How to Decrease Tire Widths on Bike Wheels

How to Decrease Tire Widths on Bike Wheels
Bike rims can accommodate a range of tire widths. Although it's physically possible for a narrow rim to hold a wide tire and for a wide rim to hold a narrow tire, it's not advisable to set your wheel up at these extremes. When your tire is too narrow for the rim, it's easier for your tube to wiggle between the tire and rim, leading to a pinch flat. When a wide tire is forced on a narrow rim, too much pressure is put on the rim's sidewall, which can potentially damage the rim. You can decrease the width of your tire safely.

Instructions

Difficulty: Moderately Easy

Things You’ll Need:
  • Bike rim
  • Measuring tape
  • Bike tire
Step 1
Measure the interior width of your rim. With your tire and tube removed, hold a measuring tape across the top, interior portion of your rim. This should be the widest point to measure. Do not measure the bottom of the rim, as it narrows and will give the wrong measurement.
Step 2
Find the width of your tire. This measurement should be marked on the tire's sidewall. If you have a road bike, this measurement will be in millimeters. If you have a mountain bike, your tire's width will be in inches and you'll need to convert this number into millimeters. Multiply inches times 25.4.
Step 3
In shopping for your smaller tire, stay within the range that's safe for your rim. A 13-mm rim can take a tire from 18 mm to 25 mm. A 15-mm rim holds from 23-mm to 32-mm tires. A 17-mm rim will hold a 25-mm to a 37-mm tire. A 19-mm rim holds a 28-mm to a 44-mm tire. A 21-mm rim takes a 35-mm to a 50-mm tire. A 23-mm rim takes a 40-mm to a 50-mm tire. And a 25-mm rim will accommodate a 44-mm to a 57-mm tire.
Step 4
Purchase a narrower rim if you aren't able to decrease your tire to the size you need. If your tire already falls at the lowest point on the range for your rim, you'll need to downsize your rim.

Article Written By Kathrine Cole

Kathrine Cole is a professional outdoor educator. She teaches rock climbing, backpacking, cycling, and bike maintenance classes. She is a graduate of the National Outdoor Leadership School, a Wilderness First Responder, and a Leave No Trace Trainer.

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