I have a 95 M3 future IP car that has stock brakes w/ upgraded brass guides, RRT cooling ducts and I have been running cobalt friction spec VR pads. When the pads wear down, the pedal travels further towards the floor before it engages the brakes. I don't like how far this makes my foot travel on the brake in relation to the accel pedal and it makes throttle blips more difficult. The accel pedal in the M3 is a very poor design, especially if you are pushing it laterally as your foot rolls over the side of it. I have had it actually rip out of the floor as I was blipping/downshifting. Is there a way to make the brake pedal engage further up as it does when you have fresh pads/rotors? Does anyone make backing plates that I could slide in between the pads and the piston of the caliper? How much pad should you leave before you chuck them? Would it be a bad idea to put old backing plates behind the pads? Ideally I would like to use up as much pad as possible, but having my brakes engage lower in the pedal range can sometimes throw me off. I have only tried the VR pads with my M3 and will be switching to Hawk 14/10 combo for comparison.

Maybe you need to bleed your brakes or something. The M3 has PERFECT pedal placement for heel-toe.

I agree. I am talking about when the pads are over half gone and the pedal engages much closer to the floor.

I agree. I am talking about when the pads are over half gone and the pedal engages much closer to the floor.

That should never happen. My track pads are now more than 50% worn, and my pedal is in the exact same position.

Hmm, what now? I just put in new pads. I guess I'll pay more attention to what happens as they wear. The pedal was not spongy as if it had air in the lines. It would just go down about half way before it engaged. Also I found my inboard pads were wearing less. I put some lithium grease on the brass guides to fix that.

mine feels the same way, the pedal falls as pads wear.

i'm wondering if you're experiencing excessive pad knock back...

does touching up on the brake pedal with the left foot before braking move the engagement point further up?

Does anyone make backing plates that I could slide in between the pads and the piston of the caliper?

IIRC, Bimmerworld sells titanium 'backing' plates. They are to reduce the heat transferred into the brake fluid, but they also could be used as you describe. They are not that thick, and maybe perhaps too expensive for your purpose...

mine does that too (i think), but if you think about how the hydraulic system works, it doesnt make any sense. In a perfectly bled system, with no hose expansion, the pedal should be the same regardless of how far the piston is pushed out. Does this make sense?

i'm wondering if you're experiencing excessive pad knock back...

does touching up on the brake pedal with the left foot before braking move the engagement point further up?

This would make sense with my theory. If the piston was pushed or pulled back into the caliper, then it would take more travel of the pedal to push it back out and engage the brake pad.

Why would knock back occur? I currently have euro blanks (not slotted) and there is no shudder or pulsing.

Wow...I have never experienced this at all. Pedal is ALWAYS at the same height & firmness.

Without more info, I'll cover the three basic problems. Pad knock-back, over-temped pads and boiling fluid will feel completely different when they happen.

Pad Knock-back
This is when the brake rotor/wheel bearing flex under corner loads and knocks back the pad and caliper piston away from the rotor surface. It will require an extra pump on the pedal prior to getting to the brake zone. Once engaged, the brakes should feel strong (provided no other problems)

Fix - new wheel bearings or learn to pump up the brakes on the straight prior to the next corner. Either with the left foot or the right, just prior to brake zone.

Over temp pads
This will feel like a firm pedal but you just won't stop that well. Probably will also get some pad deposits and will feel "out of round". If the pads out-gas when too hot, they may feel a bit soft on the pedal.

Fix - get higher temp pads or add cooling.

Boiling fluid
Water in the fluid boils and decomposes H2o and leaves it in the caliper. Pedal will feel squishy and brakes won't work very well. Could also be high temps causing the rubber hoses to get soft.

Fix - run higher temp fluid, bleed more often, use backing plates and get SS lines (best $100 spent IHMO)

If you just do DEs, high temp pads like Hawk HT10, ATE Blue, and SS lines should be sufficient, although some do run with cooling ducts, especially if on R-comps.

As the pads wear, the system should "self adjust" as the pads wear, but if you wear THAT much during a session I suppose you might notice it. In theory, you can take pads all the way to the backing plates, but that doesn't leave much margin for error.

If the pedal feel changes during session, then you have a problem as described above. (though there are other brake system problems you can run into).

My pedal feel doesn't change during the session, just over time as the pad wears. I had 8 weekends on this set of VRs front and rear. The rears wore evenly and have 1/2 life left. The fronts wore somewhat unevenly. On both sides the outboard pad had 2mm left and the inboard pad had 4mm left. I take it that this is from the guides sticking. The VRs I think handle up to 1500 degrees. I also forgot to mention that I have SS lines.

:stickoutt Maybe you need to bleed your brakes or something. The M3 has PERFECT pedal placement for heel-toe.

