Saturday, October 5, 2013

What Causes Tire Chunking Like This?

A OneHotLap reader sent us this picture and asked if we can help him diagnose the root cause of the tire chunking he's experiencing. 

My 3 month-old Michelin PSS are busted after a weekend at Thunderhill. Probably because I don't have any camber right now in my stock BMW 135i. What do you think? 2 days, Saturday was 80 degrees, Sunday 77. 5 sessions per day, 20 min per session. Tires started chunking on day 1 and it got a lot worse on day 2 when the cords became visible.


  1. 1. Michelin PSS are not track-ready tires, despite what some people seem to believe. I have seen many instances of PSS doing similar with hard driving.
    2. As a 135i owner, your viewer is correct, from the factory, front camber is set at 0*. If the alignment pins are removed, that can be adjusted to -0.3*, which is still insufficient, especially with a soft tire like the Michelin.

    Until I get around to installing my camber plates, my car is set at the previously mentioned -0.3* front camber, however, with my Dunlop Star Spec Z1's, I don't really have issues like the one presented. Sure, my tire wear is a bit less than optimal, but by no means it appalling like the picture above. Sounds like the the car is being over-driven for it's setup. Adjust the driver, or adjust the components.

  2. Tire chunking is primarily caused by insufficient warming of the tire before driving it hard. Next time take a couple of easy laps to warm the tire all the way through (not just the tread surface, but the entire tire carcass) before pushing them hard. This should extend your tire life considerably.
    I also agree, given the severity of the damage, that you are overdriving the car; that is, you are asking the tire to perform beyond its inherent performance capability.