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Reverend Hillclimb
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Discussion Starter #1 (Edited)
So I am maybe one of the few people on here who were never impressed with the MKIV stock brakes. I loved the stopping power but despise the pedal.
Now I wanted a racing setup because I am currently prepping my car for Hillclimb events.

So I went ahead and did what I always wanted, dual masters with a balance bar. I have a 5/8 cyl up front after lots of math, and 7/10 in the rear, so that I can start with the bias at 50:50 and move on from there.

Big thanks to Ken Scarbrough from Tilton, and Klint Turner from Compbrake, for making this happen and providing everything that I need.

Now the Tilton bias adjustment knob will be mounted in my carbon radio panel delete, next to the fire suppression system pull handle.

I spent weeks figuring out all the measurements, and completing this. I will be playing and adjusting with the variables as soon as the car gets the single turbo system complete. I kind of decided to do the brake setup... then go single... then go EMS, blah blah blah too much in one go.

Some must ask why? Adjusting brake bias on the fly is VERY helpful when changing road surfaces during racing, compensating for wear, and to change the pedal feel and travel (my biggest goal).

My ultimate point is that it has always been a goal of mine to MAXIMIZE the hell out of the stock braking system, but at the same time tailor it to my needs.

This hobby to me is part enthusiasm, part art. The beauty of the parts in unison is second to none in my eyes. Quality is my only goal in this build.

Here are the pics of the setup, bias knob not installed yet since the interior is apart, but pictured.

EDIT: also working on a tilton clutch (twins turbo) to upgrade the stock unit. I also finished the adjustable rod with clevises to attach this bias box to the pedal itself.
And the car does not have ABS, I think it would not react well to the vast difference in alteration.

Before the pics, one more important note - I measured the stock pedal ratio to be around 3.5:1 which is a disaster for manual brakes. I modified the pedal and rod to accommodate a 5.75:1 pedal ratio, 6:1 being perfect (according to Tilton).






 

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Drop some pressure gauges in there too.

 

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Reverend Hillclimb
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Discussion Starter #3
I am plumbing in two 2000psi brake pressure sensors to be displayed on the Racepak IQ3 Dash.
Planning ahead (;

On another note, thats a beautiful dash
 

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Reverend Hillclimb
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Discussion Starter #5
Looks great!

Are you planning on implementing a pedal box in the future or are you just gonna stick with the stock pedal setup?
Thanks! I attempted to fit a pedal box in the car, however, given my seating position, the design of the floor pan, and the total space available, I opted out. I originally planned to run a tilton 600 series box, however, after a while it hit me, that a dual master cylinder system could exist outside the realm of a full pedal box.
With this I can adjust my stock pedal height to make heel toe-ing easier, and at the same time retain my seating position, and also, I do not like the way floor mounted pedals feel, but I could of gotten over that.
Another thing, after adjusting the pedal ratio and all that, the excess work of the pedal box should be unnecessary since this should "virtually" work the same, down to the adjustment.

Edit: one downside - the pedals dont look as cool as a pedal box haha
 

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Question to suit.
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Winning!
 

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Thanks! I attempted to fit a pedal box in the car, however, given my seating position, the design of the floor pan, and the total space available, I opted out. I originally planned to run a tilton 600 series box, however, after a while it hit me, that a dual master cylinder system could exist outside the realm of a full pedal box.
With this I can adjust my stock pedal height to make heel toe-ing easier, and at the same time retain my seating position, and also, I do not like the way floor mounted pedals feel, but I could of gotten over that.
Another thing, after adjusting the pedal ratio and all that, the excess work of the pedal box should be unnecessary since this should "virtually" work the same, down to the adjustment.

Edit: one downside - the pedals dont look as cool as a pedal box haha

Hehe. Thanks for your insight. I feel the same way about floor mounted pedal boxes, i don't like the feel. If i am to get a pedal box for my track car it will be a hanging type as they feel more natural for some reason.
 

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Reverend Hillclimb
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Discussion Starter #8
Hehe. Thanks for your insight. I feel the same way about floor mounted pedal boxes, i don't like the feel. If i am to get a pedal box for my track car it will be a hanging type as they feel more natural for some reason.
They really do, I thought about that as well, but honestly I was too lazy to deal with the fab work haha
 

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They really do, I thought about that as well, but honestly I was too lazy to deal with the fab work haha
Hehe.

Keep us posted, i would love to see some pictures of the pedals as well. Even better, a picture of before/after on the modifications you have done to the pedal height etc, and also a little "review" after you have gotten some time behind the wheel with this setup.

Thanks in advance :)
 

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Reverend Hillclimb
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Discussion Starter #10 (Edited)
Hehe.

Keep us posted, i would love to see some pictures of the pedals as well. Even better, a picture of before/after on the modifications you have done to the pedal height etc, and also a little "review" after you have gotten some time behind the wheel with this setup.

Thanks in advance :)
That I will be doing, and I have a picture of the modified pedal, its not the best picture, but let me find it.
Here it is.
You can see the old hole where the original clevis was, and the new clevis with quick release pins to make adjusting easier.
Also you can see the brake light sensor is still activated, and I have a-lot of room for adjusting and playing around.
 

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Game Over
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Looks good Slack!

What is the difference in pedal effort compared to the stock power brakes? Eliminating the ABS looks mandatory in this setup, but having brake bias control on the fly is pretty cool. IIRC, the MKIV is pretty front biased. I've driven my friends old E46 M3, and I didn't really like the floor mounted pedals either, it felt a bit awkward for footwork, IMO.
 

