How to choose your MTB disc brake adapters?

How to choose your MTB disc brake adapters?

L'caliper adapter is the part that fits under the brake caliper to adapt it to the bike and the desired diameter. Although simple on the face of it, there are a number of different diameters and standards to choose from, both on the frame and the caliper. Here's how to get it right first time.

Standards

  • Frame, fork and caliper mounting standard: Postmount (PM) or InternationaI Standard (IS)
  • Frame diameter standard disc MTB: 140, 160, 180, 200 or 203 mm

Types of disc brake adapters

Standard IS or PM? That's the question you'll keep asking yourself when choosing a component for your MTB. disc brakes So it's vital to know what you're talking about! The best way to avoid making a mistake is to measure the axis-axis distance* between the 2 mounting points: 51 mm is IS, 74 mm is PM.

In the case of PM, the other point to check before choosing your adapter is the minimum mounting diameter on the frame and fork. The height of the dropouts necessarily gives a basic mounting diameter, the standard being 160 mm, but some brands may offer a different basic mounting diameter, which will create a discrepancy when you choose your adapter.

For example, an adapter given for 180 mm mounting assumes that your frame is originally 160 mm. If your frame has a 140 mm base (i.e. -20 mm), you'll need a 200 mm adapter (i.e. +40 mm) for a final 180 mm assembly. To find out this base value, you can either deduct it from the originally mounted material, or measure the distance between the wheel axle and the PM bracket.

Rotor size in mm Dimension C Dimension D
140 mm  47,5  74,2
160 mm  55,9  74,2
180 mm  64  74,2
203 mm  73,9 74,2

 

Finally, given that mounting diameters and sizes are completely standardized, it is theoretically possible to cross-reference adapter brands with brake brands. However, as the shape and size of calipers is not standardized, it's best to stay with the same brand wherever possible, to avoid the caliper bumping into the bottom of the adapter before it's properly seated on your bike's mountings. MOUNTAIN BIKE.

Which adapter to choose?

There's no special trick to choosing the right adapter, apart from identifying what you need. But be careful, they're different for front and rear.

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