320i brakes in front and now..., The rears feel undersized Options

[banderson]

I did the standard conversion to 320i front calipers and removed the proportioning valve last summer and now I think that I may have increased the stopping distance. The rears don’t feel like they are working hard enough. I overhauled the system with new rotors, rear caliper rebuild kits, DOT SS lines and street pads.

Because my front brake pistons are bigger, it takes less effort to lock the front wheels than it did before. Now the front wheels lock well before the rears come close.

I havn’t heard of anyone complaining about this before and Grassroots motorsports reported that they needed an adjustable valve to keep there rears from locking. This makes me wonder if my rears are working properly. They get hot, so I know they are doing something. The pedal is solid and they don’t bind.

I am considering changing to a high performance street pad, or putting different ones on the back, but I don’t want them to grab too much.

Your thoughts?

[banderson]

Thanks for the tips.

Herb, did you change to the 320i calipers? When you get your new Jugs, I'll come check them out.

I did set the venting clearance to a tight .004". I'll check it again. If that doesn’t do it, and I don't think it will, I will swap the fronts to the rear (after I get an inspection sticker cus' in NH they check everything but emissions). It won't be too bad to swap them out every year for the inspection, which is my only concern.

Brad, I am a mechanical engineer.... what do you want to know about thermals on the rotor? I am sure that not everyone would agree with what I think, but I do think.

As I see it, and as has been said before, your kinetic energy becomes thermal energy. First it goes to the rotors and pads. Then it goes from the rotors to air and from the pads to the calipers, then to air. So, big calipers heat up more slowly because of their thermal mass, and transfer heat to the air better because of increased surface area. Overall, it’s the same amount of heat. Why would bigger pads cause the rotor to get hotter? Cooling fins would help. Why don’t calipers have cooling fins?

Now if the front/rear bias was off and the rears weren’t doing anything, that would be a different story. I am beginning to thing that BIAS means EVERYTHING, stopping distance and cool fronts! Good bye parking brake!

I would do controlled testing but its snowing out…