Notes on brake "upgrades", What's worthwhile, what isn't. Options

[lapuwali]

QUOTE (URY914 @ Mar 31 2006, 10:43 AM)

b. unless you live at the top of Mt. Hood, I don't thnk a street car only driven on the street will EVER have a problem with brake fade. c. I have stock calipers on my car. I realize I'm stopping less car than everyone else, but even when I did track events they were fine.

Paul, I know you live in Florida, where you only see mountains in pictures, but some of us do live in areas where the best roads are full of steep downhills with lots of hairpin turns. I've never faded the brakes on a 914 on these roads, but I have cooked brakes on other cars on them.

You're stopping a LOT less than most of us. You 914 weighs less than my Mini, which is factory-equipped with drum brakes all round that are only 7" in diameter. You're probably overbraked now. Time to turn down those rotors to shave off a bit more weight...

[john rogers]

More braking on the rear, that is what I thought when I used BMW calipers on the front and rear with a tee. They worked amazingly well until I put in the six and started driving the car harder since the high torque from the stroker four was not there any longer. After the six I added the M calipers and vented front rotors and cut out a slight amount of rear brake bias.

One thing no one has mentioned is something like titanium heat sinks between the pad and piston to shield the heat some from the fluid. I have seen some old time SCCA racers use this and there were lots of racing Porsches with Titanium pistons if I remember correctly?

[URY914]

QUOTE (Eric_Shea @ Mar 31 2006, 10:50 AM)

Paul, When I saw you name up on the list, that's exactly what I thought as the thread was loading... stock brakes for that car. Helps prove the point and (IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) with all your points.

It feels good when I get it right enough that someone agrees with me. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
Lord know people don't always agree with me. (IMG:http://www.914world.com/bbs2/html/emoticons/w00t.gif)

[URY914]

QUOTE (lapuwali @ Mar 31 2006, 10:51 AM)

QUOTE (URY914 @ Mar 31 2006, 10:43 AM) b. unless you live at the top of Mt. Hood, I don't thnk a street car only driven on the street will EVER have a problem with brake fade. c. I have stock calipers on my car. I realize I'm stopping less car than everyone else, but even when I did track events they were fine. Paul, I know you live in Florida, where you only see mountains in pictures, but some of us do live in areas where the best roads are full of steep downhills with lots of hairpin turns. I've never faded the brakes on a 914 on these roads, but I have cooked brakes on other cars on them. You're stopping a LOT less than most of us. You 914 weighs less than my Mini, which is factory-equipped with drum brakes all round that are only 7" in diameter. You're probably overbraked now. Time to turn down those rotors to shave off a bit more weight...

"I've never faded the brakes on a 914 on these roads..." But we're talking about 914's here, so nuff said.

BTW I am thinking of drilling some holes in the rear rotors. That cast iron is HEAVY!!! (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

[jamara]

A bit bored this AM, so I'm rambling a little...

The 19mm MC used with otherwise stock 914/4 brakes: this results in a reduction in braking force for a given pedal force (forcing you to push harder to stop), and the actual amount is 16%. Some people like the "firm" feeling this provides, but it doesn't mean "better braking".

The 19mm MC used with BMW 320i calipers OR Porsche M calipers (same size). This results in a 12% decrease in pedal effort for a given braking force. So, you will feel an improvement, but it's not a very big one. The downsides to this swap is the bigger calipers are heavier (unsprung mass, too), and of course you're doing a lot of work for a pretty small gain. You're also doing nothing to help brake fade. You're likely making it more likely, since you can now load a bit more heat into the brakes more easily. Happily, this also won't have a huge effect on front/rear brake bias, however, since the overall effect is so small.

A 17mm MC used with M calipers would produce quite a big change in pedal force v. braking force: 33%. However, this MAY cause a problem in that the 17mm MC is small enough that you couldn't move enough fluid with it before you run out of pedal travel to fully press the pads against the rotors. You'd certainly have to push it a long way to get the brakes to come on at all, and the brakes would likely feel touchy and mushy, but powerful. Rather like overboosted power brakes...

btw, "17mm" and "19mm" (and "42mm" or "48mm" for caliper piston diameters) aren't strictly correct. Even in metric countries, brakes are actually specified in 1/16ths of an inch, so 17mm is really 11/16, or 17.45mm, and 19mm is really 3/4 (12/16) 19.05mm. 42mm is really 26/16", or 41.275mm, and 48mm is really 47.625mm. Germans just list the sizes in the nearest metric size, whereas the Japanese perversely use both systems: 10mm for some parts, and 0.50" for others, for example.

So, I bought rebuilt BMW calipers about a year ago, along with 19mm MC. I later learned that these are probably not necessary. Since I was not impressed with the stock brakes on my car before I disassembled the whole thing, then they were probably in bad shape and needed replacing rather than upgrading. However, since I've got new ones I will go ahead and use the BMW stuff w/ the 19mm MC. BUT, I understand the stock rotor does not like BMW brakes given they are solid. I saw cryogenically treated rotors that were slotted and drilled for a pretty good price. They are solid and not vented, but being a superior material and "vented" via slots and holes, they should help brake fade with the bigger MC and caliper, right? I guess the real question is whether they can perform like regular vented M rotors or are they just a mediocre compromise? Thoughts?

[Racer]

Worthy upgrades? Itmes that fight a brakes biggest problems - heat!

1) More air to cool the brakes
2) "stickier" brake pads and good brake fluid

I learned those when tracking my SC. The overall brake performance was fine, the issue was fade. Remove the fade, and the brakes are good. Sure, I may have been putting more heat into the rotors due to the change in grip of the pads, but the additional airflow helped dissipate the heat at the same time.

