Advice on Braking System….

Brookshire my · 03:22 PM

I have only had my ‘73 914 for a month and have not been happy with the brake
system’s stopping capabilities. Previous owner stated the system was “upgraded” to a BMW 3 series set up at the wheels. I bled the brake system today with new fluid. No bubbles and nothing in the system leaks. All pads are plenty thick and rotors mirror smooth. After the fluid replacement I feel no improvement. I am familiar with these systems working on my ‘64 356SC so no surprises here. The only option I can think of is a replacement master cylinder. The one there now matches pictures I have seen of the standard dual circuit for the 914. Maybe the internal parts are just worn. Any other ideas?
PS-Used DOT 4 fluid for the flush having no idea what was there previously.

John Rogers · 09-02-2025, 06:02 PM

Dave D can chime in here I imagine but I thought in the article on upgrading to BMW calipers that a 19mm master cylinder was needed and probably a replacement with a tee fitting in the back. If you do this remember that the pedal will be a bit harder to push.

If you still have the stock brake switch that has the round metal disc it can be adjusted so that the lights will come on before any breaking will take place!
John Rogers

Brookshire my · 09-02-2025, 08:08 PM

I’ll read the article and go from there. I am not familiar with the rear proportioning valve and need to look and see if I have one or a simple T installed. Also need to look myself under the front to be sure if my helper’s description of the master cylinder is correct. I may have something different. I may be over my head here….

Dave at Pelican Parts · Dave at Pelican Parts's Garage

What specifically is your complaint about the brakes? There are a number of symptoms, most of them have several possible causes.

If your brakes feel fine and don't fade and are good except for the stopping distance, think about tires and alignment. After all, brakes only stop the wheels--the tires stop the car!

If the pedal is soft, that usually means air in the system somewhere. It's hard to bleed the master cylinder if you get air into it, and it's also hard to bleed the proportioning valve (what Eric at PMB calls the "pressure valve") which lives on the firewall behind the driver's butt. Alternately, the master cylinder could be moving when you press on the pedal; the firewall can wind up flexing and giving you a softer pedal feel. A M/C brace can help with that; see Tangerine Racing for one.

Brakes that won't lock up, no matter how hard you stand on the pedal, are often caused by the pads and/or rotors being glazed or just plain lousy pads. Or there could be a serious mis-match between the master cylinder and the caliper cylinders.

Larger master cylinders make the pedal harder to press, but it doesn't travel as far. Larger cylinders in the caliper (total cross-sectional area) will make the pedal easier and it will travel farther.

--DD

GregAmy · 09-03-2025, 05:42 AM

I'm with Dave, let's hear more about your symptoms.

I race a narrow-body 914 with the BMW calipers up front (stock rears), a 19mm master, manual bias adjuster, and Hawk pads and honestly it's pretty good. I find myself able to brake deeper than I really want to with no pad fade or boiling fluid. Hoosier TrackAttackPro tires, 205/50-15, typically 20-25 minute sessions.

I keep thinking I want the Wilwood brake kit with vented rotors but I just don't think I need it...

Same setup in my street car and I'm pleased with the solid pedal and good braking forces. I have crap tires so my problem is more managing those than the braking system itself. I prefer a bit more rear bias so I did the insert-washer tip in the rear bias adjuster to push more pressure to the rear.

Let us know what you're experiencing.

Brookshire my · 09-03-2025, 06:03 AM

Later this week I will take pictures to post as I know absolutely nothing about this set up. I am also disappointed that there is no parking brake except for the handle next to the left driver's seat. I’ll look closer but initially observed that the rear wheel system has no extra port or physical lever to attache any type of parking system. Will post later with what I find.

Cairo94507 · Cairo94507's Garage

Getting your brakes sorted is critical. At 50+ years old, a lot of stuff, some bad, has been done to these cars along the way. Dave mentions all of the things that need to be checked.

I am confused by your parking brake comments. That lever, to the left of the driver's seat is the parking brake handle. If your cables are correctly installed and adjusted, nothing frozen in place from sitting, etc., as you pull the handle up you should hear the "paw" ratchet and the cable is then pulled tight and the rear calipers grip the disk. To release the brake, pull up, push the button on the end of the handle and lower the lever. I have never had an issue with a properly adjusted and maintained parking brake on a 914. Good luck sorting your issue and have fun with your 914- they are terrific cars.

Emo993 · 09-03-2025, 07:15 AM

Any chance the PO installed race pads......and are not heated up enough street driven.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

If there is no lever on the rear brake caliper, then the rear brakes have been swapped out. Could be that someone put front calipers on the rear; that has been done a number of times when larger brakes are installed up front. The lack of parking brake is one reason that we don't recommend this generally.

If the calipers have been swapped, then the braking system has been re-engineered. Possibly well, possibly poorly...

--DD

mepstein · 09-03-2025, 03:21 PM

Try different pads. PMB recommends Porterfields. They work really well. Properly bed them to your rotors. Also make sure your soft lines aren't too old. They do swell internally with age and braking power is reduced.

Brookshire my · 05:50 AM

Quote:

Originally Posted by Cairo94507

Getting your brakes sorted is critical. At 50+ years old, a lot of stuff, some bad, has been done to these cars along the way. Dave mentions all of the things that need to be checked.

I am confused by your parking brake comments. That lever, to the left of the driver's seat is the parking brake handle. If your cables are correctly installed and adjusted, nothing frozen in place from sitting, etc., as you pull the handle up you should hear the "paw" ratchet and the cable is then pulled tight and the rear calipers grip the disk. To release the brake, pull up, push the button on the end of the handle and lower the lever. I have never had an issue with a properly adjusted and maintained parking brake on a 914. Good luck sorting your issue and have fun with your 914- they are terrific cars.

There is no mechanism on these rear calipers to attach the parking brake cables. I assume they are really front calipers.

Brookshire my · Yesterday, 05:48 AM

Took off the tires this morning for pictures. Rear calipers look to actually be front calipers as there is no way to attach the parking brake cable. Calipers have “ATE” cast in side and the number nine.

Three pictures of front caliper showing “BMW G5R” on the side.

Dave at Pelican. Please help with actual order numbers for new rear calipers and pads with lever to attach the brake cable and regular replacement street pads for street use for the current front calipers. I am new to this! Thanks!!!

mepstein · Yesterday, 07:41 AM

Call PMB. Tell them what you need and what you have. They will set you up with all the right parts. I'm pretty sure Pelican gets all their rebuilt calipers from pmb so you might as well go to the source.

Brookshire my · Yesterday, 09:48 AM

Thanks for the advice. I see PMB has a complete set for all four wheels with a slight discount.

Brookshire my · Yesterday, 02:14 PM

I have my parts on order and wonder if there are any tricks or advice anyone can give to make the process smother. I’ve replaced master cylinders, soft hoses and bled multiple systems in the past but never replaced rotors, calipers or pads before. I have read in a Porsche manual the process to gauge the pads on the rear wheels to adjust for the parking brake and it looks pretty simple.

mepstein · Yesterday, 03:59 PM

Eric has videos on the PMB site. There are also YouTube videos on how to adjust. Yea, its pretty easy, especially on rebuilt calipers. Only thing is, the rear calipers from don't usually come with the small adjusters. Call them to see if you need to grab a set. (they usually advise you to remove them on your old set but in your case, that's not possible)