When it comes to automobile modification, tire stretching is a common choice among enthusiasts. The stance, a word coined by Japanese modders, is complete with lowered suspension and larger rims.
Here, I’ll go over the basics of tire stretching, but I’ll also go into detail about the legal and safety ramifications of doing so.
While stretched tires aren’t prohibited, the quick answer is that they can be used against you in an accident to transfer blame and nullify your insurance coverage.
What Is Tire Stretching – A Brief Overview
When a tire is too tiny for a rim, the technician does tire stretching to make it work. Although the terms “rim” and “wheel” are sometimes used interchangeably, I like to think of a wheel as consisting of both a tire and a rim because it simplifies things.
Stretching a tire to its limit isn’t standardized, but there are certain established methods for determining how far it may be pushed. Before we begin, I’d like to quickly go over the dimensions of the tires and rims.
Rim Dimensions Explained
The following measurements are used to calculate the size of a rim.
diameter, breadth, and offset Let’s assume that the rim is a perfect fit for your car and that the bolt pattern is correct.
When looking at a rim from the side, the diameter is self-explanatory and shows how big it is overall. There is an allowed rim diameter range for every vehicle, and exceeding it without compensating with thinner tires can lead to issues with steering articulation and suspension..
The width of the rim, which controls the width of the tire and, by extension, the complete wheel, is also pretty straightforward. The wheels may not even fit or will stick out on the sides in some regions where wheels must be totally veiled because of their excessive width.
To establish the distance between the hub mounting and the centerline of the rim, the offset must be calculated. No offset wheels will be perfectly positioned in the centre, so half their width is facing inwards and half out.
In order to attach bigger rims without creating massive wheel arches, a negative offset is required. The negative steering angle is exacerbated by a positive offset since the wheel is pushed closer to the vehicle.
The rim’s measurements are shown in the following table.
The diameter x width offset, followed by the number of bolts x bolt spacing diameter. Measurements of diameter and width are done in inches; offset is done in millimeters.
If I give a few examples, this will become clearer:
Using the 18×10 (+0) as the base rim dimensions, we will disregard bolt displacement, which is irrelevant for stretching.
Tire Dimensions Explained
Tire dimensions are a little trickier. Aspect ratio, tire size, width, construction type, rim diameter, load index, speed rating, and weather rating are all factors to consider.
Passenger vehicles (P), light trucks (LT), and special trailers (ST) all have tires that are appropriate for their respective applications.
Millimeters are used to measure tire width, which doesn’t have to match rim width exactly, but it’s usually rather close.
A tire’s aspect ratio is the ratio of the tire’s height/profile/sidewall to its width. Its height is 135mm, which is 60 percent of the width of a 225mm wide tire with a 60 aspect ratio.
Although the aspect ratio may not make sense to you, you are correct in your assumption that it should just be a number. Tires of the early days had a fixed width-to-height ratio of one hundred percent. When lower profile tires were introduced, manufacturers started using percentages instead of millimeters, and this practice has remained ever since.
Measuring in inches, the wheel diameter gives you an idea of what rim size you need to use with it.
Load index is a measure of how much weight a tire can bear.
Using a tire’s speed rating shows you how fast it is safe to drive at.
In this section, we’ll dissect a set of complete tire markings.
It is P 215/65 R 15 89 H, M+S
Matching Tire & Rim Size
Wheel size can be calculated now that we know how tires and rims are measured.
Wheel and rim sizes are suggested by the manufacturer for each vehicle. The owner’s handbook, the B column behind the driver’s door, and the back of the fuel tank lid are all good places to look for this information.
By modifying the rim and wheel size, you can go beyond what the manufacturer recommends while still operating within the constraints of the stock system.
Smaller tires require a smaller rim to keep the same overall diameter as larger tires. To compensate for the increased tire height, the rim must be narrower. That should give you a general sense of the situation.
Choosing The Right Tire For Stretching
We now know that a larger rim need a lower aspect ratio tire in order to keep the same overall diameter as a smaller one. 45:35 is considered low profile, although there is a limit to the aspect ratio.
Putting a tire on a rim that is too broad causes the aspect ratio to be stretched to the limit.
Let’s look at an example using a 205/55/16 tire mounted on a 168 rim to see what I mean. The tire would have to accommodate an extra 0. 5 inches on each sides if the rim width were increased to 9 inches.
To achieve an aspect ratio of 51, the tire wall must be angled at a 90-degree angle, which reduces the overall height by two millimeters. While this calculation isn’t quite accurate, it should give you a general idea of what to expect.
