brake pedal hard?
02-09-2017, 01:46 AM
#16
Addict
Just an observation from a recent build on a friends 968. I was asked to remove/rebuild/reinstall 928GTS front calipers. The owner said the brakes used to be awesome but now they suck. I noticed that the pads were frozen in place in the calipers. I had to break them out with a pry bar. At the time I thought that the pads had expanded with the heat and maybe some brake dust got in there.
After I put new seals on the dogs and reinstalled the calipers I went to drop in new pads and could not get them to fit. Odd. Resorted to ordering a different brand thinking they were made wrong. Second pair had the same issue. The pads were 1 mm to long end to end. Took the calipers off and cleaned them again down to bare metal and the pads still would not fit. Ended up taking the pads to my bench grinder and making them smaller.
The only thing I can think of is that the calipers shrank over time. Maybe corrosion....??? Who knows? or maybe there is some bad spec out there from Porsche?
Why do I tell this story? Because maybe your pads are stuck...as in wedged into the caliper and are not able to move freely. This would cause your pedal to feel hard and your braking performance to suffer dramatically.
After I put new seals on the dogs and reinstalled the calipers I went to drop in new pads and could not get them to fit. Odd. Resorted to ordering a different brand thinking they were made wrong. Second pair had the same issue. The pads were 1 mm to long end to end. Took the calipers off and cleaned them again down to bare metal and the pads still would not fit. Ended up taking the pads to my bench grinder and making them smaller.
The only thing I can think of is that the calipers shrank over time. Maybe corrosion....??? Who knows? or maybe there is some bad spec out there from Porsche?
Why do I tell this story? Because maybe your pads are stuck...as in wedged into the caliper and are not able to move freely. This would cause your pedal to feel hard and your braking performance to suffer dramatically.
02-09-2017, 10:54 AM
#17
Bill I think Russell was trying to help. I've read the OP a dozen times and still don't understand what he is saying. His pedal is hard??? 
that's better than soft, right??? ....and ya, you are the brake and wheel God, but Russell is there for me day in and day out. He's sent me a spare DME, AFM, ICV, and numerous VOA meters and even a pair of Recaro seats once upon a time all without expecting a dime in return. 
.... You may be offended that he isn't as knowledgeable as you on brakes, but look at what we have to work with here. Russel is at least trying.....unlike some folks that pop in a couple times a month when they see an opportunity to solicit business. Should we all just keep our mouths shut if we don't have a PHD in the topic at hand?....or should we at least try to work through it?
that's better than soft, right??? ....and ya, you are the brake and wheel God, but Russell is there for me day in and day out. He's sent me a spare DME, AFM, ICV, and numerous VOA meters and even a pair of Recaro seats once upon a time all without expecting a dime in return. .... You may be offended that he isn't as knowledgeable as you on brakes, but look at what we have to work with here. Russel is at least trying.....unlike some folks that pop in a couple times a month when they see an opportunity to solicit business. Should we all just keep our mouths shut if we don't have a PHD in the topic at hand?....or should we at least try to work through it?
The 3.2 comes with front rotors that are the same thickness as Big Reds by Brembo
02-09-2017, 11:06 AM
#18
Just an observation from a recent build on a friends 968. I was asked to remove/rebuild/reinstall 928GTS front calipers. The owner said the brakes used to be awesome but now they suck. I noticed that the pads were frozen in place in the calipers. I had to break them out with a pry bar. At the time I thought that the pads had expanded with the heat and maybe some brake dust got in there.
After I put new seals on the dogs and reinstalled the calipers I went to drop in new pads and could not get them to fit. Odd. Resorted to ordering a different brand thinking they were made wrong. Second pair had the same issue. The pads were 1 mm to long end to end. Took the calipers off and cleaned them again down to bare metal and the pads still would not fit. Ended up taking the pads to my bench grinder and making them smaller.
The only thing I can think of is that the calipers shrank over time. Maybe corrosion....??? Who knows? or maybe there is some bad spec out there from Porsche?
Why do I tell this story? Because maybe your pads are stuck...as in wedged into the caliper and are not able to move freely. This would cause your pedal to feel hard and your braking performance to suffer dramatically.
After I put new seals on the dogs and reinstalled the calipers I went to drop in new pads and could not get them to fit. Odd. Resorted to ordering a different brand thinking they were made wrong. Second pair had the same issue. The pads were 1 mm to long end to end. Took the calipers off and cleaned them again down to bare metal and the pads still would not fit. Ended up taking the pads to my bench grinder and making them smaller.
The only thing I can think of is that the calipers shrank over time. Maybe corrosion....??? Who knows? or maybe there is some bad spec out there from Porsche?
