Good luck with your project.

I personally don't have the confidence to do that kind of backyard mod on something as life and death as the brake system. Do be careful.

 

I thought when you had extra braking on the front it causes the rears to lock up because of the additional weight transfer to the front with the better brakes. SO you actually have to pinch the rear off with the bias adjuster so you dont get early lock up in the rear.

That is a little scary the way that looks bolted to the hub but I would try it. If the surfaces are not perfectly line up...wont the pads wear to the new plane after a bit....I realize thats kind of rinky dink but man what a heat sink on the front for cheap.

 

idk, you wont be able to get even torque on that bolt... something fucked up could happen. If this was like a strut tower bar then I'd say screw it, but these are the BRAKES. If a caliper bolt snaps you are fucked (excuse my language). I would not ride in any car like that. It MUST be machined FLAT!!!!

No the extra leverage in front would cause your rear brakes to be ineffective. Think of it as arm wrestling... you've got vin diesel in front and woody allen in back. Which wheel is gonna stop first?

 

sub

 

From the pictures it looks you didn't actually drill or tap anything? Cause you kept changing your mind on which part you were going to drill and tap and last I remember it was the stock bracket that you were going to drill out, but from the looks of it, the calipers are bolted right to it. Did you drill out the caliper's mounting holes then?

 

guys guys guys!!! i havent drilled or tapped or bolted anything on yet...those bolts are not threaded in, they are just there to hang the caliper for the pics to show the bolt up

ok so i'll get that surface machined down flat...another question i have is where can i buy one of those brake proportioning valves at a good price?

 

Make sure to take careful measurements so that when the hub is machined it lines the rotor up DIRECTLY in the center of the caliper... I remember I had some wiggle room to work with and get things centered better.

 

Wait I am wrong, its not only the "better" braking (higher torque from larger rotor) that causes the rear lock up its the bias caused by different size pistons and the amount of fluid moving etc. that determines which end needs the bias. So it could be the front. I am sure there is a way to calculate, I dont rememebr how.

I would try:

Summit Racing
Pegasus racing
Racer Wholesale

for the bias valve for starters. Probably cant go wrong on ebay, they are a pretty simple thing.

 

Ahhh.. Good point.. I did not think about that.

 

My concern at this point will be how much material will be taken off and how stable it would be.. You would also have to use some sort of spacer to bring the caliper back out to level with the rotor.. I'm bit concerned about removing material from this area as materials are now removed from both sides and structurally not sure how sound it would be at extreme conditions.

 

Tilton makes a brake proportioning valve that has been sucessfully used in the past on FD's.

 

was never so good in history

 

'extra braking' is not so simple. What we are dealing with here is fluid displacement. If the combined piston area is bigger than that of the stock FD caliper, then the brake pad will travel less distance than they did before. IF THAT IS THE CASE, then you will have rears hook up first and therefore you would need to reduce flow to the rears.

However, I have a FEELING that you will have to reduce the flow to the front calipers because that's what usually happens when doing these types of mods.

NB! If you are changing fronts AND the rears from the same car, then you will end up with the inherent brake balance set forth by the EVO factory engineers. That being said, you COULD end up with the possiblity that the balance is PERFECT. However, as with most things, the best thing to do is to test it out (in a safe and controlled environment) - then go from there.

As a race car driver, I (and only me) find that factory brake bias for most cars is front biased, THEREFORE I prefer to shift the balance towards the rear which may make the car less stable in some situations, but allows for better turn in under near lock.

Lastly, this is an ENGINEERING project. Engineering, like most sciences are very simple - if you follow the rules, then no bad things will happen.

My recommendation: once you have the calipers prepped and hard mounted, measure the centerline of the caliper vs. the cl of the rotor and make sure they are parallel and ideally in line with each other.

 

hey guys i found something else that may help!!

there was an issue that by machining down the mounting holes of the FD's bracket, that the rotor will not be in the centerline of the caliper, but it will!!!

i pushed everything back on the car this morning and after looking at it for about 30 minutes i noticed that the rotor does not sit flush against the hub like the rx7's rotor does, so by opening up the center bore on the rotor, it will sit flush and that will re-align it with the centerline of the caliper...and even better than that, there will be less of a spacer needed to fit wheels back on the car

 

Man everyone jumped on me when i mentioned all these problems. Yes the hub hole needs to be opened up. I took mine to a machined shop with a stock rotor, and said "just make this one match that one". shouldnt cost too much. then put the rotor on the hub, take your new measurements and then have the hub machined accordingly. Good luck... you are getting really close! Please note how much you take off of the hub, as im interested to know how much material needs to be removed to get it to fit.