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Reverend Hillclimb
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Discussion Starter #12 (Edited)
Looks good Slack!

What is the difference in pedal effort compared to the stock power brakes? Eliminating the ABS looks mandatory in this setup, but having brake bias control on the fly is pretty cool. IIRC, the MKIV is pretty front biased. I've driven my friends old E46 M3, and I didn't really like the floor mounted pedals either, it felt a bit awkward for footwork, IMO.
Thanks bruv
I am waiting on the carbotechs to truly test it. So honestly, only from depressing the pedal I am digging it.
To explain it to you I would say the pedal has half the movement of the stock pedal, but with half the movement comes full bite.
Also this should help me prevent lock up without abs, by being able to find the "sweet spot" (or g-spot for the ladies).
Again I havent taken it out but I have tested it ala pressure gauge and I have done a bunch of math.
Also for the sake of it, I did not use tiltons recommendations for master cylinders. Their choices were higher bores to decrease pedal movement more, so stiff pedal, very little movement, which is excellent in road racing. However I wanted to be able to enjoy the car on the street once in a while (safely). Also I wanted more modulation because my racing surface would not always be fully paved. The smaller MC's I have used create more line pressure which is what I wants

Nice thing is all the weight my brake system has shed, and simplicity. Eventually when I have money to play with I will buy a BBK
 

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Reverend Hillclimb
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Discussion Starter #13 (Edited)
If anyone needs help with this let me know. I have all the values stored, and the results were these.
Now the variables are:
Stock TT Calipers F/R
.625 front MC bore
.700 rear MC bore
+.150 balance offset (balance bar is .15" to the front, giving more front bias)
.45 friction coefficient (very modest)
Many other variables including weight, weight distribution, tire diameter, etc. Basically a whole damn lot.

So the big winner.

I get 1G of braking with 90lbs of pedal pressure.
I get .7G of braking with only 64lbs of pedal pressure.

As you see, the numbers are juicy.
Here is the snapshot I have taken of my calculation results.
The variables are endless but I have 26 variables used. Only thing I cant compensate for are surface conditions, but I pretty much covered every thing else

In the pics: Ignore the individual measurements for front and rear torque, only the totals matter. The individuals change with a turn of the bias adjustment knob, so that variable is ever so... dynamic


.7G/64lbs of foot force


And 1G/90lbs of foot force



If you look at the last box on the right most column in each picture, the efficiency of the system is within +-3% deviation at the most, so math aside, the system is ~97% efficient at achieving 1g of decel at 90lbs of squat rack
and ~97% efficient at achieving .7g of decel at only 64lbs of baby squats

Mathematically speaking the car should brake like an animal (remember pad coefficient, if I move up to a medium pad at .5 co-friction, I achieve 8% MORE above 100% efficiency, meaning I require even LESS pedal pressure). A frail chimpanzee could bring the car to an immediate halt.
The friction coefficient I will actually use is greater than .5, so 8% decrease in the pedal pressure as a minimum will mean my legs will not be linguine by the end of a session.



To put this in perspective, I have records of ~2500lb cars with ABS and full slicks hitting 1.2G of braking load.
I wont be hitting 1g (unlikely) due to the re71r tires I am running, so basically to make it simple, the brakes should outdo the car.
Again, all hypothetical, my math is on point, but again, infinite variables.


I will have serious results when the build is done, so then I can shatter some new supra records... (as if)


Addendum:

I forgot to add.
The pedal ratio is what is helping to decrease the leg work.
I did not have a chance of measuring the booster area to determine how much assist the stock unit has.
But for my system, 50lbs of foot force is about 288lbs because the pedal ratio is now 5.75:1
So for every 1lb of pressure, I multiply it by 5.75
I may try to raise it past 6, but the stock pedal does not have too much room to go up
 

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Reverend Hillclimb
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Discussion Starter #16 (Edited)
Like the "part enthusiasm, part art" outlook.
I kind of chalk it up to 'workmanship'.
More people should practice this.
Good job.
Thank you, to some it may not seem like much, but a lot of planning goes into stuff like this. These cars for some reason inspire many people to go way beyond what I myself have done. Many a folk here are artists in their own guise.

And now another issue because of wanting it to please my eye. I am going to, again, re-do the brake lines. Working where brake fluid is present terrifies me. You can practically use it as paint stripper

That is a sweet setup! Subscribed! :)
Thank you as well. It will look sweeter when I actually order the coupling to install the bias adjuster in cabin, I am working on some other stuff though so just a bit longer!
 

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Reverend Hillclimb
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Discussion Starter #17
Snagged a pic, so to the right of this will be the fire pull handle. Weird the carbon looks funky from that shot but in person its some of the best carbon I have ordered.
Edit: just realized the iphone 5 camera is atrocious
 

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Reverend Hillclimb
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Discussion Starter #19
Nice. Looks like you did your homework too. Keep up the good work :)
I did my best! Last thing I wanted was to have to stand up on the pedal to stop the car.
I should be able to reach the peak of lock up, and keep it there
 

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I did my best! Last thing I wanted was to have to stand up on the pedal to stop the car.
I should be able to reach the peak of lock up, and keep it there
Hehe, yeah. Just by removing ABS and the brake booster you improve pedal feel greatly. By taking it even further like you have i imagine will be a dream in comparison to the stock setup.
 
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