The joy of solving a problem

Some days ago, I noticed a new humming noise from my wheels as I drove to work. It wasn't a loud noise, just a small murmur in the background if you listened carefully. I decided to look into it on the weekend but by the next day, all I could hear was this faint nuisance that I could not put out of my mind. I had to solve this before it drove me mad.

The first problem was to figure out the source of the noise. Was it tyres, wheel bearings, gearbox or transfer case? Hopefully, it was not the gearbox or transfer case - that would be expensive. But it was also easy to check. If it was the gearbox or drive-train, then the noise should go away when the gearbox was not engaged, i.e. when car was rolling in neutral. I slotted the car into neutral and listened. The noise was still there. That narrowed it down to wheel bearings or tyres. I was wondering how to figure this one out when the road surface changed from concrete to asphalt and the noise changed too. That narrowed it down to the tyres. Had it been wheel bearing noise, it would have remained the same regardless of the surface the tyres came into contact with. This was a relief, for wheel bearings can be expensive.

The easiest solution now was to change all four tyres. But why spend Rs 40000 if I could narrow it down to one or even two tyres. On my drive to work the next day, I listened to the noise carefully trying to gauge which corner it emanated from. I couldn't pin it down with the AC on, but then I tried something else. I rolled down the windows on one side of the car and then the other. The noise was louder when the windows were open on the left. Down to two tyres. Then I tried it with the left front window and the left rear window. No difference. The oncoming wind made it difficult to notice any change in amplitude.

I looked at the odometer. I was due for wheel balancing anyway, so the next stop was the tyre dealer.
I watched as they took each wheel off the car and mounted it on the wheel balancing machine. Got the wheels done on the right side of the car first and then paid close attention as they worked on the wheels on the left. There was no visible damage on the tyres themselves, but the attendant noticed that the valve on one of the tyres was different. I had had it changed a few months ago when getting a puncture fixed. Got the valve replaced and on the drive home the noise was gone. Net spend was Rs 800 for the wheel balancing and alignment and another 120 for the valve.

Now if you will excuse me, I need to go plan how I am going to spend the 11000 rupees I have just saved.