Understanding Spring Rates

Spring rates are a fundamental aspect of your BRZ’s suspension that directly influences how the car behaves on both track and road. The spring rate, measured in pounds per inch (lb/in) or newtons per millimeter (N/mm), defines the force required to compress the spring a given distance. A higher spring rate means a stiffer spring, which reduces suspension travel and body movement but increases force transmitted to the chassis. For a dual‑purpose BRZ, choosing the correct spring rate is the first and most critical step toward achieving the right balance between performance and comfort.

Spring Rate Fundamentals

The stock BRZ spring rates are around 169 lb/in front and 151 lb/in rear (approximately 3.0 kg/mm front and 2.7 kg/mm rear). These rates are chosen to provide a compliant ride for daily driving while still offering reasonable handling. However, when you push the car on track, these soft springs allow significant body roll, weight transfer, and bottoming over kerbs. Increasing the spring rate reduces these effects, but too much stiffness can make the car skittish on rough roads and uncomfortable for everyday use.

Suspension engineers use a concept called ride frequency (or natural frequency) to match spring rates to vehicle weight and damping. A higher ride frequency results in a firmer ride. For a street‑focused car, ride frequencies of 1.5–2.0 Hz are common; for dedicated track cars, 2.5–3.5 Hz or more. Your BRZ’s stock ride frequency is around 1.6 Hz. To improve track grip without destroying street comfort, you might target 2.0–2.2 Hz. That typically translates to spring rates about 8–12% higher than stock, depending on your weight distribution and goals.

Stock vs Aftermarket Spring Rates

Many aftermarket spring kits claim to offer a “track‑ready” upgrade but often go too stiff for daily driving. A common mistake is installing 400 lb/in springs on a BRZ because they feel “race car.” In reality, such a large jump will overwhelm the stock dampers, cause excessive oversteer on bumpy corners, and make your commute a bone‑rattling experience. A better approach is to start with a modest increase—for example, 200 lb/in front and 180 lb/in rear—and test before going higher. This small bump reduces body roll noticeably while keeping the ride tolerable.

Choosing Spring Rate for Dual Purpose

When selecting spring rates for both track days and daily driving, consider these practical guidelines:

  • Track‑focused rates: 6–10% above stock (e.g., 180–190 lb/in front) reduce body roll and improve transient response. Pair with dampers that have sufficient compression and rebound adjustment.
  • Street‑focused rates: Keep within 3–5% of stock. This preserves ride comfort while still giving a slight handling edge.
  • Mixed use sweet spot: 200 lb/in front / 185 lb/in rear is a popular choice among BRZ owners who track regularly but drive daily. This provides a good compromise between cornering grip and ride harshness.
  • Consider the spring design—linear vs progressive. Linear springs offer consistent force throughout travel and are easier to tune, making them preferred for track use. Progressive springs can improve initial compliance on the street but may become unpredictable at the limit.

An excellent resource for further reading on spring rate selection and suspension theory can be found at Öhlins’ technical guide.

Damper Adjustment and Tuning

Dampers (shock absorbers) control the speed at which the suspension compresses and rebounds. While springs manage the load, dampers manage the motion. Getting the damper settings right is what transforms a bouncy, unstable car into a composed, predictable machine. The key parameters are compression damping (controls the resistance when the suspension compresses) and rebound damping (controls the resistance when the suspension extends after compression).

Compression and Rebound Basics

Compression damping affects how the car responds to weight transfer. More compression damping reduces dive under braking, squat under acceleration, and roll during cornering. However, too much compression makes the ride harsh over bumps and can cause the suspension to “jack down.” Rebound damping controls how quickly the spring returns to its uncompressed state. Proper rebound is critical for maintaining tire contact; too much rebound can prevent the wheel from following the road surface on undulations, while too little rebound makes the car feel floaty and reduces control after bumps.

Single vs Double Adjustable Dampers

Most high‑performance coilovers for the BRZ come in two flavors:

  • Single adjustable: You change both compression and rebound simultaneously (combined adjuster). These are simpler and less expensive, but you cannot fine‑tune one without affecting the other. Ideal for beginners or those who want a set‑and‑forget setup.
  • Double adjustable: Independent adjusters for low‑speed compression, high‑speed compression, and rebound. These give full control over the suspension behavior. Preferred by advanced track drivers who want to dial in corner entry, mid‑corner grip, and exit traction separately.

