General impressions and advice on doing a brake booster delete on my '92 325ic

[Todd Lemmon]

My first post. I've been fairly active on Bimmerfest and one of the moderators there, Ken (Horn Hospital) recommended this forum for my question. I just (I think!) successfully mounted my brake fluid reservoir back onto the MC with new grommets. It was not fun. At all. In fact, it made the oil pan gasket job seem easy by comparison. I hope I regain full use of my hands. Tomorrow I start the bleed again after rebuilding the Girling calipers and adding new pads and rotors. I don't know the full history of this car, so I'm doing everything. The brakes were a disaster and the fluid looked like it had never been changed. Kinda pissed me off on this beautiful car. Anyway...I started reading up on delete kits for the booster from Sikky and Chase Bays. The concept sounds totally solid and the idea of reducing complexity in there is really appealing. I do not race the car. It's literally a fun sunday driver for me and my wife. But I want it tight. Any thoughts on doing this delete for a casual driver? I have a good budget save up for this project, so the cost isn't a huge issue. Any advice greatly appreciated. Thanks.

[e30austin]

without trying to sound like an asshole, that is literally pointless. BMW engineered that car to work with a power brake servo unit. there is zero point in removing it - leave it alone. they work quite well and almost never fail.

however, while you're there, i would absolutely recommend replacing all six of the brake soft hoses (two in the front, four total at the rear, seven if you count the pressure hose going to the clutch slave cylinder, which, why not?)

[moatilliatta]

Those kits are garbage.

Repeat as above /\

And inspect the hard brake lines all the way back, especially around the Tee in the rear.

[Todd Lemmon]

Interesting. Thanks. I have replaced all 6 soft lines. I just recently learned about the 7th to the slave cylinder. The hard lines look good. The biggest problem was getting the new grommets in and THEN seating that f***ing reservoir. I honestly do not believe the brake fluid was ever changed. I rebuilt all four calipers and the sludge that came out of the calipers was just sickening. Literal chunks of stuff in there. Fortunately all the pistons were perfect. I did not take a close look at the Tee when I was back there while I had the heat shield off. I should have but all the hard lines looked so clean. In the bleeding sequence, do you do the slave cylinder first or last? Thanks again.

[e30austin]

Wurth Rubber Care is your friend for installing rubber related bits in the future, FYI.

as far as the slave, do it first and get it out of the way. have an assistant watch the reservoir carefully so the fluid level doesn't drop below the soft feed hose and suck in air (unless you're using a pressure bleeder, then disregard).

[moatilliatta]

I usually also run a zip tie around the reservoir to master to hold it down while pressure bleeding.

I hate brake fluid also.

[TobyB]

There's a reason that brake boosters became ubiquitous about the time disc brakes showed up-

it's about the only way to stop with discs. If you don't have a right leg the size of an oak tree.

I have 2 cars that didn't have boosters- a Volvo 122, and a Datsun roadster. Neither can stop
worth a damn, and that's after I did a bunch of mechanical, hydraulic AND friction material work.

On top of it, the booster delete kits you mention seem to also delete your dual circuit safety brakes,
which on anything built after 1965 is just treacherous.

Yes, you CAN design a system to stop well without the booster, but there's very little wiggle
room for anything to go wrong. You end up with a tiny master cylinder, and so if you get
any pad knockback for any reason, you're not going to get pedal on the first pump.
Which most people would call 'brake failure'.
Plus, finding a tiny dual master is really difficult, too.

One thing that DOESN'T come up much is better brake feel. Personally, I like a
hard pedal, and after the 2002, BMW and I parted ways on this.
So that may be a direction to head. I've not done it yet.
But it needs to be done in the booster, and those are hard to modify properly.

t

[iansane]

It's pretty much been covered here but on a sunny day street car with a stock engine there really isn't any reason to get rid of the booster. The benefits of having it far outweigh the issues with complexity. I deleted the booster on my car for engine swap clearance but I used the setup from Massive that at least let's you retain the stock master (keeping a dual circuit setup) and changes the pedal ratio.

[varg]

Never replace an OE style system with something like the chase bays single circuit master cylinder, it has no redundancy and chase bays outright lies on their website (see below) about the inherent safety of the product. I have covered this before. Not only are most OE reservoirs and master cylinders made in the last 50 years divided but even if you were to completely empty the reservoir and drain one circuit, the other circuit will contain enough to stop the car. Anyone who has ever had a master cylinder apart knows how they are internally constructed.


There are dual master cylinder pedal boxes and brackets that contain two separate master cylinders with a bias adjuster that bolt on where the booster does, this is the typical configuration for cars that lack a modern boosted system for some reason, like some race cars.

[e30davie]

Why do chase bays offer single circut master cylinder? surely there is a suitably sized dual circuit?

i'm not sure what the rules are like in USA but converting from dual circuit to a single circuit in Australia would be completely illegal with no way of getting it engineered etc.

I'm not against booster-less but yer it wants to be a proper pedal box with 2 master cylinders and the ballance bar and alot of testing to make sure its working right, not some half assed swap out job. Ive driven one properly setup boosterless dual master setup in a kit car, and it was pretty great but would get very tiresome as a daily drive or even weekend car.

[moatilliatta]

Bro, cuz, stance my engine bay lazyness vape trends.

Manual dual master cylinder brakes are for racecars / trackcars.

[moatilliatta]

But it needs to be done in the booster, and those are hard to modify properly.
t

944 booster. e32 master gives a better pedal feel.

In a few cars that give to much assist causing ABS issues on track we put a restrictor in line, I think its common trick on some of the Porsche race cars.

[Todd Lemmon]

I usually also run a zip tie around the reservoir to master to hold it down while pressure bleeding.

I hate brake fluid also.

Zip Tie to hold down is a great idea. I just did a puppy pad and watched very closely during bleed. Not a drop, so I guess the reservoir decided to seat itself.

[varg]

Why do chase bays offer single circut master cylinder?

Their target customer base is the stance crowd, vape and scrape. It's no surprise that people who stretch tires until they're ready to debead from a pothole, completely fuck suspension geometry up for a trite aesthetic, butcher fenders and scrape up undersides of otherwise nice cars, would also believe some slick marketing man's hollow words about how somehow the two fittings on his brake reservoir still lead to one internal passage or something.

[e30davie]

hmm fare enough. they will probably do quite well in business then! hah

Isnt this one dual master? Lots and lots of woffle isnt helping their case, but the built in brake bias controller is pretty neat.

https://www.chasebays.com/collections/bmw-e30/products/chase-bays-dual-piston-brake-booster-delete-with-bolt-on-6-1-pedal-ratio

600usd though, getting close to a tilton setup or similar.