Friday, November 4, 2011

Shake, Rattle and Roll

The next day after getting the seat belts delivered, I took the day off and went with Shelly (the heretofore unnamed patient wife) to the Waterford Fair in Western Loudoun.  It was another glorious drive through back roads to a historic setting.  Waterford was settled in 1733 and still feels like it probably did 100 years ago, so it's fun to drive the MG in a setting that makes it look new.  Since the tires were looking very low, we stopped and filled them with air.  To my surprise and horror I found they were very low (about 10 PSI) so I filled them to the max rating on the tire (about 32 PSI).  This probably explained at least some of the inaccuracy of the speedometer I'd noticed.  Since the tires were under-inflated, their effective radius was less than normal, which meant that the speedometer (which really just counts wheel rotation and translates that to miles per hour using the wheel circumference through a series of gears) was over-reporting my speed.
Waterford ca. 1930. It looks more or less like this still today, but now the town is in color.

With the speedometer closer to accurate, the seat belts in, and a trip on bigger roads than we'd been on before, I was driving a little faster.  Unfortunately I found an alarming amount of shake in the car around 60 MPH.  The body panels were audibly and visibly rattling, the steering wheel and gear shift shook at least a half inch back and forth in my hand.  Shelly wondered (out loud) if we were going to live through it all.  Below 60 it was bearable, and if I took the car above about 70 it seemed to get a little better, though I was scared to go much faster both because of the shaking and because the tachometer was showing the engine was at "red line" (more on this later).

Are these the culprits?
After researching a bit, the two most likely causes were the wheels being not perfectly round, or by something with the drive shaft.  If the drive shaft itself was bent, or the U-Joint was badly worn these would be the most worrisome and dangerous.  However, in these cases the problem should be noticeably worse with a foot on the gas, and my shaking was just as bad if I put the car in neutral and coast at the magic speed. I concluded that the issue must be related to the wheels, but just to be safe I crawled under for a look when we got home. Again to my horror I found that of the four bolts that attach the shaft to the gears of the rear axle, three were loose and one was missing entirely (confirming that I do - literally - have a screw loose). I tightened the loose ones and bought a replacement for the one that was missing (5/16", fine/24 threads per inch, one inch long hex head bolt, with self-locking nut - hard to find locally).  That definitely helped a little, but only cut the shaking down from its extreme - it was still very bad.

I decided to do what any sane person would do in this situation: I continued driving for several weeks below 60, or above 70, accelerating as fast as possible between the two. Will the car literally shake itself apart? Will Shelly ever get in the car again? Stay tuned to future episodes to find out!


  1. Assuming you are able to post.

  2. Geoff - I'm totally envious of your MGA. I inherited an infatuation of MGs from my Dad and Grandpa. I don't know if you even realized I have a '79 MGB in the garage. Love your blog of MGA adventures, too. I look forward to seeing it when I get back to NoVA. - Kevin S.

  3. Good to see they let you come up for air! I got to see your MGB right before you moved. Come to think of it, that's probably what got me started thinking again about buying an MG! We'll go out for a spin together when you're in town.