What Does Bike Tire TPI Mean
Bike Tire TPI stands for Threads Per Inch. This is the thickness of the thread and the number of times the nylon thread in the side wall of the tire crosses one square inch of the tire casing.
Tires are such an important part of your bike, and often, even if you think your tires look fine and rideable, there are many things that you may not be aware of that can seem fine, but are not.
To reiterate, TPI is a structure called the casing which is situated in the side walls of your bike tires, underneath the tread. It is made from nylon threads and is measured in threads per inch of tire.
Components of a Tire
While the rubber part of the tire is important when it comes to your tires, it is probably the least important part of the tire as a whole.
The most important components of a tire are those that actually hold the tire together. These are the bead which holds the tire in place in the rim, and the casing which is the side wall of the tire, and the tread which are the knobs on the tire that provide grip.
In the good old days, casings were made of cotton canvas. However, in the 60’s, nylon was found to have a much better tensile strength, and this is what has been used ever since. This is what Sheldon Brown has to say.
A tire is not just made up of rubber as you may think at first glance. There are 3 components to a tire:
This refers to the edge of the tire and is usually made up of steel hoops (although some use Kevlar these days) This keeps the tire firmly onto the rim.
This refers to the “fabric” or nylon thread which is woven in between the beads.
This is poured onto the bead and nylon casing and is to protect the inner tube, beads and nylon threads.
The tires’ ability to grip the ground well, protect the inner tube and keep their shape is of prime importance.
Having a bigger thread on your tire will result in a lower TPI count and a stiffer tire casing.
60 TPI casing will make the side walls of your tire stiffer and less foldable. This suits downhill and enduro bikes better. However, a 60 TPI will make your tire heavier, so keep that in mind if overall weight is an issue for you.
More recently, modern downhill and enduro tires are now using a double layer of 120 TPI, in a bid to make your overall tire weight lighter, and keep the same strength as a 60 TPI.
Bear in mind that a 60 TPI, despite being heavier, is much stronger and resistant to cuts and punctures.
Generally, 120 TPI is used more for cross country and road bikes as it is much lighter, as mentioned above.
Things To Consider
If you are starting out on your mountain bike journey, you should look for tires that can provide the best value based on cost, how light they are, what the Bike Tire TPI count is and the smoothness of the ride.