“The Lexus made a funny noise so I drove back and took the Hyundai” are not words you hear every day.

But it’s words I heard last night from Mrs P.   And it turns out there was a funny yellow light on the dashboard too.  Here it is, in the bottom right corner.

That’s the light that tells you a tyre has low pressure, part of what’s called a TPMS, or Tyre Pressure Monitoring System.  These are really good because with modern cars and tyres it can be hard to tell when you’ve got low pressures which lead to tyre damage, poor handling and maybe even a blowout.   You can buy TPMS systems and fit them to any car and even trailer, and it’s worth it.  This Lexus has one built-in, perhaps because it’s a popular car in the USA where such systems are mandatory – as they should be here in Australia.

So while it’s good that the Lexus has TPMS, it’s a pretty average unit.  All it tells you is that one tyre is low.  Not which one, or by how much.  You need to get your tyre pressure gauge and figure that out for yourself, which given this car has an electric tailgate and steering wheel adjustment seems like a lot of manual effort.  Anyway, I checked the pressures which were a bit low.  Pretty normal for a press car.  So this happened:

Connected my trusty portable air compressor to the battery to pump in a few more PSI all the way around.  I then hopped in the car and drove off…but there was this flapping sound.

Now if there’s one thing you learn about cars, it’s not to ignore odd sounds.  They tend to be expensive.  So what do you do if you hear an odd sound?  You try and figure out what it is, or gather data for someone else.  Examples:

• is the sound speed dependent – does it get louder/faster as you speed up
• is it engine speed dependent – worse at high revs, better at low
• when you turn left or right
• under brakes

and so on.  In this case, the sound was very much speed-dependent, and apparent from anything other than walking pace.  I did another little test – from about 15km/h killed the engine and let the car coast…the sound was still there.  Next was to lower all the windows and try and locate which corner the sound was coming from, because usually these speed-dependent, engine-independent sounds are wheel or tyre related.

The answer was the right rear tyre.  So I got out of the car and inspected carefully, looking for maybe loose trim, a cat stuck in the wheels and so on.  Nothing.  Then I inspected the tyre…still nothing.  This is where experience comes in, so I got back in the car, rolled it forwards half a metre and inspected the tyre again.

And found this:

That’d do it.  A big old nail or something jammed into the tyre, making a flap noise as it hit the bitumen.  The nail had jammed in such that it didn’t deflate the tyre, but had caused a slow leak which set the TPMS off, and of course made the audible noise heard from inside the car.

Fortunately all this was close to home, so it was easy to pop the space-saver spare on.

No, that is not the standard Lexus jack.  It’s my garage jack, and I may as well use that than mess around with the car’s standard jack when I’m running late.

I put the damaged tyre in the back where the space-saver had been.  As usual, it didn’t fit very well.  Typical trap with space-saver spares and one reason why I’d like to have them all rounded up and made into a bonfire.

I delivered the tyre to Toyota HQ and rolled it up to a surprised receptionist.  I thought perhaps as the damage was in the tread area it’d be repairable, and if it was a bush repair I know it’d be fixable but Toyota have played safe and ordered a new tyre.  That will be here in a couple of days, and hopefully I’ll be able to complete the test which you can read about next week.