Another brake master question

[butters]

I'm running the iX/E32 booster with E32 master cylinder.

For the past couple years I've liked the firm pedal feel. I recently attended my first HPDE and found that I really don't like it... or something is perhaps wrong.

While the pedal is firm, the clamping/bite doesn't inspire confidence like I'd expect. The pedal is firm but it keeps traveling when I stomp it and it's quite difficult to find the limit of the tires. It feels like a bleed symptom but I did bleed my brakes, spot-bled the calipers at lunch (after a small leak appeared at right rear between the hard & soft lines), and plan to bleed the entire system again.

I researched a bit and discovered that the E32 MC is constant 25mm while the E30 MC is stepped to put more pressure at the front - not something I considered previously. This has obvious drawbacks but I'm not entirely sure it's the obvious root cause of the feeling that I'm getting.

Can anyone comment on what could be addressed to improve the feel in a swap car given the space constraints? I'm already set up with the booster, and remote 2002 reservoir.

[justin_l_]

What do you have for lines? When did you flush the fluid last?

[butters]

I have the original hardlines with DOT stainless steel braided in place of the rubber. I'll be bleeding again this week and report back. It was several months since a full bleed.

[FredK]

The OE E30 master cylinder is stepped bore to give more pressure at the rear. If you look at a Girling MC, the output ports are labeled 19mm for H (hinter, rear) and 22mm for V (vors, front).

I did not have the same setup as you, but I had a 25 mm MC and a 320i booster. I didn't really like it on track. There was OK modulation, I could still brake deep-ish before a corner, but the pedal height was crappy for heel-toeing.

[butters]

I finally got the car out after a full flush. The brakes feel better but still it's not ideal that I have what feels like an inch of travel with not much reaction.