[Hendog]

I found the answer by reading through an imbeded link

Originally Posted by burgermeister

The grooves in the bar are stress risers (crack initiators). This is where metal fatigue will occur. Sanding and polishing the grooves out will remove most (but not all) of the stress riser. As the bar is locally smaller now, there will be locally higher stresses. Also, the residual stresses induced by the factory pre-stressing will be altered in a non-beneficial way. So, lower durability in the bar. OTOH, the bars in mine are WAY worse (will be replaced) and they showed no evidence of fatigue cracking, so there is some margin in these things.