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BMW E30 Brake Modifications
 
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Pelican Technical Article:

BMW E30 Brake Modifications

Robert Bowen

Applicable Models:

BMW E30 3-Series (1984-93)
The CarTech BMW 3-Series Performance Guide

Whether for on-track duty or simply improved street performance, the E30 series cars have proven to respond to well-chosen upgrades. The CarTech BMW 3-Series Performance Guide offers current and future owners a wealth of important information, including a buyer's guide, year-by-year upgrades and changes, and more. This book is a valuable addition to every BMW owner's library, and Pelican is proud to present you with the excerpt below.

E30 Brakes

From the factory, E30 brakes were pretty good for their time. Large, vented front discs were paired with rear discs on all models except the early 318i, which came with drum brakes at the rear. All E30 models except the M3 had 260-mm diameter by 22-mm-thick rotors up front; the M3 came with 280- by 25-mm rotors.

Neither street driving nor autocrossing requires a lot of brakes; there is enough time between stops to cool the factory brake rotors and pads. If your car usage doesn't fall into one of those two groups, there are several ways of improving braking prowess: decrease stopping distance, adjust brake pedal feel, reduce brake pedal fade, and swap brake and suspension parts.

Stopping Distance

Stopping distance actually has more to do with the tires than it does the brakes. Since all braking forces are transmitted through the tires to the ground, the stickier the tires, the shorter the stopping distance. The best brakes in the world won't improve stopping distance at all if the tires are hard, skinny, 14-inch all season radials.

Brake Pedal Feel

The second factor, feel, is one that you can do something about. A soggy, floppy brake pedal makes it hard to modulate the brakes on the track and on the street when braking hard. A high, hard pedal with very little travel is ideal. The harder the pedal, the better in most cases, since it allows for better modulation of the brake pressure. This won't help the car stop any better, but it allows the driver to have better control when braking hard.

Every part in the brake system contributes some wasted movement to the pedal--flex in the pedal and firewall, air in the brake system, flex in the hydraulic lines, and even very slight flex and movements of the calipers and pads. Assuming your brake system is bled well with fresh fluid, the most noticeable source of wasted movement is flex and swelling in the factory rubber brake hose at each wheel. Replace them with braided steel lines to eliminate the flex.

The second easy way to increase pedal firmness is by changing the hydraulic ratio between the master cylinder and the wheel cylinders. Lucky for E30 owners there is a larger master cylinder that bolts right in: The 25.4-mm master from the E32 7-series shares the same bolt pattern as the E30. This is a significant upgrade from the factory 325 and 318is master cylinders, with their 20-or 22-mm bore depending on the year. The factory M3 master cylinder has a 23.8-mm bore, so the 7-series master is an improvement. The larger master bolts right into non-M3 cars, but the M3 requires a slightly different fitting (10 vs. 12 mm) for the master cylinder end of the rear brake line.

Fade

The third factor in brake performance is fade. This is defined as the loss of braking power due to heat from repeated stops. In practice this occurs only in racing or on a long downhill drive with lots of corners. The easiest to fix is fluid fade. Fluid fade is caused most commonly by water in the brake fluid. Since it absorbs water from the atmosphere, it is important to change fluid regularly. If you are experiencing fluid fade with fresh brake fluid, switch to the best racing fluid and see if it goes away.

The next place to look for heat related brake trouble is at the pads. Brake pads have an ideal temperature range. Street pads, such as the factory BMW parts, stop the car effectively in the morning when the rotors are stone cold as well as when coming down a long grade. When these pads get overheated, they lose some of their friction abilities and cannot stop the car.

Racing pads, on the other hand, can have a narrower range of temperatures and work best (sometimes only) when hot. For track use, you may have to experiment with pad compounds to find one that works for you. Most Spec E30 racers use pads similar to the Hawk blue compound pads. If you have a dual purpose car it's best to have two different pad compounds- "an everyday quiet, dust-free pad and a hard, track only pad. When you get to the track, bleed the brakes with new fluid and swap out the pads.

