alpha8a

Hey guys,

Today when I went to my car, I saw my wheels and it looked like i was missing a bolt. When I looked at it closer, I saw that the bolt was still in there and that the head just sheared off. I talked to a mechanic about this and he said it was probably due to the bolt seizing due to someone not installing it right or over torquing it. I looked at it further and realized something was off because I could jiggle the remains of the stud with my finger. With a small flat head screwdriver, I was able to work the remaining part of the stud out. I'm lucky because if the bolt had been stuck, it would've had to been drilled out which I hear is costly due to all the labor. Does anyone know why this happened?

Viper98912

What kinda lugs you using on those aftermarket wheels?

alpha8a

They were cone seat "tuner" ones from Discount Tire.

mint

Posting because I have those same wheels. Did you do a stud conversion or are you just on lug bolts? I can't really tell.

Either way, were your lug bolts or nuts tapered seat (aka cone, acorn, same thing)? You cannot use the stock lug bolts or any bolt that has a ball seat; it must be tapered to sit correctly and imo, might be the reason leading to a sheared bolt/stud/whatever.

mint

Looks like I posted too late.

If they were no name brand, I would probably switch them out with something like Gorilla, McGard, RadUSA bolts. These three are the top manufacturers of lug bolts.

Viper98912

Then you've got some cheap bolts, or you got the one in a million defect.

I suggest you buy a whole new set and replace all of them.

alpha8a

No I didn't do a stud conversion. The first pic just shows the remaining part of the bolt before I removed it. Any good sites for new bolts?

Twinsin: Do you know what size bolts you used? If you did, then I wouldn't have to do some guesswork in ordering some bolts.

mint

Websites:

Gorilla

McGard

RadUSA

Alas, I myself did a stud conversion so I wouldn't run into this problem (though I did run into a couple of other problems as well in doing so).

I'm not sure on 203s what your stock bolt thread length is, but for the 208s it's 28mm. When I called James@ACGSD (forum sponsor I purchased the wheels from) he said 30-35mm should be good; I would call them up or Forgestar (ugh) to get the bolt shank you need. I honestly don't really have much to offer in terms of how long the bolt shank should be.

c32AMG-DTM

^Good advice from these guys.

Sorry to state the obvious - why can't you take out one of the intact wheel bolts and measure it?

Alternatively, as others mention, contact your vendor or Forgestar directly for the size they recommend. Too short and they won't have enough threads to bite against and hold proper torque. Too long and they can hit dust shields and/or cause other problems by sticking out the back of the hub.

alpha8a

Thought he also had a C55 with the same wheels setup so I was just asking what worked for him. If I knew exactly what I needed, I could just order some w/o having to take them off first.

moosejaw

W203 Bolt Shank Length is 39.9mm

FrankW

chroming process makes the metal brittle and easier to break off when they are over torqued. get some RAD bolts.

loudandheard

Maybe some one was trying to steal your wheels.

alpha8a

I thought about that but didn't see any signs of it. Also, if that was the case, the other 3 wheels probably would've been gone.

loudandheard

Good point

j21importer

I have drilled out lugs before and every time i broke the head off the remaining portion of the lug would spin out by hand

alpha8a

Took the car to Discount Tire today and when they took the bolts off for that wheel, they found that ANOTHER bolt was broken, so two out of the five were broken. All the other bolts for the other wheels were fine though.

1stmeez

Here's the deal. This goes way back to my days in college for Aerospace engineering. Torque settings are set for bolts/studs/etc based not only on the strength of the metal, but also on the amount of pulling force the bolt/stud has to counteract. example: If, during driving your car, the maximum amount of force the wheel could exert on the bolt is 4000 Lbs, the bolt has to be torqued so that it is under more than 4000 Lbs of tension. usually the factor of safety is 3X so the bolt will be torqued so that it is under 12000 Lbs of tension in this example. That way, as the wheel pulls/pushes on the hub with 4000 Lbs of force, the bolt doesn't even know it is happening because it is tensioned at 12000 Lbs. as far as the bolt is concerned, it is just sitting there its entire life being pulled with a tension of 12000 Lbs.

Now, if the bolt is under-torqued, let's say to 3800 Lbs, as the wheel goes around, the the load on the bolt goes from 0 to 4000 Lbs. 0 when that bolt is on top, and 4000 when it is closest to the ground. since the bolt is only tensioned to 3800 Lbs, when the load on the bolt goes to 4000, the bolt stretches a little bit (millionths of an inch) and then goes back to the 3800 Lb load length when the load comes off again.

The problem is, each time this happens (the stretch and release), according to materials science, micro-cracks form in the threads of the bolt. The load/unload cycle happens every time the wheel goes around, which happens about 1000 times per mile, so in 1000 miles, the bolt goes through 1M cycles. So, after a few thousand mikes, the micro-cracks start bumping into each other, and the bolt cracks through.

since the cracks are so small, the sheared surface often looks polished on the OD and grainy on the ID where the bolt finally stretches and fails plastically (it stretches and just pulls apart).

So, if the end of the piece of the bolt has a shiny ring around the outer edge of the surface, the bolt was under-torqued. If it is grainy all the way across, the bolt was over-torqued and just snapped from the over-stress.

That's the story.

spr

I use Rad USA bolts - they work great. You can get whatever length and size you like. I had to use custom 12mm bolts with 14mm ball for my sl55 22 spokes and spacers for the kw's. Really nice guy and fair pricing for quality grade fasteners.

alpha8a

Good to know they are quality. I ordered a set and will be putting them on tomorrow. After Discount Tire put on new bolts, I had ANOTHER one break off on the same wheel. I'm thinking their "tuner spline" nuts of whatever are just crap.

betrezra

A) overtq'd by installer, and/or
B) pre-existing defect in bolt.

Either way I would not trust that entire set of bolts for future service.