you just won't end up locking up and skidding?
OP, get a new master, flush the system to hell, forget valves or big brakes, get rid of ABS or replace it with a working unit, don't say that you know how to "drive a car at the limit" if your ABS kicks in "only in the wet". Get good pads, good tires. Done.

No offense meant to anyone.
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Old 07-28-2013, 12:02 AM   #9
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OP, get a new master, flush the system to hell, forget valves or big brakes, get rid of ABS or replace it with a working unit, don't say that you know how to "drive a car at the limit" if your ABS kicks in "only in the wet". Get good pads, good tires. Done.

No offense meant to anyone.
Go easy on the drinking chief.
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Old 07-29-2013, 09:08 AM   #10
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Go easy on the drinking chief.
What is that even supposed to mean? He answered all your questions.
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Old 07-29-2013, 01:21 PM   #11
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What is that even supposed to mean? He answered all your questions.
I means that his senseless rambling didn't answer anything. I asked these questions in hopes of a response from someone with technical experience of the braking system, not strange assumptions and opinions that a 25 year old design is somehow flawless in every way. That's just crazy "drunk" talk if you ask me.
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