I read somewhere recently of somebody using a small diameter metal hole saw that fit over the shank of the broken lug bolt and was able to cut off the spherical seat. Sounded like it took a few hole saws to do it.

 

The way this has been reacting to standard cobalt bits I would expect that you would need carbide tip hole saws. I have not had very good luck with those in the past and could see going through 3 or 4 per bolt. But the idea is worth trying. Better yet TIN or TiAIN coated annular Mag drill bits.

 

Those bolts are notorious on the W210 forum for being a right bastard to deal with if the shank breaks off.

I preemptively replaced all of them on my 210 wagon with bolts that didn't have the shank; I've been meaning to do that on my 107, too.

 

A little anti size on them and proper torque and there is no problem.

 

More recently (this Spring), my wife had a slow leak in one tire. I wanted to take the wheel off and take it to a tire shop for repair. I could not move the lug bolts. Shop had over-torqued them when swapping summer/winter wheels.

I drove the car to my local garage. They got the bolts out - Said they used heat plus an extension on breaker bar. I was happy I no longer had the necked down original bolts!

Darn tire is still leaking

 

Wheel bolts = 81 ft-lb
I'm really OCD about wheel torque for all my vehicles :wink

When I purchased aftermarket wheels/tires from TireRack.com, the wheel bolts would not tightened up properly on the front. Rear was OK. TireRack supplied special wheel bolts. Took it to a tire shop and they got them tighten. Later I got curious about why this happened and I suspect there was a plating on the threads and in addition the thread was not long enough on the shaft. I used a thread tap on those bolts to lengthen the threads.

 

TireRack should know, but to be honest, I wouldn't trust many of the aftermarket wheel bolts unless the grade of steel is specified. Especially if they don't fit or torque properly from the outset.

The 81 ft.lb torque would be based on the strength of the steel used and the surface coating of the OE studs. The chart linked below shows how much the maximum clamping force and allowable torque changes when using different grades of steel. It also shows the difference in torque needed depending on whether bolts are lubricated, plated or dry.

This UK site says their bolts meet UK/EU specs and are class 10.9 with zinc plating. After many uses, the zinc plating probably wears off, so maybe with old bolts, we should use a little lube on the threads? Or maybe not. ay depend on where you are. Salt, rust etc.

 

Some where in the MB 107 docs they discuss torquing the wheels. Back in the day of those manuals MB did not suggest using a torque wrench. They recommended technicians calibrate there impact wrench and themselves to the use of the impact wrench. This technique can be successfully done with a reasonable level of accuracy.

I'm sure today's manual say to use a torque wrench.

 

If you use the Mercedes lug wrench you will not be able to over torque them.

 

usually one of the first jobs with a new acquisition

is a set of RAD locking wheel bolts from these chaps.

Locking Wheel Nuts and Locking Wheel Bolts from Alloy Wheels Direct

They also do standard bolt sets,, and specials. I had a set of w211 adaptors to a w210 hub. Prices as keen as Mercedes, quality is easily as good or better. Can't recommend them too highly.:nerd

 

Well my carbide tipped drill bit came in. But it turned out I didn't need it. I was a bit reluctant to use the carbide tipped drill in a hand drilling operation. So I gave it a try with my regular 3/8" black oxide HSS drill followed by a 1/2" drill bit. These went right down without any issues once the bolts were piloted with the TiAIN coated smaller bit.

 

Well it finally happened to me. Three times. The old broken wheel bolt issue.

I purchased a complete rear axle assembly from a junk yard. He told me he could not get one wheels off. I told him to send as is and I would get it off. It turns out there were three broken wheel lugs. So I made myself a drill bushing and tried to drill a 1/8" pilot hole down the center of the three studs. All was going good until I got near the spherical seat which I at least needed to get beyond. I now know that MB heat treats the bolts from the top of the spherical seat to the end of the threads. using good quality new cobalt steal drill bits.
the drills went down about 1" without issue then came to sudden stop at a point just above where the spherical seat is. Changing bits did not help.

Then I remembered I had one drill bit that I was highly impressed with and figured I would give it a try. It was a number 3 bit ~1/4 so it would have been the next step up in my drilling anyway, and I was piloted enough that I could use it. This bit is called a super long life bit from McMaster Carr see

McMaster-Carr

This bit drilled out the stud to the required depth without any significant problem. Needless to say these will be my new replacement drill bits. These bits are not even cobalt. They do have a cobalt version at about 3 times the price but these beat the standard McMaster Carr cobalt by a long shot.

So for the moment Im stuck until I get a 1/2" diameter Super Long life bit of the Carbide tipped bit I ordered from Amazon comes in.

First couple of pictures show the 1/8" cobalt bit in the drill bushing. Last picture shows the Super Long Life bit with its purple coating.

@roncallo
As with everything in time, names and products and websites change. Do you know the part number or anything about the drill bit you suggest getting for this drill-out?

for me, I’ve gotten no shank outside the ball, broken off right at the ball. Both good and bad.

 

@roncallo
As with everything in time, names and products and websites change. Do you know the part number or anything about the drill bit you suggest getting for this drill-out?

for me, I’ve gotten no shank outside the ball, broken off right at the ball. Both good and bad.

If its broken right at the ball you wont have as far to drill as I did so you wont need a deep drilling parabolic bit, but it wouldn't hurt especially for the initial 1/8" pilot hole. They are almost 2 times the price. So consider using them only for the 1/8 initial hole.


1/8 parabolic

Non Parabolic

 

Thank you John!!