Stiffer is better is true for most parts on the suspension, but I'm not sure you could tell anything at all if a caliper flexes .020 under hard braking. And that would be flexing quite a bit. The only thing a flexing caliper would do is change the brake feel. I wouldn't be surprised if the flex lines end up having more give than any caliper flexing could provide as far as changing how the brakes feel.

I have aluminum calipers on both of my cars. They were all designed from the beginning to be made out of aluminum. Brembo, Alcon, PFC, Wilwood, etc all spend huge amounts of resources on trying to make their calipers stiffer. Will there be unintended consequences of changing the same design from steel to aluminum? No doubt. Are they big enough to be a problem? Don't know - that's why I asked if you had used these calipers yet.

Just becuase they were good 44 years ago doesn't mean they are good today. Wanna argue that Goodyear Blue Streaks are as good as Hoosiers? Maybe we should all use slide rules instead of computers becuase that is what they used when they engineered stuff for Vic's car?

I hope these are great calipers and work well. I think it's awesome that you are developing parts for 914s (and Porsches in general). I'm not trying to be a jerk, but changing the material a brake caliper is made out of is a major change. I think it's appropriate to ask if this was an engineered, analyzed change or just one of ease of manufacture or becuase it is lighter.

Eric, Matt has a good point. These should be tested.


I volunteer...

Sorry Rob. These will flex way too much for you.

The Brembos were cast copies of ATE steel A-Calipers. Hey Rob, how are your Brembos working out?

Tensile Strengths Steel and Aluminum

Structural steel ASTM A36 Steel
Yield strength (MPa) = 250

Carbon steel 1090
Yield strength (MPa) = 250

Aluminium
Yield strength (MPa) = 414

Human skin (mine is getting thicker with all this Internet philosophic discussion)
Yield strength (MPa) = 15

Aluminum


1. Ultimate strength
2. Yield strength
3. Proportional limit stress
4. Fracture
5. Offset strain (typically 0.2%)

Steel


1. Ultimate strength
2. Yield strength
3. Fracture
4. Strain hardening region
5. Necking region
A: Engineering stress
B: True stress

The Yield Strength of aluminum will always be the same regardless of the "caliper design". Now, let's get into real world observations: I've "NEVER" seen a broken aluminum caliper but I've seen "innumerable" steel calipers with mounting ears fractured off and sealing flanges fractured. Steel is much more brittle than aluminum. The aforementioned Brembos have been in use since the mid-70's and again, I've "never" seen one broken or fractured. Same material depth on the mounting ears and around the piston flanges. Again, an aluminum copy of an ATE steel caliper that was used on virtually every European make sedan and sports car. Finally, virtually all modern calipers are all made of aluminum now as it's lighter and stronger and better suited for the application of being hung off a cars suspension. They're using computers now and... they're using aluminum to manufacture calipers. Some "slide rule" designs were ahead of their time (Porsche seems to be famous for this).



Back it up. Can you tell me how you could possibly know these companies spend huge amounts of resources to make their calipers stiffer or is this a general claim? If I were to make a general claim it would be that their engineers look at the numbers I posted because modern (computer) design practices dictate the use of the "Yield Strength" figures.



Again, back it up. You've spoken to "All the brake companies"? I've searched for your "flex design" criteria. I think you're making general statements that people could easily confuse with facts and even those are wrong. E.G.: with 4 M8 fasteners running from the nose to back... the fasteners "definitely" do play a factor in flex or no flex. If the fasteners were made out of rubber; would the caliper flex? Aluminum? Now steel? Steel is used where it is needed in modern computer designed aluminum calipers.

So Matt... are you worried about actual "Strength" or are you concerned that these will literally "Flex" their way off the car? Or is there another point that you feel needs to be made?

May I please be on the list for a pair in Natural finish Anodized, Narrow.= lighter
Regards

If you want to play armchair engineer, which aluminim alloy are you using. Blanket statements like "steel is much more brittle than alumimum" show that you haven't worked with many different aluminum alloys. Try bending 6061-T6 and see how it does? There is a lot of work that goes into alloying a metal and picking the correct one for the application.



