Run flat and regular tires are the two different types of passenger tires. They look the same from the outside, however, when it comes to the inner structure, they become dissimilar significantly.
Regular tires are vulnerable to any outside effects like nails or even sharp rock. If you get flat, you have to change this tire immediately unless you don’t wanna break your wheel. Of course, this is not always possible. Maybe you don’t know how to change tires or you may be inadequate in terms of equipment. As a result, you have to wait for the road assistant or one of your friends who may help. That’s the point where the ‘Run-Flat’ tire idea comes up.
The internal structure of run-flat tires is designed differently. These tires can be driven at a maximum speed of 50MPH up to 50KM in case of punctures. So, run-flat tires are basically made for security and safety issues. But the trade of what? As a former Bridgestone engineer, I’m going to expose the difference between regular and run-flat tires.
At a Glance
Choosing between the run-flat and regular tires is totally up to your expectations. In this case, you have to decide between safety or performance. Well, it doesn’t mean that run-flat tires can’t provide decent performance or that regular tires aren’t safe.
These two have different focuses. The below points will explain the situation better.
| Run-Flat Tires | Regular Tires |
|---|---|
| In case of puncture, it’ll take you to tire mechanic | In case of puncture, you should replace it asap |
| You don’t need spare tire | You should have spare tire |
| Durable to external impacts | Lasts longer |
| Increase your fuel consumption | Offers a slightly smoother and quieter ride |
| You should have tire pressure monitoring system(TPMS) | Offers better handling, more responsive |
(Repairability Table) | Repairable |
I do highly recommend checking the below link before making any run-flat tire purchase. Since these are concept tires, following the people’s buying trend is crucial:
The run-flat is basically the system that keeps you on the road for a while even if your tire gets flat.
In order to properly understand how this system works, you first need to know the working principle of the tire.
I’m trying to explain this as simply as I can.
Table of Contents
Working Principle of Tire
The idea of the tire is coming from the verb roll. Rolling is the movement of objects with the least energy expenditure. In fact, most of the action happens because of the weight of the object itself. That’s why most vehicles have tires.
So, the real thing you should know out here is how tires carry the load.
Unlike most people think the answer is by the help of air pressure inside.
In order to provide traction, tires should contain fluffy materials like rubber. The rubber itself is elastic. Hence, it flexes with the load and lost its shape. In order to avoid this, rubber is supported by solid materials like steel. But that’s not enough on its own.
At this time production has two options, make a fulfilled circle that contains tons of rubber and steel or use rubber and steel as a shell and fulfill it with high-pressure air.
The first option doesn’t make sense at all because the tire becomes so heavy and even making it roll is back-breaking.
So, the second option works best. Unlike most people think, compressed air has a very high load-carrying capacity.
I explain all of this because I wanted you to know that the air pressure inside of the tire does all the work regarding load carrying. So, if you get a flat tire it basically means that one of your tires can’t carry the load anymore, and your wheel kinda runs ashore.
What does Run-Flat Mean in Tires?
Run-flat tires are tires that can still be used after a puncture.
The main idea is to get you to a mechanic or a tire dealer. Hence, after the puncture, you can use this tire for 50 Miles at a maximum speed of 50 MPH.
How does Run-Flat Tires Work?
The run-flat system absorbs the load-bearing disadvantage of the flat tire. It undertakes the tire duty for a while.
So, the idea is to support the inner structure and help the tire keep its shape and loading capability at the maximum possible level.
There are two different types of run-flat systems.
Self-supporting and support ring system. Even though these two provide the same feature, due to their way of making it, they have advantages and disadvantages. Let’s talk about them one by one.
Self Supporting Run Flat Tires
This system is mostly used for low-profile tires. In fact, that’s the reason most sports cars have run-flat tires.
Self-supporting run-flat tires have reinforced and stiffer sidewalls that are capable of temporarily carrying the vehicle load.
I hear the question says if it’s that easy, why other tires aren’t run-flat?
Here is the deal, reinforced sidewalls extremely decrease the riding comfort. The robust sidewalls don’t flex that much. Hence, they provide a rough ride. In fact, that’s the reason this system is generally used for low-profile tires.
Low-profile tires are used on sports vehicles because they’re lightweight tires because of their shorter sidewalls.
Since these tires are used on fast cars, they should have strong sidewalls for safe cornering. The short sidewall also helps in this case. The flexing capability of the short sidewall is limited. Hence, they provide decent cornering stability at high speeds.
About the low-profile run-flat tires, things are quite the same. The only difference is these short sidewalls are thicker. Hence, they offer more secure cornering but less comfortable rides.
Self-supported run-flat tires are a good option for aggressive drivers who put performance and security over comfortable rides.
The below video shows how self-support run-flat tires work.
Support Ring System Run Flat Tires
The self-supported run-flat system was invented by Bridgestone. The system had minor issues. Yet, it was doing its job and providing those extra miles that will take you to the mechanic.
As their biggest rival, Michelin wanted to give an answer to this technology. So, they did what they do always, put the bar higher and invented a support ring system.
Unlike the self-support system, this system has an extra element which we call a support ring.
Run-flat tires with a support ring system don’t have reinforced sidewalls. Hence, they provide a smoother drive compared to self-supported run-flat tires.
You all probably see the regular tires before mounting. Circle-shaped tires are hollow on one side and this part is designed to match the rim.
However, there is no hollow part for support ring system run-flat tires. In this section, there is a ring of hard rubber or another robust material that provides extra support in case of a puncture.
