Grassroots Motorsports magazine, Dec. issue has 914 brake tech article Options

[SP9146]

I don't usually read this magazine but saw on the cover a mention of the 914 article so I bought it. Excellent explanation of the upgrades to BMW front calipers, etc.

This was actually one of the last articles in a series about their 914 project car. Has anyone read any of the articles, are they worth trying to find?

Pete

[tesserra]

Its all about making heat in a consistant way then getting rid of it.
Street driving and auot-x do not need larger than stock brakes. You just need a brake system that is easy to modulate or feel what is going on and makes heat ASAP. The the bigger BMW calipers will make more heat sooner but I have heard they are more difficult to modulate.
If they start fading it is time for more mass in the rotors and, or, more cooling.
Having said this I have the BMW brakes but i have not yet installed them on my v8 914.
My stock system with the propotioning valve replaced with an adjustable valve works great. But I bought all the BMW stuff (all four calipers) when he stock system was not working 100% because I thought the stock system was not good enough.
Since i have the BMW calipers I will install them and see what the difference is.

George

[brant]

JP,

I certainly don't consider myself an expert by any means... but here is a few observations I've had over the years..

I hope this doesn't come off as condensending or angry.. I'll just try and explain my own thoughts about the momentum question.

my old car had big brakes and vented rotors front and rear... The fast guy in my class had stock brakes and could out brake me into the corners..

After years of observation, ride alongs, and lots of track time... I learned that he wasn't so much out braking me or waiting later.. he just wasn't braking at all really.

Now this is certainly not the case on every corner, but it is true on some of the fast and some of the slow corners... for example:

pueblo corner 1 (I know this means nothing to you) is a 1/2 mile straight away, and then a 180degree 90mph corner. I used to try and stay on the throttle until I saw my braking point.. then I would slam onto the brakes and turn in. My buddy who I'm referrencing would close up on me during the turn in like mad. NOW, I've learned..... this is a trail braking corner. Instead of slamming on the brakes and dragging the car from 120mph down to 90mph and turning..... I turn at 120 and then trail brake down to the apex.. I can catch 5 car lengths on people in this corner just between the turn in point and the apex. Its an entirely differnt line on the turn in to make it work. I still am about 90mph at the apex, but most of the speed is being scrubbed by the turning of the car and the (holy cow did he say that:) LOCKED DIFF, plus a little bit of dragging of the brakes... When I do this, I'm not pushing very hard on the brake pedal and its more of a dragging action than a braking action.

Thats a fast corner, here is my experience in a mid speed corner. Take corner 10 at pueblo. Its a 90degree right hander, big wide, and about 60mph. I used to go up to it.. brake and down shift to 3rd then gas it at the apex and start the eternal wait down the straight away before the above mentioned corner 1. NOW, I leave the car in 4th, coast a little bit at the turn in, and then coast towards the apex while scrubbing a little bit of speed on the turn in... NO brakes used... then ease into the gas and start the straight away.

I used to watch cars go through lots of different corners and not use their brakes.. (or not light their brake lights)... I've learned that I had to change my lines/turn ins/ and corner style to make this work for me.

Slow corner: I brake.... I also scrub some of the speed at turn in with the car. I've never over heated those vented rotors... however the same fast guy I keep referring too (dale tutey by the way). I don't think he has ever overheated his stock rotors either. I do know that he has simple dryer duct tubing dumping air into the front leading edge of his caliper....

I'm not going to claim to know what your 210hp motor would be like at the end of a straight away. I'm also not going to have any clue what brad's old tube frame car was like at the end of a straight away. I'm sure that hp changes things a bit, on the other hand the fellas I know that run 1900lbs, and twin plug 3.3 electromotive engines... don't seem to be on their brakes that long, and still run my same trail braking line in that big corner 1.

I think that my experience on the track with a 914 has taught me that the trick to going fast is not using the brakes.... I have tried faster and faster motors with more hp, and always was disappointed that I would hardly pick up any lap time... then I feel like I came to realize that the lap time would come down by focussing on this use of brakes more than any other aspect of the driving..

