Brake pedal feel - what is normal?

[Aaron_N]

I've owned my '86 944 for 5 years. It came with a very firm pedal. Two years ago I rebuilt my brakes...steel brake lines, new caliper seals, new master cylinder, Porterfield R4-S pads, and ATE 200 or RBF 600 for my occassional HPDEs. I have not been able to get as firm a pedal as before the rebuild, despite many bleeds and no air in the system.

So my question is, what is normal?

I never reach the end of my brake pedal travel in a maximum stop, but I get very close. I use 90% of the travel. Once pads are warm I can lock up a tire at 90% travel. (Tires are 200 UTQG grippy track day tires.)

Last year at VIR 944Fest the braking performance was pretty good, but I didn't have 100% confidence at the end of the long straights...pedal effort was a little variable, which I did not like at all. But it never hit the floor.

Does the above sound normal? Or should I have a firmer pedal?

I have exhausted all my options, so next step is the Wilwood kit...or just live with this medium soft pedal.

[NC944er]

I performed a similar brake system refresh on my ’88 NA about six years ago, including the addition of a new booster, check valve, reservoir, and rotors. The pedal feel was equally firm before and after the rebuild, which I would classify as very firm compared to modern brake systems.

I get about 1-1.5 inches of pedal travel before it firms up significantly, after which point I can get more stopping power by pressing harder, but it only travels about another 0.5 inches before stopping quickly.

Compared to other 944s I’ve driven, most have an equally firm pedal feel, some less so, which I can attribute to neglected brakes systems based upon documented maintenance history and personal inspection – degraded brake fluid, aging master cylinders, etc.

I suppose it’s possible that your new master cylinder is faulty – bad internal seals allowing fluid past the piston. I’m assuming you went with normal OEM equipment on the master, ATE/Girling? Does the brake pedal firm up when depressed with the engine off? It should feel rock-hard after pumping, if the pedal slowly sinks with pressure, it would point to bad seals. Similarly, with the engine running and the car stopped, if you hold steady pressure on the pedal and it slowly creeps toward the floorboard, bad seals.

[Aaron_N]

Thanks for the reply. I also have suspected a bad master cylinder, but then thought what are the chances?

The soft pedal actually started after I changed brake pads in 2023. Replacing the master cylinder was an attempt to fix it, but didn't. I put in the steel ATE master cylinder. Rebuilding calipers was also an attempt to fix it, but didn't.

However, I have both symptoms you describe...pedal does not get hard after pumping and does slowly sink when running.

I suppose it's possible when I pushed back the pistons the first time to put in the new pads, a seal in the original master cylinder went, causing the soft pedal, and then if the ATE was bad out of the box it would explain it. Just seems unlikely.

Any recommendations on master cylinders other than ATE? 944online also carries Mettali, significantly cheaper.

[Sansho]

You may be aware of this already, but as you look for another master cylinder, Porsche has superceded both the -86 944/Turbo ATE/Girling master cylinders and 87+ 944/944S Girling master cylinder with the 87+ 944/944S/Turbo/968 ATE master cylinder. (Not recommending the Porsche MC, unless you have deep pockets (list $1,197, discounted to $879), just noting the model/year coverage).

[Aaron_N]

You may be aware of this already, but as you look for another master cylinder, Porsche has superceded both the -86 944/Turbo ATE/Girling master cylinders and 87+ 944/944S Girling master cylinder with the 87+ 944/944S/Turbo/968 ATE master cylinder. (Not recommending the Porsche MC, unless you have deep pockets (list $1,197, discounted to $879), just noting the model/year coverage).

Thanks for this info. I have found rebuild kits for the new part (944.355.011.02) but not my original Girling (944.355.011.00). Do you know if the rebuild kit is backwards compatible?

Google says the ATE (.01) and the Girling (.00) master cylinders do not take the same rebuild kit, so I'm thinking they are not compatible and I'm out of luck rebuilding my Girling.

[Sansho]

I couldn’t find any rebuild kits, but did find several posts saying the ATE and Girling kits were not swappable.

While not a rebuild kit, Stoddards lists your MC 944-355-011-00 new for $400 (they comment, “ATE, made by Girling”)? May be worth a call. https://www.stoddard.com/en/master-cyli ... -944-P7520

[Aaron_N]

I couldn’t find any rebuild kits, but did find several posts saying the ATE and Girling kits were not swappable.

While not a rebuild kit, Stoddards lists your MC 944-355-011-00 new for $400 (they comment, “ATE, made by Girling”)? May be worth a call. https://www.stoddard.com/en/master-cyli ... -944-P7520

Thanks for checking. I'm not sure I want to spend that much, especially since the ATE one I bought seems to be faulty out of the box. I think I'm going to buy the Metelli cheap one which is the Mercedes part number, swap it and see if it fixes the issue. Can't be worse than ATE...

[zooklm1]

I've owned my '86 944 for 5 years. It came with a very firm pedal. Two years ago I rebuilt my brakes...steel brake lines, new caliper seals, new master cylinder, Porterfield R4-S pads, and ATE 200 or RBF 600 for my occassional HPDEs. I have not been able to get as firm a pedal as before the rebuild, despite many bleeds and no air in the system.

So my question is, what is normal?

I never reach the end of my brake pedal travel in a maximum stop, but I get very close. I use 90% of the travel. Once pads are warm I can lock up a tire at 90% travel. (Tires are 200 UTQG grippy track day tires.)

Last year at VIR 944Fest the braking performance was pretty good, but I didn't have 100% confidence at the end of the long straights...pedal effort was a little variable, which I did not like at all. But it never hit the floor.

Does the above sound normal? Or should I have a firmer pedal?

I have exhausted all my options, so next step is the Wilwood kit...or just live with this medium soft pedal.

When you did the bleeding, did you do the 2 person method (one person pump the pedal 4 times and hold and you open and then close the bleed valve and repeat at each wheel) or pressure bleed? I have not usually been successful with the pressure bleeder approach and have to finish with the 2 person approach to get the last bit of air out.
Lee

[Aaron_N]

When you did the bleeding, did you do the 2 person method (one person pump the pedal 4 times and hold and you open and then close the bleed valve and repeat at each wheel) or pressure bleed? I have not usually been successful with the pressure bleeder approach and have to finish with the 2 person approach to get the last bit of air out.
Lee

I've bled the car so many times I've got a gallon of brake fluid I can't dispose of...

I did 2 person bleed, power bleed, gravity bleed, vacuum bleed at the reservoir to pull any air out of the master, nothing has worked.

I am hopeful a new master cylinder will fix it, but it does seem strange a new ATE one would be bad out of the box. I will report back to close the loop.

[Sansho]

You’re right, you wouldn’t expect the master cylinder to be bad out of the box. It took 3! TRW master cylinders before I got one that worked on a Triumph Spitfire I worked on recently.

Paragon Products has the Metelli for $72.23. They also show the ATE rebuild kit, which is more expensive (Porsche discounts it to around $133 but Delaware shows it as backordered from ATE)