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Ep3 BMC upgrade

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13
Hello everyone, last winter i install 4-piston brembo callipers from Alfa Romeo 159 on to my EP3. Much better than OEM, but my problem Is that the brake pedal is too soft. When I hit the brake pedal it take about 10mm before you can feel the brake effect. This Winter i want to install 2-piston brembo to rear and i think that the brake pedal feel will be even worse. Any help with that? Swap BMC to bigger one? Thank for all opinions :)
And sory for bad english :D iam from Czech republic :)
 
That shouldn't occur. Brakes are a sealed hydraulic system, the only parts of it which would lead to softness are either air in the system (that you can then compress) or the flexible hoses are stretching more than usual. You could try a full flush/bleed, and if that doesn't help then replacing the hoses with some braided lines.
 
I already have braided lines and brake was bleed many times by many people. When i install a 4 Piston brake i caused that a bmc have to push more fluid to callipers because a diameter of piston Is bigger now and cannot make necessary pressure. That can cause soft brake pedal? if there Is an air in brake system shouldn't a brake pedal feel harder after 4 or 5 pumps and then fade to the floor? Sory if im wrong :)
 
If it's only a small amount of air then it won't have the same effect.

However, assuming it's none of that, is this only when braking heavily? If so is it possible you're causing the bulkhead to flex? A brake stopper might help there https://www.tegiwaimports.com/tegiwa-brake-stopper-honda-civic-type-r-ep3.html

Have you checked the rear calipers to make sure they're sliding properly on their pins and not stuck/flexing because only one side is moving properly?
 
Rear calipers were refurbished And works fine. About brake stopper, i already looked at it but still waiting to find somewhere technical drawing to make my own brake stopper :D (very overpriced in my country). Could be a problem with that I upgraded front brake and rear is still Stock? Front need more pressure and rear dont, So when i push the brake pedal master cylinder push brake fluid to brake system and because od stock rear brakes there isnt space for pressure that front brake needed? Just an idea, im boring at work :D
 
The only thing insufficient pressure in the vacuum-assist would mean is that the pedal requires more force from you (remember what brakes feel like on old cars). It shouldn't make it feel soft, or spongy. I guess your front/rear bias could be off, but I wouldn't expect that to lead to this issue, that would just mean your rear brakes locked up too easily.

Hopefully someone else can help because I'm out of ideas sorry.
 
I need to check that easy lockup of rear brakes. Thats right, i dont need to push pedal too hard, my mistake. No reasons to sorry, thank you very much for your answer :)
 
I think the OP means the bigger brakes now require more pedal travel for braking effect, so wants a larger brake M/C to compensate for this.

I'm not sure of one for the EP3.

Either way I wouldn't upgrade the rears. Totally unecessary even on a heavily used track car.
 
Yes correct. Thats my problem. I think Is necessary for me because when i go fast And brake harder, front of a car Is going Down, rear Up And car Is unstable, so that means for me the rear brakes is too weak.
 
And better rear brakes will just lock the rear wheels, so then you might spin badly.

You need an adjustable brake bias valve, or front brakes of the correct size.

The Stoptech big brake kit keeps your original brake bias
 
It could be what you describe with regards to calliper piston size. Do you know the difference in size between OEM and your alfa romeo calipers?

The other check is the honda master cylinder size vs the alfa romeo one. If there's a large difference then that's likely your cause. I'm not sure on how slave cylinders will react to different master cylinders though... Might be worth matching the system if you change one - change both?

First job is check the differences in diameter though.
 
Good idea, So... MC diameter of ep3 is 23.81 mm And AR diameter is 25.4. Piston diameter of ep3 Is 54mm And AR diameter Is 42mm. I think there is my problem with MC, i want to change the MC to bigger one but still searching for some that will match ep3 and before i spoil something i wanted to ask for advice :D
 
Good idea, So... MC diameter of ep3 is 23.81 mm And AR diameter is 25.4. Piston diameter of ep3 Is 54mm And AR diameter Is 42mm. I think there is my problem with MC, i want to change the MC to bigger one but still searching for some that will match ep3 and before i spoil something i wanted to ask for advice :D

That sounds about right then, although not a huge difference between the masters. I'd give that a try if it's not too expensive. You could always rig it up and test it before going for a full install??

The calliper piston size is significantly different, different enough that I wonder if it's enough to bridge the gap between a 54 and a 42mm calliper... Perhaps the slave is different too? Ie a different multiple of power... Civic 1:3 and alfa 1:4 or something along those lines? I'm just guessing here...
 
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