Originally Posted by StevenD
In the EU running dot or not is more of an insurance issue: if you run tyres that are not road approved and get in to an accident your not insured, even if it's no your mistake.
Wont the US insurances bother you in the same way?
It's not quite like that even in the EU, but if your bike has certain non-approved changes - that get discovered when you are in an accident - then it is likely that the burden of proof will be upon you to show that there was no causality. And rightfully so, IMO.
For example if you are running sticky racing tires then it won't be hard to prove that your stopping distance was not negatively affected, but the same can't be said for pure offroad racing knobbies if you run them on the street.
This is why in a few countries in the EU (for example Germany) the vehicle manufacturer together with the government has to establish a list of tested and approved tires, specified down to the exact manufacturer, model, load rating, and speed index.
Nanny state for sure, but it has both advantages and disadvantages. Of course this applies only if you are running on public roads, where the choices you make are possibly directly affecting others.