I have the same problem as mcclaskz. Mine brake pedal was always below the throttle during heavy breaking making heel-toe virtually impossible. New pads, multiple flushes/bleedings, solid caliper guides, etc did not work. Although it is a bit better with new pads. I finally had to space my brake pedal about 1/2 inch and it could use more.

This might mean you guys need front caliper rebuilds. I am serious. I run Spec VR's too, and do not have this problem at all.

Mine are freshly rebuilt and have only 8 weekends on them since. There is no evidence of overheating as the rubber dust boots are still fully intact and not disintegrated. Everything is normal and fully maintained.

Sound like you guys have knock-back - try a double pump on the pedal prior to getting the brake zone.

Or you DO have something wrong, and are missing it on the maintenance. :dunno

I thought knock back only happens while trailbraking or turning? This happens in the pits, on track, in a straight line, everywhere, every time the brakes are used .

Although it is a bit better with new pads.

It would make sense that pad knockback would be worse with worn pads... with new pads, there isn't much room to push the pads away from the rotors.

I thought knock back only happens while trailbraking or turning? This happens in the pits, on track, in a straight line, everywhere, every time the brakes are used .

I think it can happen anywhere. If your front wheel bearings are slightly worn, the rotor is essentially 'wobbling' from the perspective of the brake caliper anytime the wheel is rotating. This is what pushes the piston back into the caliper, thus requiring more pedal travel before the car starts braking.

IIRC, knockback has been discussed a lot here before... jayhudson comes to mind??? anyway... I remember someone replaced almost everything... brake master cylinder, brake booster, wheel bearings, calipers, rotors... I think the problem got better, but it still wasn't 'perfect'. Try searching for 'knockback'.

For me, I just left tap the brakes 2x at the end of the straight. This is right before the braking zone while I'm still at full throttle. The pedal firms up and then I can heel-toe.

hmm, anyone else experience this and then install new wheel bearings? My wheel bearings are not noticably bad. There is no toggle although they do have 122k miles on them.

http://forums.bimmerforums.com/forum/showthread.php?t=231694&highlight=brake

http://forums.bimmerforums.com/forum/showthread.php?t=231694&highlight=brake

M3 stock calipers are known to flex, causing tapered pad wear. Bimmerworld and other sell the brass guides to help reduce the problem and this is why stoptech and other bbk calipers have differential bore pistons. If you will take a look at your 50% worn track pads I bet you can measure a difference between the pad thickness on the leading edge and the trailing edge of the pad, and perhaps even between the inner and outer edge of the pad. As the caliper clamps the pad against the rotor, the leading edge is pulled onto the rotor, and will eventually wear faster than the trailing edge. Now you have a fairly flat surface rotor, and a pad that is higher on one edge so when you go for the brakes the master cylinder has to now press the uneven pad down onto the rotor. The action of pushing the uneven pad onto the rotor takes more travel than a pad that hits the rotor "square"

I am no expert, but this is a problem that I have witnessed first hand in two different M3's with stock brakes. One now has Stoptechs and no longer has the problem. If you have this problem and don't think it is the pads, I would suggest trying a set of new pads and see if the brand new (and thus "square") pads solves the probelm. If it does, you know it is a pad problem and not knockback, bearings, master cylinder, booster, etc.

Mine are freshly rebuilt and have only 8 weekends on them since. There is no evidence of overheating as the rubber dust boots are still fully intact and not disintegrated. Everything is normal and fully maintained.

same here, calipers are fine. I'm swapping booster/master cylinders soon to see if there is an issue there. I've driven other m3's on track with stock calipers and their brakes feel much better than mine.

I have a similar problem/feature with my brakes. For those with a low brake pedal, try activating your ABS a few times. While the ABS is working, does your pedal move back up?

I have a similar problem/feature with my brakes. For those with a low brake pedal, try activating your ABS a few times. While the ABS is working, does your pedal move back up?
That's what mine does. The feel of the pedal when the ABS activates is how I want it to feel all the time.

I have a similar problem/feature with my brakes. For those with a low brake pedal, try activating your ABS a few times. While the ABS is working, does your pedal move back up?
That's what mine does. The feel of the pedal when the ABS activates is how I want it to feel all the time.
Good thread. I've wondered about this since I've had the car. The pedal just doesn't feel like it should and it makes heel/toeing a lot more difficult.

That's what mine does. The feel of the pedal when the ABS activates is how I want it to feel all the time.
Good thread. I've wondered about this since I've had the car. The pedal just doesn't feel like it should and it makes heel/toeing a lot more difficult.

This is EXACTLY how i feel. I have always worried about my master cylinder...

