Rear mounted spare: To cover or not to cover?

[CQPRADO Lurker Find all posts View Profile Close CQPRADO]

Re: Rear mounted spare: To cover or not to cover?

Travelling down the road at 110km/hr sideways will ensure your heart is in the right place when a tyre lets go. I had one delaminate completely, not deflate but delaminate, and it was the spare that was left on by previous company person when I took over the car. The spare was rotated to the right rear after 4 years, and it was that one which let go. Dunlop warranted the repair to the destroyed rear panel/bumper etc, but it could have happened while towing my 23 ft Jayco Sterling. Picture pots and pans strewn down the road...
My suggestion is to not only cover, but ensure the spare is rotated in.

[Jacto Senior Member Find all posts View Profile Close Jacto]

Re: Rear mounted spare: To cover or not to cover?

This is not an "urban myth" and I have seen it happen many times during my 35 years in the tyre industry and have experienced it on one of my tyres fitted to the rear door of my 78 BJ40SWB landcruiser. I also had a dealer refuse to be interested in trading my spare because it was more than two years of age and never been fitted to my Prado. Basically what happens is that the UV rays suck the ozones out of the rubber causing the rubber to perish and weaken.

This is a photo of a Bridgestone desert dueler that failed after sitting on the rear door of my BJ40 while it was sitting in my driveway in Darwin and when it let go it shook all of the windows in the house. I actually thought there was someone outside the front door letting off a shotgun. As you can see the tyre is just about new tread depth but it had been sitting on the back door for more than two years as a spare, this tyre was only used as a spare because the rest of the tyres were Dueler mud terrains and did not match the A/T spare.



If the spare tyre is rotated in with the rest of them, this lessens the problem because each tyre is getting its turn on the spare every 10K or so and is not been subjected to lengthy periods in the sun.

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Re: Rear mounted spare: To cover or not to cover?

When I bought my Prado a few years ago it had an uncovered Bridgestone Dueler on the back as a spare which had about 80% tread left on it. On the 2nd trip to Fraser Island 1 year after I bought the car, I had it parked right next to our camping spot in the shade in the morning and I noticed the tyre was starting to let go. It was wierdly out of shape and it wasn't like that the day before. Later on that day the belts popped out of it and the tread opened up on the top like a can of baked beans.

Too bad if I got a flat while I was there, but luckily I didn't. When I bought another spare tyre I made a point of getting a soft spare wheel cover from Supercheap as it was the UV rays which made the tyre perish prematurely as the car was always parked out in the sun at the time. If your car is shaded for most of the day when you're at work then you have nothing to worry about. This issue would be unheard of in sedans unless the tyre was painfully old, as it is always shaded in the boot, and the same goes for Landcuisers with the spare wheel tucked up underneath the vehicle. But I wouldn't rely on an uncovered spare tyre that's been exposed to the sun for 2 years or more.