 

any updates on this i'm very intrested

 

ye i'm sorry guys...i'm a college student so money is kinda tight for me...i'll be able to finish the project after november 8th

 

Nice project. Sounds like it can be valuable information. I suggest a dedicated write up after it is all confirmed to work. Thanks for the time invested. This is way cool

 

any updates???

 

im sorry guys...its that time that we all have to face where our FDs just give us every problem they possibly can all at the same time...

my water seal went out on my motor this last weekend, actually i was going to do the brake kit this weekend and do the dedicated build thread...but now that money has to go into rebuilding the motor

i will finish the project, i have all the pieces at my house...the calipers, the new stop-tech brake pads, and the rotors

unless someone wants to pick up the pieces from me and finish it...i'll sell all the pieces for what i picked them up for.... $575 shipped for everything if someone wants to finish the project

the only thing that needs to be done is the center bore of the rotor needs to be opened by 1mm to fit flat against the hub of the FD, and the spindle bracket needs to be grinded/machined flat

i got quoted $100 by the machine shop by my house, so it would basically be a 4 piston Brembo big brake kit for the front for a total of $675 give or take like 15 bucks

if someone is interested then shoot me over a PM...if not then i'll finish the project after i rebuild my motor

 

i just bumped into this thread.

first off, congratulations on being creative. i applaud your efforts. it would be great if it there was a boneyard solution for the FD's woefully under capacitied brake system. the chassis is a rocket ship on a road course due to it's racecar suspension but driving it at it's limit on a road course destroys the brakes in two laps. primary problem, lack of sufficient front rotor mass.
(there is nothing wrong w the OE front caliper)

stopping fast is all about brake torque capacity and longitudinal brake BALANCE.

you MUST have both.

as was posted earlier, brake balance is one of the items a winning racer is constantly adjusting during a race. you want as much rear brake in a front engine rear drive car as is possible. adjust it up until you are on the verge of spinning at corner entry.

on a street FD there isn't a need to adjust balance going to the store but you do need proper initial balance.

the FD stock brake balance, which is a good place to start, is 68% fr 32% rear.

a dynamic proportioning valve alters this a bit at higher G.

as to your project:

using your numbers (1.5 and 1.75 front pistons and a 355 rotor) your brake bias is 77% front and 23% rear. you now have a 2 wheel brake system. at max braking effort you will be just controlling the front tires at lockup and the rears will be along for the ride.

my primary point is you need to balance the rear w the front. you need to adapt the rear brakes to the FD or use something aftermarket.

RacingBrake, being the smart guys that they are, recognised this and instead of just slapping on a set of big front rotors and red calipers designed and built a larger (322 X 20) rear rotor. brake bias is 70/30 which works perfectly. the brakes are nutso good. and of course expensive compared to a boneyard alternative.

there are many ways to get it done and in my view the key to a boneyard brake solution is the rear.

let me know what the rear caliper diameter is and the piston diameter and i will give you the balance.

good luck,

howard

 

This is true in principle, but what's not taken into calculation is the amount of fluid going to the caliper piston(s) and also the difference in weight transfer that happens with higher braking. These numbers are not linear.

Bigger brakes in the front will cause huge weight transfer compared to stock and the rears will lock up much easier. Also, a proportioning valve will limit fluid movement and therefore the entire equation will shift.

just $.02

 

"what's not taken into calculation is the amount of fluid going to the caliper piston(s)"

you are correct.

the amount of fluid going into the piston is not in the calculation because it has nothing to do w brake bias (or anything) since fluid is non-compressible.

"Bigger brakes in the front will cause huge weight transfer compared to stock"

you are not correct.

bigger brakes in front, w stock in the rear will decrease braking Gs since the rears will not be able to do as much work. weight transfer is a function of center of gravity, static weight and decelerative G force. since weight transfer is a function of Gs and too-big-fronts decreases overall braking big front brakes will create less longitudinal weight transfer, not more.

as to a proportioning valve: you don't fix too much front brakes w a proportioning valve. so you put too much fronts on the car and then add a proportioning valve in the front to trim it back to balance??? you now have negated the idea of the larger front brakes.

as previously stated, the key to brakes is longitudinal balance and there are many front brake upgrades but the key to increasing overall braking performance is the rear.

howard coleman

 

d_k, I would strongly resist the urge to get into a technical argument about brakes with Howard.

 

there used to be a big brake upgrade that used the stock calipers but larger rotors. it started with a "m" i believe. i dont remember where i saw them. it rebuilt the calipers and made them wider to accept the larger rotors, it also came with brackets to move the caliper the necessary ammount. pretty sweet really, it was about 1k. i dont know whatever happened to them though.