[Dave_Darling]

... They are solid and not vented, but being a superior material and "vented" via slots and holes, they should help brake fade with the bigger MC and caliper, right? I guess the real question is whether they can perform like regular vented M rotors or are they just a mediocre compromise? Thoughts?

Mediocre compromise. The slots and holes don't do much to give you extra surface area to radiate the heat away, nor do they do much to promote airflow across the surface area that is there. Real vented rotors have around double the surface area of solid rotors, and they actually create air flow through the vents. Both of these are good for cooling the brakes.

--DD

[wobbletop]

Speaking of airflow... does anyone know where the brake ducts pictured on this site

http://members.rennlist.com/sjanes/brakes.htm

can be sourced from? I've tried using the email from the site but it bounced.

And would they be effective?

(IMG:http://members.rennlist.com/sjanes/brakeDuct_front.jpg)

[Dr. Roger]

The Hoover vacuum company... =)

Kidding!

But seriously, looks home brewed to me.

[Jeff Hail]

I was once told by a famous race car engineer that you can go only as fast as you can stop.

As my head cocked he then said "exactly" !

That person was Mac Tilton

[nsr-jamie]

So what are some nice brake upgrades available today....I have been away for a while and am just getting back into the 914 again.

I would expect the best upgrade to be 911 brakes.

I have a 71 911T front suspension on my 914 with S/S lines, 19mm master cylinder with a rear brake adjustable proportioning valve. Discs were new when installed, calipers overhauled, new Ferrodo pads and wheel bearings installed. It was awesome!!

[woobn8r]

I have just acquired some nice alloy 4 piston Boxter brakes and adaptors for the 914 rear trailing arm and 3.5" 911 front struts.

They mate up with vented (and drilled) 911 rotors. This is an excellent conversion as it is way more brake than my 3.2 914 will ever need...even on the track.

The larger pad area (with greater potential clamping force) spreads out the load on a larger rotor surface which dissapates heat more quickly...the alloy caliper saves some unsprung weight to offset the increase in rotor weight....end result should be a brake system that requires less pedal pressure for equal clamping force...it will also have a greater potential range (which increases feel for modulation) and will dissapate heat more quickly eliminating any need for ducts, hoses or fans...oh, and as this system works at the lower end of it's potential, it should last longer as well.

The trick now is to choose a good pad that works in the right heat ranges without chewing up the rotors....and then set the bias.

Car not ready for a while...but I'll report when she is.

[race914]

Speaking of airflow... does anyone know where the brake ducts pictured on this site

http://members.rennlist.com/sjanes/brakes.htm

can be sourced from? I've tried using the email from the site but it bounced.

And would they be effective?

(IMG:http://members.rennlist.com/sjanes/brakeDuct_front.jpg)

AJ USA has them

[race914]

Speaking of airflow... does anyone know where the brake ducts pictured on this site

http://members.rennlist.com/sjanes/brakes.htm

can be sourced from? I've tried using the email from the site but it bounced.

And would they be effective?

(IMG:http://members.rennlist.com/sjanes/brakeDuct_front.jpg)

AJ USA has them

I was late for a meeting when I posted this. Here's some more info.

The brake coolers work very well. They even work better when you run the tubing to the front air dam. See vents in pic





I actually have a fiberglas version of the coolers from OGRacing that has 3" tubing v.s. the 2.5" tubing on the AJ kit. OGRacing lists replacement tubing that mentions their "cool brake kit", but I couldn't find the Cool Brake kit itself? You probably need to contact them if you are interested. When I ordered mine, I got the whole story of 3" tubing flow v.s. 2.5" and also that their kit was a copy of the Al Holbert racing coolers.. I'm very happy with the OGRacing kit. But to be honest, the 2.5 tubing is easier to route. I have some clearance "challenges" with the 3" tubing but it is workable.

[jamara]

... They are solid and not vented, but being a superior material and "vented" via slots and holes, they should help brake fade with the bigger MC and caliper, right? I guess the real question is whether they can perform like regular vented M rotors or are they just a mediocre compromise? Thoughts?

Mediocre compromise. The slots and holes don't do much to give you extra surface area to radiate the heat away, nor do they do much to promote airflow across the surface area that is there. Real vented rotors have around double the surface area of solid rotors, and they actually create air flow through the vents. Both of these are good for cooling the brakes.

--DD

Thanks for the reply, Dave.

Of course! I never thought about the vents on vented rotors actually creating air flow. But naturally, cause they are like a really narrow squire cage fan!

So, mediocre compromise on the cryo rotors... Hmm... I'll need to think this one through. I don't believe I'm ready for the full 5 lug conversion to get 911 brakes, but since I'm preparing a turbo WRX engine for my car right now, I'm gonna need to stop this thing. I'm afraid the stock brakes aren't going to cut it. But, based upon Lapuwali's assertion, the BMW brakes might not give me that much gain anyway, even if they were slotted. Oh well, I will research some more. There is a wealth of info here so I'll go find it.

[purple]

Holy thread resurrection, Batman!

[jamara]

Holy thread resurrection, Batman!

Ha! Yeah. I think in academia they call Lapuwli's contributions to the body of 914 knowledge a "primary source". (IMG:style_emoticons/default/biggrin.gif) (At least based upon the limited time I've had to peruse topics, seems like that to me.)

Not a bad place to start.

[Eric_Shea]

Drilled and slotted rotors are designed to vent hot gases that build up inder the pads in extreme braking conditions.

The AJ kit is good for cooling rotors.

I miss James. (IMG:style_emoticons/default/sad.gif)

[shoguneagle]

Eric,

You are right on when you say "Miss James". Great thread with great comments.

Steve Hurt

[dinomium]

Eric,

You are right on when you say "Miss James". Great thread with great comments.

Steve Hurt

word