I read on this forum recently about someone swapping out their proportioning valve for a "T" fitting.

Does anyone know the size/thread count of the correct "T" fitting? Any fabrication required?

No fabrication required, but you will have to move one of the brake lines to get it to reach.

The T fitting is used on early 911s. It is a bubble flare T fitting, and you should be able to get one from any of the Porsche parts places.

You can also purchase the same "T" fitting at your local VW parts and accessories store for about half the price of the Porsche dealer. The last time I purchased one at a VW store I paid $7.00 for it.

I upgraded front brakes to BWM calipers and did this mod about 6 years ago. The originak reg is still in a zip lock.

Would it be P/N 914.355.667.00 ?

I don't need to do the BMW caliper conversion for this to work, right?

Where at in Ga. do you live? I have a spare T you can have, it came out of a
1973 914. I live in Woodstock, Ga.

Well, in reality yes.

In any car you want a bias towards the front brakes for safety.
When you stand hard on the brakes, a considerable amount of weight is transfered to the front of the car.
This has the affect of raising the rear of the car.
70% of your braking should be done by the front brakes and that is how the stock proportioning valve is setup to work.
Its how all cars are setup and its why you wear out front brakes alot faster than rear brakes.
If you put larger brakes up front, you can create the same affect and thus you can use the t-fitting.

Currently our brakes are not designed this way, so the proportioning valve delivers more pressure to the front brakes and creates the 70-30 split.

There is a very good chance that in an emergency braking situation you will loose control of the rear of the car if you have stock brakes and no proportioning valve.
These cars spin like tops once the rear lets loose, and with such low HP, there is little chance to power your way back straight again.

The stock system is designed very well, and the Proportioning valve is a simple piston/spring that has few moving parts.
They are tough to learn how to bleed through, but once you learn that, its a simple system. The t-fitting makes bleeding the brakes alot easier, but in relaity, how often do you really bleed your brakes??

Rich

have fun spinning off the road backwards into the ditch/tree/parked car/etc.

I'm in FLA. Where on the car did you find the "T"? I have a '71 body that I'm using for parts.

That's the problem I'm having now. I'm planning ahead in anticipation of the proportioning valve being DOA. The car has been sitting for 15 yrs.

Cool! I look forward to it. Especially as I always race to the corner store for milk and cruise the beach @ 15mph... I can't even get the rear tires to break loose. Knowing that adding this "T" is going to get my car to spin-out is excellent. Does it really make the top speed/HP better?

i've never quite understood the reasoning for ditching the valve. for a stockish car with stock brakes why jump thru the hoops?

How much is a new (rebuilt) proportioning valve? ($275.25)

How much is a "T fitting...?

ok. what do you figure a known good used valve costs? report back with the improvements the T provides. anticipation? more like assuming. you're prob correct...while replacing all 4 rotors, 4 calipers, 4 corners woth of pads, master cly, and soft lines, the T is a good idea. anticipate everything is garbage and melt down the visa card. don't forget new front bearings and seals too. contact eric shea. he can provide you with everything you'll need.

"Known good used" - I don't do this anymore. Burned too many times by sellers saying "works perfect!"(Eric Shea now has 3 "rebuilt" brake calipers of mine that the sellers all promised were "excellent"). Almost always BS when it comes to moving parts. The only used parts I buy are body parts, etc.

Everything else on the system is new. Still have a mushy pedal. What's left? Once I discover the proportioning valve is the problem, I have the "T", throw it in and I'm on the road again. Or, I bang my head against the wall, ask a million questions here about brake bleeding, THEN find out it's the proportioning valve. Wait another week for it to arrive. So...in THREE weeks I'll be on the road instead of tomorrow.

OK.

This T fitting was located in the front brake circuit, from the master cylinder.
it was used to split the left and
right brake lines

happy motoring.

k

Cool. I'll "borrow" that one to see if it fixes my current problem.

If I do this swap, I'll post a video of my car hard-braking from 50 mph (top speed for me...I don't drive on the freeway and there are no canyons in FLA).