For racing in classes where you are not allowed to upgrade the brakes, such as Spec E30, brake cooling backing plates and ducts can direct cool outside air to the center of your brake rotors, lowering rotor and pad temperatures. This is important at some long, fast tracks where brake temperatures can spike at the end of a long straight (such as going into turn one at Willow Springs).

Parts Swap

If you still run into fade problems, then and only then is it time to consider a swap to a larger rotor. A larger rotor gives you lower brake temperatures with the same amount of use, possibly keeping your pads out of the fade zone. There are other side effects of a larger rotor, including less force required on the pedal, but the most important one is the reduction in pad temperature.

For non M3-owners, there are a few options for upgrades to the factory four-lug brake setup. The M3 is a bit more complicated since the factory brakes are larger already. M3 upgrades are available; they are just not as common.

The biggest problem with swapping to an M3 brake system on a non-M3 is the bolt pattern change to five lugs on 120 mm instead of four on 100 mm. That means you have to swap front and rear hubs, front struts, and even wheels to make it work. The result is the best factory setup for the E30, but it is very expensive to find all the needed parts these days. The E30 M3 has started to increase in price like the limited-production car that it is, and with it parts prices have skyrocketed.

To do the swap correctly requires the use of very specific parts to correct for the different location of the E30 versus E36 control arms in the chassis. They do not have the same relationship of the lower control arm pivots (which are integral with the front subframe and chassis) to the balljoint stud. There are differences in spindle geometry too.

In practice this means that swapping to the wrong front suspension parts can change suspension geometry in unexpected ways. The most common issue is one of too little caster. The front wheel is pushed too far back in the wheel well and if too large of a tire is used, it can actually rub on the rear of the wheel opening. Most importantly, this reduces the caster at the wheels and can make the steering too light and vague, especially at high speeds.

In the rear, using the wrong parts results in the hubs being pushed out too far in relation to the centerline of the car. This changes the relationship of the tire/wheel to the fender and can result in rubbing or fitment issues with wheels that otherwise fit.

Up front, you must use 1996 or newer E36 M3 or Z3 M coupe or M roadster front lower control arms and their matching spindles. The correct lower control arms are PN 31-12-22-28-462 (right) and 31-12-22-28-461 (left). The spindles are PN 31-21-22-27-907 (left) and 31-21-22-27-908 (right).

Regular E36 spindles physically bolt up; however, they reduce caster. The same thing happens if you keep your factory E30 control arms. Sure, they bolt up, but you lose (very important) caster. For the same reason you must also use an offset lower control arm bushing.

You need E36 struts to match the E36 spindles. This is one of the more expensive parts of the swap because the E36 struts do not have replaceable damper inserts as the E30 ones do. You can either convert the E36 struts to use a replaceable insert (Koni makes several designed just for this application) or use one of the many coil-over kits for the E36 chassis. This gives you more flexibility but costs more, just like any coil-over conversion. However, considering the higher cost of the E36 struts this may be a more viable option for a five-lug conversion.

At the rear there are a couple of ways to go. The first is to use E36 318ti or Z3 control arms and rear brakes as a complete replacement. These simply replace the E30 pieces and give you five lugs. You can also use Z3 six cylinder rear hubs alone with your current late-E30 control arms (early control arms require 318ti hubs). This gives you the same size rear brake as the standard E30 but with five lugs.

For M-size brakes, use Z3 M coupe or M roadster rear control arms and hubs. This is a very involved swap, since the M coupe/roadster have larger CV joints, longer axles, and wider control arms. Everything has to be changed over, even the inner CV joint flanges on the differential. Generally it is better to swap the entire rear subframe completely.

The E36 swap can be expensive and difficult and it carries a few downsides. All of the parts to make it work are inexpensive used these days, but you need to count on rebuilding any old or worn-out parts. Also, you need to step up to 16-inch wheels at both ends of the car, with more offset (around 20 mm more depending on the parts used). Be sure to double-check clearances on any wheels you plan to use with your new setup before buying them.

