My brakes feel weaker

[Splinter4784]

i have 14,000 miles on the stock rotors and for the few thousand miles my brakes seem to feel much weaker

i have to push my foot way down, i took it to the dealer and 2 people inspected it and said that my brakes are at 50%

I think there might be something wrong

when i first got the car, when i touched the pedal the car would stop, now i have to push the break 3 inches down for the car to stop

[gr8000]

I dont have that experience after 22,000km (which include 3 track days on stock brakes). Mine seem perfectly fine. During the track days I did not push the brakes to their absolute limits for too many turns (didn't want to end up with wrapped rotors) but I was giving them some hard time. Still no adverse chance in braking performance.

How did the dealer justify the 50% reduction?
(I guess you mean 50% reduction in the pad thickness - not in braking performance).

[Splinter4784]

i drive my car hard, and i really do not like the feel of the brakes as of this past couple thousand miles

they said it was a 50% reduction in pad thickness

im going to really complain until they fix it some how

[John@BMW]

brake feel is going to change through out a pads life. If you look at a brand new factory brake pad, the pads face actually gets larger as it wears down. This gives you a more gradual feel or a less touchy brake pedal..... When a pad is brand new, the caliper piston pushes down on a smaller amount of pad material which increase brake pressure or torque. As the brake pad wears down, more surface area of the pad is touching the rotor which causes the pressure to be divided over a larger area. This causes the need for more pedal effort to produce the same amount of braking. Does all that make sense? Im kinda scatter brained ATM

[FStop7]

Maybe bleeding them and replacing the fluid will help. It's best you pay someone to do that if you're not mechanical, though. If you get air in the lines you'll make things worse.

[JCtx]

Other than having less fluid in the reservoir (to compensate for worn pads), brake feel should NOT change as pads wear.

I'd suggest a bleed job. Your symptoms are typical of air in the brake lines, which means your fluid boiled at some point (if nothing else is wrong). That should fix your problem. Good luck.

[GT3 Tim]

Originally Posted by elp_jc

Other than having less fluid in the reservoir (to compensate for worn pads), brake feel should NOT change as pads wear.

I'd suggest a bleed job. Your symptoms are typical of air in the brake lines, which means your fluid boiled at some point (if nothing else is wrong). That should fix your problem. Good luck.

Agree 100% with the bleeding recommendation. Although I think travel and feel may have been confused.

Pedal TRAVEL should NOT change over the life of the pad.

Pedal FEEL (feedback, etc. is what I am refering to) MAY change over the life of the pad, although usually not the case.

If your travel is increased, you either have air in the line or a failing master cylinder......bascially, it must be one of those two things. Well, you could have a hole (leak) in the system...but that is highly unlikely. You would continue to loose fluid, and that would be evident by observing the fluid level over time. As the pads wear, the fluid level will go down to compensate for the difference in system volume, but if you did have a leak, the level would drop very quickly. I really doubt it is a leak, but I guess it is the other, although highly unlikely, alternative.

Bleed the fluid. It should make the difference. I would bet that is the issue.

An easy way to check the master cylinder is to:

Start car
Leave in park
Press brake pedal as hard as you can and hold it down
If you feel the pedal sink more (SLOWLY), the master cylinder is bad
If the pedal remains rock solid, it is ok.

[Splinter4784]

thanks guys, how does one bleed there breaks and replace fluid

im probrably going to take it to a mechanic, any suggestions on how i could do it myself?

[09E92M34ME]

i wouldn't even attempt to do that yourself if you are asking for tips on how to do it. play it safe and take it in.

[GT3 Tim]

Originally Posted by 09E92M34ME

i wouldn't even attempt to do that yourself if you are asking for tips on how to do it. play it safe and take it in.

Roger that. Just take it to a mechanic and have them do it.

[Dascamel]

Originally Posted by FStop7

Maybe bleeding them and replacing the fluid will help. It's best you pay someone to do that if you're not mechanical, though. If you get air in the lines you'll make things worse.

Go get a brake fluid flush... Air in your brake lines can effect pedal feel. Wear on the pads should not change the distance pedal travels.

[Subw00er]

On my z06, I had this problem even after a bleed. I turned out to be air in the abs solenoid. To clear the air I activated ABS a few times with some very hard stops (hard enough to enable abs and "pump" the air out). I dont know if the M3 braking system is similar, but it certainly cant hurt to try. Worked for me.. I had a tight pedal after that.

[Splinter4784]

thanks guys, im going to bleed my breaks

btw do u guys know if the master cylinder in the break pads are bad and need to be replaced,

I followed GT3 Tim's advice and i felt the pedal sink a little bit in slowly

[JCtx]

Originally Posted by GT3 Tim

Pedal TRAVEL should NOT change over the life of the pad.
Pedal FEEL (feedback, etc. is what I am refering to) MAY change over the life of the pad, although usually not the case.

That's the perfect answer indeed . Thanks for pointing that out.

And yes, doing a bleed job is fairly easy, but don't recommend learning on the M3 by yourself. Best way to learn is to offer your house for a 'tech day', and do the brake bleed with other owners who have done it before. This is a very common practice with motorcycles, and a great way to learn, and at the same time have a good time. Take care.

[Dascamel]

Originally Posted by Splinter4784

thanks guys, how does one bleed there breaks and replace fluid

im probrably going to take it to a mechanic, any suggestions on how i could do it myself?

Few DIY posts on the e90post.com tech sections. Take a look and see if it would be something you would even like to try.