Why do I tell this story? Because maybe your pads are stuck...as in wedged into the caliper and are not able to move freely. This would cause your pedal to feel hard and your braking performance to suffer dramatically.
other things that can cause the pads to be frozen are pistons rusted in place from lack of regular fluid changes, hence my reference to exercising the pads manually w/ a pad spreader at the annual fluid replacement. The rubber lines can also swell internally blocking the free flow of fluid.
The above is why I said
Assuming all other aspects of the brake system are nominal
it is also common for people new to older 911s to feel that the brakes require a lot of effort. It's impossible to separate this false perception from real issues over the internet.
The best advice if one is unsure if things are working right is to go to a shop familiar w/ these cars or at the very least bring in a friend(possibly local PCA member) to get a second opinion.
Last edited by Bill Verburg; 02-09-2017 at 11:30 AM.
02-09-2017, 02:15 PM
#19
Addict
thank you Bill for the info on the SS pad holders. Cleaning them and scouring them didn't seam to help the GTS calipers. It was as though the aluminum behind them was corroded and swollen.
Going back to the vacuum assist on the stock Carrera brakes as mentioned in the OP. Does the pedal drop at start up and does that indicate a working booster? I had stock carrera brakes for the first 8 years on my car and had several other knowledgeable guys drive it over years and nobody ever said the brakes were outside the norm. Nobody ever commented on them. To me they were weak and not something I wanted to trust in a panic situation. Unfortunately the car is currently wedged into my shed backwards with the front suspension off and the 930 calipers off or I'd fire it up and test for pedal drop.
Going back to the vacuum assist on the stock Carrera brakes as mentioned in the OP. Does the pedal drop at start up and does that indicate a working booster? I had stock carrera brakes for the first 8 years on my car and had several other knowledgeable guys drive it over years and nobody ever said the brakes were outside the norm. Nobody ever commented on them. To me they were weak and not something I wanted to trust in a panic situation. Unfortunately the car is currently wedged into my shed backwards with the front suspension off and the 930 calipers off or I'd fire it up and test for pedal drop.
02-09-2017, 02:43 PM
#20
I haddah Google dat
Rennlist Member
Rennlist Member
Bill, you are free to rebut anything you like. But don't ask for hero worship. So far, I have not seen quality statements from you.
So, you can either stop trying to give a lecture, and join a conversation among enthusiasts, and stop talking above everyone like some glory hound (Bill is the new Loren) - or better yet, go back to ruining the free chat board on the parts forum. There's a reason why I don't buy parts there anymore. I know they had to have a word with you about your posts in the past. Don't you have a boat to go fart around with? Or...I'm sorry, did you have to sell that?
So, you can either stop trying to give a lecture, and join a conversation among enthusiasts, and stop talking above everyone like some glory hound (Bill is the new Loren) - or better yet, go back to ruining the free chat board on the parts forum. There's a reason why I don't buy parts there anymore. I know they had to have a word with you about your posts in the past. Don't you have a boat to go fart around with? Or...I'm sorry, did you have to sell that?
02-10-2017, 05:32 AM
#21
Advanced
Thread Starter
I can see that it is unclear what I meant by "hard pedal"
on most cars the amount of resistance you feel increases progressively as the pedal travels, until you reach a point where it suddenly increases (i.e. you reached end of travel).
on my 3.2 the pedal travels a bit with low resistance and then suddenly is like I hit a wall or something hard, very sudden increase in resistance. if you ever drove car without power assisted brakes, this is the kind of feeling you get.
so I can modulate braking force only by applying more or less force vs other cars where you can modulate also by moving the pedal fwd and backwards a over a 1/2 inch travel or so. I remember even in my old E30 it was like this.
i just rebuilt front brakes but not yet the rears. maybe after I do that and a new fluid change the situation will improve. Else I guess I have to meet some other guys with similar car and see what they think, maybe my perception is wrong!
thanks for the interest!
cheers!
on most cars the amount of resistance you feel increases progressively as the pedal travels, until you reach a point where it suddenly increases (i.e. you reached end of travel).
on my 3.2 the pedal travels a bit with low resistance and then suddenly is like I hit a wall or something hard, very sudden increase in resistance. if you ever drove car without power assisted brakes, this is the kind of feeling you get.
so I can modulate braking force only by applying more or less force vs other cars where you can modulate also by moving the pedal fwd and backwards a over a 1/2 inch travel or so. I remember even in my old E30 it was like this.
i just rebuilt front brakes but not yet the rears. maybe after I do that and a new fluid change the situation will improve. Else I guess I have to meet some other guys with similar car and see what they think, maybe my perception is wrong!
thanks for the interest!
cheers!