For most people, sticking with the stock four-lug setup is the way to go. It's lighter, cheaper, and plenty strong enough for most cars. Big brake kits can provide increased stopping power without adding much to the weight. There are plenty of suspension and brake choices. Only powerful engine cars can justify the larger bolt pattern and brakes that the E36 swap brings.

The stock brake rotors and calipers are fine for any street driving or autocrossing with a stock engine
Figure 1

The stock brake rotors and calipers are fine for any street driving or autocrossing with a stock engine. (Photo Courtesy Vorshlag Motorsports)

It doesn't affect brake performance, but the backing plates do get pretty grungy after twenty years of brake dust
Figure 2

It doesn't affect brake performance, but the backing plates do get pretty grungy after twenty years of brake dust. The easiest way to make them beautiful again is to buy new ones from BMW.

Since any factory hoses are more than twenty years old, they are due for replacement; this is a good opportunity to improve them at the same time
Figure 3

Since any factory hoses are more than twenty years old, they are due for replacement; this is a good opportunity to improve them at the same time. Replacing them with harder, stainless-braided Teflon hose reduces brake pedal travel and helps to firm the feel.

If you want to stick with factory parts, the entire M3 brake system is a great upgrade for the non-M cars
Figure 4

If you want to stick with factory parts, the entire M3 brake system is a great upgrade for the non-M cars. Larger rotors, calipers, and five-lug hubs combine for a good street system.

The aftermarket has several kits based around Wilwood four- or six-piston calipers
Figure 5

The aftermarket has several kits based around Wilwood four- or six-piston calipers. These calipers are light and inexpensive, the pads are widely available, and the matching rotors generally have aluminum rotor hats. (Photo Courtesy Ireland Engineering)

With a huge pad selection, light calipers, two-piece rotors, and race proven reliability, you will not be disappointed in the performance of any of these kits
Figure 6

With a huge pad selection, light calipers, two-piece rotors, and race proven reliability, you will not be disappointed in the performance of any of these kits. Just make sure that they fit under the wheels you want to use. (Photo Courtesy Ireland Engineering)

Swapping to E36 brakes gains much larger rotors and better calipers, but it's more difficult than simply bolting on all the parts from an E36 donor car
Figure 7

Swapping to E36 brakes gains much larger rotors and better calipers, but it's more difficult than simply bolting on all the parts from an E36 donor car. (Photo Courtesy Vorshlag Motorsports)

This picture clearly shows the difference between E36 control arms
Figure 8

This picture clearly shows the difference between E36 control arms. Not only must the correct control arms be used, offset control arm bushings also have to be used. The result is plenty of positive caster, as long as an adjustable upper strut bearing is used. (Photo Courtesy Vorshlag Motorsports)

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Comments and Suggestions:
billdc Comments: Does it matter which brand brakes I have on the car Gerling vs ATE
August 16, 2016
  Followup from the Pelican Staff: Depends on the model vehicle Sometimes the brands are not interchangeable. - Nick at Pelican Parts  
Walt Comments: I have a 1985 318i. Thinking of putting in a larger master cylinder from an E32, per your disuccion above. MY QUESTION: what is the part number for the E32 M/C that will direct fit into my E30? Thanks!
February 10, 2016
  Followup from the Pelican Staff: I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
crazye30owner Comments: I'm trying figure out what the brakeline pressure is so I can determine what the clamping force of the caliper on the rotor would be. I have a e30 318is. The reason I'm asking is because I will be swapping e38 brembo 4 pot calipers onto the my car. I will be using a adapter to use e46 hubs and e46 330i rotors with my e30 stut assy. I'm just trying to get a idea of what my new clamping force would be over the orginal set up. I'm doing a LS3 swap with T56 trans
January 29, 2016
  Followup from the Pelican Staff: I don't have that info. You can use brake caliper pressure gauges to test before and after. - Nick at Pelican Parts  

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Page last updated: Fri 12/9/2016 02:24:19 AM