I've had the same problem for years. Stock calipers recently rebuilt, SS lines, new wheel bearings, brass guides. I've used Porterfield R4 and Hawk HT-10 pads. Currently use Motul600 fluid. None of the changes I've made, including having the system flushed using the gizmo that cycles the ABS valves, has resolved the problem.

I'm guessing it's either knock-back or a marginal brake booster.

I'm not willing to keep throwing parts at it. I just live with it. Heel-toeing is overrated.... right? Or, to put it another way, Stoptech is the silver bullet.

Jay

Does sound a bit like knockback, though if it's still occuring without cornering in between brake applications that's weird. I've only experienced knockback after a turn.

My car has been doing this too. I think it is mostly related to the brake booster more than bad wheel bearings, in most cases though. I run Turner brass bushings and SS lines.

I tried to modify my brake booster line that runs between the booster and the manifold with a Grainger-type valve. It might have been placebo, but I think it feels better, however, the pedal feels best if I slight pump the pedal before getting on it hard. I didn't want to elimate the booster completely as I still drive the car on the street, but wanted to see if I could change the boost on the brake pedal. So far so good and the pedal seem firmer.

It still isn't as firm as I want, but it'll hold me off until I got to a fixed caliper setup like a Stoptech.

Drive Safely,
Raza

I'm guessing it's either knock-back or a marginal brake booster.

I think it is mostly related to the brake booster more than bad wheel bearings, in most cases though.

I'm not calling you guys out, but I am confused. How would a bad brake booster result in the symptoms you are experiencing?

I think most would agree that Stoptechs fix the brake pedal problem. If it was booster or knockback related, Stoptechs would exhibit the same pedal feel problem. They don't because the rigid caliper and differential bore pistons allow the pad to wear evenly. There may be some other anomaly going on, but I still believe what most of you guys (myself included!) are experiencing is due to pad taper. Stock M3 brakes are pretty darn good from a thermal standpoint, but the single piston design and caliper flex issues become an issue when you really beat on them at the track.

Part of the reason the pedal is softer with worn pads is that you are compressing more fluid, which makes the system softer. Contrary to popular believe, brake fluid is compressible, though it is very stiff. With worn pads your compressing all the fluid in the lines, plus the additional fluid in the calipers.

My solution is to put extra backing plates in the calipers when the pads get worn enough to fill up the space. Just grid the remaining material off an old set of pads to clean up the backing plates. For HT-10's you'll need to drill a hole in them so they sit flush with the back of the working pad. I definitely notice an improvement in pedal stiffness after putting these in.

Surprisingly, replacing the rubber guide bolt grommets will improve uneven pad wear. Solid guides can potentially cause caliper binding since the calipers and pads are designed to ride only on the carrier surfaces.

Rich

If any of you guys believe it could be your booster, let me know as I have a perfect working E36 M3 booster fs. Willing to let it go for 85shipped. It came off my C-Mod race car and my pedal was always very firm.

I doubt that it/s pad taper (at least for me) since I put new pads and rotors on about 5k ago. I think that we are discussing two different problems here:

- Initial press of the pedal results in a low pedal. After that, the pedal height is fine.

- Pedal travel is always low.

I have the first problem. I'm suspecting that its either a run-out problem (worn bearings or bad rotor/hub interface). When I spin my rear rotor, it doesn't make consistent contact with the brake pads. I don't think that its enough to cause significant knock-back, but I'm sure it isn't helping. I'm inclined to believe that its something with the hydraulics or ABS. After activating the ABS a few times, by pedal height is fine for a few drives. I once also bleed the clutch and notices that my pedal height was "normal".

You may want to have your brakes and ABS bled by BMW. The ASC+T/ABS module doesn't bleed air out very well and you need to have BMW run their ABS cycling tool while they bleed the brakes. After replacing a master cylinder once I never achieved my initial pedal firmness, even after repeated bleedings and ABS stops, until I had it bled by BMW with their special tool.

Rich

Is there any easy way to jump the ABS pump, so it is on when you are bleeding?

Alright WTF? This past weekend, at VIR I started off with new pads front and rear and new fluid. The pedal was rock solid after bleeding. Saturday the brakes were okay, but I found the usual 1/2 spongy pedal travel. I also found that when coming down the front straight the pedal would go down 2/3 and then the pedal would start to come back towards me while I maintained the same pressure on the pedal? Why would that happen? ABS was not being engaged?

Is there any easy way to jump the ABS pump, so it is on when you are bleeding?

I'm told that you can jumper pins 30 and 87 on the ABS relay. I'll give it a try in the next few days and report back.

I've always had the same problem. Below 50% pad wear pedal travel increases. Bleeding, rebuilding, etc - no difference. After loosing the gas pedal a couple times in races I had it hinged to the floor. I've been told this is a common problem. I hate tossing the pads at 50%.

My problem at this point is that the pads are brand new and it has started again.