So, basically, if you get a flat tire with a support ring system, the support ring doesn’t let the rim touch the tread and keeps to tire usable.
So, the support comes from the center section, not the sidewalls. In fact, this makes these tires more comfortable than other run-flat tires. Though worth reminding, this system generally uses on high-profile tires. The low-profile tires don’t have enough place for a support ring.
The support ring system is better for daily driving.
What are the Benefits of Run-Flat Tires?
Implementing a new technology always comes up with disadvantages and advantages.
Run-flat is the technology that provides safe driving. Hence, it’s easy to say that safety is the biggest asset of this technology.
Even though the idea is to keep you safe, this technology has many benefits.
Safety, Safety, and Safety
Let’s say you’re going through Utah to Los Angeles at 70 mph. Do you think that you can save yourself if one of your tires gets punctured? No way.
First of all, this kind of accident is extremely rare. Yet, not impossible.
When your tire suddenly gets flat, if you’re at the high speed, you may juggle six things at the same time. It might be deadly.
At this point, run-flat technology gets into the game and provides the durability you need for this moment. Your tire still covers its shape and this decreases the force difference between the left and right sides. For this reason, the main advantage of run-flat tires is safety.
The Time Saver
Not all of us know how to change tires. For this reason, if we get a flat tire, we generally call one of our friends or road assistance. In an optimistic way, that means at least 1,5 hours. Moreover, you may even find someone or don’t have communication.
That’s where run-flat tires become a time or even lifesaver.
These tires can be running 50 miles after the puncture. For this reason, it can take you to a mechanic or any place you can change your tire.
You Don’t Need Spare Tires Anymore
The run-flat technology can take you to a mechanic in case of any puncture. For this reason, the spare tire isn’t necessary anymore. This feature brings some advantages also.
- Decreasing the total vehicle weight, hence, offers relatively better fuel economy (since run-flat tires are heavier than regular tires, the equation is so presumptive)
- You create extra space for yourself
- Spare tire cost isn’t any more part of your budget
What are the Disadvantages of Run-Flat Tires?
In order to understand the disadvantages of run-flat tires you may look into their internal structure.
I read tons of articles about this online. It seems like people find information online and share it without any fact-checking.
Here is the deal, run-flat tires have disadvantages. However, to say something for sure, you should look for the technology behind it.
I’ve already mentioned the two different methods have been using. I prefer to evaluate these two methods on their own.
Offers Rougher Ride
Riding comfort is related to the flexibility of the tire. For this reason, reinforced sidewalls always decrease riding comfort (think about all-terrain tires).
In that case, self-supported run-flat tires generally have a huge disadvantage. However, I can’t say something about support ring system run-flat tires.
Unlike self-support run-flat tires, these tires don’t have reinforced sidewalls, which means smoother drive. Though worth reminding, since these tires relatively have less air inside, they still offer slightly rougher rides than regular tires.
Weight More
Since these tires are heavier than regular tires, they consume more fuel. However, as I’ve mentioned in the advantages section, if you don’t use spare tires anymore, it might even become an advantage.
Note: Under the same conditions run-flat tires offer worse MPG than regular tires. For this reason, saying that they aren’t economical isn’t that wrong.
Responsiveness
Since the run-flat tires are heavier, they generally have a slower steering response.
TPMS System is Must
If you’d like to use run-flat tires, you should assemble a TPMS system, or your vehicle should have a TPMS system.
Since most newly manufactured vehicles have this system as a default, this isn’t an issue. However, if your vehicle doesn’t have this system, you need an extra budget.
Cornering Stability
While self-supported run-flat tires offer decent cornering stability, support ring run-flat tires provide a slight drop in that case.
Cost
Run-flat tires cost more. It’s because of the extra material inside.
Not Repairable Repairable
Even though I found this part a bit hyped. I still have to share it.
Run-flat tires aren’t repairable.
Good news! Run-flat tires are repairable now.
This is a perfect improvement because it also affects riding comfort.
New system run-flat tires have more flexible sidewalls but stiffer compounds. That increases the riding comfort also.
There is still a way to go for manufacturers. For this reason, they have some restrictions on run-flat tire repair.
Please check the below table for details.
| Brand | Reparability | Restrictions |
|---|---|---|
| BFGoodrich | Permitted | 1 repair maximum |
| Bridgestone | Permitted | Only if 15 psi maintained |
| Continental | Does not recommend | Mfg. Road Hazard Program |
| Dunlop | Permitted | 1 repair maximum for H- and greater speed ratings |
| Firestone | Permitted | Only if 15 psi maintained |
| Goodyear | Permitted | 1 repair maximum for H- and greater speed ratings |
| Hankook | Permitted | |
| Kumho | Permitted | |
| Michelin | Permitted | 1 repair maximum |
| Pirelli | Not endorsed | Mfg. Road Hazard Program |
| Yokohama | Not to be repaired if run-flat |
No matter you have a run-flat or non-run-flat tire, if anything happens close to the shoulder section, you can’t repair the tire.
Conclusion
After the latest developments in run-flat tires, they are similar to regular tires. Even though they have disadvantages, compared to the past, these cons are minor.
- If you put security over comfort, run-flat tires are good options for you
- I’m not going to stay behind run-flat tires provide poor grip. These tires just don’t make for all weather conditions. If they’ll have soft and extremely notched compounds, they provide the poorest MPG which makes them path less chosen.
- Obtaining these tires isn’t an issue as before
- You should have TPMS (tire pressure monitoring system) for using these tires
I hope the article was helpful. If you have any further questions, please leave them in the below section. Have a safe ride folks!