The length of spikes you go for will depend on a few factors. While long spikes (about 3 inches) are the recommended standard, you may find it easier to walk in sandals that have shorter spikes. As you walk, the spikes dig into the soil, and you need to pull them out to take the next step. If you have clay soil on your lawn, longer spikes tend to get stuck easily and require more effort to pull out. Ultimately, the length of spikes you go for will also depend on your soil type, and how much thatch you have on your lawn. The more the thatch build-up, the longer your spikes need to be to do a good job. How to clean lawn aerator