Today’s question is about using different width tires on your mountain bike and why that might be a good idea…

My mountain bike has a 2.5 tire on the front and a 1.95 on rear. Should I put a 2.5 on the rear?

I just bought the bike – its an older, short travel full suspension. I’ve not had this tire setup before and am looking for input. What is to be gained from this setup? Should I just match em up?

Mismatched Michael

Hi Michael,

A narrower rear tire like you have is a common setup for mountain biking. Since you bought the bike used, I’m betting it originally came with 1.95″ tires front and rear. That would have been typical for that style bike.

What most likely happened is that the previous owner wanted to run larger tires, and he probably put on the biggest tires that would fit the bike. The frame could probably only handle a 1.95″ or maybe a 2.1″ as the rear tire. However, most any front fork can accommodate a larger front tire, around 2.2″ to 2.5″ wide.

So the question isn’t really “why a smaller rear tire?,” but rather, “why a larger front tire?”

Here are the reasons you might run a narrow rear tire and wide front tire on your mountain bike:

  • Increased Traction – The front tire is extremely important when it comes to traction, especially when turning. In most cases, a wider tire will provide better traction, so it makes sense to run a larger front tire. (While you still need traction from the rear tire, it’s usually not a big deal when the rear tire loses a little traction. However, if the front tire loses traction, you could be in big trouble!)
  • Softer Ride – A wider tire holds a greater air volume, which means you can safely run slightly lower tire pressures. The lower pressure will make for a softer, more comfortable ride. With a hardtail or older short-travel full suspension bike, you probably want the softest ride possible! (Lower pressure will also help increase traction.)
  • Weight – The wider the tire, the heavier the tire will be. Running two wide tires will significantly increase the rotating weight on the bike, requiring more effort to ride fast. Sticking with only a wide front tire is a good compromise.
  • Frame Limitations – While there is generally quite a bit of room in the front suspension fork (a 2.3-2.5 tire can probably fit,) the frame can only accommodate a certain size tire. On the typical cross country mountain bike, you won’t get bigger than a 2.1 tire back there.

As you can see, tire size is about compromise. The narrow tires are light, but going with a wider tire will increase traction and comfort.

The narrow tire in the back and a wider one up front makes for a pretty good compromise between weight savings, comfort, and traction.

In general, I run 2.1″ tires front and rear on my hardtail or short-travel XC racing bike. However, if you’re out having fun on the trails, the 2.5″ front tire will probably be nice. So you can definitely stick with the tires you have.

There’s no real downside to running different tire sizes, so there’s not much reason for you to change anything. For example, there’s no need to carry different size spare tubes. A 26×1.95 tube (you could probably find one marked “fits 1.95-2.2 tires”) will fit just fine in a 26×2.5 tire.

And you could always convert to a tubeless setup using Stan’s rim strips and sealant! That would give you an even better ride, and there would be less worry about ever using a spare tube!

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