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      12-20-2012, 03:31 PM   #113
chlemaire
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Drives: 2013 335i M-Sport Line
Join Date: Nov 2012
Location: Boxford, MA

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Quote:
Originally Posted by RPM90 View Post
The M Performance brakes are made by Brembo.
Which way to go depends on what you're trying to achieve.
If you're after better/shorter distance braking, then get better tires.
If you want better brake 'feel' I think the "cheapest" route would be to go with steel brake lines.

The larger M Performance brakes are not likely to give better braking performance for a daily driver. For someone who tracks they may be worth it as the larger rotors will likely dissipate heat better resulting in less tendency for brake fade. For daily driving the stock brakes are fine, they just lack in feel.


From what others have been saying it seems the problem is not in the caliper nor rotor. The "soft" pedal has to do with the brake booster and the brake lines.
The other thing that can cause a soft pedal would be air in the lines. Maybe there is a specific technique to bleeding this brake system and that's what that one tech was referring to when he said it was a pain to install.
Air is compressible, so if there is air in the line you would push the brake pedal but the caliper won't respond as quickly or firmly as the brake booster has to compress that air as it's trying to compress the fluid.

If the brakes are bled properly and there is still a soft pedal, then another option is to try steel brakes lines, as one poster said. By their nature rubber lines can expand, so as you push the pedal and the fluid compresses the rubber lines may be expanding too much resulting in having to push the pedal harder/further to get the required pressure into the caliper, because as the line is expanding so is the volume requiring more fluid before proper pressure is applied. Steel lines don't expand, pressure is applied quickly. People who have installed steel lines always say the brake pedal feel and modulation improves.
If the system is bled properly and there are steel lines but soft pedal remains, then it's likely due to the brake booster and it's bore and flow capacity, barring a problem with the booster not building proper boost.

This is why I think it's important to find out if there is some unique or different method to bleeding this brake system. Maybe the traditional method isn't getting the job done and there is still air in the system.

Personally, I don't like the new brake system in the F30. It feels softer than my 135i with the 6 piston Brembo's. Those brakes had a nice feel for stock brakes. There was little brake pedal travel and initial bite happened quicker.
Then, modulation was better as it required more brake pedal pressure instead of more brake pedal travel to get more braking.
That's what it feels like with the F30 brakes. There is too much "dead" brake pedal travel before initial brake bit, then to get more brake force you push the pedal harder, but instead of more brake force there is more pedal travel with it. It results in feeling like the brake system is soft.
There is plenty of brake power in this system. With the better tires the F30 has shown very good and short braking distance. The problem is simply that it doesn't "feel" as strong as they are.

The other pick nit I have is that when I release the brake pedal often it will return to it's stop point with a "thunk" as it hits it's stop point. I experienced this in every F30 I test drove so it's not unique to mine.
Part of the overall complaints that the new 3 series has become "softer" is the brake system. It just doesn't feel as solid and quick as before, and the 'thunk' gives an impression of 'cheap' imo.
Softer, less feel steering, softer base and sport suspension, softer brake feel, it's no wonder a lot of people are saying the 3 series has become "softer" or "too soft".
To RPM90: This is the best description, analysis and commentary on braking I have read in this, and any of the related posts. I wish I could be as eloquent and precise in my choice of words. I agree 100%.
Any advice on steel brake lines? I assume these would have to be aftermarket? (no BMW OEM?)