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#1
Sphinx

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Is there a way of shortening brake pedal travel without creating second order problems?

 

I ran the car in Feb and the brakes seemed fine.  it was my first time driving this car - so, just getting used to my new equipment.  Afterwards, only thing I did to the brakes was bleed them and swap the inboard and outboard pads, front and rear.  Pads are well lubricated at the ears, as are the sliders.  Plenty of friction material.  GLoc pads.

 

Went out last weekend for a track day and virtually no pedal.  Yes, the car will slow down, but not in a confidence inspiring way.  Took a lot of effort to push the pedal - scary.  Bled them again last night, don't think I got any bubbles.  In the garage, (engine running) I think getting good numbers on my brake pressure sensor.

 

And they have the pad-spreader springs in place - which I wonder if it that's exaggerating pad knock back causing a long pedal feel?

 

Q#1 - Anything so far that would contribute to a long pedal that I should look for?

 

Next, one thing that I think I don't like about this car (and the 1.6 I had previously) was the pedal travel.  It feels like it goes down a couple of inches before you get meaningful engagement.  If it was possible, I'd prefer a rock hard pedal from near the top - it's been a really long time, but I think that what I used to get when I ran hawk blues on a SRX7.

 

Q#2 - If everything else is normal, is there anything that can be done to shorten that pedal stroke without creating problems?

 

And yes, I've searched and read plenty of complaints about the long pedals but I didn't see any real solutions other than "look at everything."



#2
Alberto

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Could be a minor leak at the caliper pistons.  I've been getting that a lot lately.  The brakes get so hot that the caliper seals get tired and eventually start leaking.  This is on a 1.6


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#3
LarryKing

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Just my wild ass guess. Pads seldom wear symmetrically, that is to say they develop a wedge shape. I guessing that the pads are not seating completely against the rotors and that the wedge shape is causing the knock back.

 

But I could be completely wrong.

 

Just curious, why do you swap the pads? Yea, the piston side pad normally wears faster and my solution is to just replace with new pads.


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#4
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If for a moment forget about the short pedal you'd like and please don't compare the Miata and RX7 because the only sameness is there both Mazda's.

 

When I read your post, it seems you created a situation by swapping the inner and outer pads. The leading edge of Miata pads always wears more than the trailing edge of the pads. I was never a swapper of pads on my Spec7 or my Spec Miata.


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#5
Sphinx

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Just my wild ass guess. Pads seldom wear symmetrically, that is to say they develop a wedge shape. I guessing that the pads are not seating completely against the rotors and that the wedge shape is causing the knock back.

 

But I could be completely wrong.

 

Just curious, why do you swap the pads? Yea, the piston side pad normally wears faster and my solution is to just replace with new pads.

 

 

If for a moment forget about the short pedal you'd like and please don't compare the Miata and RX7 because the only sameness is there both Mazda's.

 

When I read your post, it seems you created a situation by swapping the inner and outer pads. The leading edge of Miata pads always wears more than the trailing edge of the pads. I was never a swapper of pads on my Spec7 or my Spec Miata.

 

 

To get better, more even pad wear, longer life. I've done it in the past and didn't hurt (and read here that others have done it).



#6
gerglmuff2

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i always change my pads out at about 1/3 of the material left because the pads wear bent, and then you have to use petal travel to flatten them against the rotor before they really start grabbing. try a fresh set of pads, and if that fixes the feel, its pad flex wear. if it doesnt, then you have another issue. brake pads are a wear item, so if you dont use them up now, you can put them back on later and use them. 


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#7
Bench Racer

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Sphinx, did the current issue come about after you swapped inner/outer pads? Draw yourself a simple picture of pads touching the rotor, one with even wear and the other with tapered wear. The swap the pads and the tapered pad will have the thick end of the pad touching the rotor and where will the thin end of the pad be, it wouldn't be touching the rotor? Now visualize what happens to the tapered pad when the piston pushes on the tapered pad. NOT NORMAL by any stretch. 

 

When an issue occurs, return to where you were or return to step one with the pads having parallel surfaces. 

 

I could pull up a professional brake video which states the leading edge of of all pads wear more than trailing edge of pads. Uneven wear happens when using 4 piston calipers therefor to solve the issue the trailing pistons are larger in diameter than the leading pistons. 


