Camber bolts are arguably one of the most important bolts in your performance car, and it’s important to know that it is one of the few bolts that are also wear items on your car as well. Camber bolts are specialised bolts used in suspension systems to adjust the alignment of a vehicles wheels. The way in which they adjust the alignment are with use of an eccentric camber plate.
Eccentric refers to an offset centre / turning radius – similar to lobes on a camshaft. On the Mx-5, as well as some other platforms, the OEM camber bolts are vulnerable to rotation or shifting under heavy loading – track days, autocross events or even just hard road driving may produce enough force on the wheels to rotate the OEM camber bolts.
This is a real concern, as the steering behaviour of the car can change even halfway through a corner. You may find the steering to be off-centre or the driving characteristics of the car are less predictable, which drivers depend on for performance and safety.
These problems are exacerbated if you are running stickier tyres, stiffer sway bars or stiffer coilovers. It’s a good idea to explore the increased wear that comes with increased performance. It’s worth noting that the front camber bolts are much more likely to wear than the rears as they take more force from hard braking and steering.
There are a number of ways with which one can prevent the rotation of these camber bolts. Our solution was to create a camber bolt that resists wear better than the OEM camber bolts and can be torqued much higher as well. The increased tightness of the bolt will see more resistance to shifting and rotation under heavy loads, thus, will ensure the predictability that drivers will need to perform well.
How are we addressing these issues?
Our improvements to the OEM camber bolt design are achieved with two major features:
- The triple woodruff key design:
The OEM Mx-5 camberbolts use a dual woodruff key to prevent the spinning of the camberplate on the camberbolt. Because the key is relatively small in depth and in width, the component is subject to wear over repeated load cycles, especially over a number of years. Our design uses deeper, wider and a larger quantity of woodruff key inserts in both the camberbolt and the camberplate to increase the strength of the components and minimize rotation under load conditions.
- Increased material stiffness:
When choosing the material with which our bolt was to be made from, we chose to go with the higher grade (12.9) steel, as its higher stiffness coefficients were more desirable in this use case. A higher stiffness coefficient means that one can tighten the bolt higher than with the OEM bolt without worrying about any adverse wear/effects on the component features. If you were to torque the OEM camber bolt as high as we tighten ours, you would find that the looser-fitting, dual woodruff keys with the lower grade steel would simply shear, as they did in our experiment.
Head to Head
Rather than relying on computer simulations to assess the strength of our bolt, we decided to run a supplementary experiment comparing the OEM Mx-5 with the HFM.Parts camber bolts. As the camber plates are responsible for the position of the alignment, we decided to focus on that as the test-subject / dependent variable. The independent variable would be the torsional force being applied to the plate from the locking nut, as this would best simulate the two primary forces the bolts are designed for:
- Alignment being set and locked with a high torque coefficient
- The bolts’ ability to sustain high torsional loads / at what torque force does the camberplate yield?
Torque would be applied with the use of a nut and a torque wrench. The bolt would be held in place with the use of a bench-vice. To best replicate the use environment, a metal sleeve was placed over the bolt, in place of the control arms that the bolt would normally be seated within.
On the left side of the figure, the woodruff-style keys on the OEM camberplate have completed sheared at 60 Ft/lb. The camber bolt is completely incapable of holding any sort of alignment making the car borderline dangerous to drive.
On the right side of the figure, the camber plate does shift under the torsional force, but quickly returns to its original position. When talking about yield stresses with metals, this comes within the ‘elastic’ region of the material properties, meaning that while the material has moved, it has not taken on any permanent deformation. This means that the bolt is still capable of performing at its best and should not need replacing unless it is repeatedly seeing more than 100 Ft.lb of force.
While it is worth noting that it is very unlikely that a camber bolt would see torsional forces anywhere near as high as the coefficients listed above, what these two figures show is the delta between the OEM style and the HFM.Parts style bolts. This experiment therefore demonstrates the improvement in the camber bolt performance and justifies its promise of a more secure alignment.
In Conclusion
To conclude, a camber bolt is not only a wear item for MX-5s but also a crucial component for maintaining the predictability, safety, and overall performance of your vehicle. While wear items inevitably need replacement, the increased strength and stiffness of these camber bolts mean fewer replacements, particularly if your car sees frequent track use or requires regular realignments.
The experiment we conducted not only supports these claims but also highlights the performance improvements when upgrading from OEM to HFM camber bolts. The data gathered is more qualitative than what you might obtain from purely mathematical or FEA-based calculations. However, it effectively isolates the necessary variables to validate the key features of this kit.
This kit is ideal for anyone using performance parts on their car or engaging in performance driving. You can assess the need for this upgrade by paint-marking your camber bolt positions before your next track day—particularly the front camber bolts on the front subframe. If they have shifted after a session, we strongly recommend considering this upgrade for your setup.