Starter’s Guide to Track Prep a C4 Corvette

Once you sit in the driver’s seat of a C4 Corvette, with its V8 rumble and cockpit like cabin, the itch to get the car on track and stretch its legs will need some scratching. The C4 Corvette, even despite its age, is a very capable car on track and High Performance Driving Education (HPDE) events across the country make it easy and safe to get that time on track. In the Beginner’s Guide to Buying a C4 Corvette, we went through the thirteen year generation to highlight the model years with the most durable and performance orientated builds directly from Chevrolet. Now, whether you’re a new C4 owner or are researching for the perfect budget track car for you, this guide will review how to get a C4 Corvette ready for its track career.

In this guide we will overview Brakes, Suspension, Wheels & Tires, Motor & Drivetrain, and Safety from the perspective of a relatively stock car. Many aspects of the C4 Corvette are perfectly suitable for a novice driver to head straight to the track with. Other aspects, however, may need some preventative maintenance or upgrades before putting the car through its paces.  After investing in fees, travel time, and expenses for a track event, the last thing you want is a car that leaves you sidelined in the paddock due to mechanical issues. The C4 Corvette is three decades old now and is going to need some extra attention compared to a newer car, but taking one of these bargain performance cars to the track is still a great value. As your skills as a driver progress, the car will need to progress as well, so this guide covers some of the ideal first modifications  and progressions you should consider as you and your C4 get accustomed to the track.

BRAKES

On track, your brakes are going to work harder in 20 minutes than they have ever worked before. Hard work means high temperatures so our first focus on the C4 is brakes.  

Upgrade to stainless steel brake lines and then flush the brake fluid with a DOT 4 synthetic fluid from any reputable brand, such as Castrol, Lucas Oil, or Motul. Even for a novice on their first track day, without the right preparation, it won’t be difficult to end up boiling your brake fluid. A C4 Corvette may not be too heavy, but it is still no featherweight. Weighing around 3,400lbs with the driver and at least a half of tank of gas, the brakes will have some weight to stop so stainless steel brake lines are a solid investment at around $150. The original rubber lines have likely seen better days as well.

If you have the base JL9 brake package, upgrading the front axle to the J55 Heavy Duty brake package is a great budget option to really improve braking performance. The larger caliper and bracket can be found used on eBay readily or fresh remanufactured calipers can be purchased at RockAuto. The rotors upgrade from a 12” to a 13” diameter and also increase in thickness by 0.5” for better cooling. For 1988-96 Corvettes, the J55 package is a direct bolt on and will fit also behind original C4 17” wheels.

13″ Rotor of J55 Heavy Duty Brake Package (Image: Vorshlag Motorsports)

Another option, even for those with the J55 brake package already, is to upgrade to C5 or C6 (base model) front brakes. An adapter bracket is required for the conversion, which can found at Van Steel or on eBay for around $190, in addition to purchasing the C5 or C6 base front calipers (and bracket). As a result, this upgrade starts to get more expensive, though rotors and pads are more plentiful and economical for the C5 Corvette which is something to consider. However, most 17” wheels from the C4 generation, typically with the exception of the A-mold wheels, will not clear the caliper and will require moving to a different wheel.

Regardless of set-up, stick with blank rotors from a reputable brand and grab some extras to take with you to the track. Last is a quality brake pad. As a novice, starting with a quality hybrid street/track pad, such as the Hawk HP Plus, is fine and avoids having to swap pads out if you street drive your C4 Corvette often. Eventually though, your driving skills will start to surpass the limits of a street/track pad, resulting in brake fade. A dedicated set of track specific pads, such as the Hawk Blue 9012, would provide the braking performance needed. Though these pads would be swapped for quieter, economical pads when driving around town. It is also a good idea to bring extra brake fluid and pads with you to the track event.

WHEELS & TIRES

All C4 Corvettes from 1989 to 1996, with the exception of ZR-1 or Grand Sport models, came with 17” x 9.5” rear wheels. From 1989 to 92, they also ideally came with the same 17” x 9.5” wheels up front, but then from 1993 onwards, the front wheels were a slimmer 17” x 8.5”. Having the same sized wheel at all four corners, known as a ‘square’ set-up, is ideal as it allows for rotating of tires. When track days beat up your tires, the extra life provided from rotating tires is welcomed by your wallet. If you have a 1993-1996 Corvette and if track days are just an occasional event for weekend run, the stock wheel setup is fine.

As long as you have tires in good, safe condition with sufficient tread, they are ready for your first track day. As your track driving skills progress though, a tire that is not matched to your capabilities will hold you back as you fight the grip limits of your current tires. A novice will out drive all-season tires in a couple of weekends. A proper set of tires are dollar for dollar one of the best purchases in improving performance on track.

