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How to Adjust Camber with MacPherson Strut Suspension

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  • How to Adjust Camber with MacPherson Strut Suspension


    Once you have you done your first track day or autocross, you likely have had to get a custom performance alignment to mitigate tire wear and improve handling. Camber, caster, toe - all important adjustments, but the most crucial adjustment you can make (if the car and class allows it) is CAMBER.

    When you get serious in motorsports events where you drive your car aggressively on track or in an autocross, some things will become clear. In a modern car, once you start pushing through corners at higher speeds than Mr Magoo, you will likely end up with one of three conditions.


    Understeer is when the tires reach the limit in a corner, and the front loses grip before the rear tires. This is the most common form of handling, and how all OEM manufacturers deliver their cars, to some degree. Why is that? Two reasons - mostly that lawyers hold sway over engineers, as the natural tendency in a car that loses traction is to apply the brakes. That usually leads to a weight transfer to the front, which increases the front tire contact patch, grip (usually) returns, and a driver will hopefully avoid a spin.

    But manly men hate understeer, right? Well in reality most cars at a top level are designed with a tough of understeer, just enough to be safe. This is the easiest condition to deal with - it takes fewer "brain cycles" to keep the car at the limit.


    The days of a factory suspensions and alignments that will oversteer (the rear tires lose grip first, which leads to spins) are long over. But in rainy / icy conditions all bets are off, and this can sneak up on you. No racer chasing lap times wants a handling setup that naturally oversteers, unless you are a Drifter. Than that is the setup goal!


    This is the Goldilocks setup, one where the front and rear tires work in balance, and neither end of the car will start to slide before the other. The much vaunted "four wheel drift", which a skilled driver can sustain with some brain power and experience. Most OEM cars will not even have this level of balance, but a handful get pretty close - some Porsches, the 86, maybe a Miata.

    In a perfect world both autocross and track drivers will strive for this elusive neutral handling. And with the right suspension changes, roll control, tire selection, and alignment setup most cars can get to this. But some cannot, and end up with some degree of understeer, especially those that are both front weight biased (FWD cars) and those that have a lot of power driving only through the front wheels (FWD). In those cases we will still try all of the tricks in the books to "dial out" that understeer.


    The number one cause of the most common form of poor handling and excessive front tire wear (understeer) is adding camber. Sure, there are some other adjustments you can make, but this is by far the biggest fix of that symptom. A handful of sports / sporty cars use a double A-arm front suspensions (or some variation on that), but it is increasingly rare. The C5 Corvette below, like all generations of this chassis, does NOT use a strut suspension.


    Yet as time marches forward, many if not most modern cars DO use a MacPherson Strut front suspension design. We're going to focus on strut cars in this article, because that's my specialty. I've been making camber plates for two decades now and know how they work better than your average bear.

    Having MacPherson Struts up front does have its advantages, even if the "techno geeks" talk down this type of front suspension. Compared to other forms of modern suspension, a strut setup: takes up less room, which can allow for more front wheel room; it can be easily adjusted for camber and caster (with aftermarket top mounts) compared to shimming or eccentrics on a Double A-Arm; and they are less costly to produce by the car makers (the real reason they are so prevalent).


    Now that we have justified our "lower tech" strut front end, let's get to making it better by adding negative camber! There are four ways to add negative camber on MacPherson strut car.

    Not all cars can alter all four of these factors, and depending on the racing class rules and factory design, your car might not be allowed to have ANY camber adjustments. It doesn't seem logical to limit camber adjustment in Street classes like SCCA Solo does - but that is the current limit for some cars and classes. Luckily, SCCA Time Trial came out of the dark ages last year and they DO allow camber adjustment for even Street class cars, which saves racers money in needless, premature tire wear. A set of adjustable camber plates can often pay for itself in over the course of just one track day's worth of tire wear savings.


    This is the most common method of camber adjustment - sliding the top of the strut inboard with some form of slotted holes in the tower or within the aftermarket camber plates.

    Some factory strut top mounts have slotted holes in the strut tower, and you can maybe eek out maybe a degree of adjustment on these rare setups. Most cars have no factory upper adjustment for camber (or caster) at all, so an solution is required. Camber plates can often work with the OEM diameter springs and not raise or lower the ride height, which is crucial for "Street" classes which allow this adjustment.