I've spent probably 10 hours talking to brake caliper engineers from Wilwood, PFC, and Alcon about the merrits of different designs and caliper flex and strength. Or, if you would like, PFC will tell you at http://www.performancefriction.com/motorsp...e-calipers.aspx. Notice the number of times they tell you the calipers are forged and have gone through FEA analysis. Also notice that most new aluminum calipers have either a bridge bolt or an acutal part of the caliper body cross the pad area to hold the two halves from spreading.



Most of the flex comes in the caliper material and design. Does some come from the fasterner? Sure. Is it the majority? No. Notice most new hi-pefrormance calipers are forged out of special alloys. They are also designed [i]to be made out of alimunim, not steel.



Neither. Will they be strong enough? Probably, but I don't know. Will the flex themselves off the car? Probably not, but I don't know. Do you? Did you test them? Do the engineering? After all, brakes aren't that imporotant.

Maybe I wasn't clear in my original posts - will these flex and cause pedal feel problems? What will they do when they get hot? I'm sure you've come across the stories how the aluminum 911S calipers can be really spongy compared to the steel calipers. Wonder why?

Also, if you would like to make attacks, I'm happy to talk to you about being an "internet racer." I'm happy to put my track experience up against anyone on this site. What's you're track experience? Or better, what's your engineering background?

No personal attacks Matt... I was wondering the same. Just a general observation of all the Internet racer chatter about flex in calipers that have put others at the top of the leaderboards.

These are exact replicas of a proven design in a stronger and lighter material. Try bending a beer can... you win. I'm not going to get into it further.

My track experience? Schooled at Skip Barber and Bob Bondurant. With Skip, Terry Earwood was my instructor. With Bondurant, Bob himself at Blackhawk Farms. 18 years PCA on Mid-America, Las Vegas Motorspeedway, Atlanta Motorspeedway, Miller Motorsports Park. I haven't raced now for about 5 years. Probably not as much as you but, enough not to be talking out of my ass and, enough time on S-Caliper not to complain about them.

No engineering background. I sourced others for that. I just build thousands of brake calipers and just trying to make a quality product for the industry.

To answer your question Eric, I have had no problems at all with my Brembo front calipers. In fact they cool off so quickly it's spooky. Nothing odd in the peddle feel at all. I would have no concern whatsoever putting these on the rear where they do less work of braking...

Eric,

Are these a straight swap for my existing rear calipers?

I've done Skippy School and probably 40 days at Watkins Glen, 100+ at NHMS, 30 or more at Lime Rock, 15 at Pocono, and a couple at Summit Point, Road America, and Sebring over the last 14 years. I've helped other folks with everything from a stock 914 to a GT2 911 (running 180 mph at Road Atlanta), a couple different Formula Fords, a couple of Formula Continentals, and a bunch of other stuff inbetween. I've set up a number of schools using the most senior Skip Barber instructor and the person that drove the data car.

I can tell you lots of different things about what brakes will do on a 914 including stock calipers, Carerra calipers, Boxster calipers, and Wilwood Superlights (the best so far). Flex in the calipers can change a lot of things. Just think, when you start to go fast enough, you flex the spindle and get pad knock back from that.

Things like caliper flex, bias bar hysterisis, and compressibility of the brake fluid are real problems when you push a car hard. The alloy that you choose for the calipers makes a huge difference. The strength difference from something like 1100 to 7075 is almost double. I've purchased trailer loads of aluminum, some coming directly from Alcoa for special applications. The devil is in the details and all aluminum is not created equal (even when it's supposed to be).

I do hope you calipers work. It's great that you are restoring old calipers and bringing new things to the market, I just want them to be well engineered and as good as the originals.

Edit: Here is a good chart to show the difference in aluminum alloy strengths. Notice the difference in strengths - 7075 is basically twice as strong as 6061 (the most common machinable aluminum) http://www.aircraftspruce.com/catalog/pdf/aluminumalloy.pdf

Okay.

