Inconsistent Braking

[-cj-]

Hey guys,

Anyone have any inconsistent braking issues? Like sometimes you tap the brakes, let's say 20% and you stop insanely quick. Other times you have to go 40-50% and don't get as good of a bite as the first example?

Almost seems like the pads back away from the rotor too much, like when you first do a brake job. The parking brake also has inconsistent feel. Like sometimes 2 clicks holds you and it would be impossible to go more the. 2 clicks. Other times it takes 4 maybe 5 clicks. Maybe this is normal tho.

Oh, I also notice if you prime the brakes, ie tap them and then release and apply, you get that insane initial bite.

Am I going crazy?

[MDORPHN]

Originally Posted by -cj-

Hey guys,

Anyone have any inconsistent braking issues? Like sometimes you tap the brakes, let's say 20% and you stop insanely quick. Other times you have to go 40-50% and don't get as good of a bite as the first example?

Almost seems like the pads back away from the rotor too much, like when you first do a brake job. The parking brake also has inconsistent feel. Like sometimes 2 clicks holds you and it would be impossible to go more the. 2 clicks. Other times it takes 4 maybe 5 clicks. Maybe this is normal tho.

Oh, I also notice if you prime the brakes, ie tap them and then release and apply, you get that insane initial bite.

Am I going crazy?

Very odd.

Has any brake work been done on the car?


Neil

[ozinaldo]

Did you check the brake fluid?

[blotto649]

Yah, can't say I've noticed anything funny like that. I find the 1 has way more initial bite than my Mini, so takes some getting used to when I'm going between cars, but that's the only thing.

Sounds like it could be fluid, or maybe the callipers aren't floating correctly.

[DriveHard]

BMW designs there brake pad material to give you insane initial bite, then tapper off a little to consistent torque, and then (after repeated application at high speeds) slowly loose torque.


Its been like that for a while.. Thats why if you read other threads about brake pads being used other than stock, you always seem to get the " it doesnt have that initial bite that the oem had" but ...... statement .

as far as your ebrake goes, some times it matters if you apply the e-brake with the car in gear as opposed to the car in park.

[RJKmetal]

I don't have handbrake issues but my brakes are definitely more sensitive if I am pulling higher revs. It is very odd - almost like if I am over 4000 revs the brakes go in to a type of 'M' mode. I am a bit concerned now - after the mighty 1200 mile service fluid thread I did inform my garage but am wondering if they ignored me.

[-cj-]

Thanks for the responses guys. I have to keep an eye on it and see if I can consistently reproduce it and figure out what's happening.

I briefly talked to the shop foreman today and he said it's based on engine vacuum. So at certain RPMs you might get a different brake response... I don't buy that.

I'm going to pay more attention now that I know it isn't normal.

[MDORPHN]

Originally Posted by -cj-

Thanks for the responses guys. I have to keep an eye on it and see if I can consistently reproduce it and figure out what's happening.

I briefly talked to the shop foreman today and he said it's based on engine vacuum. So at certain RPMs you might get a different brake response... I don't buy that.

I'm going to pay more attention now that I know it isn't normal.

I'd bring your car to a different dealer!

Yes, brake are boosted off of vacuum, but feel should not change based on rpm.


Neil

[-cj-]

Yeah, some of the explanations I get always make me question their knowledge. Oh, to answer your question from earlier: No brake work done on vehicle. Car has 6k km and was built in December, never tracked (yet).

[Fundahl]

My brakes feel extremely solid even after 2 autocross events and multiple 155mph-70mph quick slow-downs.

[MDORPHN]

Strikes me as highly unlikely on a new car, but I'm wondering if you have a leaking brake booster diaphragm.

Neil

[Dan Parker]

Inspect the inside of the wheels for any fluid or excessive dirt/discoloration. Neil may be on to something. My Z4 MC had a torn seal in the first few months and your description sounds familiar.

[BrokenVert]

Originally Posted by DriveHard

BMW designs there brake pad material to give you insane initial bite, then tapper off a little to consistent torque, and then (after repeated application at high speeds) slowly loose torque.


Its been like that for a while.. Thats why if you read other threads about brake pads being used other than stock, you always seem to get the " it doesnt have that initial bite that the oem had" but ...... statement .

as far as your ebrake goes, some times it matters if you apply the e-brake with the car in gear as opposed to the car in park.

came here to say just this.

BMW pads are notoriously inconsistent when it comes to things like initial bite and bite with different application forces.



Also to address the parking brake. Mine has always done the same thing. I even had it rebuilt two years ago because I thought something was wrong with it. Its just the way it is. One thing to note on BMW parking brakes is never pull it up all the way. If you do you can actually pull the pads out of alignment and make the parking brake useless.

[juld0zer]

Bit of an old thread but OP, how has the brake been over the years? Did it improve or did you find a solution?

BMWs have not relied on engine vacuum to operate the booster for a long time. These engines have an engine driven mechanical vacuum pump. It also provides the vacuum to operate the wastegates.

Handbrakes on M cars seem a bit weak in general. Even when adjusted according to the instructions (unhook the lever under the gaiter etc) it is still not as good as a non M car handbrake. Must be something to do with the alloy hats compared to the steel hats of non M cars. At least the hat doesnt explode like on some carbon ceramic models...

[-cj-]

Originally Posted by juld0zer

Bit of an old thread but OP, how has the brake been over the years? Did it improve or did you find a solution?

BMWs have not relied on engine vacuum to operate the booster for a long time. These engines have an engine driven mechanical vacuum pump. It also provides the vacuum to operate the wastegates.

Handbrakes on M cars seem a bit weak in general. Even when adjusted according to the instructions (unhook the lever under the gaiter etc) it is still not as good as a non M car handbrake. Must be something to do with the alloy hats compared to the steel hats of non M cars. At least the hat doesnt explode like on some carbon ceramic models...

It totally went away on it's own! I think the brakes just needed breaking in.

Thanks for asking.