Brake porn!

[Thunderguts]

It took me all day, but I finally installed my BMWP brake kit. The main snag was painting the rear caliper brackets because I couldn't start until I had taken the rear brakes apart. I spent about an hour just cleaning them and then 3.5 hours painting because I had to bake them for an hour between layers. Ugh!

Some people scoff at the BMWP kit, but I really don't know why. Sure, it's just the same brakes as the 135i, but that's hardly a bad thing and the 128i is about 200 pounds less. A set of used 135i calipers is generally around $900 which is barely less than these brand new (if you include the rotors). The only problem is that they can crack pistons if you track them too hard, but a Centric aluminum piston upgrade is $230. That still puts them at less than half the price of a true Brembo front 6-pot set.

Unfortunately there are no more 4-wheel BMWP kits so I had to buy the front kit for the E92 and add the stock E92 rear calipers which have larger diameter pistons which is what the 4-wheel kit included. I added Stoptech slotted rotors in the rear also. I was too tired to recode the car tonight so I'm going to do that tomorrow and also remove all brake nannies. I bought the Protool coding license just for these, but I'm going to play around with it and see how well it works.

I replaced the pads that came with them for Hawk HPS because I've always liked the Hawks. The size difference is huge compared to the stock pads! There's so much more pad area and 6 pistons distribute the pressure more evenly to avoid hot spots. Tell me these can't take a lot more abuse than the stock brakes!

The rotors are huge next to the stock rotors and they're a two-piece design with an aluminum hat. They're just riveted instead of bolted together.

The BMWP calipers make the stock calipers look like a joke. The difference it staggering.

[Thunderguts]

I freaked out when I backed up the car because the pedal went to the floor. I thought I had left one of the brake lines undone but then I realized that all the pistons were fully compressed and I had to prime them before the brakes would work.

I also thought I got one incorrect front rotor because the slots face forward on one and backwards on the other. The internal vanes are straight, so direction shouldn't matter, but WTF wouldn't they make a right and a left so the slots would face the same way? I double-checked RealOEM and the BMWP kit does actually have two identical part number rotors in the kit. Weird!

[N54Yankee]

Originally Posted by Thunderguts

I freaked out when I backed up the car because the pedal went to the floor. I thought I had left one of the brake lines undone but then I realized that all the pistons were fully compressed and I had to prime them before the brakes would work.

I also thought I got one incorrect front rotor because the slots face forward on one and backwards on the other. The internal vanes are straight, so direction shouldn't matter, but WTF wouldn't they make a right and a left so the slots would face the same way? I double-checked RealOEM and the BMWP kit does actually have two identical part number rotors in the kit. Weird!

A lot of car makers do the same by using the same rotors for both sides. Cost savings and ease are the primary reasons I would say. My Corvette has the same rotors L&R as well.

[robblr]

Apologies for reviving an old thread, but I'm about to do the same with my 128i.

The front kit I ordered from ECS doesn't come with new dust shields. Will I need 135i shields, or are the 128i shields the same?

I went with new pads and rotors for the rears because I read you'll lose the e-brake going with the 135i calipers. Is this the case, or did you use the 135i knuckle as well?

Any gotchas with the install?

[Suprgnat]

Originally Posted by robblr

Apologies for reviving an old thread, but I'm about to do the same with my 128i.

The front kit I ordered from ECS doesn't come with new dust shields. Will I need 135i shields, or are the 128i shields the same?

I went with new pads and rotors for the rears because I read you'll lose the e-brake going with the 135i calipers. Is this the case, or did you use the 135i knuckle as well?

Any gotchas with the install?

The stock shields will need to be trimmed with tin snips. No big deal.

[robblr]

Originally Posted by Suprgnat

The stock shields will need to be trimmed with tin snips. No big deal.

Thanks!

[Thunderguts]

Originally Posted by robblr

I went with new pads and rotors for the rears because I read you'll lose the e-brake going with the 135i calipers. Is this the case, or did you use the 135i knuckle as well?

I don't think you'll notice a difference, but technically you should upgrade to the rear calipers from the E9x because the piston is 2 mm larger. It's only $150 (for ATE-branded parts) and you can use the pads and rotors you already bought. You'll need 34216768697 and 34216768698.

