Broken bolt in wheel hub.

Last week I was called out to a Mercedes SLK with a flat tyre. The customer had tried to remove the wheel himself to fit his spare, but found that he could not move the nuts.

We carry better tools than those in the cars tool kit, but even I was struggling with two bolts. I explained to the customer that they had been greatly over tightened and possibly cross threaded as I could only get them to move 1 or 2 mm before they locked up. The car had been to his local garage only a week ago to have new brake pads fitted, and he knew they put the bolts in with an airgun. He needed to get the car back on the road so asked me to continue trying even if it broke the bolts.

I gave them a squirt of WD40 and continued to move the bolts back and forth, at which point one did come out. It was then possible to see the problem, the previous garage had somehow bent the bolt which caused it to jam in place. I continued to work on the second bolt but with the strain of being bent it broke off half way through the nut, leaving nothing to put a socket on, but also leaving the wheel still stuck on the hub. There was not enough of the nut head to even get our locknut removal tools to grip on.

The only option was to drill it out. We started with a 5mm drill and managed to get a hole straight down the middle, the centre of a bolt is softer steel. We then moved onto an 8mm drill, then a 10mm drill. The problem was that now as we neared the edges of the bolt the steel was hardened. It took two 10mm drills before we go the hole deep enough as the first one burned up. We then went up in one mm increments until we got to 13mm at which point the nut head came off, and I was able to remove the wheel. Once the wheel was off, I was able to get an easy-out bolt extractor onto what was left of the bolt and removed it from the hub. It was easy to see that the bolt was badly bent which had caused it to jam against the wheel. The threads in the hub were OK, so all that was needed were two new bolts.

I then checked the tyre to find it had worn right down to the wires, which is why it had deflated (not sure why the garage that replaced the brakes last week didn't see this, as the car had only covered a 3 miles in that time, so the problem must have been visible).

Luckily when we come out to a flat tyre we always opt to bring a new tyre just incase it is required. This was one of those times…. I soon had the old tyre removed, the new one fitted & balanced, then refitted it to the car. It was only held with 3 bolts, and the customer was going to go to Mercedes to get further bolts. Job complete.

We at Hometyre always replace nuts and bolts by hand, then finally tighten them with a torque wrench, this way they don't get cross threaded or over tightened.

Similarly I have been called out to remove locking wheel nuts on two vehicles this week where the locking wheel nut keys have been damaged by over zealous mechanics trying to remove the locknuts using an air gun. Most locking wheelnuts come in a plastic box, on the box lid it states…. 'do not use air guns'. They never learn, and unfortunately the vehicles owner is often left to pay for the removal.

For more info on locking wheelnut removals take a look on our website here.