The Stretch Stages
When it comes to creating an optimal setup, the modding community has come up with the idea of categorizing stretches into stages.
Stage 0 is the stock configuration. For safety reasons, only stage 3 can be deemed a safe level of advancement in the game.
Increasing the stretch stage by:
Reduce the stretch stage by:
At first glance, this may appear to be a difficult concept, but it’s actually not that difficult. As long as you keep inside the first three steps of the setup, you can mix and match the settings.
Stage 0 stretching is achieved by the 255/35/18/10 rim and tire combination since they are precisely square. The settings that have an impact on the stage are shown in bold in the following stretch configurations.
As you can see, it’s all about allocating values. This means that you can increase the other two values to make up for a drop in one. Adjustments must, of course, be reasonable.
Stretching tires can also be done in the opposite direction by mounting larger tires on a smaller rim. The same rules of measurement apply, but you must use them in the opposite direction. Stage 2 is regarded the maximum because it is the reverse stretch that works best for track-ready vehicles.
Factors To Consider When Stretching Tires
Stretched tires have a bad reputation because of the evident damage and wear they cause. There is a difference, however. When it comes to the legality of tire-stretching, I’ll also explain why it’s a complicated issue.
In terms of tire wheel wear, it’s evident that a stretched arrangement has some drawbacks. The tire will wear out faster and be more prone to bursting a chord if it is not properly maintained. This occurs when the tire’s metal wires are exposed and the tire is further damaged, resulting in a rupture.
Deflating occurs when the tire’s bead loses contact with the rim’s rim and is known as “debeading”. Finally, the rim’s outside edge is vulnerable to damage because it is the initial point of contact with any surface.
Performance & Safety Concerns
You alter the tire’s geometry, which has an effect on its performance, by stretching it. The proper sidewall geometry, which is lost when tires are stretched to an extreme degree, allows tires to bend in corners so that they can maintain contact with the asphalt.
Hydroplaning is a more serious problem with tires that have been stretched. In order to keep their grip on the road when it is raining, tires must expunge any water they come into touch with.
A thin film of water will form between the tire and asphalt and produce hydroplaning, an event where the vehicle loses control due to the lack of traction on the road.
Legally, stretched tires are a bit of a catch-all. Excessive stretching may result in a traffic stop from a police officer. What worries me the most is what might happen in the event of an accident involving a vehicle with overly stretched tires.
If the insurance company determines that the tires were a factor in the accident, they may refuse to pay the claim. Since I am unable to provide you with a definitive answer to this topic, I suggest that you conduct your own research before making a final decision.
Stretching Tires – The Reality
Tire stretching’s perils and risks have been exaggerated to absurd levels. The negative connotations of extending tires are obvious, but that does not imply that it is a significant matter.
Most folks have no idea how prevalent tire stretching actually is. As you’ve seen in the stretching tutorial, it takes very little effort to achieve a barely perceptible stretch in stage 1.
Even if you drive your automobile every day, you can still benefit from stage 1 or stage 2 stretching. It’s possible to modify your driving style and habits to better match the aesthetics of this vehicle alteration rather than the performance benefits.
Stage 3 should only be used by weekenders and display cars, just to be on the safe side. Extending the track beyond the third stretch is extremely risky, yet it is done for display cars with low mileage.
How To Stretch Tires
Sadly, I won’t provide you with a step-by-step tutorial on how to extend tires. I don’t believe that following a written guidance will help with the process, which is rather risky.
Don’t hesitate to hire the services of a neighboring tire shop if they’re willing to do the mounting for you. Otherwise, you can watch the demonstration video below to get a better idea of how things work.
Are stretched tires safe?
Although the solution is dependent on the extent of the stretching, it is safest to stick to the more common sense techniques. When it comes to safety, you can think of it as the difference between brand new tires and those that are only half worn.
What’s the point of stretching tires?
The major goal of tire stretching is to improve the aesthetics of your car. For decades, people around the world have been modifying their vehicles in this way, which makes them sit even lower to the ground. It is possible to boost performance by stretching the tires a little, but it is recommended to go with a stock performance-oriented tire.
Can you stretch a 15-inch tire on a 16-inch rim?
There is no such thing as tire-stretching based on the diameter of a rim. In the second dimension (rim width), an increase of half an inch results in one stretch stage.
Not as dramatic as people make stretching tires out to be. In order to avoid any problems, it is important to choose the correct tires and rims. If you follow the stretching guidelines in this article, you’ll be able to construct a configuration that’s attractive and useful.