How adding negative camber can improve lap times and tire life

Option 1: Moving the Top of the Strut

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.

Option 2: Tilting the Strut Relative to the Spindle

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. 

Option 3: Installing Different Lower Control Arms or Bushings

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. 

Option 4: Lowering the Ride Height

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.

Now Set the Toe

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.