Spank

iTrader: (1)

Guys this is a brake question. Spank1 is a autox car and is set up as such. My problem is I want to stop faster and I do not know how to make it happen.

With 285/30/18 V710's on front, I can hit the brakes as hard as I can, and unless their is surface problems, I cannot engage the ABS. I want to stop faster.

Not being a wrench, I would say I want the calipers to clamp harder, how can we make this happen?

System works fine, braided lines, good fluid, everything is working as it should be. HP+ pads, slotted rotors ect.

Any help on what I can do? A big brake kit is great for disapating heat, but that is not my problem. I just want the car to stop NOW. Other people have been in my car and say the brakes are great. However I have been in other cars where the brakes are better. So any suggestions on what I can do to make my clampers clamp harder?

Allan

Smilodon

Hm. So. You have more traction than braking. Nice to hear that.

Supposing you have good rotors, do you have stock calipers?

You aren't using silicone fluid, I hope. Too springy. I've tried it.

How stiff are your calipers? Are they flexing under load? You can tell this sometimes by your being able to keep pressing the pedal down after the brakes are engaged.

Stiffer calipers will give you and your ABS system more direct and immediate control over the braking force at any given moment.

Another benefit of stiffer calipers is that you can use more leverage on your brake pedal without making the pedal travel excessive.

With an infinitely stiff caliper, no-bulge brake lines and tubing, you can set the leverage on the brake system to whatever you want. But. Calipers don't tend to be infinitely stiff.

However, the more dimensional stability the braking system components have, the easier it is to depress the pedal and expect immediate braking response.

Bigger calipers have more surface area to apply to the rotor, which means that there is less concentration of heat per square inch of brake pad. If your combination of rotor and pad thickness is great enough, the calipers can be made all in one piece, aiding stiffness even more. Porsche used one-piece aluminum brake calipers on their endurance racers. This was possible because the brake rotors were about an inch thick, and the pads were each an inch thick, so it was possible to machine the piston holes. From inside the caliper. They were real works of art. Best-designed calipers I have seen. They straddled the rotor so that a large central portion of the rotor protruded through the middle of the caliper. Great for cooling.

Pistons on the trailing side of the caliper were smaller than the ones on the leading side, so the leading piston could apply more pressure to the pad, and produce a less wedge-shaped wear pattern on the pad.

If you ever see brakes with the smaller pistons mounted toward the leading edge of the pad, (leading edge, as in, the part of the pad that the surface of the rotating rotor contacts first) then they were installed incorrectly.

Mushy, pistons-on-one-side calipers are not what anyone uses when performance is of paramount importance.

Are your pads at the right temperature for the intended braking loads? If the pads are too high performance for your average driving, you can glaze them. If they are too low, you can overheat them. Either way, they won't have much grip.

One indicator of overheating is when they perform better when first applied than later in the same session.

Mahjik

iTrader: (1)

Spank,

Basically, you want more torque and/or more friction applied to the brakes. The easiest way to start would be pads with harder intial bite as well as a higher coefficient of friction.

I would look into the Carbotech Pads. I hate Hawk pads with a passion.

If you are unable to find a pad with a higher coefficient of friction that can work at lower temps for AutoX'ing, then the next thing is to look at doing something with the calipers. Moving the caliper out further (i.e. using a larger rotor) will increase the braking torque. However, this is a more extreme way of getting to it so I would look at the pads first.

Interestingly enough, I was unable to find any real specs on the Hawk pads. Here's a list of the products Carbotech offers:

http://www.carbotecheng.com/prod-ct-compounds.htm

Spank

iTrader: (1)

Thanks for the info guys. 1. I do not know how to get a stiffer caliper, how can we get such a beast?

As for pads, I have tried lots of pads but I do not know if I have tried those. I will mark those and start doing a search looking for .6 or higher. Thanks for the tip on the pads. I have used Hawk HP+ because I have always been told they bite the best.

Allan

RETed

Run more aggressive brake pads?
HP+ is not what I would call the most aggressive.
Try Porterfield R4's?
The R4 will need some heat initially, but after the first run, they should work fine in autocross.

The other option is to run a brake master with a larger bore...


-Ted

DamonB

First thing I would do is try different pads. Stiffer calipers will cost much more money and will have practically no effect compared to what the pads can do.

Bukwild

I kinda had the same problem but when I put in the SS brake lines it cleared all that up. Might have had a pin hole in one or something like that before I changed them over but after it would lock up the brakes no problem.

Rotofire

Hit a wall

jgrewe

iTrader: (1)

I second(or third?) the brake pad change and the braided lines. In auto-x it is easier to find a pole to hit instead of a wall though...

65Imp

iTrader: (8)

The 929 master cylinder upgrade was one of the older mods to the braking system that many professed significantly more confident braking and brake feel, both with, and without a big brake kit.

Spank

iTrader: (1)

I already have the lines, but will try different pads. So far it looks like Carbotech XP10 have the best coefficient. However I have also heard that those numbers are like tread wear numbers, they vary between manufacture.

I will be trying either Carbotech or something better if their is such a thing.

Spank

RotorMotor

iTrader: (5)

is this true that if you run larger tires up front you can significantly increase your braking ability???? i would not have assumed that was the case. if so... why arent we all running HUGE tires up front?? (sorry to digress) -heath

Spank

iTrader: (1)

Not sure of your question heath? My brakes are ok, and with the tires I stop pretty quick, I just need better clampers to stop faster.

If you have never run a very grippy tire then you may not have experienced the above.

Allan

Spank

iTrader: (1)

Brakes. From my research Ferodo makes a brake pad with great friction however not for our car. Porterfield R4's have a friction coeficient of .4. The Carbotech Panther XP 10 look like they are the ****. Mahjik, you the man.

Thanks

Allan

P.S. How has the best prices? I will try them next.

DriveFast7

iTrader: (1)

what are the specs on the 929 master cylinder? smaller bore?

rynberg

More tire = more traction = stronger braking before tire lockup = quicker braking

No, larger bore, which is why it shortens pedal stroke. The 929 has a 1" bore, the FD has a 15/16" bore. Only 1/16" but it makes a difference.

RotorMotor

iTrader: (5)

with the same tire compounds... wouldnt your coefficient of friction on your smaller contact patch (with more weight), be equal to the coefficient of friction of a larger contact patch with proportionally less weight?

also, if larger tires up front can SIGNIFICANTY decrease your stoping distance... what size would you recomend as a healthy balance between added friction, and steering etc? id imagine at a certain point a tire that is too large up front would negatively affect steering charachteristics. thanks again. -heath

rynberg

The classical physics description of coefficient of friction does NOT work for tire grip. More rubber on the road = more traction, period. Feel free to read the thread about it in the archives section if you want a THOROUGH explanation, LOL.

The only problems with too big of a front tire that I can think of would be tramlining and the inability to get the tire up to full temperature (more of an auto-x problem with DOT-Rs). I don't know if too wide of a tire would reduce steering feel or similar.

Spank

iTrader: (1)

Rynberg is right. A large tire up front will slow down the steering some, but it will provide you more grip, provided it can get warm. Andy runs 315's up front, and he lives in CA. It is warm there all the time. However in ID it is not the same temp so a narrower or smaller tire is called for in the cold.

So pick your tire based on your ability to get it warm when you need it to.

AMRX7

Hi Allan,

Sorry, just saw this thread. I ran the HP+'s on our car and concluded (as others have said) that they kinda suck. Went back to Carbotech Panther+ as I think it is a great autox pad. Way better than the HP+'s. Tell Carbotech what you are doing with the car (autox) and they should be able to tell you which pads are more track oriented than autox.

-Andy