86 alignment info

Disclaimers: Performing any modifications to your car based on advice from this FAQ page can be dangerous, might hurt you and/or kill a kitten somewhere. IOW, read, assume, implement at your own risk (don’t sue us if you mess your car up and crash)
These settings may not be compatible with your vehicle, driving style or conditions.

Ride height
  There are several ways to measure ride height. The most common are fender height & pinch weld height. If you are always using the same tire diameter, we recommend using pinch weld height as it’s easier to get more precise and repeatable measurements. For the same reason all OEM’s and pro race teams measure ride height from the frame rail or body seam (pinch weld), we always use pinch weld height method of measurement. The pinch weld is lower edge of the body seam OEM jacking point.

Measuring pinch weld height
Requires that you always measure with the same size tires. Take measurement from forward most and rearmost straight area of lower unit body pinch weld at its lowermost edge. If you measure frequently, a small dot of contrasting paint or other mark on your measuring point is a good idea. Pinch weld heights listed below are assuming a 25″ to 25.3″ tall tire which, when loaded, will have a static loaded radius of about 12.4″. Verify tire pressures before measuring ride height.

Testing
 There is no single “best” alignment for every condition, only the best compromise that suits your particular driving conditions and set up. Fine tuning alignment is fine tuning for your car setup, roads and driving habits. 

To maximize the performance in a competition environment you need to test, test, test. That means same tires, same driver, same conditions, change one thing at a time. Record tire temps with a probe type pyrometer (no lasers!), lap times, tire wear patterns, tire pressures and most importantly, driver impressions immediately after run. The more you are trying to squeeze out of the car on a given course or track on that day, the more you have to test, record, adjust, repeat. What works that day with the sun out, might be less than optimum 30 minutes later with the sun behind the clouds. You shouldn’t expect to be able to copy the settings published on this page verbatim and have it turn out 100% perfect for every possible car, driver, or course. That’s why race teams have highly skilled full time engineers constantly tweaking the cars to milk more speed for the conditions at that instant. Two different drivers under the exact same conditions can generate very different tire temps and require different set ups. The settings you finally settle on are your setup, which is different than our setup. Our setup optimized for a given track, weather, hardware, will not be ideal for you. We are merely providing you with a starting point.

Most DOT R compound race tires will develop their peak steady state lateral (cornering) grip at camber, toe and pressure settings that won’t necessarily show even tread temps or wear. The tires on the outside of the track (left tires on clockwise course) are the key to base adjustments off of. Generally when temps are evenly stepped across the tread and peak temps are within 15° at every corner, you are pretty close. The pyrometer is your friend, learn to use it!  Using Tire Pyrometer
I usually shoot for tire temps 20~30° hotter on the inside than the outside with an even gradient to the cooler outside shoulder. Don’t assume anything when reading tire temps or any other measurement. Drive it hard, pay attention to the car, and experiment. Clocks don’t lie.

My 86 isn’t symmetrical!
The unitbody on any car is rarely perfectly symmetrical. This means one side might have pinch weld heights that are not even with the other side. In this case, average out the measurements to reach your target. Test drive then determine if you need to make further adjustments.  Don’t attempt to get it dead even left to right without using corner weight scales. Pay closer attention to the physical spring preload distance on each shock left to right. This is a better method to ge the suspension level left to right, assuming you do not have access to scales.

Corner weighting vs making it level
These are two different things. A corner weighted car with fixed length shocks may not have equal pinch weld heights at front and rear. Corner weighting invloves adjusting preload so the LF/RR diagonal pair of wheels carries exactly half the total weight of the car as the opposite RF/LR pair. This is called “cross weight” and your goal should be <40 lbs difference for each diagonal pair. This would be 40lbs cross weight, for example. If the preload is not balanced this way, the car will have more weight transfer turning one direction as the other. Meaning your car might oversteer in left turns but be neutral or even understeer in rights, for example. This adjustment is done by placing the car on scales. For more info, google “corner weighting”.

Because the weight of any car is not equally distributed left to right with a driver onboard, the actual pinch weld heights may not be level after corner weighting. Do not attempt to exactly match pinch weld heights on your car if it means increasing cross weight. Even though the car will often sit lower on LR than RR, it will handle more prediictably with cross weight near zero.

