911 brake conversion

[Thor Fjellstedt]

I recently upgraded the brakes and wheels on my 74-914. Actually, it started with a gift of a set of Fuchs 5-bolt wheels from a 914-6. I purchased and installed 911 front struts, vented rotors and 911s calipers. I also replaced the stub axles, bearings and bolt plates on the rear with 914-6 parts. I also installed the 19 mm master cylinder. The brakes are much better but there still is a bit of a mushy pedal. I have read all the postings about the merits or pitfalls of removing the proportioning valve in the 914. Now that I have essentially a 911 brake system is it advisable to remove the proportioning valve and replace it with a "t" fitting? I understand that 911's do not have one.

My complements to Pelican Parts for a great technical article on this conversion. I did develop a few tricks of my own for the conversion.

[John Rogers]

As JP has said, this has been debated a lot here and other sites. I know 1987 Turbos do not have a prop valve and there is no rear wheel lock up and I have removed the valve on both our 914s and they have no rear wheel lock up. I'd recommend trying it for yourself, test it somewhere safe such as an autocross and see what you think. You can always put the prop valve back in.

[Thor Fjellstedt]

Just to follow-up on the proportioning valve. I removed it, installed a "T" fitting, bled the brakes and there is an amazing difference. The pedal is now VERY solid and the brakes are fantastic. Of course it has 911 calipers and vented rotors in the front. I have tried it in the wet and the dry and no rear brake lockup. Thanks for the advice.

[Dave Bell]

I have also read the back-and-forth on the prop valve vs. no prop valve... and about 2 weeks ago the alternative of adjusting the stock prop valve showed up on the rennlist.

"Normally you can hear a faint click in the factory proportioning valve at the knee of the pressure curve. You can change the knee of the curve by adjusting the set screw in the valve. The set screw is pretty short which limits the range of adjustment. I removed the set screw and replaced it with a longer bolt and turned it in so far that you never get to the knee, never proportion.... This effectively negates the ralph naderesque engineering"

So here is another option which apparently allows you to elminate some or all of the proportioning, if you desire, while still maintaining the stock prop valve, and of course avoiding the cost of a newer prop valve.

Having just done my own brakes and still finding them a little mushy, I decide to "adjust" the stock prop valve by screwing in the adjustment bolt and did notice improvement. Maybe after some testing I will be bold enough to by a longer bolt like the rennlist poster and obtain a wider range of adjustment.

Perhaps someone with more expertise like, Dave Darling, could comment on this use of the stock prop valve.

- Dave

[Dave at Pelican Parts]

No experience with it.

--DD