Should spare wheel and installed wheels have the same size?

Our tech guru has the answers to your car questions
by Ferman Lao | Aug 12, 2013

Good day! I noticed that the spare wheel that comes with the Chevrolet Trailblazer LTZ has a tire size of 245/70 R16, while the tire installed at the four wheels of the SUV is 265/60 R18. The Chevrolet Service Center staff said that it was really like that, just like in the United States.

If that's the case, then why does the 2008 Ford Ranger Trekker, which I drive, have a 245/70 R16 spare tire, similar to all the tires installed? Is what the Chevrolet staff told me true? Thank you.

Pedz Magtajas


Hi, Pedz. What the Chevrolet Service Center staff told you is somewhat true. In most countries, the spare wheel is usually not an alloy wheel and is not mounted with the same kind of tire as the four wheels and tires at each corner of the vehicle.

The reason supposedly is that the spare wheel/tire is never meant to be a permanent replacement for one that was originally mounted. It's a temporary wheel that's designed to function within a narrower range of performance. However, it is good enough to get you to a service center or a dealer, where a permanent solution to your primary wheel/tire can be done in the case of a flat or some other tire problem. The spare tire is also usually of a narrower width and is mounted on a smaller wheel.

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Another reason is that compact spare tires save space and weight, freeing up cargo space for more important things that you may want to carry around. They also cost the car manufacturer less, which means the pass-on cost to the consumer is less as well. This keeps the vehicle's selling price down. But some manufacturers choose to equip their vehicles with full-size spare tires.

Here in the Philippines, I believe that the norm for most cars is the use of an alloy wheel that is not similar to the ones attached to the vehicle. Exceptions include the vehicles that you own and a number of premium Euro makes. Some of the premium makes actually have no spare tires at all--their makers choose to go with tire inflator and repair kits, or even run-flat tires.

The guys at the Chevy service center you went to should have explained it more thoroughly than they did.

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Hello. Thank you for giving us info about the latest rides as well as road safety. I look forward to more Top Gear feature stories and articles.

I currently have a project car, a 1992 Mitsubishi Lancer (Singkit). I have been busy restoring it to its original luster. What makes this more interesting is the fact that it has an automatic transmission with three-speed gear classification. The car is still original all throughout the engine bay as well as most of the mechanical parts.

The only problem I have is that the electricity being supplied seems to be insufficient (is that referred to as grounding?). I already replaced the alternator. The battery is new. But every time I turn on the headlights, they seem to dim with the idling of the car. If I press on the gas, the lamps would increase brightness, then lose it if the rev goes idle again.

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I have heard of aftermarket parts like voltage stabilizers. My question is: Are they safe to install and do they work at all? Since the car is automatic, proper maintenance of the voltage or electricity is my main priority.

Thank you, and I hope you can give me info.

PS: Singkit's stock steering wheel looks like a joke, and I intend to replace it with a stock three-spoke from other Mitsubishi cars. Do you think this is possible? I don't want to use other aftermarket wheels like Momo as I want to make the car look more traditional than tuned. More power and many thanks.

Francis Martinez


Hi, Francis. Congratulations on your project car. That was one of the most feature-packed compact sedans back in the day.

As a vehicle ages, its electrical system somewhat degrades, as long-term deterioration of the wires in the car starts taking its toll. It's a problem that afflicts all cars, and the best manifestation of the problem is exactly what you just described.

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It can be caused by a number of things. You can try a number of fairly affordable fixes, all of which, however, aren't sure-fire guarantees to resolve the problem.

Volt stabilizers are among the fixes. They do work well enough to justify investing in them. I've never opened one up, but they're essentially capacitors that continuously get charged and discharged while in use. They're designed to keep the battery output--as the name implies--stable at a certain voltage during instances of increased electrical load just long enough for the charging system to "catch up."

You might also want to look into a set of add-on grounding wires to help your electrical system become a bit more "solid."

If the idle rpm of your car is lower than 800, that would also account for the problem you are encountering. A very low idle rpm would mean that the alternator is barely charging or producing enough electricity to keep things running properly.

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Regarding your steering wheel, you might want to look into getting the steering wheel from the 1991-1992 Mitsubishi Lancer GTi. It will fit correctly onto the steering column spline, and will match the rest of the interior. You might also want to check out the steering wheels that came from the same-generation Galants. I vaguely recall that they are interchangeable.



Best regards,

Ferman Lao
Technical Editor

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