Sprint Filter P08 F1-85 Air Filter for Racing – Triumph Bonneville Bobber (2017–2021) SM225S F1-85

The honest place to begin with a racing element on a Bonneville Bobber is with the rider. This is a single-seat machine with a low, minimal riding position and no wind protection at all: how long it can be held at high revs is decided by the person on it, not by anything in the intake tract. So the headline figure of the SM225S F1-85 — 15,000 l/m²/sec, three times the rate of the standard element — is not going to be redeemed on this bike, and no description should pretend otherwise. What remains is narrower and entirely real: the highest retention Sprint Filter publishes for its road media, in a part that is washed instead of bought.

Key Features

• Woven polyester, dry, with the aperture opened out to 85 µm for maximum throughput
• Retention measured at 95.22 % on 100 µ particles — ahead of the standard weave's 93.13 %
• Four-layer oiled cotton, measured on the same scale, returns 76.42 %
• No oil anywhere, so nothing can be carried onto the sensor or the throttle bodies
• Roughly twice the filtering area of other performance filters, in the standard airbox
• Two years of warranty from purchase, and an element built to outlast every service interval

The number that stays on the shelf

Flow ratings describe how much a square metre of medium can pass in a second. They only turn into anything while an engine is asking for that much, and a Bobber asks rarely: the seating position, the bars and the exposure end a full-throttle stretch long before the intake becomes the limiting element. Buying this medium for its flow figure on this motorcycle means buying a capacity that will sit unused. That is worth saying before the order, not after it.

The number that comes with you

Retention is collected on every kilometre, at any throttle opening, which makes it the figure that actually travels with the bike. The comparison above is the manufacturer's own, measured on 100 µ particles, and it is the honest reason to consider this element on a road machine. What it will not do is add power — a drop-in filter does not make a series Bonneville noticeably stronger. It holds one predictable resistance and resets to it at every clean. Read the media as a trade and not a ladder: finer holds more back and flows less, coarser does the reverse.

Care and cleaning

The SM225S F1-85 is cleaned with compressed air on the clean side, blown outwards through the weave. After a hard season wash it in lukewarm water with a mild detergent, rinse it until the water runs clear and dry it in open air — never with heat, never near a flame. It goes back into the airbox dry. The maintenance sheet is in the Downloads tab.

Fitment & Compatibility

For the Triumph Bonneville Bobber of 2017 to 2021. The Triumph Bonneville Speedmaster of 2018 to 2021 shares the airbox and the same part number — two machines covered by one element. Check your model year in the Fitment tab.