    Factory and OEM style lowering springs are usually 70-130mm on the inner diameter, which can often limit camber travel inboard just from "spring girth". But on about 90% of strut based cars with OEM diameter springs, there's still enough room to allow worthwhile travel and camber adjustment. We try to shoot for an adjustment range of 2.5 degrees from the stock top mount setting, but even if you can get 1.5 degrees of movement, that's still useful

    Once you move to "coilovers" the spring diameter gets much smaller (2.25", 60mm, or 2.5" ID), which almost always unlocks more camber adjustment range. The 2016 Ford Focus RS shown above has relatively large OEM springs inside a small tower. We couldn't slide the top of the strut inboard even 1/4" before the spring hit the tower with those. After we switched to modest Bilstein PSS coilover struts and 60mm ID springs, with camber plates we could then get a full 3/4" of camber travel.

    This let us dial in 4.0 deg of static front camber (also at a lowered ride height). That was a game changer for this formerly softly sprung, poorly damped, very camber limited AWD car. The RS went from HEAVY understeer in stock form to only a mild understeer, and dropped 5.7 seconds a lap on a 90 second road course on the exact same tires, with just these suspension changes. Tire wear radically improved as well. With the wider and stickier tires shown above the RS dropped another 2.5 seconds, with no alterations to power or aero.

    On some cars, when the geometry of the tower and opening plays nice, we can also afford the room to adjust caster via the aftermarket top mounts. Adding positive caster helps (to a point) with the dynamic camber as you turn the wheels. If your car can get to around +6 to +8 degrees of positive caster, the tires are going to be even happier. We're not going to overemphasize caster here, as the static camber setting is much more crucial.


    This is the second most effective method for altering camber - "kicking" the strut relative to the front spindle and hub. This works on roughly half of all strut equipped car models, if the strut bodies have brackets to attach to the spindle with bolts. If this is what your car has, continue on below. Sadly many German automakers cars have fixated on a clamping style attachment at the spindle (most VWs + BMWs from 1998-up) and do not have any tricks to "kick the strut" for camber.

    In the S650 chassis Mustang Darkhorse example shown above, the aftermarket MCS strut housing has a significant slot in the upper bracket hole. Even utilizing the "full sized" factory bolts, you can use the slotted hole to add 0.5 to up to 2 deg of additional negative camber travel. Now these particular Ford strut bolts are splined, so you have to install them loosely to be able to dial in the camber at this spot - once tightened enough to engage the splines, they have to be hammered out of the spindle to allow it to slide. But you don't want these bolts coming loose on track, so the splines are welcomed.

    Then there are "crash bolts", which can do the same strut kick, just to smaller degree. Often these are shaped with a "cam" that can be dialed in, other times they are simply smaller diameter bolts than stock. Sometimes the spindle is factory designed (often even as authorized repair or "TSB") to have a larger than necessary upper strut mounting hole, like the 2023 Subaru BRZ front spindle above. The factory upper 16mm hole uses a bolt has a massive shoulder, but replace it with another M14 sized bolt like the bottom hole uses and you just gained a 1/2 degree of additional negative camber.

    This is an easy way to gain camber if you cannot get enough at the top with the camber plate (or if the class doesn't allow such a device). Our stock 2023 BRZ shown above went from -1 deg stock to -3.5 deg front camber with camber plates and the M14 upper bolt trick, with stock springs and no ride height changes. This was worth 1.3 seconds a lap on a 90 second track, on the same tires.

    There's no free lunch and "kicking the strut" comes with the potential loss of inboard wheel room, at least with very wide fitments using the same offset wheel as before. Kicking the strut often brings the need for a wheel spacer, or wheels with a different offset, but if you can balance this wheel-to-strut relationship correctly this slotted hole adjustment + camber plates can make for two reliable camber adjustments. The slotted bracket trick just takes a bit of time to dial in right, but it needs to be done during the initial suspension install. Normally you dial in the "Gross" camber adjustment on a slotted aftermarket strut housing first, then fine tune the camber setting at the top mount where it is much easier to adjust.

    continued below
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

  • #2
    continued from above


    Some series like SCCA Time Trial Tuner classes allow for either top mount OR lower control arm camber adjustments, user's choice. Changing the lengths of a lower control arm(s) on the front of a strut car cam alter both camber and caster, and this is often the preferred method for adjusting camber on rear suspensions.


    Adjustable arms are not super easy to adjust in fine increments, but can allow for a lot of camber adjustment. Sadly the rules for SCCA Tuner classes don't allow spherical bearings, and the best adjustable front lower control arms tend to have spherical bushings. But you can also use an offset bushing to achieve the same thing - moving the bottom of the wheel outboard to add camber - but it is even harder to adjust. Normally we only change to an adjustable lower arm when the rules allow sphericals and multiple camber adjustments, and these are again used for "Gross" camber gains and the alignment is fine tuned at the easiest spot, the top mounts.


    This is the 4th and final spot where you can alter camber in a strut car, but gaining negative camber it really just a byproduct of lowering a car's ride height.