Don't make the mistake I made and buy new boots, bleeder screws, etc. because the calipers already include most of it. You might buy new caliper guide bolts if you think yours are rusty. Don't forget the rear pad sensor. It's a mild pain to replace it because you need to go behind the splash guard.

If you upgraded the rear knuckle, you'd want to go full bore and get the two-piston rear caliper setup. It would be nice to have, but you'll replace a lot of parts to get there.

Originally Posted by robblr

Any gotchas with the install?

I'd go ahead and get new brakes lines while your at it. I would never pinch a brake line to seal it off. They make little silicone plugs that you put in your brake fitting to keep the fluid from leaking out. If you don't have a pressure bleeder, you'll appreciate it for this job. Get plenty of extra fluid. It takes a lot of flushing to get all the air out of new calipers. Don't forget to bleed your clutch while you're at it.

You also need to code your new brakes. I used ProTool, but there are around 3 options that can code them. Your standard Foxwell-type scanner can't do it.

[lakefront]

Any time you open your brake system for calipers, lines, etc, just put a 2x4 or something to depress the brake pedal about half way. Check valve in the system will not let any brake fluid leak out.....other than the little bit in the line. Works great.

[Papa Popov]

Was the upgrade worth the money? I'm due for pads+rotors, and I'm tempted to return the zimmerman/akembono FCP kit and upgrade to this instead.

[Thunderguts]

Originally Posted by Papa Popov

Was the upgrade worth the money? I'm due for pads+rotors, and I'm tempted to return the zimmerman/akembono FCP kit and upgrade to this instead.

Worth it? Hmm...

Well, it's nearly the same price as buying used 135i calipers which may need to be rebuilt before you even install them. If you were going to upgrade anyway, yes the BMWP kit is actually a pretty good deal. You're getting 6-piston calipers, splash shields, 2-piece rotors, and a wear sensor.

You simply can't argue that these calipers don't have significantly more thermal capacity than the tiny stock brakes on the 128i. The rotors are much larger and the pad area grows substantially as well. Can the stock brakes lock up the front tires (ABS notwithstanding)? Sure. Can they do it for long without overheating and cooking your pads? Probably not.

Stock brakes are fine for street driving. These will hold up significantly better for canyon carving and track days (if you upgrade to aluminum pistons).

[rex n effect]

Do you know or done the math regarding how the brake bias changes with just the front calipers? Or both front/rear? Did any 128i come w aluminum calipers or never? Thanks!

[asbrr]

Originally Posted by rex n effect

Do you know or done the math regarding how the brake bias changes with just the front calipers? Or both front/rear? Did any 128i come w aluminum calipers or never? Thanks!

There's quite a few posts where the brake bias calculations have been done - do a search and they should pop up. I recall some posts by "The Stig" that went into detail, or user "Supergnat". The Bmw performance kit increases the rear caliper piston diameter to 42mm vs stock 40mm, so that helps maintain similar bias. You're also supposed to code the car for the BMW perf system which may also help calibrate the car to the changes.

I've been running the 135i calipers/rotors up front for 5+ years, with stock rear brakes and I haven't made any coding changes. Car has run fine....so unless you're tracking heavily and you're going to really be threshold braking, it's probably not a huge concern.

[rex n effect]

Originally Posted by asbrr

... unless you're tracking heavily and you're going to really be threshold braking, it's probably not a huge concern.

I tend to do those things

Great info thanks!!

[asbrr]

Originally Posted by rex n effect

I tend to do those things

Great info thanks!!

No worries. Another cost effective upgrade is putting 335i calipers and rotors on the front. Not the fancy 6-pot brembos, but they stand up very well to abuse on a track.

[Thunderguts]

Originally Posted by rex n effect

Do you know or done the math regarding how the brake bias changes with just the front calipers? Or both front/rear? Did any 128i come w aluminum calipers or never? Thanks!

As I recall, there were 3-4 different parameters that "Reinforced Brakes" alter. Unfortunately I didn't record the values for them before I changed the setup. It should be fairly easy to do. Just record the stock values and then the new values once you add reinforced brakes. I used ProTool to code them.

On a side note, I really love these brakes (and uncoded nannies)! I've gotten used to the extra effort required and they are so linear and easy to modulate now.