Wheel studs breaking off

so this happened. Today I am thankful for this one single lugnut and stud

 

How does this happen?????

 

Impact Wrench.

 

Can’t trust any shop

 

Would be wise to visually check the studs on the other 3 wheels for cracks...

Could also be tightened with hand tools to the wrong torque setting. I say that because the spline drive socket is often a thin-walled chrome socket, which in most shops indicate it isn't impact-rated.

 

So did they break off while driving?

 

At 70mph

 

I'd be checking all the other wheels. If I found one more missing, then I would replace all wheel studs on every wheel. Torque each nut to 85 ftlb with a torque wrench, not an impact wrench or a bubba titenuff wrench.

This is an area to be extra cautious. It would be an exciting ride to see your wheel passing you on the road...............

 

What is the proper torque on a vehicle that has, changed from flat(hub centric) to conical(lug centric) seat lug nuts, though?

For the same torque value, flat seats have a greater clamping force than conical; most of the torque used on conical seat is used overcoming nut-to-seat friction.
Torquing to factory spec may not be enough.

 

Bought a bunch of new studs at $9 a piece

 

Oh boy, that gets lost in the wash with all the other variables that change friction: zinc/black oxide/IVD coating on the wheel studs (esp. if studs aren't OEM), any overspray of oil/antiseize/grease in the threads, chrome on lugnuts vs any other finish, health of the coating on the wheel's lug holes... Speed will be a factor as well (manual torque wrench vs. impact with torque stick).

 

Rock Auto has them at $10 for a pack of 10, $1 apiece: https://www.rockauto.com/en/moreinfo.php?pk=1060129&jsn=839

That's the exact P/N I used when I snapped a single stud on my truck (cheap torque wrench didn't click...)

 

Not a "rule" by any means but I put one drop of oil on each stud and torque to 88 ft-lbs (wet) on my SCS wheels (which are still hub centric) that us conical seat extended thread splined lug nuts and wheel the crap out of it and have driven aggressively and never once had an issue with breaking a stud or having anything come lose always takes more torque to take them off than it does to put them on.

I swear I have I have seen this happen with those wheels before IIRC they aren't hub centric at all and Toyota needs hub centric wheels or you start snapping studs from stress.

Just my .02 for ya.

 

The lube would be better served on the lug seats.
Of applied torque on conical lugs; 50% is consumed by nut-to-seat friction, 40% is consumed by thread friction and 10% is actual clamp force.
Both practices have the same result; more clamping force from the same torque value.

I would argue your wheels are lug centric despite having a matching bore.
If the hub circle doesn't coincide with the bolt circle, the bolt circle will want to influence the position of the wheel. If the hub to bore fit is so tight as to not allow lug centric centering, it results in interference in the lug nut and lug seat interface...which can lead to wheel stud failure.
I invite you to measure your hub bore; betcha it runs closer to 108 than 106.

 

Exactly...
"Proper torque" was determined with known OEM properties.

 

Torque is 83 ftlb. Most folks will round that to 85 ftlb.

If you are putting lube on anything, then you run the chance of over torque on the lug system.

Suggest you stay with the recommended torque for this.

 

When I got the truck I did find a smashed up one of these in the bed, none of the wheels have these center caps on them, could that be the problem?

 

Are/were you using correct lug nuts?

 

Center cap has no function other than decorative. Not the cause of the broken stud.

 

The small procomp ones that are made for the wheels