Building a Fun e30 Street Car

Taking the performance of your retro Bimmer up a notch.

There’s no denying the e30 BMW has seen just about every form of modification over the years. For those of us that spend the majority of our driving on the street, it can be a delicate balance to build a car that retains its sporty performance without compromising its practicality and comfort. Since more than 30 years have passed since the introduction of the e30, it’s fair to say there are some improvements owners can make to their cars to genuinely enhance the driving experience. Whether you have a stock engine, or even a motor swap, here are some upgrade options that will make you even more eager to hop behind the wheel of your favorite boxy 3 Series.

Wheels & Tires

Most non-M e30’s will probably come equipped with the 14-inch bottlecap or basketweave wheels, but the skinny tires and extra tall sidewalls can make the steering feel a little vague. Upgrading to a set of 15-inch wheels (as found on many of the European spec models) provides more predictable steering inputs, as well as the opportunity for wider, grippier tires, and still retain ride comfort. To retain fitment within the factory fenders, 15-inch wheels work best with a width between 7 and 8 inches, with offsets in the 15-25mm range.

For all-wheel drive 325ix owners, the unique suspension and widened track means aftermarket wheel choices aren’t as abundant. Fortunately, the 325ix came with 41mm offset 15x7 inch BBS wheels as standard equipment. If looking to switch things up, aftermarket wheels will likely be in the et30-40mm range, similar to wheels used on contemporary 4-lug Volkswagen or Honda vehicles.

In terms of tires, the factory 15-inch rolling diameters of 205/55/15 and 225/50/15 have a handful options available compared to the 14-inch size. However, the extra sticky summer tires with even better selection will require using the shorter diameter (yet more common) 205/50/15 and 225/45/15 sizes.

Brakes

For a factory setup, the e30’s stock brakes are surprisingly potent when in good condition. Aside from the early m10 powered cars that have drum brakes in the rear, the rest of the US lineup features 4-wheel discs. For a street car application, a quality set of replacement rotors and pads can help restore brake performance, but the often overlooked aspect of the braking system is usually the lines and fluid.

It’s not unlikely that the braking system is overdue for a fluid change, so flushing it with fresh fluid can make a massive difference in pedal feel. If your brake lines are showing signs of age, replacing them is a wise move, especially from a safety standpoint. New rubber lines are an affordable way to restore the performance of the braking system, however stainless-steel braided lines are a popular upgrade for just a few bucks more. It should be noted that many stainless brake lines claim to be “DOT compliant”, while brands such as Goodridge and Bimmerworld/StopTech are actually DOT approved.

Big brake kits are available from suppliers such as Ireland Engineering, Massive, and UUC, but are more eye candy than necessary for a primarily street driven e30. Depending on the BBK, you may run into wheel clearance issues, so fitment can vary between different wheel designs.

Shocks, Struts, Springs, & More

A highly debated topic, the spring and shock combo you choose is completely subjective. Rather than pick a 1-size-fits-all option, we’ll discuss some of the popular combos. Before purchasing a suspension setup, it’s strongly encouraged to ride in somebody’s car with the setup you’re considering. That way you can experience first-hand how the suspension behaves before spending any money.

Stock: If you have no desire to lower your e30, simply replacing the shocks and struts will likely be a massive improvement over blown factory suspension. For a factory like ride, Bilstein B4 or Sachs shocks will be more than enough. If you’d like something a little firmer (and arguably more durable), consider using the Bilstein B6 shocks & struts (formerly known as the HD). The factory rear shock mounts have been known to fail, so for a few bucks invest in the bolt-on reinforcement plates, even with a bone stock suspension.

Mild: Probably the most common e30 lowering spring, H&R Sport Springs drop the car around 1.25 inches and utilizes mildly stiffer spring rates. They work well when paired with Bilstein B8/Sport shocks. For a little more money, Koni Sport shocks are rebound adjustable, which allow you to dial them to your personal preference.

Extra Sporty: While H&R Race springs are a popular drop in spring setup for increased spring rates, they lower the car a bit excessively for a street application (H&R Race spring rates are also intended for the weight distribution of the M3 and its 4-cylinder engine). For firmer spring rates and ride height adjustability, look into Ground Control coilovers. Whether it’s their conversion kit, or the custom housings with short body shocks, the Ground Control setups are designed to work with Koni dampers (as they can handle the increased spring rates).

Ground Control can help select spring rates, but for the e30 application common front/rear combos are 375lb/475lb, 450lb/600lb, and 525lb/700lb (now the Spec e30 setup). The rates may seem overly firm, but ride quality is very civil when paired with adjustable Koni shocks. Bilstein B8’s can be used as well with coilover springs, but aren’t ideal and require a revalve for rates higher than most off the shelf sport springs.

If you don’t have core strut housings available to be converted to coilovers, KW produces their entry level V1 and damping adjustable V3 systems featuring new forged spindles that will bolt right up to your e30. You will need to install front wheel bearings and top mounts, but the KW system is a nice off-the-shelf coilover approach that doesn’t require any custom fabrication.

Sway bars can also be used to fine-tune handling once satisfied with spring rates, but sizes larger than factory will likely need mounting point reinforcements. Additionally ,camber plates can help with desired alignment specs over the stock factory strut mounts (which can prevent excessively chewing up the outside of your tires during performance driving situations.) The rear end is not adjustable from the factory and requires eccentric trailing arm bushings or weld-on brackets to gain alignment adjustability.