If your skin continues to thicken at the rate this chart suggests, thereby becoming less flexible and losing elasticity, as a precaution, have you now forbidden your Venezuelan maids from wearing those short skirts? You know, in case you have any, um, flex?

I am the 99%












(of the guys that are stoked, and wouldn't ever worry about these calipers flexing too much)

you didnt loose this...did you ??

hey I can do ultimate breaking numbers and expansion numbers to that point ...through destruct testing if you want. both steel/alum.

Awsome news Eric, will be looking to get a set down the road sometime.

Likewise. I don't race my car, nor have I autocrossed. I would like to upgrade my braking system however, and to me this seems to be right there. While my brake system works fine, I'd like to replace my rear AA calipers (with the broken adjuster screw on one side).

So, how would these work on a 4? Will I need to convert to 5 lug, along with vented rotors? I'd need to get a pair of hubs then, and upgrade the front end along with it, no? Also a 19mm master?

I think a car this light should be able to stop quicker than it does now.




What's a necking region?


I thought that was the back seat of Dad's Impala, circa 1977....

But wouldn't the flexing technically result in a stiffer piece

excellent point, Scotty. We need an expert - Is there a doctor in the house?

Not in Erc's case ... you can't stiffen what is already flaxen.

Strength of materials of human skin.....hmmmm....


Nice peice of work on the castings Mr. Erc.'s.

Matt and Eric, standing on the Golden Gate Bridge, suddenly feel the call of nature. No traffic coming, they step to the railing...

"Damn! This water's cold!"

"Yeah, an' it's deep, too!"

Seriously, guys. Discuss in another thread or by IM, please?

Apologies to Richard Pryor, who prolly didn't *write* that joke but is the first guy I heard utter it.

From a completely non-professional layman's point of view, I applaud Eric for taking on this task and making these calipers available to us for a reasonable price. Good job Eric and put me on the order list.

SWEEEEEET !!!

Wow great item !!!! By some chance might there be anything in the works for an Aluminum front 911 'M' style caliper, that will bolt on to the stock struts (3") and use stock rotors ???? (minus the .103" that needs to be shaved off the 'M' calipers mounting surface)

Just asking, as I would be in for a 4 wheel set immediately !!!!!!


I know I should just change the front end to 911 but I like the stock torsion bar spring rate and using stock sized brake pads (easier to remember and order)

Bembo's - There on Eric's website. http://www.pmbperformance.com/catalog/item...552/6862358.htm

Awesome!! thanks for the response !! So after reading the description ...... these are for 911s ..... so I would need to machine the .103" off the mounting surface for the 914 struts ....... I actually made a machine fixture for this exact job for the used steel 'M' calipers I bought, but my mill is a tad too small for it .... so needless to say I have not gotten around to it ................ maybe I can send the fixture to Eric?? Does he do machining?

Also not to be any more of a pain ........ but the brake pads for these Brembo cals are not stock 914 (or stock 911 'M'). They are a tad bigger according to the PMB description, he mentions it is the 320i pad size ..... but not the year of 320i.



Thanks again for the help and link!!!

The Brembo's will work on 914 struts in two configurations:

1. Without the spacers on an "early" 914 strut and a solid rotor.
2. With the BRAG hub that Mike Mueller designed for Brad Roberts, on a late strut and a vented rotor.

Regardless, I would move to a 3" 911 Boge strut and have the 911 hub, vented rotors and beefier bearings. Not that 914 bearings have been problematic... it's just that the BRAG hubs are NLA and as expensive or more expensive than a nice set of 3" 911 struts.

I think machining the calipers would be good money for bad.

Eric, thank you for the response. Have you tried to machine steel 'M' calipers? Sounds like it may be difficult.

If you do not offer the machining ....... then ...... if I were to send you my pair of steel 1968 ATE 'M' calipers already machined at the mounting flange, would you be able to rebuild them? Maybe I can search for someone with a larger mill ...

