No brake assist


#1

Does anyone run with the booster bypassed in the e30? What have you liked/disliked?

I’ve had issues with the booster and just swapped it out today but has anyone decided to run without the assist? I’ve driven other race cars with assist bypassed and wanted to see what the experiences have been here. Fyi: booster not working correctly is not a bypassed booster.


#2

I’m not aware of anyone running wo a booster connected. The reason being is that the MAster cylinder piston size was designed to be used with assist. If you disconnect the vacuum assist, the required brake pedal pressure to stop the car will be too great. Cars wo a booster have a smaller master cylinder piston size making it easier to compress and make pressure. Hope that helps.


#3

Thanks Brad. The disconnect was going to be my last resort if swapping the booster didn’t solve the problems I was having. There was much discussion that it wouldn’t, but it did so I’m a much happier person in the braking zone these days. Thanks for the reply though. It brought up another question I had. If I understand correctly aren’t there 2 piston size MC’s for different model years? Is there a benefit to either? I run the ATE but not sure if it’s the smaller or larger.


#4

A year or two I was trying to understand why our brake pedal is so much softer than Porsche’s. In that effort I got to looking at MC bore diameters. Smaller bore means more pedal throw, but less pedal effort. Less pedal effort means less stress on the firewall so it deflects less.

To my surprise I found a number of different MC sizes marketed for our cars. Some had same dia. front and back, some not. I think what’s happening is that a lot of our parts are actually kinda generic so someone makes a call that an MC from a Saab, or whatever, will fit an e30. Then the MC with a different bore gets cross referenced to e30 and the next thing you know it’s handed to you across the NAPA parts counter.

I bought an MC last month that had an extra port on it’s underside. It came with a plug. So it’s a perfectly serviceable E30 MC, but it obviously is a more generic part that fits a number of different cars. I cross referenced it’s # and sure enough it fit a half dozen non BMWs.

Think about what that means for other parts. There’s a whole universe of parts out there that are marketed as E30 OEM replacement by major retailers, but they actually vary in functional ways. So not just a shiny MC, but a MC with a different bore size. Not just a shiny valve, but a valve that has been necked, or whatever.

I don’t have a solution. It’s not reasonable to require that all parts are bought from dealers because a) They charge 5x as much, and b) Their parts may well vary too.

The only thing I can suggest is that folks be wary. When you are shopping for items that may be performance enhancing, be careful about what you buy. Do what you can to confirm that the parts looks/functions like the OEM version. If it’s iffy, maybe keep the receipt and a screenshot of the image on the website it came from. If the item offers performance advantage, the day may come when an official is looking at you suspiciously. Be thinking what handy things you might want to have that day to support your case that the part is kosher.

These are the kinds of issues that have been debated furiously over the last several months as the directors debated valvegate.


#5

The Widshield Wiper motor is in the same catagory. It is a standard part which crosses to many other auto’s. Mainly European but can be found cheaper thru crossing the Bosch part number.