Anyone taking bets that the car won't stop in a straight line?

LOL. As I mentioned previously, the car sat for 15 yrs. So yes, all the stuff you mentioned above had to be replaced (except the rotors...they are in spec).

However, regardless of my bottomless wallet, I am not about to spend $275 for a proportioning valve when a $5 "T" fitting will suffice. If I install it and the braking doesn't improve, or becomes unstable, then I'll work another 1.5 hrs. to pay for the correct part. If the "T" works, then I'll take the $270 I saved and put it toward something else.

The proportioning valve is really a simple piston and spring.
I have never met a bad one.

If you still have mushy brakes its because you have not bled the air THROUGH the proportioning valve.
This is not as easy as it sounds.
the spring requires 750 PSI to activate, and most people dont get that when bleeding brakes.
It can be done using the old school two person brake bleeding system, but honestly I have never had success with that, nor a power bleeder, nor a miti vac bleeder.
The reason I suspect that I have never had success is because I am the bleeder, not the pumper.
If I was pumping, I would pump them till they were firm and then try to push the pedal through the floor...that will do it.

The only way I know I have rid myself of the nasty bubble is to bleed them the best I can, then go for a ride and STOMP on the brakes about ten times...this produces the required PSI to move the air past the valve.

Then I go home and bleed them again, and I am all set to go.
Be careful because when you finally get the air bubble past the valve, it will feel like you have almost no brakes at all...pedal to the floor.
I stay close to home...its a ten minute ride.

Rich

Yep, I've tried all this (contrary to the other posters in this thread who think I'm a dumbass who doesn't do his research).

So, I'm assuming (shhh...don't tell "Rhodyguy" I'm assuming something...he doesn't approve!) the proportioning valve is stuck solid. The calipers & master cylinder were totally gunked-up. I didn't even think about removing the proportioning valve when I had everything apart (as you said...it's just a simple spring/piston...not much to go wrong). As I have to move the car around, I figure I'll throw in the "T" so at least it's driveable until I do my 911 brake conversion (sooner/later).

Can the proportioning valve be "saved" by removing/cleaning? Not sure what's involved in a rebuild...(off to do more homework)

its emergency situations when the brakes will surprise you

not when your running to the store for milk at 15mph

but more when you decide to take a longer trip that involves the highway
and suddenly when your going 50mph, something drops off of the trunk in front of you... then when you least need to be unsafe, thats when it will bite you...

have fun
I've done it.
brant

I wouldn't automatically blame the proportioning valve yet. If you've just rebuilt the calipers, replaced the pads, and turned the rotors, you will often have a somewhat spongy pedal for a while. The pads and the rotors are not yet making full contact on their faces because they need to wear into each other a bit, and the caliper pistons will need to smash through the paint and/or insulating material on the back of the pads. The just replaced calipers may also not be sitting perfectly true and square due to little bits of grit or corrosion on the mounting surfaces, but they will work their way into a solid position after some use.
Also, you didn't mention having gone through the fun process of adjusting the air gap on the rear pads for the parking brake, if that's maladjusted it will give you a long pedal. If the pistons in the calipers are clocked at the wrong angle, the high part of the lip on the piston will push more on one side of the pads than the other, as it's designed to, but in the wrong spot, thus wearing the pads unevenly. This should be corrected as it will shorten pad life significantly and it will take longer to get a firm pedal until the pads have worn flat to the rotors which would be at an odd angle in relation to the brake pad backing plate.
As you can see, there are several potential problems that a tee won't address.

sure it will. only, you'll be locking up the rear brakes instead of the front brakes. if that's what you want, go for it ...

if you are married, please make sure you have a life insurance policy with plenty of cash to burn for your soon to be single again wife ...
Andy

People here are trying to help you out with real, time-tested knowledge and you're throwing it back in their face. You're talking about a system on your car that's crucial for safety. Cutting corners to save a few bucks in that department is just foolish man. Seriously...suck it up and buy a new p-valve or outfit your front brakes for the t. If you can't afford it right now, save up for a little bit. Nobody wants to hear another story of a wrecked teener.