If your C4 Corvette isn’t your daily driver, and you’re just looking to hit the track a couple times in the summer in between cruise nights, Ultra High Performance Summer tires are a great option for the street and track. These tires are typically in the 300 to 340 tread wear range and provide excellent warm weather grip while still being an economical option with plenty of available life. The Firestone Firehawk Indy 500 is a very popular tire along with the Continental ExtremeContact Sport in this category.
For someone seriously looking to dedicate more time on the track than on the street, the next progression in tires would take you to Extreme Performance Summer tires with a tread wear rating around 200. Falken Azenis RT615K+ tires are a popular choice here, especially if you are driving your car to the track and back and aren’t interested in trailering a separate set of wheels/tires with you.

Those with the 17” x 9/9.5” wheels would use 275/40/R17 tires and those with 17” x 8.5” wheels upfront would use 245/45/R17 tires. These sizes have plentiful tire choices. Be aware that Chevrolet used some odd tire sizes from the factory, like 255/45/R17 on the 8.5” wide wheels, which have very little options on the market today. You do not need to be locked to that odd tire size.

17″ x 9.5″ Square Wheels w/ Falken RT615K+ Tires (Image: Vorshlag Motorsports)

Make sure to bring a tire pressure gauge with you to the track as well. Ideally, you want to be running around 34-35 psi once the tires are up to temperature. You could always leave for the track with 35psi cold, do your first run out on track, and check you tire pressures once back in the pits and let a bit of air out to adjust.

SUSPENSION

With a C4 Corvette, the stock suspension is a bit soft, but it is going to be up to the task of a novice driver. The age of certain suspension items at this point though may be a concern. Inspect your control arms bushings, tie rod ends, sway bar bushings for deterioration and your shock absorbers for any leaks. If everything is in good shape, go out for your first couple of track events as-is. If those components aren’t in good shape though, it will be time for upgrades or replacements.

For a C4 with the base FE1 suspension, that will just see occasional track events, stay with Bilstein B6 HD shocks. These shocks are excellent quality and will maintain a comfortable ride out on the streets. For those looking to get a bit more serious on track though, the stock FE1 suspension will need upgrading as your driving skills progress. Bilstein B8 Performance Plus shocks are going to be the next move up in performance. These shocks were equipped to the Z51 package Corvettes from Chevorlet and will provide much firmer handling over the base level B6 shocks. Another upgraded option, which are highly regarded in the paddock, are Koni Sport shocks. Recognizable from there all yellow color, these shocks are externally adjustable to fine tune the rebound to your driving style or environment. Drive them hard on track and then soften the shocks a bit in between events to maintain a reasonable ride on the streets.

Bilstein Rear Shocks (Image: Vorshlag Motorsports)

While you can use the Bilstein B8s or Koni Sports shocks on an otherwise base suspension, to get the most out of these upgraded shocks, you will need to pair them with the right springs and sway bars. The 1988-90 Z51 equipped Corvettes offered the most performance tuned suspensions of the generation, serving as the base for the Corvette Challenge cars. These cars were equipped with a 30mm solid sway bar up front and a 24mm solid sway bar in the rear. Most C4 Corvettes actually used the 24mm solid rear sway bar, so your Corvette may already have it or it would be an easy find on eBay. Use this C4 Corvette suspension chart to identify the year and suspension package of your car to confirm which suspension components are factory equipped on your car. The 30mm solid front sway bar however were only attached to the Z51 or Z07 Corvettes, while most base suspension cars had a 26mm tubed sway bar, so these may be more difficult to find.

The leaf springs are another important part of the upgraded suspension package. The 1988 to 91 Corvettes, even with the base FE1 suspension, were already equipped with high spring rates. Eventually the spring rates softened at the front axle for 1992 and then again in 1996 at the front and rear. Following the Z51 formula, the suspension package included a 115.5 rate (N/mm) spring up front and a 57.2 rate spring in the rear. All leaf springs on C4 Corvettes are identified by a code which is stamped on the spring to distinguish between spring rates. For the Z51 set-up, we have a FHB spring up front and an NYU spring in the rear. The NYU rear spring can usually be found on eBay, but again the front FHB spring can be a difficult find. An alternative to those without a 1988 to 91 Corvette, the base suspension of those years came with a 93.1 rate front spring identified by an FHA or FHC code. These are more likely to find a still offer an upgrade to the 73.2 or 60 rate front springs found in 1992-1996 cars.

The combination of the upgraded shocks, sway bars, and leaf springs will absolutely transform the handling of your C4 Corvette. Polyurethane bushings will also help tighten the suspension and provide crisper steering response, but you will sacrifice some road comfort.