My problem at this point is that the pads are brand new and it has started again.

Rob, I'm putting Stoptechs on next week before VIR. I'll let you know if it helps.

Rob, I'm putting Stoptechs on next week before VIR. I'll let you know if it helps.

You won't like 'em. Just send them my way :rolleyes

Jay

My brake pads got only less than 1mm less, and i'm getting the same issue with the pedal, but not to that extent (I can't still heel-toe). Changing pads tuesday, let's see then.

I think I am driving myself nuts. I went through the entire system with my tech and couldn't find anything obvious. Is there any reason to believe changing the master cylinder would improve this condition? I pulled the vac hose to the booster and the valve is fine as is the booster. I would assume the booster is either good or bad, not going bad. Anyone else change the master cylinder?

New brake pads and pedal action is back all the way up.

I think I am driving myself nuts. I went through the entire system with my tech and couldn't find anything obvious. Is there any reason to believe changing the master cylinder would improve this condition? I pulled the vac hose to the booster and the valve is fine as is the booster. I would assume the booster is either good or bad, not going bad. Anyone else change the master cylinder?

I was told this was a common issue w/ E36's... however, when I had James Clay codrive this past weekend he immediately old me afterwards "ERIC.. REPLACE your booster!"

I asked him whether or not it was the
usual" E36 soft pedal thing.. and he said it was WAY worse. I replaced front/rear rotors, pads, rebuilt front calipers and flushed the fluid the day before the race. Bedded in the pads/rotors during the friday practice session and the brakes were ROCK solid. After a few sessions (not even at 50% pad wear), I was exhibiting the same issues.

I have spoken to dmwhite before about this also... he replaced everything including the booster before and it wasnt until he went to StopTech's that the "spongy" feel went away. Whether or not his level os spongyness was as great as mine (or mcclasz) I do not know.

I asked this question earlier in this thread, but I got no response, so here goes nothing:

How in the world would a bad booster translate into a low pedal? <shrug>

Sorry--late to this thread.

I have experienced a similar problem (thus my heel-toe gas pedal modification described on another thread). Last year, I had an issue with my brake pedal gradually getting slightly closer to the floor during the course of a run. The way I noticed this is that my h-t downshifting was fine at the start, and got rockier and rockier (because the brake pedal was getting lower and lower relative to the gas pedal).

Anyway, it turned out that my mastercylinder was leaking (very slightly) where the shaft from the brake pedal went into the cylinder. This was discovered by sticking a finger (inside the car) up along the firewall, under a rubber seal around the shaft. Replaced that, and now my pedal position is constant, but still low.

I have yet to use race pads, but I may check my current pads and see if they have any taper...

In my previous e36 M3 I didn't notice this at all, perhaps there is some production variation that produces this issue?

Kent- I agree with you, but what is left for me to check? I have new pads, rotors, rebuilt calipers, brass guides, ss lines, rrt cooling ducts, new fluid before every event and the only thing I haven't touched is the booster or master cylinder.
Scotty, was there fluid leaking out of the master cylinder down the fire wall in the engine bay? Did you replace the master cylinder with a new one or a used one? If it was used, what year was the one you replaced it with?

Not even really dripping, just wet (a very slow, slight leak)--it was inside (not in the engine compartment that I could see--it never dripped on the ground). Replaced with a new unit (my shop said they are impossible to find rebuilt). I had a two month warranty when I bought the car, so it cost me nothing.

On the drive home tonight I activated the ABS once or twice, then tried the pedal--was firm (and a bit higher) for an application or two then lower and slightly softer again (I use this relatively). Any thoughts?

I ended up buying a new brake booster and installed it yesterday. The master cylinder and all other components looked fine with no visual leaking. I have yet to drive it, but it appears the problem is only slightly better. Before with the car on, the brake pedal when depressed was at the level of the fully depressed clutch pedal. After the new booster, the enguagement is maybe 1-2 inches higher than the fully depressed clutch pedal. I am definetly at the point of driving myself crazy with this, but with the car off it feels much better. Is there a way to limit the boost other than running unboosted brakes? While bleeding (with the car off) the brakes were better than before. Any thoughts?

I ended up buying a new brake booster and installed it yesterday. The master cylinder and all other components looked fine with no visual leaking. I have yet to drive it, but it appears the problem is only slightly better. Before with the car on, the brake pedal when depressed was at the level of the fully depressed clutch pedal. After the new booster, the enguagement is maybe 1-2 inches higher than the fully depressed clutch pedal. I am definetly at the point of driving myself crazy with this, but with the car off it feels much better. Is there a way to limit the boost other than running unboosted brakes? While bleeding (with the car off) the brakes were better than before. Any thoughts?

