Alignment Analysis

[A4_Mike]

I recently replaced my Pirelli P6 Four Seasons with Dunlop Direzza Sport Z1 Star Spec's so I decided that this would be an opportune time to do a full alignment on the A4. The P6's suffered from severe wear on the outer edges from monthly autocross events even though I made sure to maintain relatively high tire pressures on all four corners. I personally felt that the soft sidewall of the P6's compounded with the nose heaviness of the A4 caused this wear. My primary concern is to make sure the same does not occur to the Z1's. From my understanding, the three main factors that contribute to outside wear tend to be camber, tire pressure, and side wall stiffness. Considering the readout below, should I be concerned about the Z1's suffering from the same fate or will the alignment and significantly stiffer sidewall of the Z1's prevent this from happening again?

Regardless, I will find out this weekend considering I will be doing my first HPDE track event on Saturday and an autocross event on Sunday. I should have over 400 miles on the tires by the end of the week so the mold release compound should be gone.

[3ohAvant]

Wow, your alignment was pretty off. Was your front left tire the worst inside tire wear offender?

So, what these cars need to handle better is more camber and caster. Camber is hard to come by up front. So, to combat that, get a front way bar. You are likely rolling over onto the side too much, thats why the outter gets worn faster. Pumping up the air can only do so much to fight that. And at some point, you're going to pump up the tire so much that while getting a stiffer sidewall, and less outside tire wear, you get less traction overall, because the tire will be crowning, and you're really only on the centers of the tire.

Rear camber is adjustable, but you're probably fine there.

Depending on what you'd rather have, good long lasting tires, or a good handling car, or something in the middle?

Toe in keeps the car steady. Toe out makes it a lil sketchy. With that said, toe in up front promotes turn in. Toe out in the rear promotes oversteer.

I would say to run slightly in to zero up front. Then in the rear, toe slightly out. (ASSUMING you want a good handling car, and are able to handle and catch oversteer).

[diagnosticator]

Outer tire edge wear is often caused by too much positive toe (toe in), and that is evident from the alignment pre adjusted measurement shown for the front left. Depending on your needs and preferences, alignment settings used will be a compromise for most driving conditions. Settings that will enhance steering response, are front negative toe, more positive rear toe, (compared to the front,) and negative camber (top of tires tipped in) helps maintain tread grip during turns. For high cornering g forces, more negative camber is better, but will effect inner edge wear also. To much toe out results in touchy straight line steering needing constant corrections for maintaining lane position and increases tram lining in ruts and wandering tendencies, and reduces under-steer, and increased tread wear. However, for autocross, these settings will be more responsive. Positive toe settings increase straight line stability, increase steering self centering force, and reduce responsiveness to steering inputs, and increase under-steer while minimizing tram lining behavior on the freeway lane ruts. Variation of front vs. rear toe settings will vary the handling accordingly.* Excessive toe, either negative or positive causes high tread wear rates, especially on the highway. Slightly negative static toe settings minimize tread wear.
For perspective, consider that 1/8" toe variation from true zero dynamic toe, results in the effect of dragging the tire tread sideways, perpendicular to the direction traveled, 25 feet for every mile driven.

For casual street driving, with OEM sport ride height, slightly negative toe, about ~ -0.01, nominal zero toe per side front and rear, and camber equally divided side to side, ~ -1.2 to ~-1.5 front/rear has been demonstrated to provide balanced handling with even tread wear.

*This is an important handling tuning variable, but a detailed review is beyond the scope of the forum. Try a Goggle search for more info.