Disc brakes use one of two caliper designs: floating (sliding) or fixed. They clamp the pads onto the rotor in different ways, and knowing which your vehicle has helps you understand how it works and what to service. Here is the difference.
Floating (sliding) calipers
A floating caliper has piston(s) on only one side - the inboard side. When you brake, the piston pushes the inner pad against the rotor, and the reaction slides the whole caliper on its guide pins to pull the outer pad in from the other side. It is simpler, lighter, and cheaper, which is why the vast majority of everyday cars and trucks use floating calipers. The trade-off: the slide pins must stay clean and greased, or the caliper sticks - see caliper sticking and the guide pin kit.
Fixed calipers
A fixed caliper is bolted solidly in place and has pistons on both sides of the rotor - often two, four, or more. They clamp both pads directly and evenly without needing to slide. Fixed calipers give firmer pedal feel and more even clamping, and they handle heat well, which is why they show up on performance and luxury vehicles and in big brake kits - see big brake kit basics. They cost more and are heavier.
How to tell which you have
- Look through the wheel: a caliper with visible pistons or a symmetrical body on both sides of the rotor is likely fixed; a caliper with a body on only one side and slide pins is floating.
- Most mainstream vehicles use floating calipers, especially in the rear.
- Performance and premium models more often use fixed calipers up front.
What it means for service
For floating calipers, keep the slide pins clean and greased and use fresh hardware - see where to apply brake grease. For fixed calipers, pad replacement is often simpler (pads drop in), but the caliper itself is pricier if it fails. Either way, start with the right pads for your vehicle.