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Dave, I have seen this before on regular customer's cars after new brake pads have been installed for several months. My boss would have me change them out again with a different brand and the problem was resolved. My only thought is that the lining material must have some give to it when applying pressure. Once you release the brakes, the lining expands back to the regular thickness, requiring more pedal travel to reapply the pads to stop.
James
Well, now there's a thought! I'm running ceramic pads, with this problem , but , if I double pump, the pedal gets tighter. Like all of you guys, I've tried everything ,short of new M.C.
Well, now there's a thought! I'm running ceramic pads, with this problem , but , if I double pump, the pedal gets tighter. Like all of you guys, I've tried everything ,short of new M.C.
Just catching this issue. I had soft pedal twice, both at the end of winter and after car bascially was stored for the majority of the time. Bottom line was -- storage causes the soft pedal and most of the time it is usually from incorrect brake fluid. I had a german shop flush and fill mine 2 years ago and no problems since then. Try a flush first and make sure it's the proper fluid.
Well, now there's a thought! I'm running ceramic pads, with this problem , but , if I double pump, the pedal gets tighter. Like all of you guys, I've tried everything ,short of new M.C.
I read that the double pumping effect is because the pads are not free enough on their sliding faces to come back farther away from the rotor. True or not that is what I'll check tomorrow. As I do each wheel I will bleed them again. I cannot say if I have looked too closely at the calipers on this car, I'll report back my findings.
I am using Akebono ceramics and I cannot see them crushing up too much at all.
Dave, you might try some Permatex Ceramic Extreme Brake Part Lubricant like I did.
I lubed the pins, the contact surface of the pad to the piston and all the points where the pads slide on the caliper frame. Seems to have made a little difference.
I am using Red Stuff pads.
As a side note, I just replaced the front rotors, calipers and pads on my old Ford Probe with all NEW, not refurb parts for a sum total of $32 SHIPPED from Rock Auto. Go figure.
Dave, you might try some Permatex Ceramic Extreme Brake Part Lubricant like I did.
I lubed the pins, the contact surface of the pad to the piston and all the points where the pads slide on the caliper frame. Seems to have made a little difference.
I am using Red Stuff pads.
As a side note, I just replaced the front rotors, calipers and pads on my old Ford Probe with all NEW, not refurb parts for a sum total of $32 SHIPPED from Rock Auto. Go figure.
I have brake lubricant and I shall use it, I have new pads and rotors for the back but will only use them if there is too much wear.
The car has always been like this for six years. I do not know what is going on but it should not be like this.
Thinking about the sticky pad idea I have decided that this is no way to cause the problem as the pads are not connected to the cylinders so it would have to be the cylinders that are not returning.
Last edited by onehundred80; Oct 14, 2017 at 08:46 AM.
Thinking about the sticky pad idea I have decided that this is no way to cause the problem as the pads are not connected to the cylinders so it would have to be the cylinders that are not returning.
I have looked into this farther and found that the pistons rebound back into each cylinder as a result of the piston seal returning to the normal shape it was prior to getting deflected by the oil pressure moving it and the piston forward. The face of the seal against the cylinder wall stays where it was due to 'stiction' caused by the oil pressure forcing it against the wall. The rest of the seal moves outward under the pressure of the oil.
Now if the piston was moved back too far when putting a new pad, in the seal went back to far and stiction occurs farther back than it should.
This causes the piston to move too far outward to contact the pad. Normal cylinder movement appears to be about .005" out and then .005" back in on brake pressure letup. If the cylinder moves .010" then twice the oil has to be pushed down the line, with large diameter pistons this can be quite a lot of oil. As the master cylinder bore is smaller than the brake cylinder bores then the master cylinder has to move much more than it should.
Twice the oil means twice as much piston travel than there should be, remember that there is some travel that just takes up the slack in the system caused by gaps between the push rods.
So we have the pedal taking up the slack and then we will say twice the normally required travel. As the pedal lever uses mechanical advantage of about 3 : 1, we get the extra travel multiplied by 3 to make the pedal travel seem to much.
I got the seal info from this post by Glyn M. Ruck on MBWORLD.org in this post of his.
See pad break-in procedure on the Stoptech website.
This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. So tell us - did you change all the pads? If not - do so & then do the break-in procedure
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.
There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.
If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.
The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.
Good luck - I hope your problem is just not replacing all the pads at the same time.
As always , great info and help Dave. Do you think there is a solution if ,in fact I (we) have over withdrew our piston to far inwards? I used a C clamp , with the old pads still in place when I try to reset the pads for clearance. Hoping , not to push it in to far! I did this on an old 280Z , without using the pads! To far is when piston goes back , an fluid starts running out around the dust cover.....
As always , great info and help Dave. Do you think there is a solution if ,in fact I (we) have over withdrew our piston to far inwards? I used a C clamp , with the old pads still in place when I try to reset the pads for clearance. Hoping , not to push it in to far! I did this on an old 280Z , without using the pads! To far is when piston goes back , an fluid starts running out around the dust cover.....
The method to reset the pistons is outlined in the MBWORLD post. I guess it works.
Today i
took some pics as i put BB to bed . these are Raw pics.
24 leds with remote control color changing dimming strobing and everything ) in the Dome light
just what we all need,a mobile light show !
$8 or something from epay .
Mood lights, colour du jour :
Last edited by daveesrt6; Oct 15, 2017 at 03:52 AM.
I beg to differ, having had a six speed which I really liked, I'll stick with the SRT.
To each their own, but that 5 speed has a mind of its own sometimes, when I am on track, I would gladly give up the HP to have a transmission I can count on staying in the right gear - whichever one I select.
To each their own, but that 5 speed has a mind of its own sometimes, when I am on track, I would gladly give up the HP to have a transmission I can count on staying in the right gear - whichever one I select.
Have just fitted Latemodel 21 Paddle shift kit. Also have had the Eurocharge TCU tune so now my SRT drives in the gear I choose when I want it
Re: What did you do to your Crossfire today?
