Sprint Filter P08 F1-85 Air Filter for Racing – BMW R 1200 RS (2015–2018) K142S F1-85

The largest number in Sprint Filter's tables belongs to this cloth: 15,000 litres per square metre and second. On this part number it applies to twice as much material as on the standard-size racing element, which puts the element's total ceiling twice as high again. It is a genuinely large figure, arrived at honestly, and it is worth being clear-eyed about what a ceiling is: a limit that only matters to whatever is pressing against it.

Key Features

• The racing weave of the P08 family: dry woven polyester, oil-free at every stage
• 85 µm aperture at a rated 15,000 l/m²/sec, the highest flow figure in the range
• Twice the filtering surface of the standard-size element for the same housing
• 95.22 per cent retention of 100-micron test particles in the maker's comparison
• Direct replacement for the paper panel; the housing untouched and the mapping as written
• Cleaned with compressed air and used again, two years of warranty from purchase

A rate is not a quantity

Flow figures in this catalogue describe a square metre of material for a second of time, which is the only fair way to compare media of different shapes. To find what an element passes you multiply by its area, so the doubled surface here genuinely doubles the maximum the part could ever deliver. The engine, however, asks for what it asks for. A boxer twin of this size at road revs draws a fraction of what the standard cloth already supplies, and multiplying an unused reserve produces a larger unused reserve.

When the reserve gets used

On a closed circuit and, in practice, almost nowhere else. There the wide-open state is held deliberately, repeated for twenty minutes at a stretch, and the most open weave available stops being decoration. A faired RS on a public road reaches that condition for a second or two between gearchanges before traffic, a bend or the law shuts it down. Either way it is not a power part: no filter dropped into a series airbox makes a standard R 1200 RS noticeably faster, because intake, injection and exhaust were developed as one piece of work. What the doubled area reliably buys is a longer run between services.

Care and cleaning

Compressed air against the clean side, worked outwards, and the weave is open again — on a cloth the load sits at the surface rather than in the depth, which is why the job is quick. When something has settled that air will not lift, warm water and the least mild detergent that works will do the rest, and the rinsing goes on until nothing more leaves the cloth. The element then dries completely in circulating air, with no warmth of any sort and no flame permitted near it, and the K142S F1-85 is refitted dry and unoiled. Its servicing sheet sits under Downloads.

Fitment & Compatibility

For the BMW R 1200 RS built from 2015 to 2018, in the standard airbox with nothing altered. Six catalogue entries cover five machines on this part number — the RS and RT of the 1200 generation and the three 1250 road boxers — and the Fitment tab names the years against each.