Spongy pedal feel

[Bayona135]

Hi all.

As you can see I don´t write many messages here... hope to fix that soon...

The thing is I really don´t know what going on my 135i.

Here is the thing. Since I bought it (last year, car from 2009 135i N54 with 55000km, great shape) I felt very spongy brake pedal feel. At the dealer, they told me that front pads were too old/worn down and need to be changed.

I track the car in Nürburgring so I directly changed front pads to EBC yellow, stainless steel hoses and Motul RBF660. Pedal feel improved a little bit, but still far away from being ideal.

Apart of the pedal feel on NBR, which goes completely down after 1 lap... on the highway I also have inconsistent feel:
In general I have 1 or 1.5 cm of travel without bite/power and fluffy feel and sometimes after WOT pedal comes stiff with nice bite.
I have pumped the system 3 times already to check air bubbles...always perfect.

Obviously I have to change many things for the track (now I got Pagid RS29 on front and I can do almost 2 laps before increasing the pedal travel and braking power), but why I cannot get proper feel on daily driving, anybody experienced that?? Maybe something with the vacuum system??

[Dackelone]

You need to use a pressure bleeder AND use BMW INPA tool to cycle the ABS block. That will purge the ABS block of trapped air. Most dealers only charge an hour's labor to do this service.

Dack

[Bayona135]

Thanks Dack!

I will do so. Just wondering if BMW dealer can put Racing brake fluid instead of original BMW DOT 4 while bleeding. As far as I know they a especial device to do it.

Just for my information, is the original pedal of the 135i not very responsive at the beginning or should be stiff and rather harsh like VW cars??

[E82MSport]

For a point of reference my pedal feel changes based on the types of pads I'm running. Dack is right though, get it flushed using a pressure bleeder and have the ABS activated, that should help a lot.

My normal daily pads have a little more pedal travel than my track pads, but that's more to do with how the pad bites and modulates. I'd ditch the EBC Yellows and get some real endurance pads if you're running the ring. I've ran Red's and Yellow's and didn't really care for either set. I run Performance Friction 08's on track and they have great feel and hold up to a lot of abuse. Maybe try Project Mu HC Plus or Endless MX72's for a pad that can be used on street and track. Or you can opt for dedicated track pads. In that case I'd run RC09's, ME20's, PFC08's or Hawk DTC-60's.

[John_01]

I don't think the 135i has great pedal feel. Its always had a longer pedal than I would like. I have tried different fluids. I have tried braided brake lines. I have had the fluid bled and flushed by the workshops many times. I bled and flushed my brakes with a pressure bleeder every time I go to the track. Braided-teflon brake lines make the pedal travel a bit less, maybe 10~20% shorter pedal travel. My 325i with single piston calipers have better pedal feel with everything stock and normal CBS maintenance.

What I think, is the stock master cylinder on the 135i is possibly not big enough to feed the larger volume 6 piston "brembo" calipers. It requires a longer pedal simply to move enough fluid into the pistons.

[John_01]

Concerning inconsistency in the braking feel during track driving you may want to read the following post, about "ready alert brake" feature.
http://www.1addicts.com/forums/showp...3&postcount=52

Personally I never changed any of the codes for my car, so I'm not the best person to advise you. I tolerated any variations due to electronic controls, brake fade compensation, ready alert brake, etc.

[lowbudgethero]

Originally Posted by John_01

I don't think the 135i has great pedal feel. Its always had a longer pedal than I would like. I have tried different fluids. I have tried braided brake lines. I have had the fluid bled and flushed by the workshops many times. I bled and flushed my brakes with a pressure bleeder every time I go to the track. Braided-teflon brake lines make the pedal travel a bit less, maybe 10~20% shorter pedal travel. My 325i with single piston calipers have better pedal feel with everything stock and normal CBS maintenance.

What I think, is the stock master cylinder on the 135i is possibly not big enough to feed the larger volume 6 piston "brembo" calipers. It requires a longer pedal simply to move enough fluid into the pistons.

my 135i has one of the best pedal feel of any car ive driven

[Ginger_Extract]

The extremely inconsistent pedal just seems to be a quirk of the platform during hard use. Unsure if big brake kits and/or coding will alleviate the issue.

I always tap the pedal once before braking so I know there's pressure in the pedal. Ideal? No, but not much else to be done.

[Dackelone]

Originally Posted by Bayona135

Just for my information, is the original pedal of the 135i not very responsive at the beginning or should be stiff and rather harsh like VW cars??

A friend of mine Swadeness went thru this just before our Sella trip thru the Alps.

Yes... if you bring your own high performance brake fluid to a dealer... they will use your fluid. That's what Swadeness did. I believe he brought some Motul fluid.

The 135i's brake pedal should have great initial bite when stepping onto the pedal. And it should remain firm and responsive. I've never felt a spongy pedal on my car. Our brake calipers are not the floating type like VW's... so no, they won't feel like that. The brakes feel much better than what I have experienced on VAG cars.

Dack