When I get some other projects out of the way, I was thinking of making some of those NLA alloy hubs for late 914 struts. Because everytime I go looking for 911 struts I end up wasting a ton of time trying to find and identify years etc.. I always have the worst luck when it comes model compatability and fitment

911T struts go for cheap on pelican. Place a WTB for the model and what your willing to pay. Many 911 guys replace them with 3.5 spacing. I got mine for 100 and there were plenty of guys willing to sell for that price.

I have heard about (and tired of) the subject of flexing of aluminum calipers.
It started with Wilwood calipers in the '60s.
No matter what material is used, flex is always present in a cantilevered grip design.
Friction materials and fluids have advanced since the '60s and allow less
pedal input, (clamp pressure).
In the '90's metal matrix composite rotors were 40 percent more
thermally conductive than steel, heavy, and chewed up pads really fast.
During the turn of the century, composite and ceramic rotors evolved increasing
friction ten fold.
Carbon composite rotors were used on the Galaxy C5A way-back in the '80s, and
used on the LM X35 Rolls-Royce Allison Liftfan transmission in 2000.
Aircraft actuators, and pressure manifolds have always been made of aluminum alloys
and other exotics operating at 6,000lbs or more, far more than our brake pressures.
If you have a Cadillac, use steel to bring that barge under control.
If you have a nimble, light-weight sports car, that could reach 1g using stock tires
and solid rotors with single puck, steel calipers, then think what you could do on
the skid pad with proper tires, suspension settings and less unsprung weight.

Yea Eric, my Brembo's are working great too. Thanks for asking! (I kid of course, I know Rob volunteered)

So yea, I'd be happy to test out the aluminum 911 rear variant for you Eric to go along with these.

Sweet!!

I need these to go along with the S calipers I bought for you. I can't spare the coin just yet. Just a matter of time.

We can rebuild anything.

Steel isn't difficult to machine. You're still talking about good money for bad.



I take it you are talking about machining a solid rotor (68) m-caliper to fit on a late model 914 strut. After reviewing all of these options many times, I fail to see the value in that. Here's why:

1. Exact same pad size as a 914 caliper.
2. Same solid rotor will not shed heat any faster.
3. Need to machine 914 rotor/hubs to 5-lug every time you need a new ones (if that's what you're doing).
4. Larger 48mm piston will throw off the bias unless you go with a rather expensive rear solution, but then...

....again, why not put that money toward 911 struts that offer a real benifit (larger bearings, lightweight hub assembly with vented rotors that weigh the same as a solid 914 rotor/hub assembly)? They simply bolt to your a-arms. Or - just stick with the stock late model 914 front caliper. It has thicker pads anyway.

So... Rear Calipers. Should go into final machine consulting today. I hope to have final pricing this week as well.

Mark told me about these about a year ago and I kept my mouth shut. Except to bug Mark and Erc about when they would be done!

Wing, you clearly don't know about Erc's house. He lives with three women and has an almost endless parade of his wife's Brazilian - supermodel friends coming in and out of the house. If it weren't for Rio his dog, he would have the only Y chromosomes in the house.

Bottom line - there aren't any 'toy' car parts on his kitchen table!

Thank you for your time Eric. Yes, I have the solid rotor 'M' caliper and was gonna use them on stock late rotors (1973). I don't want to be a pain, I understand what you are saying and yes, what you describe is certainly 100% better but I have already bought new strut inserts, new brake pads and pin set, 19mm master and machined/drilled my stock rotors (5 lug). I only need to machine fit the 'M' calipers and this part will be done (for now). Down the road, if I ever get to drive this car and wear these rotors out, I will look into it again.

This car is not my main project and I unfortunately cannot just keep adding "while I am in there" parts, effort and time. I spent more years and money than I planned on and would hope to drive it before I die. This whole car project seems to be good money after bad .... I have already spent plenty on the very nice 2056cc and I still need to:

weld the flares
buy flared rockers / valences
do all body work
add body deadner
paint the whole car
install new weather stripping

then

the entire interior still needs to be done
buy tires and space the 7 & 8 x 16 fuchs to fill the flares
intall rear sway bar (front is done )
maybe rebuild gear box (probably big project in itself)
install new fuel pump
put the fuel tank back in
redo engine wiring / fuel lines for carbs
setup shift linkage, throttle / clutch cables
etc.......