For dual‑purpose use, double adjustable dampers are a worthwhile investment because you can set compression to handle track loads while keeping rebound softer for daily comfort. Many BRV owners report that with double adjustable units (like those from KW, Ohlins, or BC Racing with custom valving) they can achieve a ride that is at least 80% as comfortable as stock on the street, yet vastly more capable on track.

Setting Dampers for Track Performance

Track driving demands firm damping to control the higher forces generated by sticky tires and aggressive cornering. A typical track starting point:

  • Compression: Increment from full soft to about 60–70% of the adjustment range. Add compression slowly; over‑damping can make the car understeer (too stiff front) or oversteer (too stiff rear).
  • Rebound: Set rebound stiffer than compression, typically around 70–80% of the range. The goal is to keep the tire planted during high‑speed transitions and after braking.
  • High‑speed vs low‑speed: If your dampers have separate high‑speed circuits, keep high‑speed compression moderate (so the suspension absorbs kerbs) while increasing low‑speed compression to control body roll.

A helpful baseline is to set all adjustments to the manufacturer’s recommended track setting for your specific coilover model, then adjust 2 clicks at a time based on lap times and driver feedback. Remember that temperature and track surface can change ideal settings, so be prepared to adjust throughout the day.

Setting Dampers for Daily Comfort

For daily driving, the priority shifts to absorbency and compliance. A good starting point for the street:

  • Compression: Set low‑speed compression to 20–30% of the range. This allows the suspension to soak up road imperfections without transmitting jolts to the cabin.
  • Rebound: Use a softer rebound, around 30–40% of the range. This lets the wheel follow bumps more freely and reduces the stiff, choppy feel.
  • High‑speed compression: Keep a moderately soft setting so that sharp impacts (potholes, expansion joints) are absorbed rather than transmitted.

Many drivers find that after a track event, they can move both compression and rebound back to the street settings in just a few minutes if their dampers have external adjusters. This ability to change settings without tools is a huge advantage for a dual‑purpose car.

For a deeper dive into damper tuning principles, check out Suspension Secrets’ shock tuning guide.

Balancing Track Performance and Daily Comfort

The Art of setting up a BRZ for both roles lies in finding the point where the car is engaging on track yet not punishing on your commute. This section covers practical strategies to achieve that balance.

Incremental Tuning Strategy

Do not change spring rates and damper settings all at once. Instead, follow a methodical process:

  1. Choose your spring rate first. As discussed, a modest increase (8–12% above stock) is a safe starting point. Install the springs and drive for a week on your daily route without adjusting dampers. Note the ride quality and any handling quirks.
  2. Set dampers to a neutral baseline. Most coilover manufacturers provide a recommended starting setting for street or track. Use their street setting initially.
  3. Evaluate on track. At your next track day, drive the first session on the street settings. Then begin adjusting compression and rebound in small increments (2 clicks at a time) to see how the car responds. Keep a logbook.
  4. Transfer learnings back to street settings. After the track day, revert to your street damper settings. If you found the car too understeery on track with certain settings, you might raise rear rebound slightly for the next event, but keep street settings soft.
  5. Re‑evaluate every 3–6 months as your driving skills improve or if you change tires/alignment. A setup that worked when you were on 200 treadwear tires may need tweaking with 100 treadwear slicks.

Using Adjustable Coilovers

Adjustable coilovers are the most straightforward way to achieve dual‑purpose performance. Look for coilovers featuring:

  • Separate rebound and compression adjustment (double adjustable preferred).
  • A wide adjustment range (16 clicks or more per circuit) so you have fine control.
  • Ride height adjustment (which does not affect spring rate but alters center of gravity and roll center).

Popular coilover brands for the BRZ include KW V3, Ohlins Road & Track, and BC Racing. The KW V3, for example, offers independent low‑speed compression and rebound, enabling a comfortable street ride with excellent track capability. Many owners report that after setting the compression 8–10 clicks from full soft and rebound 12–15 clicks from full soft on the street, they can simply add 4–6 clicks of compression and 2–4 clicks of rebound for track days without changing the spring rate.