Wow, I didn't know I could write a whole book...
have a good day all
brant

[Dominic]

Just my $.02, but I'd rather have the solid stopping power of my BMW calipers up front and the rear proportioning valve removed when driving on the streets. When the Dumb A$$ in an SUV or new lexus cuts you off in your old school 914 with your stock brakes from 1970....good luck stopping.

It's a safety issue with me being able to stop as well as the car in front of me on the street. I'm not talking about racing for 12 hours with this set up, just an affordable solution for the street driven 914.

[brant]

Oh.. Oh... oh.. (horseshack impression)
I wanted to add another thing too..
When stock brakes are rebuilt for street use with good pads (don't have to be race pads).. they can work amazingly well.. Bleeding is a big key to this, but wheel lock up is easy in a well set up system on street tires...

and once you've locked em up... what more do you want.

brant

[seanery]

Yes, lockup is easy!

on blue car I had a 19mm with stock 4 parts front and rear. So damn easy to lockup on the street. I almost bought a couple cars in front of me cause they locked up easily.

A BIG BIG BIG factor here are tires. I didn't have the right size & compound tire to stop. -4 Brakes on a -4 car are more than sufficient when setup correctly. Unless your car is repowered or a big track car I don't see the need for more brake.

[F4i]

-4 tires are sr165 I am going to a performance 205. Are stock up to that? Post experience. I agree that tires are the most
important factor in the equation. With the better tires I would think the bmw units would be ok Yes?
Also, I have heard that one of the problems with the vw stock stuff is that they flex. I do not know if this
is true or not. I think that what works for racing might not be good for the street. This is where I feel a lot
of people are coming from different schools of thought. Race pads, tires and the lot need a particular set
of circumstances to be effective. That said it the zone they rock. On the street in the rain etc. they become
dangerous. I can never find my pit crew when it rains (IMG:style_emoticons/default/laugh.gif)
I guess what I am saying is that you have to take your needs into consideration when modifying.

[seanery]

I ran the previously mentioned setup at the track with 205/15 BFG R1's (sticky tires) and it stopped really well. I didn't ever lock them up, but I didn't try to (IMG:style_emoticons/default/w00t.gif)

[Dave_Darling]

Wow, I didn't know I could write a whole book...

Brant, can I quote you? That was very nice!!

--DD

[fiid]

Just my $.02, but I'd rather have the solid stopping power of my BMW calipers up front and the rear proportioning valve removed when driving on the streets. When the Dumb A$$ in an SUV or new lexus cuts you off in your old school 914 with your stock brakes from 1970....good luck stopping.

It's a safety issue with me being able to stop as well as the car in front of me on the street. I'm not talking about racing for 12 hours with this set up, just an affordable solution for the street driven 914.

Yup - when that happened to me the other day I locked up all 4 wheels, like a dumb shit. With stock brakes.

[1973914]

I just installed boxster calipers with vented rotors up front, with carrera (M)and vented rotors in the rear. Not because i couldnt outbrake almost every car on the track, but because I wanted expanded heat reserves for longer sessions/enduros and the ability to expand the motor size without having to update brakes. We have had this issue brought up many times, the main distinguishing variable has always been the application (street vs Track use). The key of course is to not use your brakes on track ( (IMG:style_emoticons/default/smilie_pokal.gif) ), and apparently have back breaking decel on the street ( (IMG:style_emoticons/default/headbang.gif) ).....

[Gint]

When stock brakes are rebuilt for street use with good pads (don't have to be race pads).. they can work amazingly well.. Bleeding is a big key to this, but wheel lock up is easy in a well set up system on street tires...

and once you've locked em up... what more do you want.

FWIW - My brown car with stock brakes, Porterfield R4 pads front and rear and stock prop valve would lock up all 4 with no trouble whatsoever. Best braking 914 I've ever driven. There was absolutely no need to upgrade the stock brakes (on that car anyway). The only trouble I had was getting all of the air out of that damn stock prop valve.

