What is Camber, caster and toe?
Photography Credit: David S. Wallens
An easy adjustment that can unlock both increased speed and tire life? Likely just adding more negative camber, especially up front.
Increased negative camber–how much the tops of the tires tilt inward– simply places more of the tire’s tread against the pavement during cornering. The result: increased efficiency courtesy of more grip.
Most street cars are delivered with very little, if any, negative camber–maybe -1° if you’re lucky, although zero camber and even positive camber aren’t uncommon. For track work, many cars start to get happy closer to -2.5° and can wind up closer to -4.5°. (The perfect camber depends on so many factors, and testing beats all rough guesses. Lap times and tire temperatures–even across the tread surface–will tell you much.)
So, how to get that desired negative camber? On MacPherson strut suspensions, so common up front over the past 40 or 50 years, there can be four easy paths to success.
Not all cars can alter all four of these factors, though, and your journey to increased camber may depend on the factory design as well as any competition rules. (SCCA Street rules for autocross, for example, limit hardware changes that can add negative camber, while the club’s Time Trial program does allow hardware changes in the Sport classes.)
Aftermarket camber plates can easily add more negative camber. Some, like these, are adjustable; others simply reposition the top of the strut to a new, fixed location. Photography Credit: David S. Wallens
This is the most common method of camber adjustment: simply sliding the top of the strut inboard. Some factory strut top mounts have slotted or at least loose holes, and you can possibly eke out a degree of adjustment on these rare setups.
Since most cars don’t have provisions for adjusting the top of the strut, new hardware is required–specifically, new upper strut mounts. Some of these strut mounts–aka camber plates–are slotted to allow a range of adjustment while others offer only a fixed change. Camber plates can often work with the OEM diameter springs and not raise or lower the ride height, which is crucial for many stock-type classes that allow this adjustment.
The diameter of the stock springs will often limit the amount of negative camber dialed in, however, as tilting in the tops of the struts too much can cause the springs to contact the strut towers. On most strut cars with OEM-diameter springs, however, there’s still enough room to allow worthwhile travel and camber adjustment–often -2.5°, but even if you can only get -1.5°, that’s still useful.
Aftermarket coil-over setups that use smaller-diameter springs can unlock more camber adjustment range. On a particular Ford Focus RS, for example, replacing the stock springs with a modest Bilstein PSS coil-over kit with camber plates freed up enough room for -4.0° of negative camber. The RS went from heavy understeer in stock form to only a mild understeer, dropping 5.7 seconds a lap on a 90-second road course–no other changes. Tire wear radically improved as well. (Even wider and stickier tires, by the way, shaved another 2.5 seconds.)
On some cars, when the geometry of the tower and opening plays nicely, you can also afford to dial in more caster–the angle of the steering knuckle as viewed from the side of the car. 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° of positive caster, the tires are going to be even happier. We’re not going to overemphasize caster here, though, as the static camber setting is much more crucial.
More negative camber can sometimes be gained at the junction between the strut and the hub–slotted bolt holes or narrower bolts can help. Photograph Courtesy Vorshlag Motorsports
Changing the angle of the strut relative to the front spindle and hub can also yield increased negative camber. Either work within the factory tolerances or make your own.
This works on roughly half of all strut-equipped cars–basically those that attach the strut to the spindle with bolts. (Sadly, many German automakers–think most VWs and BMWs built in the past 25 years–now clamp the strut to the spindle, eliminating this trick to “kick” the strut for increased camber.)
Sometimes the factory spindle is designed with an oversized upper strut mounting hole–like the latest Subaru BRZ, for example. Replace the factory upper 16mm bolt with an M14 bolt, as used in the bottom attachment point, and you just gained half a degree of additional negative camber.
This bolt trick, along with camber plates, helped that same BRZ go from -1° to -3.5° camber up front. On stock springs and with no other changes, this was worth 1.3 seconds a lap on a 90-second track.
Then there are “crash bolts” that can also provide some adjustment here–so named as they’re intended to restore factory alignment settings to a car that might have gotten a little bent. These often feature a cam that can be dialed in; other times, they simply feature a smaller diameter than stock.
There’s no free lunch, though, as this change can also reduce inboard wheel room, at least with very wide fitments. Kicking the strut often brings the need for wheel spacers or wheels with a different offset.
It’s also easier to make this move when assembling the suspension. Dial in the gross camber setting at the lower end of the strut before making the fine adjustment at the top via easily managed, slotted camber plates.
Aftermarket lower arms and/or bushings can also help gain negative camber. Photograph Courtesy Vorshlag Motorsports
Changing the lengths of a lower control arm on the front of a strut car can also alter both camber and caster, and this is often the preferred method for adjusting camber on rear suspensions. (Note that some programs, like SCCA Time Trial Tuner classes, allow for either top mount or lower control arm camber adjustments–builder’s choice.)
Adjustable arms are not super easy to adjust in fine increments but can allow for a lot of camber adjustment. Offset bushings can achieve the same result–moving the bottom of the wheel outboard to add camber–but can be even harder to adjust. Again, use these for the big camber changes and make the fine adjustments with upper camber plates.
Read the rules, too, before buying new hardware. In SCCA Time Trial competition, for example, the Tuner classes don’t allow spherical bearings, and the better adjustable arms tend to have them.
An often desirable benefit to lowering the chassis: increased negative camber. Photography Credit: Chris Tropea
Gaining negative camber can often be a byproduct of simply lowering a car’s ride height. Lowering a new Mustang Dark Horse, for example, by as little as ¾ inch increased the negative camber at both ends by about -0.5°.
Of course you can “over-lower” any car, and this additional camber trick is just a bonus of shaving ride height, not really a prime way to adjust camber. But ride height lowering does gain negative camber in a strut car; it is both real and repeatable.