Limiting boost is easy. Use pieces of steel or aluminum rod that fit inside the hose between the intake plenum and booster. Drill different size holes in them for different amounts of restriction. Use a hose clamp to hold the device in place and seal it around the edges.

I think the one I'm using has a fairly small hole. IIRC, less than 1/8th inch.

It's trial and error.

Jay

Are you saying you have cured this problem by restricting the boost? This setup would be similar to what the power steering return hose has. That would be easy.

Are you saying you have cured this problem by restricting the boost? This setup would be similar to what the power steering return hose has. That would be easy.

No. It did not cure the problem. Still have no idea of how to do it. I've tried almost everything except new booster and new master cylinder. I'm going to try the extra backing plate deal next. Problem seems to be less with new pads.

Jay

Did the restrictor make it better? Would you try one with more restriction?

I'm about to replace my MC and booster, since my pedal is pretty low, and cottage cheese like :eek: I had some wetness around the vac hose, so I'g guessing that the there is a tiny leak, and brake fluid is getting sucked into the intake (my idle goes weird if I rapidly pump the brakes).

I should get to it this weekend, so I'll report if it makes any significant difference ... I currently have HT-10s, about 1/2 done.

FWIW, solid caliper guides do help brake feel a fair bit for me. Given how cheap they are, it might be worth a shot.

Read original post...

No. It did not cure the problem. Still have no idea of how to do it. I've tried almost everything except new booster and new master cylinder. I'm going to try the extra backing plate deal next. Problem seems to be less with new pads.

Jay

I was thinking about this for a while. Why would the pedal be squishy and low when the pads were worn, but high and tight when the pads were full. It must have something to do with the cylinder in the caliper, because the rest of the system is not effected by pad thickness. Then i started thinking why this would be.

Could there be a small amount of air trapped behind the piston that wont bleed out? It might go away when you push the piston back in, while changing pads, but develop again as the pads wear. Does this seem like a posibility?

Did the restrictor make it better? Would you try one with more restriction?

I can't remember if I thought it made a diff. But, I likr the feel of having to press a little harder on the pedal. Seems like I don't slam into ABS as easily. It's easy enough to try several. I think mine is more like a 1/16th of an inch. Pretty small hole.

Jay

I was thinking about this for a while. Why would the pedal be squishy and low when the pads were worn, but high and tight when the pads were full. It must have something to do with the cylinder in the caliper, because the rest of the system is not effected by pad thickness. Then i started thinking why this would be.

Could there be a small amount of air trapped behind the piston that wont bleed out? It might go away when you push the piston back in, while changing pads, but develop again as the pads wear. Does this seem like a posibility?

It's not air. Air would make the pedal squishy. Pump it once and it's up where you want it and firm. For some reason the piston retracts into the caliper more when the pads are worn. Tapered pad wear? Knockback? Who knows? Caliper flex when they're farther over on the bushing pins? Bushing pin flex? It's a mystery.

Jay

i have some thories. i used to have the same problem with stock brakes, using hps pads, changed master cly, no change.
got a good deal on stoptechs, same problem eventually came back and pad knock-back was really bad on top of that.
replaced front bearings and knock back is now gone.
as for the low pedal at the track, my theories:

1. i had overheated my hps pads (fact) and i was led to believe that the friction material on the pad became more compressible, thus allowing the same friction level, but increasing the pedal travel. fluid was not an issue.
since the material is now softer and thinner, the destructive cycle happens sooner into a session

2. the less material you have, the farther out the piston is. the farther piston placement stretches the piston boot causing elasticity to bring the piston back slightly. this i can compensate for by tapping the brake LFB before i get to the brake zone.

i have long ditched hps pads for track use. eventually they would get to the point where i could feel the difference in pad compressability on the street.

i can't see a booster doing this. as for restricting vacuum with a small hose, i see this as causing inconsistent boost levels. if you apply engine vacuum for a long time, eventually, the two sides will become equal and full boost returns. bead boosters may cause running problems due to vacuum leaks and harder pedal pessure needs. not softer pedal.

feel free to de-bunk my theories. i'm always ready to learn.

i1. i had overheated my hps pads (fact) and i was led to believe that the friction material on the pad became more compressible, thus allowing the same friction level, but increasing the pedal travel.

Interesting. I had a set of Ferodo pads bought from Korman. I bought them in the fall, but didn't use them until Spring. They were compressible out of the box (to the point that the pedal went to the floor). No warranty or compensation for all the trial-and-error at the shop to figure this out, from either Korman or Ferodo. :mad (I have a long memory for being screwed.) Might be worth swapping pads just to check this theory out.

Also, I had this complaint when my car was in warranty and a new Master Cylinder did fix it. Just one data point.

i can't see a booster doing this.


feel free to de-bunk my theories. i'm always ready to learn.

