Performance difference between 25mm and 30mm fans

The announcement of the CORSAIR RS MAX performance fans marks CORSAIR’s very first 30mm thick PC fan. So, the fans are 5mm/20% thicker than normal PC fans, but what does that mean? How does the performance compare? Well, let’s take a look at the RS MAX fans while we figure that out.

While “better” is a huge catch-all that won’t apply in the same way to each person, it’s generally safe to say here, especially when it comes to performance.

Basically, the thicker the fan, the more air it can push at any given speed as compared to a thinner fan at that same speed. This means that if you go from 25mm fans to 30mm fans, you can run them slower, and therefore more quietly without sacrificing cooling performance. In fact, you can expect improvements anywhere between 15 and 17% over 25mm fans. the chief benefit here is that with 30mm fans, your PC will be quieter doing whatever it normally does, and remain as cool, or cooler, than it used to be.

The same principles also apply to water cooling. For water-cooled PCs, fans must blow air through radiators. These radiators are densely stacked with fins. The surface area of these fins is what dissipates heat when the air blows through.

The more densely packed the fins are, the more heat can be removed. However, with more density comes a more restrictive path through which the air must go. This means that the ideal fans for water cooling must have high “Static Pressure”, usually measured in mm-H20. The higher that stat, the more static pressure the fan in question is capable of.

The reason 30mm fans are better than 25mm in this application is because that additional 5mm of thickness allows the blades to be larger in size and thus have a greater surface area so they can “scoop” that air more aggressively. This means they have an easier time shoving air through the restrictive route created by the fins of a radiator.

The airflow, noise, and static pressure benefits of the RS MAX fans (and 30mm thick fans in general) are all well and good. However, you must be aware that 30mm fans are pretty uncommon, as such, many PC cases are not designed with this standard in mind. Remember to check the clearances!

Where the front of most mid-full PC towers might fit extra thick fans with no problem. (The gigantic sizes of GPUs these days necessitate a lot of clearance in this dimension anyway,) you’ll probably run into issues at the top of a lot of PC cases. Motherboards are often right up against the top of the case, and you need the small amount of remaining space to route the power cables. This effect if exacerbated if you have an AIO cooler mounted at the top of the case, as the radiator will eat a lot of this space.