Spare tires and similar solutions are crucial for keeping us going forward, specifically because each of us encounters a puncture every five years. However, you can’t drive on a spare tire like you could on regular tires.
That’s especially true for driving fast. See, spare tires are only designed for emergency driving, and not for aggressive acceleration, cornering, or braking. For those reasons, you should drive much slower when you have a spare tire attached.
But how fast can you drive without worrying about safety? Let’s revisit all popular spare-tire solutions and answer that question.
Why You Need to Drive Slow on Spare Tires
Before I tell you the numbers, let’s see why spare tires aren’t suited for fast driving. Most spare tires have a narrower tread design, which significantly reduces grip and traction. This means that your car will have longer braking distances and less stable cornering.
Moreover, having one tire that doesn’t have good traction, together with three regular tires, will make the handling unpredictable, something that can surprise amateur drivers.
Now, even if you have a full-size spare tire, it probably won’t be inflated properly – tires lose pressure over time. Besides, most full-size spare tires are pretty old – no one pays for a new full-size spare tire. And, older tires also have worse traction, grip, and braking.
Ultimately, spare tires are more prone to smaller punctures, but also blowouts. And, having a blowout while driving at highway speeds might make things very difficult for the driver and result in a crash.
For all these reasons, you should be careful when driving on a spare tire, regardless of the type.
Full-Size Spare Tires
Overall, full-size spare tires are still the best solution in terms of safety and ease of mind. Provided the tire in your trunk is still usable, you can use it for driving at higher speeds, at least in theory.
However, no one can tell you how fast you can really go. Some people have some really good full-size spare tires in the trunk, others don’t. That’s why you should ask the technician for the state of your tire each time you visit the tire service.
As a general rule of thumb, I would say that you should lower the speed for around 20% at highway speeds and around 10% around town. That way, you will ensure that your car performs safely.
What you should definitely avoid is driving over the speed limit. This applies even when you drive on four normal tires, but it’s particularly true if you drive on a full-size spare tire. Otherwise, you risk your safety but also the safety of your passengers and other traffic participants.
Donut tires, also called space-saver spare tires, are much smaller and narrower than regular tires. Car manufacturers started employing these tires to reduce the weight of the cars, but also to free trunk space. And, interestingly, car buyers often don’t complain about this.
Nonetheless, due to the narrow tread width, donut tires perform much worse than normal tires. The traction is severely reduced, to the point of being almost non-existent at some speeds. Moreover, having one donut tire attached will result in unreliable handling.
For those reasons, car manufacturers put a large sticker on each donut tire, which says that you shouldn’t exceed 50 mph (80 km/h). And, there is a reason for the warning – donut tires are not safe to drive at highway speeds.
Moreover, these tires are prone to punctures and blowouts, which is another reason why you should avoid using them for high-speed driving. And, finally, the tread compound on these tires isn’t very durable – it won’t last long if you drive too fast.
Tire Repair Kits and Sealants
The latest “innovation” in modern cars is installing tire repair kits and sealants instead of spare tires. This solution works as advertised, but it also has many disadvantages. First of all, tire repair kits don’t work on punctures larger than 4 mm, so in case of a blowout, you are stuck.
Furthermore, these kits aren’t a long-term solution – you will still need to repair the puncture at the earliest opportunity properly. Crucially, though, driving on a tire repaired with sealant isn’t very safe, especially at higher speeds.
For those reasons, the tire repair kit in your car comes with warning stickers, which say that you can only drive up to 50 mph. You can even put the sticker on the A-pillar inside the cabin to remind you not to drive faster.
And, adhering to this limit is extremely important. Tires filled with a sealant don’t work well at higher speeds and adversely affect stability.
Run-flat tires are an ingenious solution – they can be used even without any air inside. That’s because these tires have much stiffer sidewalls, which can carry the weight of the car easily.
However, that doesn’t mean that you can use these tires carelessly when improperly inflated. The stiffer sidewalls should only be utilized in case of an emergency. Otherwise, you risk damaging the sidewall and rendering the tire useless. And, the last time I checked, run-flat tires aren’t exactly cheap.
Moreover, despite the stiffer sidewalls, these tires aren’t safe for driving at higher speeds when punctured. Most modern run-flat tires can only be driven up to 50 mph (80 km/h), and no longer than 50 miles (80 km/h).
Accordingly, each time a run-flat tire loses the air inside, you should never drive above 50 mph – it’s simply not safe enough.
I hope that you learned a valuable lesson today. Driving on a spare tire is only safe when you drive slowly and carefully. Otherwise, you risk losing control of your car, and if that happens at higher speeds, it’s usually much harder to get it back in line.
But what are your thoughts and experiences on this matter? Tell us in the comments below – we’d really like to hear. Also, Also, if you found this article useful, share it with your friends – they might learn something valuable, too.