I don't think I've ever seen brake misspelled as break more often than here. Or any other term spelled incorrectly as often.

Threshold braking is the important thing. If you have too much brake for the tires / road surface / conditions then all you do is lock up and slide. At best you flat spot your tires, at worst, well I shudder to think. When you slide you don't have full control, and you don't stop as quickly as with threshold braking. ABS will put you in between.

I don't think I've ever seen brake misspelled as break more often than here. Or any other term spelled incorrectly as often.



I speeled it rong on purpus.

Wow Joe. Who pissed in your Cheerios.

1. It's not a race car. Those pictures were taken during the first assembly. I hope it's OK with you that it was new at one time.

2. The MXs are an obvious compromise for the street. I made the decision based on the fact that I was going to drive the car 900 miles to WCC05 when the car was first complete.

3. I don't have a G meter, but thanks for the attitude anyway.

that's exactly what I'm doing (making a decision based on experience)

seeing that you are using a 19mm master cylinder changes things
that would give you more control over those big suckers

yes, I think it's cool that you pulled it off to mount those on your car
but I also think they're overkill and you can get equal braking performance for less money without adding unsprung weight

I'm going to be installing '89 Carrera brakes all around on my V8 conversion. I'm thinking this will be a good base line in case future upgrades are considered. My initial impression was how heavy those cast iron calipers are, and thinking maybe the pad area was a bit small. To my surprise though, the pad area is nearly the same as 4 pot NDL Wilwood's.

A couple of observations regarding brakes and braking. First, if you look at any modern semi-performance auto, they all have very large rotors and calipers; Mercedes, 350Z/G35, etc. Perhaps they're better suited to ABS; I don't know. Second, in-experienced racers tend to have a common approach to driving until they gain more experience. That being they often feel the need to brake hard and deep to be fast and lack attending to other areas. This leads to over-using the brakes which results in overheating and fade; blaming the in-adequate brakes. As such, the tendency is look to the braking system to correct or reduce lap times. So, on go the huge brakes.

Andys

A couple of points that need to be made here.....

Use of the car has to be determined first. If you run on the track and generate a lot of heat, you need more heat capacity in the system (brakes and rotors) If you run on the street, too much heat capacity will hurt you and cost you needlessly. Most brake pads like to be warm to work properly. On the street, they don't get real hot and it may truly be a waste of money to upgrade since you will never get them real hot (or even hot enough) Ever notice that lot's of pads work better after you make a few stops and they get warm?

I also disagree with a blanket statement of "more hoprsepower requires more brakes". It only applies again if you are racing (or significantly raise the weight of the vehicle) and it assumes you will get a higher top speed from point "A" to point "B", again generating more heat that will need to be off loaded. It also assumes thaat the original brakes were borderline to begin with. You could have more horespower and not significantly increase the loads on the brake system when used on the street. There is of coure more "potential" to generate more heat.

Anyway, I only suggest that brake suggestions need to be stated for their intended use. Most everyone is correct, just the way they are used is different.

Over simplified:

Smaller brakes for street
Bigger brakes for track

Another issue is the ability of the system to stop the vehicle with reasonable peddle pressure. I have a 71 Chevy truck, you had to stand on the peddle with both feet to stop the thing. VERY scary. I tried everything including bigger booster, new calipers, 4 different brake pads. The brakes never faded though even towing. Solution: A hydra boost system. It stops just like a late model truck now. Again, not a fade or heat issue, I just couldn't get enough pressure on the system.

Andy,
my theory about modern cars having big brakes is because most cars average around 3300lbs a piece. I'll bet trucks average over 4000lbs/each. So I believe that

1) they need lots of heat dissapation due to their grossly fat tonage. In fact someone tell me if Heat friction from braking is linear with weight or is it exponential?

and
2) manufacturers would rather put an extra 20lbs of rotor on a vehicle than face any liability for brake fade.

Manufacturers have ALWAYS built vehicles to the lowest common denominator.. or in other words: "the most stupid consumer"
at least with the current state of world affairs on liability and law suits they will.

