Just lost a wheel on my spider. I have mwb 56mm studs on the way. I don't remember where I got the current ones from. But they stripped big time
There was less than 5 miles on these driving. The current thought is I over torqued the nuts (100 lbs) which weakened the threads, then they came loose and BANG! Off came the wheel. Was glad it was 1/4 from my house under 25 mph. So my X also lost a wheel way back but that one I know was my mistake by not checking the nuts before I flat towed. Seeing the other wheels were not tight I am betting that was the issue. So whe. We put new studs back In (serpent auto) we tack welded each one. Now reading, I probably shouldn't have done that as apparently that makes them more bittle by ruining the heat treat.
My current thought is to use loctite red on the new ones coming in. Then torque it properly. The lug nuts I am getting say 80 lbs. I heard fiat says 65 for the wheel bolts. So what do I torque it to?
Lastly, how does one as they get older loose the fear of it happening again? Heck in my 20s I would have jb welded the wheel on and drove it as fast as I could down a winding road with no worries.
Odie
Where did the idea of torque the nuts to 100ft/lb come from?
~Majority of threaded fastener failures occur due to over-torque during installation.
Fiat wheel cap screws/bolts are M12 x 1.25 thread and usually grade 8.8, this means a torque spec of 60 to 65 ft/lb dry as delivered, not oiled or lubed. If the cap screw/bolt is oiled or lubed, the torque spec is lower by about 20-30%..
M12 threaded fastener torqued to nee 100ft/lb dry will develop about 14,000 pounds of clamp load which is well above the specified ratings for a grade 8.8 M12 threaded fastener.. or strip-rip out assured.
Post threaded fastener rip-tear out, know the internal threads in the hub are wrecked and they will NOT "clean up" by running a tap into the once threaded hole. The proper fix is to remove the destroy hub, take it to a machinist, have them locate, drill, tap a new set of bolt circle holes in the hub ... or replace the hub with a know good hub.
As for installing wheel studs in place of the OEM cap screws/bolts, know the OEM thread fit is for a screw/bolt to be threaded in and out of the hub's internal threads. This means a tight specified thread fit for clearance (folks that have never made threads on a lathe or used precision threading tools have no idea of the precision/accuracy involved (typically 0.001" or 0.03mm range) with specified and proper thread fit.
Industry practice for proper threaded stud installation means the internally threaded hole is very slightly under-sized and the external threaded stud slightly over-sized producing significant friction when the thread parts are assembled. Majority of wheel studs as OEM are pressed in to a non-threaded hole with threaded studs that have a cap/head and serrations on the area under the cap/head. The stud's serrations compress producing what is essentially a friction fit to hold the stud in place..
To properly convert hubs designed for cap screws/bolts, the threaded end of the conversion stud is installed into a clean (use brake cleaner Q-tip/clean brush), ascertain the internal threads in the hub are GOOD. Repeat this cleaning procedure on the threads of the conversion wheel stud.
Apply red Loctite (# 271) on the conversion stud threads, install the conversion stud by hand.. if the stud does not easily thread in by hand, there is a problem. Stop and figure out why.. torque the conversion stud to
NOT more than 4 ft/lb or 48 in/lb...
Loctite is an anaerobic adhesive, it sets once air is essentially removed, the goal is to snug up the threaded parts just enough to produce a non-air seal to allow the Loctite to set. Once the Loctite has set, it will NOT come out easily. To remove, apply heat to about 400-500 degrees F to break the bond.
Once the conversion studs are installed, lug nuts Must be torqued to no more than spec of 60-70ft/lb dry or about 20-30% less if oiled or lubed. Exceeding this on grade 8.8 threaded fasteners will greatly increase the risk of threaded fastener failure or.. the wheel comes off when least expected.
As for the wheel to hub joint, hub piloted wheels are more important than most understand. The hub centric piloting locates the wheel to the hub, the threaded fasteners apply tension to hold the wheel to the hub.... and the entire joint like any other joint is flexi.. this means metal that appears to be "solid" moves like rubber.. or why it is essential the wheel to hub is located by the hub to wheel center fit with the threaded fasteners clamping it all together as the whole assembly moves and flexes within design margins under load.
BTW, JB "weld" is epoxy... it is a glue-adhesive. The "weld" is a marketing moniker... specifically designed and intended to lure-bait potential users in need.
Bernice