Quote:
Originally Posted by CanAutM3
IMO, over-torqued bolts/studs used at the track is the most probable cause for studs or bolts to fail (unless the wheel is coming loose). When torquing a nut or bolt, it is not the torque per se that is sought after, but rather it is the amount of stretch of the bolt or stud that is needed. The bolts/studs act like a spring that squeeze the two surfaces to me mated together. It is the friction between the two surfaces that actually carries most of the load. If the nuts or lugs are over-torqued, this means the lugs or studs are also overstretched. Combined with the heat expansion of extreme track conditions, the lugs/studs can be stretched beyond their tensile strength limit causing them to fail. Every time you brake, the bolts/lugs are stretched, which could also cause fatigue failure.
Implying regular torquing and un-torquing of the lugs/studs as the reason for failure implies a very low cycle fatigue failure, which I think is unlikely if they are properly torqued to begin with.
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I agree. What's odd is I've seen 4 cars loose a wheel at the track. One was a D-Force LTW5 splitting at all 5 spokes at 100mph...but I digress. The other 3 were old model BMWs using OE BMW lug bolts.
Those lug bolts might have been old. But I'm curious if the lug bolts offer any reliability disadvantage vs the studs and lug nuts that every other non-EU car maker uses. I'm sure there are plenty of older Japanese and US cars with owners that aren't regularly changing their studs and are regularly over-torqueing them.