    Just lowering the ride height on our 2024 Dark Horse as little as 3/4" (before and after shown above) increased negative camber at both ends of this car with no other changes (the rear went up by -0.5 deg and the front had a similar gain similar). Of course you can "over-lower" any car, and this additional camber trick is just a bonus of lowering, not really a main "camber adjustment". But ride height lowering does gain negative camber in a strut car, it is both real and repeatable.


    If you have done any of the above listed adjustments yourself at home, great! You're going to save time and money at the alignment shop, which is usually the next step after you have been prying and tweaking camber at home. But one thing you HAVE to do before you drive to any alignment shop with a tweaked setup: SET THE TOE.

    Driving with any amount of TOE OUT at either end of the car will really chew up your tires quickly, and it also makes the car very darty (and dangerous in inexperienced hands or bad road conditions). A rare segment of autocrossers will dial in a bit of front toe out to help with turn in, but this isn't done on street driven cars. Toe out wears tires MUCH faster than negative camber ever could. All my daily driver strut cars have -2.5 to -3.5 degrees of front camber, but I keep front toe at zero - and do not see aggressive tire wear on the street.

    Just know that there is a relationship between toe and camber on a strut car - front toe settings WILL change when you adjust camber. Depending on whether our car is "Front steer" (the steering linkage is in front of the front axle centerline) or "Rear steer" (behind) the toe change will either toe OUT with negative camber (front steer) or toe IN with negative camber (rear steer). Luckily with bout $75 worth of Toe Plates and two measuring tapes, plus a few hand tools, you can adjust front toe yourself, pretty accurately. Setting camber or especially caster is a lot harder to do at home.

    Toe is so critical that I feel that every racer should own a set of toe plates. We have a set at the shop and one in the race trailer, and a spot check takes "ones of minutes", which we do often. There are lots of online videos showing how to use toe plates and adjust front toe, so get to Duck-Duck-Going on that.


    Before you tackle all of these tricks you will want to find a good, local alignment shop that ca do a custom alignment. Asking for some of these numbers will rule out 80% of all shops, who normally don't know caster from camber, and just push and pull on adjustments until "it's in the green". Ask your local cone heads or track rats where they get their cars aligned and go there, but prepare to spend $150-300 for a track alignment.

    Know what you want up front is key, and I always bring a printed sheet to any alignment shop with details like: make / mode / year, list all suspension modifications, list the goals for camber / caster / toe at both ends of the car, point out any non-stock adjustments, and then add my cell number for them to call if they have ANY questions. This up front preparation will save you a LOAD of heartache and poor alignment.

    Should you align your own car? Well you can, but it's not as easy as people like to admit. If you want to invest in $100-1000 worth of equipment to "string" your car, and then prepare to spend 2-4+ hours each time you make a change, then go for it. You really have to have a flat, level floor and good work space. As a professional who can do a string alignment, I'd rather spend $150 on a shop I trust to use one of those fancy "laser" machines to give me the numbers. A proper alignment rack takes HOURS or time out of any alignment, as long as the technician knows that they are doing.


    This is a subject that I could write a book on, because it depends on so many variables. I have been testing camber settings on track and autocross cars for thirty years, and my data always pushes my cars to higher numbers than some people can fathom. But the pyrometer, lap times, and long term tire wear don't lie. People love to argue absolute numbers but I remind them that sloppy OEM bushings and flimsy chassis need more than a super rigid carbon-tubbed race car like a Formula1 car. And on street circuits they run a LOT of negative camber, especially on the front end.

    On a strut front suspension I will usually start with at -2.5 degrees of camber, but often dial it in to -4.5 degrees or more. The "perfect camber" depends on so many factors, and testing trumps all rough guesses. It is impossible to throw out a golden alignment setting, so I usually ask a number of questions before giving folks a number.

    If you press me for an answer, for most strut cars that are tracked aggressively with a wider-than-stock sticky tire (200TW or better) I will target -3.5 degrees camber up front and maybe 3/4 degree less than that out back, if possible. With over 20,000 customers over the last 20 years, we have given out a lot of alignment suggestions, and more often than not, that ends up being pretty close.


    We also put a lot of the answers in this article into a video, which might be easier for some of you to watch rather than "Read words".

    To close this article out I will say that getting camber is so crucial for any track or autocross car that it can and should guide you on what car to even buy. Some factory suspensions are so poorly designed that they are often better off campaigned in competition classes that allow one or more of these 4 camber tricks listed above. In stock form these camber limited cars will spend their brief time on track chewing up front tires and understeering like crazy. For these cars Solo "Street Touring" or Time Trial "Tuner" classes are your best bet. Don't let a lack of camber destroy your tire budget!

    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev