How to pick a Flux rim for the riding you do, and why the front and rear don't have to match.
Which Flux rim should you be on? It's fairly straightforward once you understand the ASTM ratings, and it comes down to three decisions, in this order: the profile, which end of the bike it's going on, and the tier.
The short version. Pick the profile for the hardest riding you do, run a lighter one up front than in the rear, and let budget pick the tier. The shape doesn't change between tiers.
What Flux rims have in common
Traditional rims are convex, bulging outward. Flux inverts that: a low-profile, concave section, so the rim itself flexes and absorbs impacts rather than passing them straight to you. Against a traditional convex profile, our testing puts it up to 33% higher in angular deflection and 19% higher in vertical deflection.
Every rim in the family shares that shape, a 30mm inner width, hookless beads, a Class 1 E-MTB rating, and nipple washers. Tire fit and ride feel are identical across the range; only the strength changes.
The five Flux profiles, 33 through 66 GR. Same 30mm inner width, same inverted concave section, all the way across.
1. Pick the profile
The numbers are model designations, not measurements. What actually changes between them is the layup, the wall thickness, and how much impact the rim is built to survive.
- Flux 66 GR, 19mm deep. The toughest in the family. Gravity riding, bike parks, downhill.
- Flux 55 Enduro, 19mm deep. Race-day toughness for enduro without full DH weight.
- Flux 54 All Mountain, 19mm deep. The middle of the range and the one most people want.
- Flux 43 Trail, 17mm deep. Lighter and more compliant, for daily trail riding.
- Flux 33 Trail, 17mm deep. The lightest in the family. Pro Carbon only.
Weights, in Pro Carbon 29": 425g for the 33, 445g for the 43, 500g for the 54, 550g for the 55, 610g for the 66 GR.
2. Front and rear don't need to be the same rim
This is often overlooked, and it's where you can gain some ride quality. We designed the new Flux rims with this idea in mind.
A front wheel doesn't take the same abuse as a rear, so it can be built lighter and more compliant. That compliance helps it find traction and makes a wheel feel less harsh. A rear wheel needs to survive square-edge hits and put power down, so it gets a stiffer, stronger profile. Rear rims are also rated to a higher ASTM category than fronts, because of the loads they take.
Same 30mm width at both ends. Different carbon layups and wall thicknesses to hit a different target at each end of the bike.
So run a lighter profile up front than in the rear. That's how we build our own wheelsets:
| Wheelset | Front | Rear |
|---|---|---|
| Optimus, trail | Flux 33 | Flux 43 |
| Sylvan, all-mountain | Flux 43 | Flux 54 |
| Grappler, enduro | Flux 55 | Flux 66 |
| Grappler, DH | Flux 66 | Flux 66 |
A Pro 54 also makes a good enduro front, paired with a 66 GR behind it, if you want more compliance and less weight at the front of an enduro bike.
3. Pick the tier
The profiles, the widths, and the front and rear tuning are the same in all three tiers. What you're buying is material and weight.
Flux Pro Carbon. The lightest and stiffest, high-modulus fiber with discipline-specific layups, and the only tier that offers the 33 Trail. From $459.95.
Flux Pro Aluminum. Welded AL-6069. Roughly 70g heavier than the carbon equivalent, at about a fifth of the price. From $99.95.
Flux Aluminum. The same AL-6069 with a sleeved joint instead of a welded one. Available in 66 GR, 54 All Mountain, and 43 Trail. From $69.95.
What happens if you break one
The tier decides this.
Carbon rims are covered for life, regardless of how they failed. Crashes included. If it breaks, we replace it.
Pro Aluminum rims are covered for life against rim failures, meaning dents that won't hold air, seam separation, and cracked spoke holes. Crash and misuse damage gets a discounted replacement.
Flux Aluminum carries ten years against manufacturing and material defects, with discounted crash replacement.
Quick picks
- Trail, counting grams. Flux Pro Carbon 33 front, 43 rear.
- One rim, everything. Flux 54 All Mountain, in whichever tier suits the budget.
- Enduro racing. Flux Pro 55 front, 66 GR rear.
- Bike park and DH. Flux 66 GR, any tier.
- Best value. Flux Aluminum in the profile that matches your riding.
Built into complete wheels, these are the Sidekick Flux wheelsets.
