Reposting here since I got no replies in the EF forum:

Road race EF drivers with front/rear big brakes installed- I need some input

What are big brake kit users doing to upgrade their rear calipers?

I'd like to retain the use of my parking brake.

Current setup is 93 DA fronts w/ knuckles, Si rear discs, 15/16" MC & 4 disc prop valve.

I'll be installing Fastbrakes 11" upgrade front & rear + ITR front calipers.

The reason I ask is that I drove a friend's upgraded CRX with only the 12.2" 4-piston Wilwood kit on the front. Stock brake bias was right out the window. The car felt unpredictable and dangerous under heavy braking outside of straight line situations.

Obviously there will be a difference in how this feels in my hatch vs. his CRX due to the difference in weight distribution and wheelbase but:

What are you doing to resolve such a disproportion in brake bias?

Is there a beefier OEM caliper that I should be running in the back instead?

What aftermarket proportioning valve systems has anyone used to dial this in better?

Will the disparity be as noticeable when braking with ITR fronts as opposed to the Dynalite 4-piston?

Thanks all in advance for any input.

 

As you've found out first hand, larger front brakes will defiantly move your brake bias forward making the rear end lock up easily. The solution to this would be to install adjustable proportioning valves (as wilwood recommends) or install larger rear brakes (like the Type R rear brake kit).

There are down sides to both, so I'll try my best to explain them.

Larger rear brakes:
The quicker you can stop the vehicle (because of sticky tires), the less work the rear brakes actually do. This means that larger rear brakes increase weight with no real benefit to braking performance (other than balance of course).

Adjustable prop valves:
Honda uses two separate brake line systems on their vehicles (LF/RR & RF/LR) for safety & redundancy. You would either need plumb in two separate proportioning valves or redo the whole system into one line w/ one prop valve.

 

Thanks for the reply on this, much appreciated.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94eg! &raquo;</TD></TR><TR><TD CLASS="quote">As you've found out first hand, larger front brakes will defiantly move your brake bias forward making the rear end lock up easily. The solution to this would be to install adjustable proportioning valves (as wilwood recommends) or install larger rear brakes (like the Type R rear brake kit).</TD></TR></TABLE>

So I'm not alone on this, I find it too unpredictable to even consider going w/o some kind of bias modification.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94eg! &raquo;</TD></TR><TR><TD CLASS="quote">
Larger rear brakes:
The quicker you can stop the vehicle (because of sticky tires), the less work the rear brakes actually do. This means that larger rear brakes increase weight with no real benefit to braking performance (other than balance of course).</TD></TR></TABLE>

This would be the "quick n' dirty" solution? Is this a bolt-on affair or would I be fab'ing brackets? Who has done this mod on an ED/EF?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94eg! &raquo;</TD></TR><TR><TD CLASS="quote">
Adjustable prop valves:
Honda uses two separate brake line systems on their vehicles (LF/RR & RF/LR) for safety & redundancy. You would either need plumb in two separate proportioning valves or redo the whole system into one line w/ one prop valve.</TD></TR></TABLE>

Thank you for breaking that down. I was aware of the diagonal biasing scheme, but I'm a little confused: I count only 4 lines on exit from my Prop Valve. Are you refering to a more modern dual line scheme in ABS-equipped cars? Am I misunderstanding you?

A re-plumb from scratch is not out of the question. If the car sees any serious track time, I would want cabin mounted proportioning controls. Any recommendations on valves or am I stuck thumbing through the Bosch catalog like I did w/ the 914?

Thanks again


Modified by tmeracz at 7:58 PM 4/27/2006

 

Do you know what the piston sizing is on the Willwood kit?

 

I don't remember for sure, sorry.

A quick glance at their catalog lists piston sizes from 1.25"- 1.38" for Honda/Acura 4-Piston & 6 Piston Dynalites. From what I remember visually, that sounds about right.

The one thing I do remember about the caliper is that the setup was horizontally opposed and squeezed the rotor from both sides as opposed to the Honda design that uses 1 or 2 large pistons to squeeze the rotor against an immobile bracket. (sorry for the oversimplified explanation)

This made the whole assembly MUCH thicker and it's why Fastbrakes is recommending 16" wheels or larger with gross offsets and/or spacers.

We did get the 12.2" kit under a set of 15" wheels but it will require some machining to remove some excess material on the caliper.


Modified by tmeracz at 7:57 PM 4/27/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tmeracz &raquo;</TD></TR><TR><TD CLASS="quote">Thank you for breaking that down. I was aware of the diagonal biasing scheme, but I'm a little confused: I count only 4 lines on exit from my Prop Valve. Are you referring to a more modern dual line scheme in ABS-equipped cars? Am I misunderstanding you?</TD></TR></TABLE>

Your master cylinder has two separate lines coming out of it. One line powers the left-front & right-rear calipers, and the other operates the right-front & left-rear calipers. Those two lines travel separately to the prop valve & remain separate within. Inside the prop valve each of the lines are divided into two and sent to their corresponding caliper (4 total). It's like having two separate prop valves inside one valve body.

What this does is allow your brakes to still function if one part of the system is compromised. If you didn't have this, you would loose operation of all four brake calipers (instead of just two).