Turbo Calipers and Floating Discs

[ShakinJoe]

Rob,

Welcome back from the dusty/sandy middle east. I and many if not all here appreciate your service and are happy you are in good health upon return.

Now, you have some explaining to do. The last time I saw your car at Sebring, the paint color was silver and I do not remember a brake booster?! Did you get a new ride and what happened to the old one?

You need to go have a professional discussion with the garage who did this work without removing that proportioning valve. They should have this knowledge!

[ncseahawk]

Joe, Good to hear from you. It is great to be back. What kills me about the shop is that I did a lot of research and ended up going with a highly acclaimed...at least on this forum ...shop in Charlotte. (the pic is not of my trunk area...just one that is similar and already uploaded.)

I did a complete suspension and brake upgrade. In addition to the failure to get the brakes right, they also failed to secure the bolts fastening the drive axles. This resulted in the unfortunate circumstance of being stranded on the highway.

It has taken a good deal of self discipline to not hold them accountable on this forum.

Despite all this I am trying to get the car ready for some Spring track runs at Pocono Raceway.

Perhaps Bill Verburg will chime in later today.

best

Robert

[Bill Verburg]

Originally Posted by ncseahawk

Is the the proportioning valve a different item than the brake regulator?

Based upon written description I found this. The PET diagram includes a regulator and a distributor...I would think the distributor would be plumbed in the rear and the regulator in the front (trunk area)






This is an 85 911 Carrera plumbed system that has been upgraded to a 23 mm MC and 930 Turbo calipers.

Do I need to simply take the regulator valve out of the system? If so, will any jointing solution do the trick? Anyone out there who has done the conversion please let me know.

thanks. It is my hope that the incredible stopping power of Turbo calipers is still in reach.

No, 2 different names for the same device, it limits line pressure above a set point called the knee. That is a 3.2 Carrera p/v in the pic,

for a 930 brake setup it should be eliminated, either remove the line and replace it w/ plain line or you can just gut it

the p/v come apart fairly easily, here's what you will find inside one

[bkreigsr]

Why is it so important to remove the proportioning valve with this conversion?
I did the conversion this winter on my 85 and everything seems okay for the street. (first track session is in three weeks in Florida)
thanks
Bill K

[Iciclehead]

I installed the proportioning valve when I added my Turbo brakes (it is the higher pressure one - I think 77 bar or similar) and it seems to behave fine.

I actually like the fact that I keep the rear wheels behind the front ones under braking, and I have no shortage of braking power.

Not sure why removing it is the right answer, but it may be the "low" pressure version versus the one I have that sends more pressure to the rear before it tapers it off....

Dennis

[Bill Verburg]

Originally Posted by bkreigsr

Why is it so important to remove the proportioning valve with this conversion?
I did the conversion this winter on my 85 and everything seems okay for the street. (first track session is in three weeks in Florida)
thanks
Bill K

on the street you are operating so far below the systems potential that you will rarely if ever experience any issues w/ or w/o the p/v

w/o the valve 930 brakes apply 1961/1242 N-M of torque @70bar line pressure w/ the stock 33bar 3.2 Carrera vlave in place that changes to 1961/671 any time you are below 33bar of line pressure the 2 setups are identical so you will never notice anything in normal driving

in other words the brake torque bias goes from 1.579(a normal place for 911s to be) to 2.924(extreme front bias)

[cdrik915]

I've turbo brakes at the four wheels , 79" turbo models , 2 parts discs floating , and absolutly no noise , with the factory master cylinder.

Carbone Lorraine pads ,


And an incredible braking.

[bkreigsr]

Just to be clear - if I remove the valve, the torque values will be at the preferred 1.579.
If I leave the valve, in torque values can reach 2.924? (that might explain why I kept locking up the fronts while bedding the pads)
thanks
Bill K

p.s. I just got done changing fluid and bleeding, so if I remove the valve, gut, and re-install, can I get a good bleed by doing the left front only, or should I go around all four again?

[bkreigsr]

sorry if I did a bit of a hyjack, but does anyone know the answer to the above questions?
thanks
Bill K

[Bill Verburg]

Originally Posted by bkreigsr

Just to be clear - if I remove the valve, the torque values will be at the preferred 1.579.
If I leave the valve, in torque values can reach 2.924? (that might explain why I kept locking up the fronts while bedding the pads)
thanks
Bill K

p.s. I just got done changing fluid and bleeding, so if I remove the valve, gut, and re-install, can I get a good bleed by doing the left front only, or should I go around all four again?

The p/v is on the rear lines only

yes, removing or gutting the valve allows the full line pressure to reach the rears, torque ratio will then be 1.579 at all times. This is a good place to be, there is a lot of debate as to the ideal ratio but the above is what the factory always had on 911s untill the modern era of abs and stability control but even the most modern Gt3s are near that ratio

[Quicksilver]

Don't gut the proportioning valve. Put it on a shelf. Go to any hydraulic hose vendor and have a hose made up that goes from the factory rear brake line straight to the master cylinder. The ability to return your car to unmolested stock shouldn't be undervalued.