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#8
Sphinx

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Sphinx, did the current issue come about after you swapped inner/outer pads? Draw yourself a simple picture of pads touching the rotor, one with even wear and the other with tapered wear. The swap the pads and the tapered pad will have the thick end of the pad touching the rotor and where will the thin end of the pad be, it wouldn't be touching the rotor? Now visualize what happens to the tapered pad when the piston pushes on the tapered pad. NOT NORMAL by any stretch. 

 

When an issue occurs, return to where you were or return to step one with the pads having parallel surfaces. 

 

I could pull up a professional brake video which states the leading edge of of all pads wear more than trailing edge of pads. Uneven wear happens when using 4 piston calipers therefor to solve the issue the trailing pistons are larger in diameter than the leading pistons. 

 

yes, it started after the swap.  I did that swap before on my 1.6 with no ill effects.

 

I'm convinced - will swap them back, hopefully better.  Will report back.



#9
FTodaro

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Have you ever replaced the brake master? If its original, replace it, they are cheap. 


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#10
Jeff Wasilko

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I've found that the rear pad/rotor thickness seems to have a pretty significant impact on the pedal depth. If you haven't looked at your rears, maybe try that.



#11
Sphinx

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yes, it started after the swap.  I did that swap before on my 1.6 with no ill effects.

 

I'm convinced - will swap them back, hopefully better.  Will report back.

 

Well, not surprisingly, that worked.  Wish there was a better way to make the effective range of the pedal narrower.

 

 

Have you ever replaced the brake master? If its original, replace it, they are cheap. 

 

No idea - just got the car a few months ago.  Not sure if the prior owner did or not, but I suspect so given the state of everything else.

 

I've found that the rear pad/rotor thickness seems to have a pretty significant impact on the pedal depth. If you haven't looked at your rears, maybe try that.

 

On a related note, is the rear affected by pad flipping too?  (I suspect it is of limited to no value there too).

 

Pad and rotor look to be in very good shape.



#12
Jeff Wasilko

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Have you adjusted the e-brake/pre load with the hex screw?



#13
LarryKing

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Have you adjusted the e-brake/pre load with the hex screw?

That should be gutted from the caliper.


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#14
Sphinx

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That should be gutted from the caliper.

 

Correct, gone.



#15
Ron Alan

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Been MIA for a week so just seeing this...uhgg :(

 

DONT flip pads!!!!

 

When you run a pad down to 2mm(either side)...chuck them. The wear will always be uneven/tapered inside an out! A perfect flat wearing pad in a Miata is a unicorn...and frankly who cares! OK...yes I have a few corners on different cars that wear nice...but not perfect. 

 

Now take and swap inside to outside the pads on all 4 corners(lets say 50-75% pad life)...none of which wore perfectly and some worse than others. You might as well suck a bunch of air into the system because this is going do the exact same thing...BAD PEDAL!!!!  Because the pads are now hitting a surface(rotor)with high and low points...the piston has to travel farther to get an equal amount of pressure on the pad to rotor surface to slow car. Its fractions but you have 4 pistons...it is knock back...EVERY TIME you lift the pedal(for awhile!) 

 

Another thing to look for with new pads and a bad pedal...or after taking pads out and back in...BENT pad!  Pad hangs up on bracket and you bend it eventually trying to get the car to slow down with a big cramp in your leg!

 

I'm as frugal as the next guy but stopped flipping pads and tires our 1st year! That was 9 years ago. Watching pennies as the dollars fly off in the breeze :(

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#16
Brandon

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Is there a way of shortening brake pedal travel without creating second order problems?

 

I ran the car in Feb and the brakes seemed fine.  it was my first time driving this car - so, just getting used to my new equipment.  Afterwards, only thing I did to the brakes was bleed them and swap the inboard and outboard pads, front and rear.  Pads are well lubricated at the ears, as are the sliders.  Plenty of friction material.  GLoc pads.

 

Went out last weekend for a track day and virtually no pedal.  Yes, the car will slow down, but not in a confidence inspiring way.  Took a lot of effort to push the pedal - scary.  Bled them again last night, don't think I got any bubbles.  In the garage, (engine running) I think getting good numbers on my brake pressure sensor.

 

And they have the pad-spreader springs in place - which I wonder if it that's exaggerating pad knock back causing a long pedal feel?

 

Q#1 - Anything so far that would contribute to a long pedal that I should look for?

 

Next, one thing that I think I don't like about this car (and the 1.6 I had previously) was the pedal travel.  It feels like it goes down a couple of inches before you get meaningful engagement.  If it was possible, I'd prefer a rock hard pedal from near the top - it's been a really long time, but I think that what I used to get when I ran hawk blues on a SRX7.