That is not a commentary on JoeRS brakes or anyone else on this forum.
I appreciate the neat things that have been done by people on this forum.
but If I have to anne up my opinion, I believe that a properly rebuilt, properly rebled stock system with GOOD (pagid) PADS, and modern tires will be very sufficient for race/street cars that aren't able to top 140 - 150mph

brant

My take on this is that the original poster wanted BIG brakes for the sake of having them, not needing them....if he was serious about building a "race" car, then he would have thrown the BMW calipers in the trash and not even considered using them on the rear.

Nothing wrong with overkill or having more than what is needed if that is what you WANT..the only time overkill is really a bad thing is if you are paying someone for something that you don't need yet the seller insists you need it just to make a buck....

I don't see Joes brake system as true overkill since he never said he needed those huge calipers...it was something he wanted.

Do I need 12" rotors?? He// no, but I want them, so it's not overkill since I am not trying to justify the need for them by saying something smaller won't work.

You might as well say a 3.2 is overkill compared to a 3.0 if you don't need the extra power....

Braking converts kinetic energy into heat. Kinetic energy is basically mass times velocity. In a car you have two kinds of velocity, linear speed and rotational speed.
Braking involves the coefficient of friction times the surface area, and those areas are the pads and the tire contact patch.

You could say the braking heat dissipation is roughly linear with vehicle weight. Note that a significant amount of heat is generated in the tires when braking, not all the heat has to be dissipated in the brake rotors. Larger tires have more surface area for cooling purposes as well.

Not sure if I missed it - and maybe I'm thinking incorrectly.
I would assume if you go to a larger diameter wheel, you have just increased the rotational mass, and hence, it would be harder to stop that mass (sorry, I am no physics major). Anyway - My biggest mistake was tossing my /6 Calipers , but that's another story.
So - I see lots of SUV's and such that have gone to "DUBS" (i.e. 20 inch wheels), but have kept the same brakes. Far as I can tell, they stop OK, but guessing it's a lot more wear and tear on the pads ?

The stock /4 rotors are larger diameter than many modern cars, in fact our 3200 lb Volvo has smaller brakes than a stock 914 except on the Volvo they are vented

Even my 2001 Huyndai has smaller brakes than the 914...the 914 was ahead of it's time for the size of rotors used...

Sweet posting fellas! So, if I remove my P-valve and use a T, will this in any way change my breaking power/feel with the setup I have now. Like I said, I was not impressed with the stock breaks so I went bigger.

JPB,

you have a good way of starting the #hit storm around here.
your comment about removing the proportioning valve is bound to start the next round!

let me ask you:
- did you rebuild, re-bleed, and service your stock brakes in any way?

I'd recommend that you do that, and that you get the fresh fluid through there to alieviate some of the spongie-ness you feel.

might want to rebuild your pedal cluster if it happens to have shot bushings too...

then buy good brake pads (have I mentioned PAGID makes nice pads for the street?) and decent tires.
Yes the pads will cost you 200$ for all 4 wheels.

MANY guys race in PCA production class with exactly that set up.
you would be surprised what that set up is capable of.

brant

Yup, yup, yup. All blead, all new, SS break lines, new fluid dot3 .......,19mm master new but the pads might be the culprit being like $20 for the fontsLOL.

Stuff on the car for those who think of upgrades:
Konis F/B
FG bumpers 916
CF lids
front swaybar stock for now, have rears but won't install
Break upgrade? or just more crap, you be the judge
POS tired four banger looking to be, upgradedLOL
At the paint shop
Role bar
long stiffener kit like available here but my own
galv. floor flat
header & S-trap
stiff rear shocks of unknown dinomination
holding a continous hard on for carbon fiber parts gimme gimme

Breaks, the "hand of the break god" kind would be nice

Never undercut the beer funds and let the schmit fly!

I've actually taken cars in to have them power bled
(a teener 15 years ago)
after failing to get rid of the spongy feeling.

I'm thinking that you need to buy some ATE and take it to a shop or at a minimum bleed it again.

some times cracking a line can help (although it plays hell on new paint)
I've even gotten rid of the stock P-valve in exchange for an adjustable valve

(didn't like the T.. don't recommend it for street use on stock brakes or anything that you can't extensively test out... doubt you want to go off the road backwards into a guard rail? I went off the road backwards at 80mph in my testing, luckily no guard rail was involved though)

so go buy good pads
maybe an adjustable valve
buy some ATE
do another bleed or pay someone to do it until the spongy-ness is gone.

brant

1st off, do you drive another car with POWER brakes???

That alone could be a huge factor in why you feel your brakes need work....

You are aware that the floor where the brake assembly is mounted can weaken and can flex during braking??? ( someone sells a brace in the resource area)

The system might still have some air in it, did you bleed in the following order??

pass side rear, drivers side rear, pass side front, drivers side front

Did you tap the calipers when bleeding to get more air bubbles?

Pressure bleed or pump'n the pedal?

I am a physicist. As the wheel size increases more of the mass tends to move outwards thus increasing the inertia of the wheel and thus its kinetic energy. The velocity of the outer rubber surface will be the same as the road speed of the vehicle. That means the taller wheels tend to rotate more slowly, that is fewer revolutions per mile.

If you go to a vented rotor from a solid rotor the mass is usually greater, thus it takes more energy to spin up to speed and more energy has to be dissipated to slow it back down. However, a vented rotor tends to dissipate heat faster into the air than a solid rotor. Eventually all heat generated goes into the air or into the ground.

Maybe its that not power break thing that gets me. The feel is just like stock and at 1/2" of travel, the pedal gets hard just like it should. Good ATE stuff might do the trick and some real pads. I must mention that there is alot of feel though and good response when using these standard breaks. I've called spongy when you hit them hard and the car slows down but they don't seem to want to lock at anytime during the stoping process. It's probably the pads and me together that is the problem.

That darn PROPORTIONING VALVE is probably the biggest problem right fellas, the biggest problem of the spongy, squishy, inadequate, usless POS part ? Should I put in the DAMN TEE or what?

I need the healing hand of God.

BMW's are similar in piston size with the M. He could use the T but I agree... check the balance in a light pole free parking lot.

I am going to replace mine with a adjustable valve, PP has them amongst others.

Your brakes, in an ideal world should not lock up, the stock brakes on my teener

do not lock up but it stops fast enough to submarine a 200 lb construction worker

into the foot well. (time for 5 point harness's) If they lock up you will slide instead

of stopping. Try the new pads and fluid, bleed all the air out and you should feel

the difference. Boy this was one of those " My dick is bigger so it's better" kind

of threads. Everyone is going to have a different opinion on brakes, if you want

big brakes... get them, because someone is going to try to talk you out of it

anyway.

Battle of the penises!!! My dick is big so I'
m keeping my small breaks. :stones:LOL Gonna do the right thing as you have mentioned and hope for the best. If they wind up locking, I will get some big meats to hold the road better and be the Biggest Dickust!


Sweet. No desire to do the paint shop thing since two weeks has turned into three months now. At least I'm wearing them out going 1-2X per week to check on the progress.LOL

:beer1:Must remove Pvalve at all cost.

Eric has consistently made sense in this thread.
Seperate what you need vs what you want & spend accordingly.

I reccomend installing Subaru brakes. :

Well sence we are there you can get Yugo brakes cheap...

RS, WRX, or STI???

Brakes (w/o ABS) should be able to lock the tires up. If they are not capable of doing so, they are not strong enough.

The fastest way to stop (besides hitting a mac truck head on) is to be on the verge of lock-up (known as threshold braking) w/out actually locking up any tires.

I'm not a fan of the BMW caliper "upgrade." the stock brakes are capable (when in good shape) of locking up the tires (assuming no super wide slicks...) and have enough problem dealing w/ the heat generated. BMW calipers transfer slightly more braking to the front tires, adding to their heat load, and warping rotors even faster.

I'm a fan of more brakes then your car will need. I'd rather know my car will stop like it is supposed to every time, and not have to sit there and wonder if the rotors, pads or fluid have overheated and wont work now (Been there, 2 turns after the cheapo tires turned to greased dog doodie )

The 914RS's brakes are about perfect as far as i'm concerned. Hell the whole car is (assuming i can swap in some Boost inspired HP )

BJH

it is B R A K E not BREAK

The part about stock brakes good on a track car up to ~140 mph is not true, at least in the Northeast at NHIS, Watkins Glen, Limerock, Pocono, Mt. Tremblant. You can include Road America and Sebring too.

I was switching out calipers every other track event to rebuild, always fresh fluid, lots of cooling, SS lines, etc. At those speeds, they simply develop too much heat and the pads don't have enough surface area.

I could kill Raybestos ST-42 pads in less than a day. The brakes would start to fade after about 15-18 minutes of tough track driving.

To give you an idea of the heat generated on a stock body 914 running 205-55 Kumhos, I would get fender temps of over 180 degrees, wheel (rim) temps of over 400. Tire temps of over 230. I didn't have anything to measure the heat in the calipers, but I would get pad faid, which was somewhere over 1300*.

On stock 4 rotors that I slotted, they would actually warp radially. I'll dig up some pictures to post tonight.

IMHO, when a 914 gets over about 130 mph constistently, it needs some break work done that is beyond what the stock system can offer.

I should probably just let this thread die...
but some times I've noticed that people significantly over brake.
in the Stock-ish 2.0/4 classes, a person Would RARELY need to brake at all.
and those cars are able to hit 120

sometimes the pro's use less brakes than an amateur
I'm not calling you names either pro or amateur, but most of the time as an instructor I have noticed that the different driving styles and braking styles can significantly alter a person's perspective in regard to their brakes ability to cope.

perhaps you could use the cars abilty to drift to scrub speed ... or some other technique to reduce the load upon your brakes?

a locked diff will teach you this technique VERY well.
you'll end up going in faster and using your brakes much less.

Matt,
what car
what motor
what top speed are you working with?
maybe a vented, M/S/A caliper and rotor will be necessary

It sounds like your speaking with experience and know what you need. But don't overlook trying to change a driving technique or style to accomodate a car/track/tire/day.... its a great way to learn.

brant

Brant,

I definatly agree that many beginners overbrake, but that wasn't my problem.

I didn't have problems with a hot 2 liter. Nothing ever until I put in a 2270 and started passing everything up to a 911 C2. To give you an idea, I'm an instructor and running in the top group with every group I drive with. I can pass Carreras, 951s, SC are not a challenge....corner with 911 with wide body kits.....hitting about 138ish at the back straight at the Glen.

The car is a stock fendered 72. 205 width tires. Hot 2270 motor. Koni shocks, 21 mm t-bars, 19mm front sway bar, 180 lb springs, bushings etc. I've run 1.01s at Limerock, sub 2:15 at the Glen. You can ask anyone that has ridden with me about being able to keep momentum.

What people constantly leave out is the pad area. I was able to get the stock brakes to work and just about last a whole session, but I would wear them out in less than 8 sessions.

I went with vented fronts and vented SC rears. Wilwoods all around. I was able to drop a 2-3 seconds a lap at NHIS by being able to break later and more consistent.

And Matt is not a small person

I could get a 400hp stock braked 914 to stop from 150mph twice before I had NO brakes..LOL NO stop what so ever..

The Boxster Spec group just went round and round with this subject. I argued for stock brakes.. the big money guy's wanted BIG brakes. I told them I use the brakes 2 times at Willow Springs..LOL

I have started using them more to "settle" the car prior to braking in a rough area of the track. It weighs 2850 with me in it and has 170 RWHP. It doesnt need bigger brakes. I'm still on the same pads we installed a almost a year ago after 8-10 track events and 8-10 AutoX's with multiple drivers.

Matt has a point.


B

Brad thanks for chiming in. I know you have a lot of experience racing 914s and have probably been down this road once before.

Wait a minute! Are you calling me fat?

I agree. I think John Rogers should weigh in. It seems that brake fade is eliminated when you go with a set of Mike Mueller's hubs and vented rotors.

(little neener for Bradhole pickup your phone!)

AGAIN, this is only on a road course under race conditions with a car that is now traveling over 130 mph!! (just want people to keep it in perspective)

He called you fat... for sure.

How did I miss this one?

I have ALL stock rebuilt calipers, M/C, prop valve, SS lines, Porterfield R-4's, and Motul.
( a fully functioning system )

I go through the front pads 2x faster than the rears.
The fronts are lasting me about 8 track days ( 20 hours ).

They cost about $100 per axle.

My set-up is perfect for me. They do not fade and I have never felt under braked. My max speeds are between 110-120 mph.

I run fresh air ducted to the fronts. No dust shields.
After a 30 minute session the rotors are too hot to measure, 500+, but the calipers are under 275. They don't fade.

On the street, my set-up would be considered over-kill.


KT

Crap, I just got a break on my brakes! Sorry for the miss spelling since then Eng language is my second and still working on it.LOL

It sounds like we have many here form the Purist Minimalists who agree that less is more and big breaks are a big waste of time and extra weight? I am impressed.

Less is more!! And that damn Pvalve must go!!

Eric,

Call me in 10min (4:55pm) if you see this. I'm leaving work now to get on a plane for SJ.

My point with Matt's example: There are *some* instances where more brake will end up saving you money/time in the long run. You have to decide *why* you need something larger than stock. I know a LOT of fast people on stock brakes. Could they be faster on bigger brakes?? I doubt it. They only touch them on rare occasions.

Ask the EP and FP guys in SCCA 914's. Last time I checked.. they are still on stock caliper/rotors and most of them would drive circles around us.

You want your brakes to work consistantly? Get the heat out.


B

If you remove the P-valve, do NOT follow me, i dont want you backing into me the 1st time you get on the brakes hard...

Th p-valve removal works well w/ 911 fronts. beyond that, an adjustable is needed (and i recomend not having it in your reach, the stock location is great) and if you find yourself running the adjustable wide open, then a t-can be installed in it's place.

BJH

Awsome!!

I'm in with the big boys. Yes......ahhhhh, serenity......

BRAKES! I agree with Joe. I COVET YOUR FRONT BRAKES JOE! Pic # 1 Jeff Hayes the best 914 pilot I have ever known. Pic is 4 or 5 years old. (3.8, 8 Piston brakes) Pic # 2 One of my boss's collection GT40. Jeff's car had much more stopping power. Power in the GT40 is unreal! I have driven both. Pic # 3 My WRX with 18 inch wheels from Japan and a Cool Rotors braking system. Some how the car has found it's way to my Son-in-Law's garage! Jeff Hayes is the Founder of Cool Rotors.

Dan

[quote name='Matt Romanowski' date='Oct 20 2006, 11:22 AM' post='798873']
Brant,

I definatly agree that many beginners overbrake, but that wasn't my problem.

It's DEFINITELY not DEFINATLY ! How'd you make it so big AA?

Putting huge brakes on a 914 that rarely sees more than 120 mph makes about as much sense as putting a huge rear wing on it

Sorry, couldn't resist.
The last two 914s i had I put the 320 calipers up front and a Tee instead of a prop VALVE. Worked just fine, but didn't lower my lap times. Not using the brakes would have done that. BTW, they both had significanty more HP than stock.
I had 205 victoracers on it, if i had more tires I might have gone with more brakes but I could lock up the 205s at will. I could find no logical reason to spend big $$$ on bigger brakes I could not fully use, unless I was trying to impress someone. If I did need more brakes I would have probably gone to more agressive pads first.
Note: I recommend you do not remove the prop valve unless you increase your front brake capacity significantly.
Stopping in a straight line aint the point, it's all about stopping in a panic situation in a corner, possibly in the rain. With no prop valve on a stock system you are likely to see where you've been, not where you're going.

Wow, go on travel for a couple days and look what I missed!

One thing I think needs to be framed here... A small increase in speed can result in a much greater load on brakes, no it's not linear. Brakes turn the kinteic energy of the car into thermal energy by friction generated at the pad/disk interface. Kinetic energy, Ke=1/2 mv^2. That's the -square- of the velocity. Double your speed and you -quadruple- the energy you need to dissapate in the brakes. So a car with stock brakes that can go all day on the track topping out at 120 mph, may very well exceed their capabilities at 140 mph. That makes a roughly 15 % increase in top speed yielding over a 27 % increase in energy. A little bit goes a long way...

That having been said, I've only had problem with my brakes at the track was when they weren't in top shape (old fluid, wrong pads, insufficient cooling). But I run a stock 2.0L, not a hopped up 3.6 monster.

-Josh2

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