Getting your Nitro Mousse fitment guide right is the single most important step before installing any mousse insert. The wrong size means a loose, dangerous fit — or a mousse you simply cannot seat inside the tire. This guide walks you through every size chart you need, explains why fitment varies by tire brand, and helps you confidently choose the correct Nitro Mousse part number for your setup in 2026.

Why Nitro Mousse Fitment Is Not One-Size-Fits-All

Here's what surprises most riders: two tires with the exact same size label can require completely different mousse inserts. Tire manufacturers use their own internal mold dimensions, so a Kenda Parker DT 110/100-18 and a Metzeler MC4 110/100-18 are sized differently on the inside — even though both are labeled identically on the sidewall.

That gap matters a lot with mousse. Nitro Mousse parts are matched to a tire's internal carcass volume, not just the printed size. Fit a mousse that is too small and it will shift inside the tire during hard cornering. Fit one that is too large and you may not be able to seat the bead at all. Even two mousse sizes apart can mean a 40mm difference in diameter — so checking the fitment chart before you order is non-negotiable.

⚠️ Critical: Always cross-reference your specific tire brand and model, not just the tire size. Two identically labeled tires from different brands frequently require different Nitro Mousse part numbers.

Nitro Mousse Fitment Guide: Understanding the Part Numbers

Nitro Mousse part numbers follow a logical format once you know the pattern. The number begins with the wheel size (17, 18, or 21), followed by a three-digit mousse diameter code. For example, NM18-285 is an 18-inch mousse at 285mm diameter, while NM18-325 is the same wheel size at 325mm. That 40mm jump is two full sizes — the exact difference between a Kenda Parker and a Metzeler MC4 in 110/100-18.

The Nitro Mousse fitment guide covers three wheel sizes: 17-inch, 18-inch, and 21-inch. Most enduro and motocross bikes run a 21-inch front and either an 18-inch or 19-inch rear, though 17-inch is common on some European enduros and hard enduro machines.

Nitro Mousse Size Chart: 21-Inch Front Wheel

The 21-inch front is the most common mousse application for off-road riding. Below are typical fitments across popular tire sizes. Always confirm against the full Nitro Mousse fitment chart for your exact tire model.

Tire Size	Common Brands	Nitro Part #
80/100-21	Dunlop MX33, Bridgestone M404	NM21-220
90/90-21	Michelin Starcross 6, Pirelli Scorpion	NM21-230
90/90-21	Metzeler MC4 / MC360	NM21-240
90/90-21	Kenda Parker DT, Maxxis IT	NM21-220

Notice that 90/90-21 tires alone span three different mousse sizes depending on brand. This is exactly why the Nitro Mousse fitment guide exists — and why skipping it costs money and time.

Nitro Mousse Size Chart: 18-Inch Rear Wheel

Rear wheel fitment is even more critical, since rear tires carry more load and see greater lateral forces. The most common rear sizes are 110/100-18, 120/90-18, and 140/80-18. Here is a condensed reference from the Nitro Mousse fitment guide for 18-inch applications.

Tire Size	Common Brands	Nitro Part #
110/100-18	Kenda Parker DT	NM18-285
110/100-18	Metzeler MC4 / Dunlop AT81	NM18-325
120/90-18	Michelin Starcross 6, Bridgestone M403	NM18-325
120/90-18	Maxxis Maxxcross IT	NM18-340
140/80-18	Michelin Enduro, Pirelli AT81	NM18-370

Pro Tip: If your tire brand or model isn't listed, email the team at TheDudes@LiveTheGnar.com with your tire brand, model name, and size. They'll look it up and point you to the right Nitro Mousse part number.

About the Nitro Mousse Platinum: What Makes It Different

The Nitro Mousse Platinum is the top-tier offering in the Nitro Mousse lineup. It is made from a high-density micro-cellular foam compound that provides 100% flat-proof performance — no air, no valve stem, no risk of a race-ending puncture.

Compared to standard mousse inserts, the Platinum compound runs cooler at high speeds and resists deformation longer during extended enduro stages. It gives the feel of a properly inflated tire without any maintenance burden. For hard enduro, desert racing, or any discipline where a flat ends your day, the Platinum is the right choice.

Key benefits:

• 100% flat-proof — no air pressure, no punctures
• High-density Platinum compound runs cooler than standard mousse
• Simulates approximately 12–14 PSI tire feel
• Compatible with most major tire brands (always verify with the fitment guide)
• Designed for enduro, hard enduro, cross-country, and motocross
• No maintenance between races — just install and ride

How to Use the Nitro Mousse Fitment Guide Step by Step

Following this process ensures you order the correct size every time. The Nitro Mousse fitment guide is organized by wheel size first, then by tire brand and model — not just the size on the sidewall.

Step 1 — Read your tire sidewall. Write down the full tire size (e.g., 110/100-18) plus the brand name and model name. "Dunlop 110/100-18" is not enough — you need "Dunlop AT81" or "Dunlop MX33."

Step 2 — Open the fitment chart. Go to the LiveTheGnar Nitro Mousse fitment chart and locate your wheel size section (17", 18", or 21").

Step 3 — Find your exact tire model. Search by tire brand and model name. Locate the matching Nitro part number in the right column.

Step 4 — Order with confidence. Add the correct Nitro Mousse Platinum to your cart. If your tire is missing from the chart, reach out before ordering.

Mousse Fitment FAQ

Can I use any mousse in a tire of the same printed size?
No. As the Nitro Mousse fitment guide makes clear, internal tire dimensions vary significantly between brands. Always look up your specific tire model, not just the size label.

What happens if I install the wrong size mousse?
An undersized mousse can move inside the tire under load, causing unpredictable handling and possible bead separation. An oversized mousse may prevent the tire from seating on the rim at all.

How long does a Nitro Mousse Platinum last?
Under typical enduro use, most riders get 40–80 hours from a Platinum mousse before the foam begins to break down. Always inspect for crumbling or permanent deformation between rides.

Do I need mousse lube for installation?
Yes. Use a dedicated mousse lube (not tire lube) during installation to prevent tearing the foam and to help seat the mousse evenly inside the tire carcass.

Final Word on Getting Your Nitro Mousse Fitment Right

The Nitro Mousse fitment guide exists for one reason: mousse fitment is tire-specific, not just size-specific. Spending two minutes with the fitment chart before you order protects your investment and keeps you on the trail. The Nitro Mousse Platinum is an exceptional product — but only when it's the right size for your tire.

Use the size charts above as a quick reference, then confirm against the full chart for your exact tire brand and model. When in doubt, reach out to the LiveTheGnar team before ordering.

Ready to go flat-free? Get the right Nitro Mousse Platinum for your tire. Shop Nitro Mousse Platinum → Not sure which size? Check the full fitment chart or email TheDudes@LiveTheGnar.com