The outside diameter is bigger on the MT tyres yes, but the inside diameter looks to be the same, I mounted them to check before I posted before. The only issue is they need to be squeezed inwards a little to fit as the MT tyres are wider - but this gives the cool bulged look I was after as opposed to a stretched look. The big issue is the groove on the tyre that you would normally glue onto the rim - on the MT's it is thicker and has the side wall webbing, hence why I need to get a spacer made to fit under the beadlock. They will fit with a bit of modding.Hi, The rim's are made for the FG ST Tires only, the FG MT Tires will not fit! The rim's are not as tall & wide as the FG MT one's are.