Gerald81
Well-Known Member
Just wanted to throw this out for discussion with fellow trackies - do you guys use camber bolts or top mounts when dialling in camber for track days? For the purpose of this thread, I would like to distinguish between camber adjustment based on the location of the adjustment, i.e. via:
1) Upper - top mounts (i.e. camber plates)
2) Lower - wheel hub (i.e. camber bolts, offset mounting bolts, etc.)
I've observed that a lot of trackies who have installed aftermarket coilovers with adjustable top mounts naturally use those for camber adjustments, perhaps due to its ease and convenience. Adjustments via the wheel hub (eg. camber bolts) take a little more time as you have to raise the vehicle and/or remove the wheel to get to them. Also there appears to be some sentiment that the bolts do not hold their alignment very well under hard driving or on harsh terrain.
However, I have read that camber adjustment for the front axle via the top mounts can sometimes be undesirable, because you will inevitably change the vehicle's steering axis inclination (SAI) angle. The following picture probably helps define SAI angle better than I could possibly explain with words:
As you can visualise from the above picture, most camber plates/top mounts work to increase negative camber at the wheel by tilting the upper location of the suspension strut inwards towards the chassis, which will result in an SAI angle that is higher than OEM-spec.
I'm no expert on wheel alignment angles, but my understanding is that the SAI angle defines the scrub radius for the front tyres when they turn, and is necessary on most passenger vehicles. On the flipside, one drawback of the SAI angle is that in order to ensure that the wheel remains perpendicular to the ground despite having an angled steering axis, the attachment between the wheel hub and the suspension strut will need to be angled to compensate for this. Ignoring other alignment parameters such as caster angle, the net result of having a positive SAI angle is that the front wheel actually gains positive camber as steering angle increases, which is generally undesirable.
On the other hand, camber adjustment done at the hub itself (assuming you are adjusting for more negative camber) actually reduces the angle between the hub and the suspension strut, and therefore reduces positive camber gain as steering angle increases.
At this point in time, based on my understanding of the SAI angle and how it interacts with the wheel, I'm inclined to believe that adjusting for camber via camber bolts and/or using the elongated mounting holes that some coilovers offer might be a superior alternative to making adjustments via the top mounts. Of course I could be missing out on something that I'm unaware of as well, perhaps the difference in suspension design (Macpherson strut vs double wishbone) might play a signficant role as well - what do you guys think?
1) Upper - top mounts (i.e. camber plates)
2) Lower - wheel hub (i.e. camber bolts, offset mounting bolts, etc.)
I've observed that a lot of trackies who have installed aftermarket coilovers with adjustable top mounts naturally use those for camber adjustments, perhaps due to its ease and convenience. Adjustments via the wheel hub (eg. camber bolts) take a little more time as you have to raise the vehicle and/or remove the wheel to get to them. Also there appears to be some sentiment that the bolts do not hold their alignment very well under hard driving or on harsh terrain.
However, I have read that camber adjustment for the front axle via the top mounts can sometimes be undesirable, because you will inevitably change the vehicle's steering axis inclination (SAI) angle. The following picture probably helps define SAI angle better than I could possibly explain with words:
As you can visualise from the above picture, most camber plates/top mounts work to increase negative camber at the wheel by tilting the upper location of the suspension strut inwards towards the chassis, which will result in an SAI angle that is higher than OEM-spec.
I'm no expert on wheel alignment angles, but my understanding is that the SAI angle defines the scrub radius for the front tyres when they turn, and is necessary on most passenger vehicles. On the flipside, one drawback of the SAI angle is that in order to ensure that the wheel remains perpendicular to the ground despite having an angled steering axis, the attachment between the wheel hub and the suspension strut will need to be angled to compensate for this. Ignoring other alignment parameters such as caster angle, the net result of having a positive SAI angle is that the front wheel actually gains positive camber as steering angle increases, which is generally undesirable.
On the other hand, camber adjustment done at the hub itself (assuming you are adjusting for more negative camber) actually reduces the angle between the hub and the suspension strut, and therefore reduces positive camber gain as steering angle increases.
At this point in time, based on my understanding of the SAI angle and how it interacts with the wheel, I'm inclined to believe that adjusting for camber via camber bolts and/or using the elongated mounting holes that some coilovers offer might be a superior alternative to making adjustments via the top mounts. Of course I could be missing out on something that I'm unaware of as well, perhaps the difference in suspension design (Macpherson strut vs double wishbone) might play a signficant role as well - what do you guys think?