I didnt think so either, but I was told the diaphram may be worn inside causing issues.

I replaced my booster and the pedal feels more springy... cant judge the engagement point yet till I get back out on track.

Alright, you may all now begin to say, "I told you so." I did 3 days at VIR last weekend and the problem is now almost worse after new booster install(more miles on original wheel bearings). I think that it is indeed pad knock-back. I had to left foot tap the pedal at EVERY brake zone, 1, 3, 4, 10, 11, Oak Tree, back straight, top of carosel, bottom of carosel and so on. When I did tap the pedal, it comes up and feels quite strong. The brakes would stop very well. The down side is that I was dancing so hard that I would miss turn ins and it hurt my overall concentration as well as braking confidence. I got better as the weekend went on, but it is still obviously not optimal. My car was a 120k mile street car when I bought it a year and a half ago and i have since added 2k track miles. The wheel bearings are the only suspension piece that I have not replaced. I guess I can see where they could be the major culprit. The strange thing still is that when I check the wheels in the air, they do not move. Is it possible that they move enough under load for knock-back, but do not move when not loaded? Needles to say, new front bearings are ordered. We will see what gives after install. My next track event isn't untill July at Road Atlanta.

Just so you know, my front wheel bearings were pukin' grease out all over my wheels before I replaced them. I couldn't move the wheels when jacked up either. New wheel bearings helped the brake problem, but definitely didn't fix it. I still have the problem.

Something else is going on.

Jay

Alright, you may all now begin to say, "I told you so." I did 3 days at VIR last weekend and the problem is now almost worse after new booster install(more miles on original wheel bearings). I think that it is indeed pad knock-back. I had to left foot tap the pedal at EVERY brake zone, 1, 3, 4, 10, 11, Oak Tree, back straight, top of carosel, bottom of carosel and so on. When I did tap the pedal, it comes up and feels quite strong. The brakes would stop very well. The down side is that I was dancing so hard that I would miss turn ins and it hurt my overall concentration as well as braking confidence. I got better as the weekend went on, but it is still obviously not optimal. My car was a 120k mile street car when I bought it a year and a half ago and i have since added 2k track miles. The wheel bearings are the only suspension piece that I have not replaced. I guess I can see where they could be the major culprit. The strange thing still is that when I check the wheels in the air, they do not move. Is it possible that they move enough under load for knock-back, but do not move when not loaded? Needles to say, new front bearings are ordered. We will see what gives after install. My next track event isn't untill July at Road Atlanta.

I just replaced my master and booster, going to race at barber this weekend. I'll report back.

Hope the pedal feel & travel improves!

Hope the pedal feel & travel improves!

it couldn't get much worse right? :lol

Jay, did you replace your MC? The hard thing to compare all our cars is that they are all 10 year old cars now with other things going on. To recap my car: Rebuilt calipers, SS lines, fresh ATE fluid always, new pads/rotors, new booster- original ABS pump, original MC, original wheel bearings F+R, 120k street miles, 2k track miles.

Jay, did you replace your MC? The hard thing to compare all our cars is that they are all 10 year old cars now with other things going on. To recap my car: Rebuilt calipers, SS lines, fresh ATE fluid always, new pads/rotors, new booster- original ABS pump, original MC, original wheel bearings F+R, 120k street miles, 2k track miles.

Nope. New wheel bearings, pads, rotors, fluid, rebuilt calipers and SS lines. Original booster and MC ~75K miles.

Jay

Other than pad knock-back, what else could make this happen? Anyone got a line on some new MCs? I think the only ones I could track down were ~$350. Of course the non-M MCs are $130 and also have rebuild kits.

What is pad knock back?

heinz - http://www.stoptech.com/tech_info/wp_knockback.shtml

heinz - http://www.stoptech.com/tech_info/wp_knockback.shtml
Thanks.

Okay, I replaced the front wheel bearings...
Yeah, still low pedal, but marginally better. I will now bite the bullet and order a new master cylinder. I was reading Ron Stygar's website and he has a interesting BMW Brake flow chart http://www.unofficialbmw.com/all/brakes/all_brake_system_troubleshooting.html
Basically, if you have this low pedal symptom and you have replaced the brake lines, fluid, pads, rotors, brass guides, rebuilt the calipers, wheel bearings, brake booster, bled the brakes, bled the brakes, bled the brakes, it should be the master cylinder. What a relief. Hopefully I will report back with success from the MC. Has anyone replaced the MC? It sounds like others have just chosen to buy used.

I just re-read the 2006 BMWCCA rules and it states that in Prepared you can, "modify the master cylinder to increase volumetric flow." How does one do that? Are there other master cylinders that would fit with the E36 booster? I found a stock M3 one new for $380, but the non-M versions are less than $200. Anyone have other thoughts?

just to update. The new booster/master didn't fix my problem. The pedal has less travel and is firmer, but still is low.

