Originally Posted by JDNSW
Even the biggest usual tyre size upgrade is only about 10% larger in radius than standard, so the increase in stress on the driveline from the larger tyres is only in the same proportion. Any increase in tyre grip increases the possible stress, and although this grip is independent of tyre diameter, those who increase tyre size usually seek to increase grip as well.
Failures are usually caused by impact loads, when the tyre is slipping and then grips suddenly, and larger tyres may increase the frequency of this because the higher unsprung weight makes it harder to keep the wheels in contact with the ground.
But probably the major reason for the association of larger tyres with driveline failures is simply that people who go for oversize tyres are often (usually?) the same people who drive in a manner likely to result in driveline failure.
John