After doing quite a bit of research on this topic myself, I'm not sure I would yank out the proportioning valve on a stocker. The folks that yank out the valve install 2 different pads. A high quality race pad up front (porterfields) and junk pads out back. They use the pads different bite characteristics to achieve the bias. These guys race their cars and have loads of testing under their belts. Running the same pad material front to rear without a proportioning valve will lock the rears up first.

BTW - Wilwood sells a cheap adjustable proportioning valve if the $275 is too spendy.

You also might want to look at installing a master cylinder support to stop the flex and improve your pedal feel.

The pedal is beyond "spongy". It goes almost to the floor. The car will only stop after some pumping and there is no way it will lock-up the brakes for a sudden stop.

I'll dismantle the proportioning valve and inspect/clean. That's really the only thing left that hasn't been addressed. Perhaps it is preventing a full bleed...?

Now why would I want to screw up my life and do something like getting married?

When married guys stop by my shop and see all 14 cars/motorcycles, the first thing they say is "You're not married, are you?".

That sounds like a long pedal. Did you adjust the air gap on on the rear pads?

Dont take this the wrong way.
You have not bled the system.
Know that the proportioning valve is adjusted at the factory. keep track of how far in the set screw it...how many turns.

BUT
Try this first, please.
Crack the line that goes from the master to the proportioning valve.
Bleed it there first.
Then, once you remove the large air bubble in that line (trust me there is one)
you will have a better time with the remaining air in the system.

What happens is that you probably introduced alot of air when you changed all the parts...the bubble in the main feed line to the back of the car is the largest bubble that you need to get out.

Also, you need to set the venting in the rear brakes or you will never have a firm pedal.

Rich

Make sure your steering wheel is straight otherwise you'll end up in YouTube blooper hall of fame.



Have you ever seen one go bad? They "basically" don't. There can be extreme cases but it would have to be just that, extreme.

I have a brand new "T" sitting on the shelf. I'll throw it in with your rebuilds. It's my last one (and I do mean "last" one). Don't tell your life insurance agent where it came from.

I'm not a fan (if that's not coming through in the writing).

* Do the two man bleed process and have the person inside the car "REALLY" cram on the pedal.
* Use a plastic mallet or a small wooden drift to tap on the p-valve (and rear calipers) when bleeding.
* Once you get a decent pedal, drive the car and hit some bump-itty-bumps. Do some panic stops in a vacant parking lot. Come back home and rebleed.
* Make sure the venting clearance is set to .004" on the high side of the runout.

It's funny, the other thing I see is people wanting adjustable proportioning valves in their cars and they never look to see that they already have one.

The poor stock valve gets a bad rap because it can be notorious for trapping air. Look at Jeff's factory manual thread or a post I made last month and you'll see the inner workings of the valve. The big spring can trap bubbles. The valve body can trap bubbles. Work around those issues with the bleed and you'll be much safer and have a great brake system.

Spongy brakes after rebuilding the calipers is a plague few professionals, much less amateurs, have avoided. I once sent a guy with a '67 911S off on a thousand mile round trip with a TERRIBLE "pedal". He absolutely HAD to be at work that night.He called me 6 hours later from way out in the sticks in Northern California, raving about how good his brakes were. I'm gonna ask this again: Did you go back and fix the venting?

Now, for the Krustiness. If you ask us, a group with an IMMENSE accumulation of knowledge and experience on 914s (not to mention a lot of other stuff), and you ignore our answers, you're gonna piss us off, and the spigot will close, and you'll not get any more help. I've seen it happen. The WORST thing you can do to me is shop a question around (after I've given my carefully considered and worded answer, based on my 35 years professional 914 experience) until you get the answer that confirms your preconceived notions. I WILL get rude to you in front of everybody.

It's a good thing you're on the right coast; You're unlikely to be driving behind me or someone I care about .......................

The Cap'n

Thanks Eric, but don't worry about the "T". I will spend some more time with the p-valve and see what happens.