Tire wear

For most street driven 86, tire wear is often the most important parameter. Excess toe in or out will usually cause more tire wear than aggressive camber will. The OEM alignment numbers with more rear camber than in front, are designed to induce a bit of understeer. Lawyers ultimately dictate the OEM alignment, not the clever engineers that designed the suspension. Our street alignment is conservative and intended for cars that never slide their tires and spend almost no time at maximum cornering loads. Street alignment works best with 280tw or higher, OEM rear sway bars. Our record setting 86 trackday build “Blub” runs -5° front and -3.5° camber.

Street Alignment
135 – 155mm front pinch weld height
10mm rake, rear higher
Front camber: -1.7°
Caster: >5°
Front total toe: 0
Rear camber : -1.7°
Rear total toe: 0

Race Alignment
GT86/ GR86/BRZ
120 – 135mm front pinch weld height
5-10mm rake, rear higher
Front camber: -3.5° to -5°. Optimize with pyrometer readings https://supermiata.com/using-a-tire-pyrometer-949-racing.aspx
Caster: >5°
Front total toe: 0
Rear camber : -3.5°
Rear total toe: 0

 The 86 seems to work best with 5 to 10mm positive rake (rear higher) measured at the pinch welds without driver in car and about 1/4 tank. The roll center axis doesn’t like to be too far out of sync with the roll centers. In general, you can lower the rake to increase rear grip and improve transitional stability up to the point that the rear suspension begins to bottom. Lower the front to increase front grip and turn in response, again, until it begins to bottom the suspension excessively. In general, once we have an alignment we like, the only tuning we do at the track is to raise and lower the rear to fine tune. Lower to add rear grip, raise to reduce it. Too low and the suspension will bottom so that’s your limiter.

What ride height?
If you do not have front RCC (Roll Center Correction), we recommend staying above 140mm pinch weld height. Below this height without RCC, the front roll stiffness is effectively increased too much and it will be very difficult to eliminate understeer. We see many 86’s with understeer band aid of huge rear sway bars. Don’t go that route as it leads to a twitchy, unpredictable balance that hates bumps. Once you have added RCC, you can drop it lower. Then the limiters are bump travel and ground clearance. If your suspension bottoms too frequently, bouncing over bumps instead of soaking them up smoothly, it’s too low. Ground clearance for street driven cars is really up to you. Decide how much ground clearance you need to clear obstacles in your daily driving such as steep driveways, speedbumps, drainage dips, etc. For track use, we generally start with 125mm front, 130mm rear pinch weld with driver. Tune spring rates and sway bars to get basic balance. We will then fine tune mid corner, steady state balance by making small adjustments to rear ride height.

Sway bars (anti-roll bars)
 In general, 86’s likes a slightly stiffer front sway bar and OEM rear. For street only use, we prefer stock sway bars. Don’t make the mistake of thinking big sway bars will “fix” your handling. They may improve transitional response but they will also reduce ride quality. For track use, slightly bigger bars are a good overall compromise.  As mentioned earlier, a common mistake is to lower the car too much without adding roll center correction, which induces massive understeer. Owners then add a huge rear sway bar in an attempt to reduce understeer but end up with a twitchy car that’s unpredictable at the limit and is easily upset over any bumps. Set up right, your car should actually feel plush, neutral, responsive and completly planted over rough pavement. Our very quick track build runs a 24mm front and OEM rear with RCC.

Toe
OEM alignment is roughly zero toe front and rear. We pretty much stick to this. Autocrossers forced to run wheels much narrower than optimum for the tire width can improve turn in with front toe out but that greatly increases tire wear.

Camber
We are faster on on track with as much as -5° front camber. Record tire temps and test to see what works for you. If you can’t get enough front camber with your 86, welcome to the club! Adjustable camber plates make a huge difference here. Some race shocks like our Xidas also have built in camber adjustment to allow even more camber than plates will get you.

The last bit

We have attempted to make it clear that no single alignment specification can be ideal for everyone. Copying one of our alignment specs exactly will probably be good enough for you and it might even be perfect. If you are looking for more speed however, you will need to experiment and tune for each track, tire and weather condition. At the national level of road race or time trial, alignments are often asymmetrical. Meaning different adjustments at each corner. Deliberate wedge where the car turns one direction better than the other. Very different ride height left to right. An extreme example might be an alignment we succesfully won a national championship with that had one side 1/2″ lower than the other, longer springs on the one side, -2° difference in camber left to right and about 8% wedge. Hot tire pressures on that setup varied about 7psi, each tire different. While that is an extreme, the point is that the more you want to push the performance of your car, the more time you will spend aligning it and that is changing constantly for conditions. Be open minded, be willing to experiment, look at your data, test.