I'm out of ideas now.

My post earlier in this thread--replaced master cylinder--no significant help. I ended up moding my gas pedal to make heel-toe downshifting easier. I agree with what others have said--with a firm, HIGH brake pedal the e36 pedals are set up great to H-T, but that all changes if your brake pedal is lower. My first e36 was great, my current one the pedal is too low. I have a track event in the middle of June--will be my first use of new Hawk HT-10's, I'll report back if that helps.

just to update. The new booster/master didn't fix my problem. The pedal has less travel and is firmer, but still is low.

I'm out of ideas now.


I'll say....

:lol

So Scotty and SG, you both put in new master cylinders? I just want to make sure. I know others have put in different used ones from ebay. When you say low, where is the brake pedal compared to your fully engaged clutch pedal? My brake pedal is at the equal hight to the fully engaged clutch pedal.

Yes--a brand new BMW master cylinder.

When you say fully engaged clutch pedal, what do you mean? To me, there are two absolute clutch pedal postions--where it is when nothing touching it, and when it is fully depressed. If you clarify what you mean, I'll try to answer the question as best I can. Also clarify what I should be doing with the brake pedal--for example, car running, brake pedal pressed down "hard"?

Sorry, with the car running and both the clutch and brake pedal fully depressed.

Just to throw in my experience:

I have replaced my MC and vac booster. The MC was from a 12k mile car, so not new, but near new. The vac booster was from Zionsville ... also used. My weird weezing sound is gone when I pump the pedal, but the idle still get rough, and threatens to stall if I pump it fast enough. This definitly seems to be a vacuum issue, but probably not related to the brakes (minor vac leak somehwere else?).

As for the pedal feel, my pedal still feels pretty mushy, but it no longer sinks to the floor (which it did before, very slowly). Sorta like there is major flex somewhere (I do see the reservoir moving slightly when I really press the pedal). It is still low ... the height was not affected at all by the replaced parts. I have yet to drive it on track, but I don't think it will have made any significant difference. I'll try your clutch/brake pedal height test and report back.

OK, this is what I've got--car running.

Clutch pedal fully depresses to the floor. Brake pedal depresses one to one and a half inches below gas pedal and stops, so that is like 2-3 inches off of the floor--so I'm estimating my brake pedal (when pressed hard) sits at least 2-3 inches higher than my fully depressed clutch.

Hope that helps some.

Sorry, with the car running and both the clutch and brake pedal fully depressed.

By fully depressed, do you mean to the point where the clutch disengages? Different clutches might have a different take up point, and most of us have a clutch stop. Maybe a better test would be to measure the difference between the fully depressed brake pedal and the top of teh gas pedal, since this is where the issue becomes crittical?

By fully depressed, do you mean to the point where the clutch disengages? Different clutches might have a different take up point, and most of us have a clutch stop. Maybe a better test would be to measure the difference between the fully depressed brake pedal and the top of teh gas pedal, since this is where the issue becomes crittical?

Yup, that's why I'm talking about the gas pedal brake pedal relationship. I would think there is little car to car variation in where the gas pedal sits "at rest".

It seems like there are a number of brake pedal problems, with at least some posters it is low but firm (behave Maranelloman). I found this site which suggests that the brake pedal height is adjustable.

http://www.unofficialbmw.com/all/brakes/all_adjust_brake_height.html

It seems like there are a number of brake pedal problems, with at least some posters it is low but firm (behave Maranelloman). I found this site which suggests that the brake pedal height is adjustable.

http://www.unofficialbmw.com/all/brakes/all_adjust_brake_height.html


Nice find:buttrock . I'll have to take a look under there.

I looked for a way to adjust mine. No luck. Besides, you'd have to adjust as the pads wear. Unless it was way easy, it'd be a PITA.

Jay

It seems like there are a number of brake pedal problems, with at least some posters it is low but firm (behave Maranelloman). I found this site which suggests that the brake pedal height is adjustable.

http://www.unofficialbmw.com/all/brakes/all_adjust_brake_height.html

I looked for a way to adjust mine. No luck. Besides, you'd have to adjust as the pads wear. Unless it was way easy, it'd be a PITA.

Jay

This works on E30s, didn't think it did on E36s.

-Carlos.

This works on E30s, didn't think it did on E36s.

-Carlos.

My hopes crushed again:(

Woah! This would be a miracle for me and my size 14s. Can someone please confirm this?