If you go back and read, I only responded negatively to the folks who had nothing to add except pablum and insults. If you can't answer my question, or just want to throw in a jab, don't post!

I did respond politely to those who provided the requested information.

Yes, the venting has been adjusted.

Thanks, I'll give this a shot.

Read this, It will explain the problems if you install a T fitting with a stock brake
master cylinder

http://www.pelicanparts.com/techarticles/9...MW_calipers.htm

Man I wish that article would go away but... it won't.

Upgrade it is not.

There are "real" ways to upgrade a 914 brake system (which 90% of the time doesn't need "upgrading"). They all cost money. Once you delve into a real rear handbrake solution, they usually cost more money than 80% of us have in our 914's

Just the facts mame, just the facts.

I've personally gone off the road/track backwards into a 12foot ditch at 85mph
its real fun...

I'm not being a smart ass, I just don't recommend this modification
at least I tried it in a controlled environment.

bleeding a stock valve when a system has been opened up is a real challenge.
I've bled literally 100's of non-teener myself, and once on a 914 restoration I couldn't get my brakes right after a dozen bleed attempts and a few cans of fluid. I took the car to a porsche shop, literally to bleed the brakes. a 250 mile distance by trailer if that helps make my point.

try a professional power bleeder, break the lines open, uses the mallet... everything... you'll be impressed with the brakes when you get the air out.

oh... pads... the key to good brakes is good pads... try the RS4S

Rich, respectfully, you're wrong about this. The proportioning valve doesn't OPEN under high pressure, it CLOSES. This behavior has the effect of clamping rear brake pressure while still allowing front brake pressure to rise.

I agree though, that the p-valve traps air.

Want my input? Use the long-hose bleed method. It worked for me and it kept the wife out of the garage. No high-effort stomping on the pedal required.

Eric and brant both mentioned tapping on the p-valve with a mallet. That is the old school solution that a lot of new guys don't know about.

And I too got stung by a "pro." After complaining about the spongy pedal the "pro" just popped in a new master cylinder at about 2 1/2 times the going rate plus labor.

I shoulda used my mallet on his head. But I've not been back to that shop in 15 years.

the adj valve is a SUPER idea! be sure to mount it in the stock location.

frivolity aside. i'm not a brake expert but with the pedle going to the floor, after replacing all of the system components leads me to think (not assume), you may have made an error in your repairs. listen to what eric is telling you. or not...your choise. happy motoring . free tees for EVERYONE! FREE THE TEES!!

k

Dave, did you get it working the way you'd like? I'm curious about your impression on the pads. Please share.

Dave is correct on the p-valve. It was always explained to me the other way. I don't think Rich was saying it "opened" though, just activated. Jeff Bowlsby's thread on Factory Manual postings gives the (very interesting) specs as to pressures involved.

If you slam on the brakes and the rears lock up, you will have a hard time controlling the spin... ESPECIALLY in a 914. Mid-engine you say? Correct. I think it's in the first few pages of Vic's handling book. Once a mid-engine car starts a spin it can be much more difficult to control. It basically spins like a top. This is why the 968 with a balanced 50:50 distribution engine in front, tranny in rear, has been the benchmark for handling with the factory engineers.

This is why the p-valve shuts the rear brake off in a panic stop situation.

I don't mean to hijack, but since everyone is already here and I've considered this modification I'd just like to hear some opinon on my situation. My car is not stock, it's a 71 six conversion (3.2) with Carrera calipers/rotors up front, and stock /6 brakes out back. It locks up the fronts way before the rears (I'm not sure if I can lock them up to be honest) and the pedal is not spongy but pretty high effort (not sure if I have 17 or 19 mm MC).

I'd like to increase rear brake bias, so I plan on first trying to adjust the valve. Is it correct that turning the adjuster counter-clockwise increases rear bias? Does anyone know how much can it be adjusted? Will it ever reach the equivalent of a T? Can that screw be backed out completely opening the system, or is there a stop?

