This is how I regroove the Michelin 255/100R16 XZL tyres on my truck. I have followed the Michelin specification for these tyres, and their regrooving guide. Michelin go on to say that they can be remoulded, then regrooved again once the remould is worn out, effectively giving the tyres 4 lives! My tyres are not remoulded and I don't intend to do that. I normally change these tyres when they are down to about 3mm (for a car the limit is 1.7mm and a truck like mine 1mm in the UK!). It is legal in Europe for front and rear tyres to be regrooved on trucks, but some countries only allow it on the rear tyres of buses and coaches - hence for safety I put them on the rear. Note: these are not car or 4x4 tyres, they are a military/construction-site tyre and are designed for regrooving and are clearly marked as such on the side wall.