Dave
98 M3/4

I thought I would update: I recently replaced the master cylinder in addition to new booster, front hubs et al. I went to Road Atlanta for the first time last weekend and as my pads were wearing, I again was starting to get the dreaded low pedal. I plugged the booster line (thanks spectre) and tried that out for the rest of the weekend. It took a lot of getting used to, but I made it work. The good thing is that the pedal feel is greatly increased, the bad is that you really have to stand on it to get anything, oh and your pads have to have heat. I will now try to get the ABS cycled from my local shop and see if that changes anything. After that I will try to bypass the ABS and see if that changes anything. At this point, everything in the system is new except the ABS.

I might be a total moron. I got my ABS cycled and now my pedal is consistant. My overall problem was that the pedal would go most of the way to the floor on the first pump and then if I pumped it again, the pedal would come back up. It would happen in the driveway, down a straight, everywhere. My shop said that when they cycled the ABS, some air did in fact come out. I will test it out on track soon, obviously things are different on track, but my pedal is the best it has ever felt. I don't really know how or when it happened, nor do I think all the problems were associated just with the ABS before I changed front hubs, booster, and master cylinder. I know how to bleed brakes and I would always bleed them until I would see no air. I'm sure that before I changed everything there may have been some pad knock back. Anyway, if you have anything similar to my problem, cycle the ABS while you bleed first. You might save yourself some $ and time.

This is what I've been suspecting. If you activate the ABS (a lot) and then your pedal is "normal" for a while, then you are a canidate for the ABS pump flushing. See post #38.

I tried to get my ABS cycled, but the dealers machine wouldn't communicate with my ABS pump. They couldn't get them to talk to each other.

I think it's time for me to visit the dealer and get a proper bleed. I have changed all parts (MC, booster, wheel bearings) and even with new HT-14s, the pedal is feeling soft after a couple of track sessions. Bleeding results in no air. I also find that my booster moves a bit when I really step on the brakes ... I think I'll fab up a plate to reinforce the firewall at the booster mount.

I think I may have a bandaid fix. Or at least some help as to brake pedal to gas pedal relationship. There's an adjustment on the gas pedal cable at the throttle body. There's an adjsutment as to how far the gas pedal will move on the floor. Seems to me you could lower the gas pedal some instead of trying to raise the brake pedal. Not sure if there's enough adjustment to make a diff. Just need to make sure the butterfly is fully open when the pedal is fully depressed. I'm going to try it to find out.

Jay

I think I may have a bandaid fix. Or at least some help as to brake pedal to gas pedal relationship. There's an adjustment on the gas pedal cable at the throttle body. There's an adjsutment as to how far the gas pedal will move on the floor. Seems to me you could lower the gas pedal some instead of trying to raise the brake pedal. Not sure if there's enough adjustment to make a diff. Just need to make sure the butterfly is fully open when the pedal is fully depressed. I'm going to try it to find out.

Jay


I think the brake pedal is adjustable too. I don't remember where I read this, but it was probably during a search of the UUC or the E36M3 list.

I remember from it, though, that it is a PITA to do, especially because the bolts are on super tight and probably lock-tited on for insurance reasons. I haven't had the time to try it out, but someone more adventurous (and without an interior and easy access to the pedal box) might have more luck.

Drive Safely,
Raza

It's an urban myth. Brake pedal is not adjustable. At least on my car.

Jay

I think the brake pedal is adjustable too. I don't remember where I read this, but it was probably during a search of the UUC or the E36M3 list.

I remember from it, though, that it is a PITA to do, especially because the bolts are on super tight and probably lock-tited on for insurance reasons. I haven't had the time to try it out, but someone more adventurous (and without an interior and easy access to the pedal box) might have more luck.

Drive Safely,
Raza

It is adjustable on an E30 M3, not on an E36 M3.

It is adjustable on an E30 M3, not on an E36 M3.

Rob, did that fluid help at least a little bit or give a slightly noticeable pedal feel change?

E-
I really couldn't tell since I haven't been on track yet w/ GS610. The major thing for me was the aparent air in the ABS. Now that it is flushed, my pedal is at least totally consistant and I should be able to feel the difference. As far as compression/density, I think the stock M3 brakes flex more that the higher density fluid can help. I might go to front Stoptechs like everyone else in IP (if I ever make it.)

Do you experience a shift in the ABS engagement point? Does it seem to be more/less sensitive?
Could it be due to a faulty brake position sensor?

No M3 here but I am experiencing the same issue and I am pretty much out of ideas.

So I went out today and adjusted the bowdin (?) cable which brings the gas pedal closer to the floor. Then I adjusted the gas pedal stop to allow the gas pedal to go further toward the floor and fully open the butterfly valve in the throttle body.

My theory is if I can't adjust the brake pedal up higher, I'll adjust the gas pedal down lower. Drove it up and down the street. Not sure I like having to push my foot farther forward to get full throttle. I'll decide after the races next weekend.

It's fairly east to do but takes 2 people.

Jay