Your customers will spend a lot of money on your services, and they will place a lot of trust in you as they do so. If for whatever reason they are not satisfied with your work, they may make a claim against you, on the grounds of alleged negligence or faulty workmanship. Your insurance could cover any subsequent legal fees or compensation that may arise as a result of the claim. But without cover, you would have to pay these fees yourself.
Tyre and exhaust fitter insurance will give you essential peace of mind that you will be covered for this scenario, along with many of the other risks you will face as part of your work.