Several factors can exacerbate this:
* Uneven braking: If you apply the brakes too hard or unevenly, the rear wheels are more susceptible to locking up because of the reduced weight.
* Poor tire condition: Worn tires, under-inflated tires, or tires with poor tread will have less grip, making them more prone to locking up.
* Road conditions: Slippery surfaces like ice, snow, or wet roads significantly reduce traction, increasing the likelihood of rear wheel lockup.
* Brake bias: Some vehicles have a brake bias that favors the front brakes. An improperly adjusted bias could make the rear brakes more likely to lock up under hard braking.
* Vehicle load: A heavily loaded vehicle will have more weight on the rear axle, but still, hard braking can shift enough weight forward to cause issues. An unevenly loaded vehicle can also impact weight distribution and make one rear wheel lock up before the other.
In short, it's a combination of physics (weight transfer) and the condition of your vehicle and the road. Anti-lock brakes (ABS) are designed to prevent this from happening by rapidly pulsing the brakes and preventing the wheels from locking up completely.