MOTOR & DRIVETRAIN

This category is all about reliability when getting started. Start with fresh fluids, including coolant, engine oil, power steering fluid, differential, and transmission fluid. The power steering pumps on a C4 Corvette runs hot out on track and while a novice may not run the car too hard at first, using a synthetic power steering fluid, such as Royal Purple Max EZ, will help keep temps cooler. For the ZF 6 speed manual transmissions, a high quality MTF such as Redline 75W80 GL-4 MTL, will improve shifting feel and get you ready to work through the gears smoothly. Whichever fluids you use, make sure to put some miles on the car before heading to the track to get the fluids worked in. There are also short throw shifter options from Hurst, B&M, and ZFdoc that are often favorite mods among C4 owners, though installation is a bit difficult.

While around the engine bay, make sure to check the condition of the radiator hoses, the radiator itself, and around the water pump to ensure there are no leaks. If everything looks dry and no cracking is visible on the rubber hoses, the C4’s stock cooling will be fine for your first track day. As you progress in your track career with your C4, and especially if you live in a hot climate, the car will benefit from an all-aluminum radiator. With an aluminum radiator, the cheap plastic end tanks are eliminated, coolant capacity is increased, and the cooling surface is drastically increased from stock to help keep temperatures down. Most aluminum radiators available for the C4 Corvette are a direct fit.

Aluminum Radiator in Vorshlag C4 Corvette (Image: Vorshlag Motorsports)

For full track duty C4 Corvette’s, adding an engine oil cooler and a power steering cooler will keep the car running at a sweet spot during hard 20 minute sessions in blistering heat. However, for the occasional track day while you still you daily or weekend drive you’re Corvette, these extra coolers won’t be necessary. If you live in a colder climate, the coolers will only make it difficult to get the car up to temperature while just driving around town.

If your Corvette is new to you and hasn’t been maintained well in the past, fresh spark plugs and plug wires would be a good step to round off this tune-up. On LT1 powered Corvettes though, tight access to the spark plugs and the distributor can make this swap time consuming and frustrating, so set aside some time.

Let’s also cover rear differential gearing. Most C4 Corvettes with ZF 6 speed manual transmissions came with either 3.45 or 3.54 rear gearing. If you check your RPO tag, the code starting with ‘G’ will help you confirm the rear end gearing of your car. The two most common swaps is either a 3.73 or 4.10 rear end gear ratio which will provide a solid increase in acceleration. This is often a very preference orientated modification though. The preference mostly boils down to how quickly and how often you’ll want to shift the transmission since the lower gearing will move your tachometer much quicker. For autocross and small road courses, with the right gearing, you can do almost the whole lap in one or two gears and still have strong acceleration at lower rpms. This allows you to free up some focus away from shifting which is perfect for the amateur driver. A low rear gear ratio, such as 4.10, will add shifts to your lap. For a novice driver, this isn’t a modification you need to consider but as you get serious about tracking your C4, consult other Corvette drivers on track as to their experience before making an expensive gear swap.

SAFETY

The image of fixed back racing seats and 5 point harnesses often gets drivers day dreaming about being a race car driver. For someone starting in HPDE with an instructor though, just simply keep the car stock, leaving the original seats (or equivalent adjustable seat), 3 point belts, and airbags (if your C4 is equipped). The safety components of a car work together as a collection. The OEM 3 point seat belt is designed to go with the reclining seats.

Trying to partially balance racing specific safety equipment with a street driven car is difficult and potentially dangerous. A fixed back racing seat requires a 5 or 6 point harness. The harness requires a welded roll bar or cage with a proper height harness bar for the shoulder belts. As the driver then, you will need a HANS device to keep your head fixed with your body. If you decide to seriously track your C4 Corvette, that commitment to safety equipment will be necessary. For your first track day though and the occasional weekend event to follow, the best investment is a good helmet.

IN SUMMARY

Vorshlag 1992 ‘Danger Zone’ Corvette (Image: Vorshlag Motorsports)

As every driver in the paddock will tell you, putting the time in on track is what will make you a better, and quicker, driver. Therefore, getting your C4 Corvette prepared to hit the track has to start with making sure the car is going to be durable and reliable lap after lap. As your driving skills progress, the C4 Corvette offers a great platform to grow with. The C4 can also accommodate plenty of tire width and with all its model years and variations, you’ll likely be able to get upgraded components for your car right off another model C4 Corvette. This includes the J55 Heavy Duty brake package, Z51 sway bars and leaf springs, and other components that you’ll be able to find at an affordable price on the typical marketplaces. Otherwise, plenty of aftermarket parts are available to continue your journey in building your dream C4 Corvette track car.

Most importantly, enjoy your time on track.

For more inspiration, check out Vorshlag’s 1992 Corvette “Danger Zone” track build in full.

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