 

Q#2 - If everything else is normal, is there anything that can be done to shorten that pedal stroke without creating problems?

 

And yes, I've searched and read plenty of complaints about the long pedals but I didn't see any real solutions other than "look at everything."

 

Couple of questions:

1. The subject of the post implies a too-long of pedal travel and then your post notes "a lot of effort". Those are two distinct situations with respect to brakes. Is it a long pedal with minimal slowing or a same length but more effort to slow?

2. Flipping pads is a good way to even wear, but as Ron notes, once they're below a certain threshold they're not worth flipping. Flip only if there's still plenty of pad thickness left.

3. Post-pad flip - caution on braking heavily as it will take a few laps for the pad to wear down the "peak" of the flipped pads to where the rotor makes a more thorough contact with the pad. Just something to keep in mind.

4. Regarding well-worn pads. I experienced what I dubbed a "variable high, hard pedal" with minimal slowing and it wouldn't happen every lap. Quit a pucker-inducing experience when you're going into T6 at Watkins Glen not knowing if you were going to be able to slow down!

 

Investigating the issue found nothing untoward about the pad itself besides being well-worn (about 3mm left). Swapping to new pads fixed the issue so my only thought in that situation was pad knockback combined with the brake hardware/springs were pulling the pad away from the rotor and upon brake application the pad was managing to get clocked at an angle and not contacting the rotor fully. Resulting in a "variable high, hard pedal".

 

The smaller NA6 brakes may not be subjected to a similar situation of the angled pad issue but clarity of the issue may help in better diagnosing it.


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#17
Sphinx

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Couple of questions:

1. The subject of the post implies a too-long of pedal travel and then your post notes "a lot of effort". Those are two distinct situations with respect to brakes. Is it a long pedal with minimal slowing or a same length but more effort to slow?

2. Flipping pads is a good way to even wear, but as Ron notes, once they're below a certain threshold they're not worth flipping. Flip only if there's still plenty of pad thickness left.

3. Post-pad flip - caution on braking heavily as it will take a few laps for the pad to wear down the "peak" of the flipped pads to where the rotor makes a more thorough contact with the pad. Just something to keep in mind.

4. Regarding well-worn pads. I experienced what I dubbed a "variable high, hard pedal" with minimal slowing and it wouldn't happen every lap. Quit a pucker-inducing experience when you're going into T6 at Watkins Glen not knowing if you were going to be able to slow down!

 

Investigating the issue found nothing untoward about the pad itself besides being well-worn (about 3mm left). Swapping to new pads fixed the issue so my only thought in that situation was pad knockback combined with the brake hardware/springs were pulling the pad away from the rotor and upon brake application the pad was managing to get clocked at an angle and not contacting the rotor fully. Resulting in a "variable high, hard pedal".

 

The smaller NA6 brakes may not be subjected to a similar situation of the angled pad issue but clarity of the issue may help in better diagnosing it.

 

 

You're right, they are two different issues.  Once I fixed the pad flip, car will now stop and it is certainly more consistent - Ron, promise, won't do it again.  Now, it is a general feel/modulation/precision feel.  Maybe that's a GLoc thing.  So, being able to release enough pressure to trail brake feels almost impossible, a skill I'm not good at to begin with.



#18
Tom Hampton

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For the Long pedal there is an adjustment for the pushrod / master cylinder clearance.  You can close up the clearance to gain some pedal height.  You must be careful with this adjustment, because it is important that the master cylinder completely retracts when you let off the brake.  So, you want high and "almost" tight.  If its fully tight, then the brake pressure will not completely release after each stroke.  Each subsequent stroke will bulid a little more pressure.  After about a pace lap and two race laps the brakes will be permanently ON and you will think you've completely lost power.  

 

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#19
Sphinx

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For the Long pedal there is an adjustment for the pushrod / master cylinder clearance.  You can close up the clearance to gain some pedal height.  You must be careful with this adjustment, because it is important that the master cylinder completely retracts when you let off the brake.  So, you want high and "almost" tight.  If its fully tight, then the brake pressure will not completely release after each stroke.  Each subsequent stroke will bulid a little more pressure.  After about a pace lap and two race laps the brakes will be permanently ON and you will think you've completely lost power.  

 

Ask me how I know....

 

Ah yes, the school of hard knocks learning... :)  Kinda like my genius idea to flip the pads.

 

Yeah, exactly right.  I want minimal play but I want to be able to get to max pressure quickly too.  






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