Miscellaneous (Common Tyre Problems)
Tyre Conicity Problems:
Conicity problems can also arise when the beads are not in the same plane. The resulting difference in sidewall height and loading will create the same unbalanced steering forces that make the tyre want to roll towards the shorter side.
Conicity problems are usually most noticeable on the front wheels, but may affect tracking and induce some rear axle steer on vehicles with independent rear suspensions. Vehicles with less caster also seem to be more sensitive to conicity probably because high caster angles have a stabilising effect on the steering.
It is important to remember that vibrations are caused by excessive radial (vertical) and lateral (sideways) runout in the tyre, wheel or hub. Loose, worn or damaged wheel bearings as well as certain kinds of tread wear can also cause vibrations.
Another source of vibration can be uneven tread wear. Run your hand across the tread in both directions. If one way feels rougher than the other (like toe-wear), lack of rotation may have caused a heel-and-toe or sawtooth wear pattern to develop on the tread blocks.
Consult a competent workshop for necessary corrections.
Tyre Noise problem:
Tyre noise usually shows up as a whine due to abnormal tread wear or as a thumping sound caused by ply separation. Tyres make noise because the tread elements squirm under the weight of the car. The other reasons can be low inflation pressure, bubbles and knots developed by hitting any curb, misalignment and shredding. Sometimes tyre pattern can also be a reason for noise while driving. Tyre replacement is required to correct these common problems.
The wheel/tyre assembly on a vehicle shall invariably have a degree of unbalance. This unbalance must be evened out with suitable machines in two planes. Improper balance or load will cause the tyre to spin with a wobble due to unbalanced centrifugal forces. This wobble will cause the tyre to wear improperly and probably show up as a vibration as well.
This is offset by adding counter balancing weights on the rim at the light spot, ensuring requisite wheel balance.