02-10-2017, 07:26 AM
#22
Addict
One trick I found interesting when I entered the world of Porsche was to change the color of the brake fluid when you change fluid. Switching from blue to gold at one flush then back to blue at the next allows you to know for sure that you really did flush out the old. Would you believe that the law changed though, and now retailers can only sell one of the colors?!?
What you perceive as a hard pedal may actually be a good thing. A soft pedal can be caused by a number of problems. You could have moisture in your fluid, or weak soft lines that expand under pressure, or a leaking O-ring in your master cylinder. Unless there isn't an increase in stopping power when you apply more force to the pedal, I think you are good to go.
Any idea how old your master cylinder is?
Just judging by the color of your calipers your car has had a hard life. My front calipers are still a beautiful rainbow cad....Granted, they are now just sitting in a trash bag on a shelf...LOL...I even have a full set of brand new driller Zimmerman rotors on the shelf.
Where in Los Angeles do you live? Maybe you could join in when we have a wrenching party out here at my place in Alta Loma.
And about what you say is just moving the pedal a half inch....You increase force on the parallel to move it that half inch...That is normal. I am guessing that you don't notice the increase in force needed.
Any chance your pedal is just out of adjustment and has to travel too far before it contacts the plunger in the MC?
Anyway, sorry about my ramblings....I had similar concerns about my brakes so I am interested and can't wait to test my booster.
What you perceive as a hard pedal may actually be a good thing. A soft pedal can be caused by a number of problems. You could have moisture in your fluid, or weak soft lines that expand under pressure, or a leaking O-ring in your master cylinder. Unless there isn't an increase in stopping power when you apply more force to the pedal, I think you are good to go.
Any idea how old your master cylinder is?
Just judging by the color of your calipers your car has had a hard life. My front calipers are still a beautiful rainbow cad....Granted, they are now just sitting in a trash bag on a shelf...LOL...I even have a full set of brand new driller Zimmerman rotors on the shelf.
Where in Los Angeles do you live? Maybe you could join in when we have a wrenching party out here at my place in Alta Loma.
And about what you say is just moving the pedal a half inch....You increase force on the parallel to move it that half inch...That is normal. I am guessing that you don't notice the increase in force needed.
Any chance your pedal is just out of adjustment and has to travel too far before it contacts the plunger in the MC?
Anyway, sorry about my ramblings....I had similar concerns about my brakes so I am interested and can't wait to test my booster.
02-10-2017, 04:07 PM
#23
yes, the law changed to prevent idiots from using the wrong fluid
the sides of your caliper pistons indicate that your brakes have not been taken care of - so you may have what is known as "PO disease" which is sometimes fatal - if a PO neglected this most important maintenance then you cannot trust anything on the car and need to act like an aircraft mechanic doing a full "airworthiness" inspection on the entire car
There are 3 levels of Disasters:
1. neglected thing kills you
2. neglected thing strands you (maybe in an area where your life is in jeopardy if you cannot get help soon)
3. neglected thing causes a big big repair bill when it kills something related, or makes you (or your boss) very unhappy - this can be remedied with a divorce from your boss
you can DIY or send all the calipers out for a full refurb - one guy who does great work is in Sandy Utah, Eric IIRC
after all the excitement, I forgot if you have power brakes, but if so test the power booster & associated hoses
measure the runout on the disc with a dial indicator and measure the thickness; check carefully for any tiny cracks starting
replace all 4 rubber flex hoses with new rubber - do not use racer boy bling "stainless mesh covered hoses"
check the pad thicknesses & torques of everything nearby - maybe the grease in the F. hubs too with a full inspection of the surfaces
Look in the Bentley and follow their procedure, incl. the 20 degree angle, etc.
I'm sure that Dr. Brakeberg has a fuller exposition posted somewhere as he has used his engineering degree to investigate Porsche brakes
attached photo shows some useful tools (except the spreader shown is a cheapo version and there are much better ones available)
- after this, start looking at the fuel delivery system (rubber hoses all need to be replaced after xx decades of use & need to be correct for pressure and EtOH mix)
- then start thinking about other fluids
the sides of your caliper pistons indicate that your brakes have not been taken care of - so you may have what is known as "PO disease" which is sometimes fatal - if a PO neglected this most important maintenance then you cannot trust anything on the car and need to act like an aircraft mechanic doing a full "airworthiness" inspection on the entire car
There are 3 levels of Disasters:
1. neglected thing kills you
2. neglected thing strands you (maybe in an area where your life is in jeopardy if you cannot get help soon)
3. neglected thing causes a big big repair bill when it kills something related, or makes you (or your boss) very unhappy - this can be remedied with a divorce from your boss
you can DIY or send all the calipers out for a full refurb - one guy who does great work is in Sandy Utah, Eric IIRC
after all the excitement, I forgot if you have power brakes, but if so test the power booster & associated hoses
measure the runout on the disc with a dial indicator and measure the thickness; check carefully for any tiny cracks starting
replace all 4 rubber flex hoses with new rubber - do not use racer boy bling "stainless mesh covered hoses"
check the pad thicknesses & torques of everything nearby - maybe the grease in the F. hubs too with a full inspection of the surfaces
Look in the Bentley and follow their procedure, incl. the 20 degree angle, etc.