So I just need some help fitting the 'M' calipers, so I can put the rotors on and bleed the brakes. Otherwise I will just throw the 'M' calipers in the ocean and put the stockers back on ...... which now, almost sounds like the thing to do ... .......................

Yeah! That is how I felt when I was looking for 911 struts !


Edit: Do these struts use a standard 914 strut insert and fit the lower ball joint of my 1973?

http://www.914world.com/bbs2/index.php?sho...p;#entry1727150

No, you would have to change to the early style ball joints ( 1/2 round moon cutout instead of the later wedge).

do you need some wedge bolt T struts ??? i know of a few..

some 7&8x16 fuchs (al reed refinished)
2.0-3.4 6cyl

Thanks for the response Slits! It has always been something when I was looking for struts


So would the early ball joint fit my late a-arm?

and lastly would my stock new 'strut insert' fit in these struts? .......... edit: this question answered by seller


Yes, with hubs, vented rotors and M calipers that will fit my 1973 and use stock 914 inserts ..... and not bent

I moved conversation about the struts to strut link.

Sorry for the high-jack Eric ...

Oh no worries... I'm going to take all of the pictures of my flexible aluminum calipers out so we can discuss your front end needs... Ad nauseam.

The A arms are the same and YES an early ball joint will fit your late A arm. It is the strut you are applying that determines the ball joint needed or the ball joint determines the strut needed. Swap back and forth all you want, but you must match the ball joint to the strut.

An early strut has a slit in the bottom. A bolt with a nut goes thru the hole and when tightened "pinches" the bottom of the strut to hold the shaft of the ball joint. The ball joint shaft has a 1/2 round (1/2 moon) cutout in it for the bolt to pass.

A late strut does not have the slit. It uses a "double taper pin" (wedge) held in place by a nut. The ball joint shaft has a "wedge shaped" cutout in the shaft so the double taper pin locks it in place.

914 shocks fit 914 struts. 911 shocks fit 911 struts. They are different, as I remember, the 911 strut has a taper to it towards the bottom and the 914 does not.

Just for confusion, there is at least one more style ball joint fitted to early 911s ('65 - '68) or something like that.

Before we do that, can you share what alloy they are? People here seem to think that all aluminum is the same.

And if it's not too much to ask, your last 10 years of tax returns.

A356-T-6 My Guess

I started out with a Schwinn Paramount racing around the Cotton Bowl in Dallas way back in the 70's. Johnny Milsap (and you know who Johnny is ! ) was my first coach, semi retired after earning 4 olympic medals ! Then I moved onto several progressively stouter stronger and lighter steel alloy bikes from Guerciotti to Bianchi to De Rosa. DAMN! After all those stiff steel frames, the DAMN BRAKES JUST KEEP ON GETTING LIGHTER MADE OUT OF ALUMINUM AND BOY DO THEY FLEX! Just 2 weeks ago Lance Armstrong was caught by a reporter lamenting - and I quote - "Where have all the Steel Brakes gone?"

Now that I've hung up the cycling clips, I stare endlessly at my old Raleigh with the Steel Brake Calipers (Chrome Plated no less) and dream of those happy ball busting stops on Steel! Nuff Said! Live Long Steel Brakes!

Great post and thank you Slits! These details you noted are the kind of things that are known with first hand experience! I tried to find this stuff out by searching and asking in the past ..... but you know how that goes, sometimes questions do not go over very well

Are the early ball joints not as good as the later ball joints? I am wondering why they changed the design ......... unlike many people I cannot just dump endless money and time, on each and every part of the car .... so I have to be careful that a misinformed decision could end up costing me extra dough. because then the project stops

Thanks again for your great help, patience and for sharing your knowledge!!

Thats not correct. Inserts for Boge struts fit the struts from either car.
Any differences would be based on the weight distribution of the vehicle.