Steering Rack

The stock steering rack is one of the biggest letdowns of the e30. Its factory ratio is too slow, and really makes the car feel dated. With an assortment of quicker ratios available from the e36, z3, and e46, any of them will be a drastic improvement and make the car more fun to drive. Save yourself the headaches though and buy a refurbished steering rack that will have new seals and look a lot better than any grimy part pulled off a junkyard car.

When performing the rack swap, airbag cars (1990+) require the firewall opening to be slightly enlarged due to the steering shaft angle. Non-airbag cars on the other hand (1989 and earlier) need the steering linkage modified to accept the later model racks.

The e30 M3 has a marginally quicker steering ratio for owners that want a plug-n-play solution without any modifications. Unfortunately, the e30 M3 steering racks can be expensive, and the costs can easily surpass that of an e36/e46/z3 style rack swap, which offer noticeably faster ratios.

The 325ix models use a completely different steering rack than a rear-wheel drive model. A quick ratio option is now available, but modifications and installation are significantly more involved.

Skid Plate

Due to the e30’s front sump design (325ix owners are off the hook on this one), the oil pan hangs rather low and can be easily damaged on lowered vehicles. Thankfully a few companies, such as Race Skids and Red46 have stepped in to produce skid plates to provide some peace of mind while driving over less than perfect roads. Just be sure to get the correct skid plate for your engine and oil pan application.

Bushings & Ball Joints

The e30’s suspension isn’t particularly complicated, but the factory bushings and ball joints are known to wear out, especially on high mileage cars. This is one of those instances where it pays to get it over with and replace all the parts at once.

On the front end, the control arms, control arm bushings, inner & outer tie rods, and sway bar links and bushings can all contribute to a car that feels tired. Stock replacements are perfectly acceptable in these cases. It’s worth noting however that the control arm bushings are an area worth upgrading. On a streetcar it’s best to stick with rubber for NVH purposes, but the webbed design of the stock bushings are known to tear. However, utilizing the control arm bushings from an e30 M3 or later e36 M3 will allow you to have upgraded solid rubber bushings without the drawbacks and harshness of aftermarket bushings. The e30 M3 and 1995 M3 use offset bushings for additional caster, while the 1996-1999 M3 bushings are centered for those who’d like to keep the caster as-is.

The rear end of the e30 is best handled out of the car. In most cases just the subframe and trailing arm bushings need replacement to restore handling, but it can’t hurt to press in a new differential bushing if yours look worse for wear. Due to limited access, it’s required to remove the subframe and trailing arms from the car as an assembly, making it much easier to remove and install the bushings. As an added bonus, with the rear subframe removed, the inner rear brake lines are easier to access.

Aftermarket bushings are available for the rear trailing arms, but to prevent any unwanted creaks or squeaks, fresh rubber units are the preferred choice for a streetcar. If you want to get fancy, now is the time to weld in eccentric brackets for rear alignment adjustability, but not a requirement for modestly lowered cars.

The subframe bushings on the other hand allow for an upgrade without sacrificing comfort. The OE rubber subframe bushings are a perfectly acceptable replacement, but soft polyurethane bushings (such as AKG’s 85a street bushings) are just as comfortable and have the benefit of easy installation and durability.

Differential

Depending how your car was equipped from the factory, your e30 may have been installed with a limited slip differential. The limited slip differential sends power to both wheels (vs and open differential), ensuring better traction during cornering, launches, or even bad weather.

Fear not if your e30 wasn’t equipped with an LSD, as they are readily available second hand. If your car is a manual transmission with the 3.73 ratio, you may consider swapping to the more aggressive 4.10 ratio from some automatic 325i models or also found in the M3. Acceleration will be improved at the expense of increased RPMs for a given speed, which should be taken into consideration for drivers who spend a lot of time on the highway.

Bluetooth Capability

The world has moved on from 1980s car phones, but that doesn’t mean people don’t talk on the phone while driving. Adding Bluetooth capability to your e30 can really bring it up to date and make your life a lot easier when behind the wheel. The most common way to do this is to install a modern head unit, but the purists may dislike the look (vintage style modern deck options are available as well). If having an OEM radio deck is absolutely necessary, check out the Cantaloupe MDeck retrofit kit, which replaces the factory cassette player with a Bluetooth capable board that functions through the stock BMW e30 radio deck. Up and Running

Air Conditioning

If your e30 doesn’t have functioning air conditioning, the summer months can be brutal. Since most e30’s were equipped with the R12 refrigerant, updating to the more current R134A system can be an involved project. This is a job best left to the professionals as they can safely remove and fill the system with refrigerant in addition to the retrofit of new o-rings and other miscellaneous hardware.

One Step at a Time

Clearly, there are a lot of projects listed in this guide that can help to improve the drivability of your e30. Before embarking on any of these upgrades, make sure your e30 is mechanically sound (such as a timing belt & water pump job for 325 owners), as the best e30 is one that runs reliably (and has no rust!).

Not all of these upgrades are necessary either, but if you want the best bang for your buck, we advise that you flush the brake system, replace any worn suspension components, refresh the shift linkage, install a quality set of shock absorbers, and mount a nice set tires. The rest of the upgrades are nice to have but can be performed as time and money allow, so don’t feel pressured to do everything at once.

With some elbow grease and some spare weekends, restoring your e30 BMW can be a fun and rewarding process that will have you smiling each and every time you fire up the engine.

-JC