I recently took my non-Z4 for an oil change and tire rotation and was told I had 6/32 of tread remaining. Not knowing what this meant and when the tires will need to be replaced, I searched on tire rack's site. I think I'll be able to make it through the summer or fall before having to replace the tires based on the excerpt below. I hope this helps.
"If rain and wet roads are a concern, you should consider replacing your tires when they reach approximately 4/32" of remaining tread depth. Since water can't be compressed, you need enough tread depth to allow rain to escape through the tire's grooves. If the water can't escape fast enough, your vehicle's tires will be forced to hydroplane (float) on top of the water, losing traction.
If snow-covered roads are a concern, you should consider replacing your tires when they reach approximately 6/32" of remaining tread depth to maintain good mobility. You need more tread depth in snow because your tires need to compress the snow in their grooves and release it as they roll. If there isn't sufficient tread depth, the "bites" of snow your tires can take on each revolution will be reduced to "nibbles," and your vehicle's traction and mobility will be sacrificed. Because tread depth is such an important element for snow traction, winter tires usually start with noticeably deeper tread depths than typical All-Season or summer tires. Some winter tires even have a second series of "wear bars" molded in their tread pattern indicating approximately 6/32" remaining tread depth to warn you when your tires no longer meet the desired tread depth."
"If rain and wet roads are a concern, you should consider replacing your tires when they reach approximately 4/32" of remaining tread depth. Since water can't be compressed, you need enough tread depth to allow rain to escape through the tire's grooves. If the water can't escape fast enough, your vehicle's tires will be forced to hydroplane (float) on top of the water, losing traction.
If snow-covered roads are a concern, you should consider replacing your tires when they reach approximately 6/32" of remaining tread depth to maintain good mobility. You need more tread depth in snow because your tires need to compress the snow in their grooves and release it as they roll. If there isn't sufficient tread depth, the "bites" of snow your tires can take on each revolution will be reduced to "nibbles," and your vehicle's traction and mobility will be sacrificed. Because tread depth is such an important element for snow traction, winter tires usually start with noticeably deeper tread depths than typical All-Season or summer tires. Some winter tires even have a second series of "wear bars" molded in their tread pattern indicating approximately 6/32" remaining tread depth to warn you when your tires no longer meet the desired tread depth."