Does anyone know a sucessful setup for up a system like mine (with much larger calipers in front) short of a front proportioning valve (I don't like that idea) or dual MC / balance bar setup?

Lastly, since I expect it's my best solution.. Anyone have any experience with balance bars in a street 914? Is there a kit perhaps?

Thanks, and my appologies to the OP.

You used "frivolity" in a post

For those not at WCR2008......you shoulda been

Jim

I have a T fiting in mine. What should I have?

I have 911 fronts and 914 rears with Pagid orange pads. What do you guys recomend I put in? My car is mostly for AX.

You have what are called "Wide A-Calipers" up front. This is a standard A-Caliper (very similar to what Jon has as well) with a wider spacer to accommodate the 24mm wide rotor. The standard A-Caliper that Jon has rests on the same 20mm 911 rotor that the M and S-Calipers went on. I reference Jon because he was asking a similar question over the phone a few minutes ago. While I personally think the A-Calipers are heavy, I like the 20mm vented rotor for many reasons.

I'm not a fan of the Carrera system because I think it is too heavy for a 914 as there's generally too much rotating mass (24mm rotors) for such a light car BUT... that being said and the fact that you have the system and 914-6 rear calipers; let's review.

The "bias" is generally set from the factory with piston and pad sizes. This is something that you've fallen off a bit by installing the Carrera calipers up front. The Carrera was the first car to get a larger 42mm piston in the rear, yet it was also the first 911 with a p-valve. The p-valve in a 914 will simply act as a safety feature under extreme braking. By turning the screw counter-clockwise you will take some preload off the regulator spring. This means your rear brakes will be engaged longer in the braking cycle before being shut off (not engaged) -or- you'll have to push harder on the pedal to get it to shut down (stop from braking) the rears. Ideally, you'll want your rear calipers to come loose as soon as the fronts shut down or lock. You never want your rears to lock on a 914. They should ride that ragged edge for best braking.

Because A, S and M-Calipers with their 48mm pistons have been matched up with the rear M-Caliper with it's 38mm pistons on all 911's from 1969 through 1983 I still think you're OK with the brake bias that you have (your rear 914-6 calipers have the 38mm pistons). You just have huge front rotors. Depending on the master cylinder you have, you may want to back out the regulator spring adjuster however... the factory manual shows a lower changeover pressure of 525 psi for a 914-6 (vs. 685 psi for the 914-4). Again, they are comparing 19mm MC vs. 17mm MC. The 914-6 has 48mm pistons up front and 38mm pistons in the rear. The main difference with your set-up is the pad size on the (wide) A-Caliper; it is larger than the 914-6 front M-Caliper. So again... you may want to back the regulator spring adjuster out a bit to compensate.

This is tricky stuff and these are your brakes we're talking about, approach with knowledge and caution. I would have a friend with a video camera set up in an abandoned parking lot. Set up a panic stop staging area and let the video roll. Have a 5mm hex and a 13mm socket available to adjust the valve so the rears are never locked when the fronts are. You will have to break off the JB Weld type sealer the factory has around the adjustment rod to get everything to move (it is very brittle now and usually chips right off). I would back it out one turn at a time until the rears begin to lock. When they lock, screw it in 1/4 turn at a time until they no longer lock up. Once you have it adjusted, JB Weld it back in place and LEAVE IT ALONE.

E.

P.S. Fasteners and spacers from a 911 rear M-Caliper will make your 914-6 rear calipers 914-6/GT calipers. Vented rotors all around. Might be a nice upgrade. Remember... heavier rotating mass again (slight though).

E, I think you've got the adjustment directions backwards. Turning in the adjuster increases diaphragm preload, thus raising maximum rear brake pressure, thus making the rear calipers more likely to lock up.

Summarizing: if you want the calipers to lock up, turn the adjuster in.

Right?

Thank you Eric!
I was a bit confused at first since my name is also Jon, but figured it out eventually. I appreciate you input but I think I probably provided the wrong information. I doubt my rear calipers are off a 6, just the rotors. Does your advice change in that context?