Sway Bars and Other Suspension Components

Springs and dampers do not work in isolation. Upgraded sway bars (anti‑roll bars) can further refine your BRZ’s handling without hurting ride quality. A larger front sway bar reduces understeer, while a larger rear bar reduces oversteer. However, stiff sway bars can increase cross‑axle coupling and reduce independent suspension compliance, making the ride harsher over bumps. A common recommendation is to use a medium‑rate sway bar (e.g., 22–24 mm front adjustable) and keep the rear bar at stock or slightly stiffer. This helps maintain daily comfort while improving cornering response.

Don’t forget that bushing upgrades (especially subframe and control arm bushings) can sharpen steering feel but also transmit more road noise. For a dual‑purpose car, polyurethane bushings in key locations (such as the front lower control arm) offer a good compromise without being too harsh. For more on sway bar tuning, see Improved Racing’s sway bar guide.

Testing and Fine‑Tuning

You cannot tune based on speculation alone. Real‑world testing is essential. Here is how to evaluate your BRZ’s setup on track and on the street.

On‑Track Evaluation

During a track session, focus on these specific behaviors:

  • Body roll through corners: If the car leans excessively, increase compression damping (low‑speed) or consider slightly higher spring rates.
  • Stability under braking: Excessive nose dive indicates too little compression damping in the front. If the rear becomes light, increase rear compression or reduce front rebound.
  • Corner entry feel: If the car pushes (understeers) on entry, reduce front compression or increase front rebound. If it oversteers, do the opposite or soften rear rebound.
  • Mid‑corner grip: If the car feels like it is sliding both ends, your spring rates might be too stiff for the tire compound. Try reducing both compression and rebound by 2–4 clicks.
  • Exiting corners: If the rear skips or hops, rebound in the rear may be too stiff. Soften rear rebound by 2 clicks and test again.

Use a data logger or a passenger with a stopwatch to time long corners and identify trends. The goal is to find a setting where the car communicates well and you feel confident to push harder.

Real‑World Daily Driving Assessment

After a track day, reset your dampers to the street baseline and drive your usual commute for at least three days. Pay attention to:

  • Ride comfort: Do you feel every expansion joint? If yes, soften both compression and rebound by 2–3 clicks.
  • Noise levels: A very stiff suspension can increase suspension noise (clunks from sway bar links, creaks from bushings). Grease bushings or replace worn parts if needed.
  • Highway stability: The car should track straight without constant steering corrections. If it darts over ruts, your rebound may be too stiff or your spring rate too high for the road surface.
  • Passenger feedback: Ask a friend or family member if they feel nauseated or uncomfortable. Their feedback is valuable for assessing real‑world livability.

If comfort is unacceptable on the street, consider dropping spring rates by 5–10% or using progressive springs. Some coilover systems offer different spring rates for street and track that can be swapped in an hour with proper tools.

Common Mistakes to Avoid

Many BRZ owners fall into these traps when setting up for dual purpose:

  • Going too stiff too quickly: Spring rates above 300 lb/in are almost never daily‑drivable for a BRZ unless you have a dedicated race car. Stick to modest increases.
  • Ignoring bump stops: If you lower the car significantly, make sure you trim or replace bump stops. Hitting the bump stop prematurely will ruin ride quality and can damage the damper.
  • Setting dampers to full stiff for track: Full stiff is usually not the fastest setting. It can cause the tire to bounce and lose grip. Always work from a baseline, not an extreme.
  • Neglecting alignment: A good alignment is as important as springs and dampers. For dual purpose, a track alignment (e.g., -2.0 to -2.5 degrees front camber, 0.10–0.15 degrees toe out front) can be acceptable on the street if tire wear is monitored. Avoid extreme camber that causes poor braking in the rain.
  • Forgetting driver skill: No suspension setup can make you a faster driver. Invest in instruction and seat time alongside hardware changes. Track conditions, tire pressure, and driving style have huge impacts on what works.

For a comprehensive look at BRZ suspension tuning from an experienced track driver, refer to this FT86 Club forum thread on dual‑purpose setups.

Conclusion

Adjusting the spring rates and dampers on your BRZ is a rewarding process that unlocks the full potential of the car, whether you’re chasing lap times or simply enjoying a spirited back‑road drive. By starting with a modest increase in spring rates, selecting adjustable coilovers that allow independent tuning, and methodically testing on both track and street, you can achieve a setup that is sharp on track without being punishing in traffic. Remember that suspension tuning is an iterative process; no single click or spring rate works forever. Stay curious, keep a log, and don’t be afraid to experiment. Your BRZ will reward you with a driving experience that feels both capable and livable.