Tuesday, June 21, 2005

Manly ritual + overly hot day + absent minded stupidity =

...Almost getting my fat ass killed.

So I engaged in the manly ritual of home car maintenance the other day; finally getting around to changing the brake pads and wear sensor that had been complaining for the last couple months.

Oh and thank you very much to the reader who donated the Minitex high performance low dust brake pads, and wear sensor (you know who you are, and feel free to sound off if you like; I just didn't want to do so without your say so). Vastly increased braking performance over the stock pads that came with the car; even though they are jsut the direct replacement part number.

Honestly, I dont know why more people don't change their own brake pads. It's the easiest job in the world, and other than brake dust (of which there was almsot non surprisingly enough), it's nowhere near as messy on most cars as an oil change is. On a BMW they charge you a MINIMUM of $200 jsut to do the fronts, when you can do it yourself for $50, and get better pads in the bargain.

The basic process is pretty simple:

1. Loosen lug nuts (but dont try and remove them, especially on a BMW, which uses wheel studs not nuts)

2. Chock the wheels and raise the car. I use a bottle jack that I keep in my trunk organizer rather than a scissor or lift jack. It takes up a hell of a lot less space than a scissors jack (about the same as a 1 liter soda bottle), and is still very safe and effective.

3. Finish removing the lug nuts, and remove the tire, placing it behind the rear wheel (as an extra chock).

4. Spray with brake cleaner and wipe down if necessary (you may want to wear gloves for this bit)

5. Remove the caliper. For my 5 series you remove retaining clip, then pull off a pair of plastic caps on rubber boots, and you use a torx driver to remove the very not corroded or gummed up caliper studs; which takes all of 30 seconds. Some other cars are not so friendly. I did my brakes on an early Ford Escort GT lo these many years ago, and you had to damn near take the suspension apart to get the calipers out. If you have one, you should also disconnect the wear sensor.

Be careful not to let the caliper hand from the brake lines. Some vehicles have handy protrusions to hang from or shelves, but a bent coat hanger works jsut fine.

6. Pop the pads off, and the wear sensor if you have one (I do) and inspect for any abnormal wear.

You know what pissed me off.. the damn things were still well within spec; but they were cheap outoparts store special pads that chatterd and squealed all the time anyway. But the best bit? The reason the brake sensor kept going off, was that some genius had put the wear sensor in BACKWARDS (which takes some doing BTW, it is NOT designed to fit that way).

Also Inspect the rotors/discs (whatever you want to call them) for unusual wear. If you have ABS inspect the ABS sensor rings, or sensor notches or pads.

Mine were within spec, with no scoring; but they ARE somewhat dished, so I should probably order a new set. The thing is I want to wait until I have the new wheel and tire combo, that way I can put in the bigbrake kit. Even at an online discounter a new set of front rotors is going to run me $100 (plus shipping... hmmm, pelican has brembos plain rotors for $50 each. Not bad).

7. Compress the caliber with a c clamp or something similar; and fit the new pads. Remember to use antisqueal on the backing plates. I also recommend buying a pad with a syntetic bonded antisqueal backing plate (like the minitex).

8. Re-hang the caliper, and bolt it down; making sure you properly route any lines, and the wear sensor.

9. Replace the wheel, carefully threading the lug nuts, or wheel studs (as on my car), wrench tight, but don't try and torque down.

10. Lower the car, torque the nuts/studs down throughly, in a star or cross pattern. Then drive the car around for a few minutes, stop, and retighten your nuts, roll the car 1/4 wheel rotation, and tighten again, another half rotation, again, until you've retightened all nuts to the proper torque.

Repeat for both sides. At this point it is advisable to bleed the brakes, but we did a bubble test, and got nothing; plus the brake fluid is more than a bit toasted, so I didnt want to bleed it right now until I can do a full flush and clean out the system. We did the overpump, top-up pump-out mop-up routine, then I went around the block over heating the brakes as I went, and did it again. That's about as good as you are going to get without a full on flush and bleed.

Now on to the "fun" part...

I was driving from work to my mothers house tonight, and I started hearing a clopping sound, that was at about half wheel speed, but that seemed to get worse up to about 30mph, then as I sped up it would smooth out as I got faster, and get worse again as I slowed down.

Obviously this worried me, so I stopped and inspected the wheels, tires, lines etc.. but I couldn't see anything.

I picked my brother up, and we were heading to the movies, and it was getting worse. I pulled into the parking lot, and I had a thought, maybe one of the wheel studs had come loose inside the cover...

When I pulled the cover off the wheel studs, one of them was sticking half way out, and the rest were finger tight at best.

You see I did my passenger side brakes first, and my drivers side second. It was 108 out, and I was pretty damned tired out . I had followed step 9, and the first part of step 10, but I forgot to re-torque the nuts after driving around; and they had loosened up completely.

The clopping sound was the wheel flapping back and forth, working it's way off the hub. As I sped up to 30 it accelerated the flapping, but over thrity the gyroscopic effect was enough to keep it smooth... or at least it would be until I hit one good bump at 70 mph on the highway, wherupon my drivers side front wheel would have gone flying off, my front suspension would have dug in to the road, and most likely I would end up on the roof over the median...


Then drive 10 miles, and CHECK THEM AGAIN

Then check them 1 more time after 100 miles, and you should be fine.

They are now torqued down so much that I actually slightly bent a brand new autozone brand chromoly lug wrench (yes I am that strong). I am reasonably certain that I overtorqued them, but I know how strong those Dornan studs, are, never mind the wheels and rotors, I'm not worried about them being damanged, and most importantly, they are not going ANYWHERE.

And I'm STILL going to check them again after my drive in to work tomorrow.

UPDATE: Torque Wrench acquired ($25 GreatNeck screw handled ratcheting one from autozone. Yeah its junk, but it works til I can afford a matco), and torque checked. I wasn't as far overtorqued as I thought.