I'm sure that Dr. Brakeberg has a fuller exposition posted somewhere as he has used his engineering degree to investigate Porsche brakes
attached photo shows some useful tools (except the spreader shown is a cheapo version and there are much better ones available)
- after this, start looking at the fuel delivery system (rubber hoses all need to be replaced after xx decades of use & need to be correct for pressure and EtOH mix)
- then start thinking about other fluids
02-10-2017, 06:06 PM
#24
Addict
Ah, I thought it was so that emergency crews that had to clean up crashes knew that gold colored fluid was brake fluid like they know red fluid is tranny and/or power steering fluid.
Isn't it the ATE DOT4 Super Blue that is now only for off road use?
I think this is who Richard was referring to. My calipers looked this good after 80,000 miles and I know they hadn't been swapped out because nothing had been touched on my car.
http://www.pmbperformance.com/mid-911-brakes.html
Isn't it the ATE DOT4 Super Blue that is now only for off road use?
I think this is who Richard was referring to. My calipers looked this good after 80,000 miles and I know they hadn't been swapped out because nothing had been touched on my car.
http://www.pmbperformance.com/mid-911-brakes.html
02-10-2017, 06:59 PM
#25
yup - that's the guy
I dunno why the color restriction - if it was done by DOT or some other federal agency then there will be an explanation published; if Congress did it, they who knows...
I dunno why the color restriction - if it was done by DOT or some other federal agency then there will be an explanation published; if Congress did it, they who knows...
02-13-2017, 01:45 AM
#26
Advanced
Thread Starter
There are 3 levels of Disasters:
1. neglected thing kills you
2. neglected thing strands you (maybe in an area where your life is in jeopardy if you cannot get help soon)
3. neglected thing causes a big big repair bill when it kills something related, or makes you (or your boss) very unhappy - this can be remedied with a divorce from your boss
you can DIY or send all the calipers out for a full refurb - one guy who does great work is in Sandy Utah, Eric IIRC
after all the excitement, I forgot if you have power brakes, but if so test the power booster & associated hoses
measure the runout on the disc with a dial indicator and measure the thickness; check carefully for any tiny cracks starting
replace all 4 rubber flex hoses with new rubber - do not use racer boy bling "stainless mesh covered hoses"
check the pad thicknesses & torques of everything nearby - maybe the grease in the F. hubs too with a full inspection of the surfaces
Look in the Bentley and follow their procedure, incl. the 20 degree angle, etc.
- then start thinking about other fluids
1. neglected thing kills you
2. neglected thing strands you (maybe in an area where your life is in jeopardy if you cannot get help soon)
3. neglected thing causes a big big repair bill when it kills something related, or makes you (or your boss) very unhappy - this can be remedied with a divorce from your boss
you can DIY or send all the calipers out for a full refurb - one guy who does great work is in Sandy Utah, Eric IIRC
after all the excitement, I forgot if you have power brakes, but if so test the power booster & associated hoses
measure the runout on the disc with a dial indicator and measure the thickness; check carefully for any tiny cracks starting
replace all 4 rubber flex hoses with new rubber - do not use racer boy bling "stainless mesh covered hoses"
check the pad thicknesses & torques of everything nearby - maybe the grease in the F. hubs too with a full inspection of the surfaces
Look in the Bentley and follow their procedure, incl. the 20 degree angle, etc.
- then start thinking about other fluids
So the risk of being "stranded" somewhere on a freeway in Los Angeles doesn't seem too scary now :-)
However, I did everything you said for the front brakes (20 deg angle, new hoses and rotors, rebuilt calipers). As soon as I have the lift free and some time I will do the same for the rears... and I got a gallon of Castrol Delvac on the shelf for the trans, and was thinking about fuel lines as well.
Will keep posting how it goes. Thanks for the input.
02-13-2017, 01:52 AM
#27
Advanced
Thread Starter
This is my shop, in west LA, feel free to stop by to chat, play some ping pong, wrench etc. Call me when in the area 310 384 7428
Would love to join a wrenching party at yours as well, just let me know ahead... I could probably learn a few tricks from you!
Cheers!