2001 Toyota Sienna van has much more dust and black soot on front hubcaps than on rear hubcaps. I'd think that all four hubcap would get equally dirty given same driving conditions, yet within the past 6 months, the front ones are becoming much dirtier than the rear ones.

What are some probable explanations?

1 Answer 1


Much of what makes wheels appear dirty is brake dust. Brake dust is wear particles from the brake pads and rotors (or from linings and drums, in the case of drum brakes). The braking effort in most vehicles is not equally distributed between front and rear wheels--this is by design. Generally the front wheels do most of the braking work, since weight naturally transfers to the front tires during braking, giving them better grip.

More of your braking is taking place at the front wheels, so more brake dust is being generated on the front wheels. This is generally not a cause for concern.

That said, if one wheel is suddenly far dirtier than all other wheels, it could indicate a stuck brake caliper causing the brakes to drag. I don't suspect this in the case you described, where both fronts are dirtier than both rears. I think if you look closely at most cars on the road you will find that it is normal for front wheels to be dirtier than rear wheels.

  • 1
    Remember that brake dust is corrosive so, while it is common to see, it isn't a good thing.
    – Bob Cross
    Nov 18, 2013 at 20:12
  • Also, to limit brake dust, use ceramic pads when replacement is necessary. They have far less visual dust than metalic/semi-metalic brake pads. Jan 7, 2014 at 11:32

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