In replacing these bolts I noticed a difference in diameter of the bolt for about 1/8th off the bolt head then it necked down slightly and remained a uniform diameter to the threads. This was the case on all the bolts. Question. If these bolts are replaced by the same grade and length bolts without that slight taper, how critical is it? The replacement bolts having the same diameter as the thickest point on the factory bolts.

Thanks

My car has some really crazy replacement bolts from the previous owner. One is even a hex head!

I've put at least 15K miles on them, and I drive very hard. :D

So I say the taper is not needed.

My guess it it helps for the bolt part to "press" into the control arm bushing so the rotational travel of the bushing won't start to loosed the bolt? I have not looked at the setup in close detail though.

Oops. just saw this was for the lowers too. That part of the bolt hleps to make for a snug fit of the shaft inside the bushing. Thus limitting instant sheer from an impact-like force.

Perhaps this is true for the upper retianing bolts also?