Dialed in more negative camber? Great. But before driving anywhere–to the next event, or to the alignment shop to check your math and make sure the chassis still sits square–you need to set the toe, the relationship of the tires when viewed from above.
Driving with any amount of toe-out at either end of the car will quickly chew up tires while also making the car very darty–and dangerous in inexperienced hands or bad road conditions.
How will those new negative camber settings impact toe? It depends. If it’s a front-steer car, meaning the steering linkage is in front of the axle centerline, more negative camber will increase toe-out. And the opposite is true, meaning a rear-steer car will gain toe-in with negative camber. Luckily, with about $75 worth of toe plates, two measuring tapes and a few hand tools, you can adjust front toe yourself pretty accurately.
Would you rather just use a professional alignment shop? Talk to the local racers for a good recommendation for a shop that does more than push and pull on things until the numbers are in the green. Knowing what you want up front is key, and dropping off your desired settings can save a load of headaches.
The big thing here: Don’t let a lack of negative camber slow you down and destroy your tire budget.
Terry Fair owns Vorshlag Motorsports, manufacturer of aftermarket camber plates.
I'm here to answer any questions about this article...
It is my first one written for GRM, so be gentle! ;)
Fair said:
Love the triple red.
In reply to Fair :
Covered everything I can think of option wise. How do you go about reading a tire in order to determine the correct amount of camber? How do each of the options impact inner and outer tire clearance? Camber is often directly related to being able to fit those chonky bois on there.
Colin Wood said:Fair said:
Love the triple red.
The gloves seal the deal
Good job on the article. First time I have seen anyone mention the toe changes with a reference to front steer vs rear steer. Well done.
In reply to theruleslawyer :
Camber does sometimes get pushed to the limits just to be able to fit wider tires under stock fenders - we get that compromise - but it rarely causes "bad things", and often opens people's eyes to how much camber they REALLY needed after all. More camber is still better than less. The big myth is "big camber" will cause adverse tire wear (it doesn't - most premature wear on street cars is toe out) or that it will impact grip under braking (I have tons of data to show that this is absolutely not the case - the best braking g traces we saw on this '24 Darkhorse in multiple stages of testing was with the most front negative camber).
Of course direct probed pyrometer testing is "the gold standard" for dialing in camber, but in my experience, this can give somewhat misleading data. When you have used real time spread sensor IR tire temp readings, correlated to some GPS data, you will see HOW MUCH tires cool off on just a short straight after a hard corner. These real time tire temps focused on the loaded (outside) tires only in cornering tell you so much more. Even coming into the hot pits straight from a hot lap and having someone quickly probe the tires directly - by then your tires may have cooled off 30-50°F or more. How can you trust that data? The IR array sensors + data collection and crunching is a relatively expensive way to dial in camber (and air pressure and toe), but it beats everything else.
I like to look at "alternative sources" for camber data, and it has paid off over time with potentially better data than the old school probe pyrometer. My first method is to look at the loaded (outside) tires mid-corner, like the images above and below. This SHOWS me the dynamic camber (vs static), with the tires loaded and bushings at max deflection. THAT tells me when I need to add more camber better than a probe pyrometer could hope to.
This image above of our '23 BRZ (SCCA TT T3 class) shows our "massive" camber settings all get gobbled up in bushing deflection and roll. This was loaded up in the fastest corner (Big Bend) at our test track MSR Cresson. When you can visualize what the car is doing dynamically, loaded mid-corner like this, these alignment settings don't seem so radical anymore.
Another method is monitoring tire wear over the life of every set of tires. I will take pictures like this above and mark how many events were on the tires, to show folks what careful tire management, proper static camber, and correct tire pressures can give you. That car (2018 Mustang GT prepped to NASA TT3 / SCCA TT T2) was driven hard for 2 seasons and I marked how many track days we got out of each set, and I could tell by lap times when they had fallen off. We rotate the tires after every event, and do tend to "flip" the tires on the wheels once during their life (this doesn't affect the feel or performance, just extends the life). It is still a challenge to get perfect shoulder wear on most cars, even with -4° camber like we ran on this car, so flipping them once can extend their life by 50%.
After 36 years of running competition events, with 25-30 events per year in a variety of cars, we've moved to these standard + "alternative" camber (pyrometer + loaded visualization + tire wear monitoring) testing methods. And those methods have pushed us to "run more negative camber" than most folks think works, but most people don't test as much as we do, or won't even attempt the camber settings we end up at. I share this experience with as many racers who will listen.
I hate seeing people shred the outside shoulder of any tire prematurely, which is why we pushed SO HARD for SCCA TT "Sport" category to get camber adjustment for every car. This finally passed in 2023 and we're seeing more Sport class racers move to adding camber within the limits of that class. And that is pushing my crew at Vorshlag to develop more camber options for the OEM style suspensions that Sport class limits racer to (like this 718 Cayman setup we made last month). I just wish SCCA Solo Street classes would finally move to the same rule set. #CamberForAll
Cheers, Terry Fair (Camber Junkie)
All solid advice.
I use a combination of tire temps and tire wear to set things and yes I always check the toe.
As an aside the Datsun only uses -1.5 degrees of camber (it's what the Hoosier vintage tires require) and even that little bit changed the toe.
I need the article, "How to add more negative camber than the suspension system allows." I'm maxed out at -1.5° and still seeing the need for more
In reply to buzzboy :
On the Datsun we originally slotted the strut tower itself. That is what the Nissan Competition prep manual said to do.
It is a Mercedes bastardization of double A arm. I cranked the eccentric to the max. Can't find a good diagram or photo of it for some reason.
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