[Matt Romanowski]

I have to say that I believe that everyone is right on about the stock brakes being more than adequate. I have a very healthy 2270 with all stock 4 brake bits. My first event at NHIS with Ferodo pads, I was able to get about 6 true hot laps before I had major brake fade. Next event was at the Glen were my girlfriend and I proceded to eat up a set of pads in 4 run groups. Put in a new set of fairly stock pads and killed them in 3 runs. Now I have switched to Porterfield R-4 and added some ducts in the A-arms. I went 24 sesssions total - 12 at Limerock and 12 Pocono North - and just finished the first set of Porterfields. The difference in price for these pads is far overcome by the performance.

My only concern now is how fast I may eat up pads when it gets really warm out.

Matt

[Brad Roberts]

I dont get it. Plain and simple, someone please tell me why I want my brakes to lock up sooner in a panic stop (like when the BMW's are installed??) I just had a 944 Turbo in the shop that had Twin Turbo big reds installed on the front and stock 944 turbo calipers in the rear. Touch the brake pedal and this thing locked the fronts in a uncontrolled SKID. The bias was all F-'d up. I took out the stock prop valve to the rear and ran it wide open.. worthless.. fronts still locked up. My point: Porsche did their homework. BMW did their homework. Neither of them intended for our cars to have BMW calipers on them. Fix your stock system. Bleed the brakes. Run good pads.

Great story Matt. We love the Porterfields.



B

[ArtechnikA]

...We love the Porterfields.

i have a perfectly good set of factory 930 pads in my 'S' calipers. when those wear down, i'll switch to Porterfields all 'round - by all accounts, they are the class of the field.

[fiid]

As long as your brakes are capable of locking the wheels up they are adequate. After that the only thing you can do to increase braking performance is to increase the rate at which you are dissipating heat. You can do that in several ways.

1) bigger discs mean more heat energy is required to heat the disc until it is ineffective.
2) better airflow over the discs increases the rate at which the disc loses heat to the air
3) venting and drilling increase the surface area of the disc, which mean that the air can absorb heat from this disc over a greater area. Plus, venting actually makes the disc work like a centrifugal fan.

Drilling your own discs is not recommended - it is better if the holes are cast with the disc because the metal structure of the disc is compromised if it is drilled afterwards.

Someone made the point that stopping a car from a given speed will produce a given amount of heat, which is correct. There is the SAME AMOUNT OF HEAT, and it doesn't matter what sized pads put it into the disc. It is the heat you need to get rid of.

Bigger calipers do interfere with the bias between the front and the rear of the car, which can be extremely dangerous, and can substantially decrese the effectiveness of your brakes.

If you want to not hit that SUV that swerves in front of you, you should learn to cadence brake, because that's the only thing thats really going to help you. Cadence braking is the art of keeping the braking level at just below where the tires lock up. Most people are pretty bad at this, which is why ABS was invented (which does the same thing, only it does it for you).

[J P Stein]

I run stock Pagids on my S&M setup.
Last fall they went 5, 30 minute sessions.....got to stinkin' a bit, but never faltered. They have that DE and about 100 AX passes on em' and look fine as frog hair. They do blow dust all over hell, tho.There is considerable more tire tthere than you'll find on most street cars. I can lock em' up....but that is not the gud way to stop or slow....flatspots the hides, also. Mostly Chuck does this......he's a late trail braking fool. The unloaded tire usually gives off a bit of smoke when he's at work.

I need barkes that work NOW, not some that take a while to warm up....just like you need on the street.

[seanery]

Does anyone have the part #'s for a '72 for the Porterfield R4S pads?

[Brad Roberts]

Yes. But you have to order them from me. :finger2: :finger2:

We stock them.


B

[Matt Romanowski]

We stock them as well. We actually have a special going on kits including pads and rotors for front and rear, with a bottle of ATE Super Blue.

Matt

[crash914]

My thoughs on porterfields....

Great pad. On the 914 20+ drivers ed days....good on the street too. a little noise every now and then...

I liked them so much that I talked a friend of mine to put them on his Supra...

Wow, great stopping...except he needed rotors after 3 sessions. Tore them UP!!!

I had never seen rotors like that. 1/4 inch gouges out of them...He stopped good though.

Matt....I need brake ducts!! are you still making them? Ready to buy a set....thanks, herb