I have changed a BUNCH of stuff from stock on my car but I have kept all the parts to return it to stock. The big changes that can't be returned are:
- 4 holes under the front valance for lighting mounts (can't be seen with the valance on)
- 1 hole under each seat to mount the sub strap.
- 1 small hole under the dash to route the remote brake bias adapter.
- 1 small hole near each headlight bucket for large gauge light wiring.
- Additional deck lid shock mount in the rear for the heavier rear wing.

If it comes time to sell the car I can pull all the parts off and sell the car as original and sell all the upgrade parts for reasonable money.

[bkreigsr]

Originally Posted by Quicksilver

Don't gut the proportioning valve. Put it on a shelf. Go to any hydraulic hose vendor and have a hose made up that goes from the factory rear brake line straight to the master cylinder. The ability to return your car to unmolested stock shouldn't be undervalued..

thanks for the tip - but this is a street-legal, dedicated track car that is well beyond returning to 'unmolested stock'.
as an aside - would you be willing to re-install a 28 year-old valve after it's been sitting on a shelf for a couple of years? especially if it is in the brake system?
Bill K

[bkreigsr]

here's mine
what's the best way to attack this?
lock down fitting #1 (closest to camera), then loosen fitting #2 (middle) , or #3?
#3 would remove the entire length, while #2 would remove only the valve?
thanks
Bill K

[Bill Verburg]

Originally Posted by bkreigsr

here's mine
what's the best way to attack this?
lock down fitting #1 (closest to camera), then loosen fitting #2 (middle) , or #3?
#3 would remove the entire length, while #2 would remove only the valve?
thanks
Bill K

What ever you do double wrench it, one on the fixed part and one on the rotating part

[Sdgg91]

Originally Posted by Iciclehead

I have floating rotors too, the noise drove me a little batty until I figured out a solution. I disassembled them, put a tiny dab of high temperature silicone on each of the rotor tangs and reassembled. They still make a little noise but it is way down. I figured I removed a bit of the lateral (axial?) play and still left the ability of them to move as they were designed to.

It has been about 5 years so far, including a track day and no issues at all....

Dennis

This is from soooo long ago but hoping you see this. Where exactly did you put the silicone and what brand type did you use?


Noise is driving me nuts!

[Cloggie]

Saw this post, I know Ice and he refuses to post here any more....but what I understand, the rotor is held to the hub through a plate and ring that has bumps that mate with slots in the rotor.
He just added the dab on the tangs of the rotor (the part that engages with the plate/ring) and essentially limited the play with the high temperature silicone...which was just high temp RTV

I think that is it....

D.

[Bill Verburg]

The floating part of the system can be eliminated w/o issue, just hard bolt them up.

or use the silicone treatment as above.

There are also spring-loaded floating mechanisms that also eliminate the noise,

you can see the spring-loaded fasteners here.

[Uwon]

I have had 930 calipers and 930 7 and 9X 16 rims on my ‘86 since about 1999 which I moved over to my ‘78 based RST hot rod some years back. I did remove the proportioning valve after a hairy weekend on the track where I almost ended up in the ruhbarb backwards. I replaced it with an adjustable valve which has served me well and hazard to guess that it’s probably close to fully open for road use. The nice thing about the adjustable valve is that I can set it to both dry and wet conditions- I have learned that half a turn clockwise is perfect for a wet track.
I don’t think anybody has mentioned having to shave off the fins on the front calipers and add a 5 mm spacer in the front to accommodate 7x16 930 rims in a G-body. I think but not really sure that this is a must with solid hats.
Here are a couple of pics of the 930 calipers on my current build. Front fins are fully shaved and rear fins are partially shaved (optional).
Front

Rear

And as others have already commented, they are awesome for street and high speed track.
Cheers,
Johan

[Bill Verburg]

Originally Posted by Uwon

I have had 930 calipers and 930 7 and 9X 16 rims on my ‘86 since about 1999 which I moved over to my ‘78 based RST hot rod some years back. I did remove the proportioning valve after a hairy weekend on the track where I almost ended up in the ruhbarb backwards. I replaced it with an adjustable valve which has served me well and hazard to guess that it’s probably close to fully open for road use. The nice thing about the adjustable valve is that I can set it to both dry and wet conditions- I have learned that half a turn clockwise is perfect for a wet track.
I don’t think anybody has mentioned having to shave off the fins on the front calipers and add a 5 mm spacer in the front to accommodate 7x16 930 rims in a G-body. I think but not really sure that this is a must with solid hats.
Here are a couple of pics of the 930 calipers on my current build. Front fins are fully shaved and rear fins are partially shaved (optional).
Front

Rear

And as others have already commented, they are awesome for street and high speed track.
Cheers,
Johan

It's true that in the wet you want less rear brake.

also, true that w/ stock 930 calipers and 911 7" Fuchs the calipers fins need to be shaved or a small spacer used. The hat has no influence on this.

alternatively, if you want Fuchs 7s use the 944 Fuchs, same ET, same look but more caliper room. they can be id'd by part # or the countersunk lug holes.