Monday, November 7, 2011

Space-saver spares

Quick quiz.
A space-saver spare tyre is:
(a) a get-you-to-the-tyre-place remedy
(b) a good substitute for a blown tyre at motorway speeds
(c) a good substitute for three blown tyres at motorway speeds
(d) a good substitute for a missing 21" hoop

If you said (a) then you have a brain, but sadly, the other three answers appear to be the most commonplace now. I see people flying along the motorways at 80mph or so every day with space-saver wheels on their cars. I've also seen cars on the motorway with three of the four wheels replaced with space-savers, and you guessed it, I've seen people with tricked out cars with big wheels missing a wheel but using a space-saver (meaning one wheel is radically smaller than the other three).
It really baffles me how people's brains can malfunction so badly that they don't understand how dangerous this is. (Once again, I believe that you should understand everything about your vehicle if you are to be allowed to drive it.) Most drivers will never have to use the spare that comes in their car, meaning most of us pay it little attention. The rubber sits there under the floor, perishing slowly, leaking air and when the time comes that we actually need to use it, it's all but useless. But for some people, they see it as the perfect replacement. It's not. The rubber isn't designed for heavy loads and high speeds - it's narrower than all your other tyres and doesn't have the same strength or number of steel belts and cords in it. The tread is generic, so it's no good in the rain at anything other than walking pace, and the wheel itself is pretty flimsy, lightweight steel, not the decent load-bearing stuff your normal wheels are made of. Space-savers should only be used as the manufacturer intended. If you zip along at 80mph on the motorway on a stormy day with one of these things, you're pretty much going to get what you deserve. The only problem is that your stupidity will likely cost someone else dearly at the same time.
There's no excuse for doing this. If you have to use one of these things, don't drive home with it - drive to the nearest tyre change place and just get the damn thing fixed.


Silas said...

And this would be why, when I found out one of my wheels was warped, and I'd got hold of a set of replacements, I took one of the old wheels, with a nearly-new tyre on it, and slung that in the spare wheel well to replace the space-saver. It gets its pressure checked when I check all the others every week, and in about 5 years when the rubber's died, it'll get re-shod with something similar to what's on the running wheels. I prefer having the option to find a decent tyre place instead of a back-of-beyond place that'll charge through the nose because most people have no choice.

One bit of nannying I'd be fine with - I suspect recent cars can almost certainly tell if you've got the spare on, and I'd be perfectly happy with them messing with the fuel maps to make the engine run like a sick dog until the proper wheel's back on.

Kristaps B. said...

I'm wondering: apart from messed up handling and dangers of rupture - does space-saver tires cause additional wear to differential gears? Because of the constant rotational speed difference the planet gear inside differential's carrier box is constantly spinning.

Chris said...

I like Silas' idea. Could use the TPMS sensors - when one of them isn't spinning (meaning it's off the car or in the trunk), hobble the engine :-)