29er Carbon MTB Rim 28mm — Hookless Tubeless-Ready | Bola

• Material: Toray carbon fiber
• Rim depth: 23mm
• External width: 34mm
• Internal width: 28mm
• Size: 29er
• Profile: U-shaped
• Weight Tier: Standard (375g), Superlight (330g), Ultralight (300g)
• Max Tire Pressure: 75 psi

• Weight vs Durability: Three weight grades—Standard 375g, Superlight 330g, Ultralight 300g—allow riders to choose between rotational weight savings and impact tolerance. The Ultralight version is 20% lighter than Standard but reduces impact resistance, making it ideal for race-day XC rather than rocky trails.
• Tire Volume vs Speed: The 28mm inner width supports 2.1–2.4" tires, optimizing traction and pinch-flat resistance at lower pressures, but this wide stance adds rolling resistance compared to narrower rims that favor speed on smooth terrain.
• Stiffness vs Compliance: The 23mm profile is designed for responsive steering and lateral stiffness, but the low height reduces vertical compliance, transmitting more trail chatter to the rider on rough sections.
• Versatility vs Specialization: The rim is specifically engineered for XC and light trail use within a 100kg rider weight limit, trading the all-mountain durability of heavier rims for a competitive weight advantage that suits race-focused riders.

• Fatigue Test: 750,000 cycles @640N (ISO 4210-7 Annex A, informative only)
• Impact Resistance: >40J (ISO 4210-7 reference)
• Flatness: <0.25mm (internal QC)
• Roundness: <0.3mm (internal QC)
• Max Spoke Tension: >300kg (internal QC)
• Ultimate Strength: >100kg (internal QC)
• Dynamic Equilibrium: <3g (internal QC)
• Radial Stiffness: 90–110 N/mm (internal lab)
• Lateral Stiffness: ≥8N/mm
• Max System Weight: 110kgs

• Cross-Country Racing: Excellent. Ultralight and Superlight options reduce rotational weight for climbing and acceleration.
• Light Trail Riding: Suitable. Standard weight option adds durability for varied trails, but the rim is not designed for aggressive downhill.
• Endurance Rides: Good. Low profile and tubeless setup reduce fatigue over long distances.
• Training / Daily Riding: Suitable. The 28mm inner width provides stable tire support for daily training, but the hookless design limits tire pressure to 65 psi.
• Not Recommended For: Not recommended for enduro or downhill riding, or for riders exceeding 100kg, as the rim's impact tolerance is optimized for XC conditions.

• Frame Compatibility: 29er (ISO 622mm) mountain bike frames
• Tire Type: Tubeless ready, hookless, ETRTO-compliant tubeless tires
• Tire Width Range: 2.1-2.4" (53-61mm)
• Brake Standard: Disc brake only
• Drivetrain: Hub-dependent (rim does not affect drivetrain)
• Rotor Standard: Hub-dependent

What is the recommended tire pressure for the Bola MTB34-C23-29 rim?

The hookless design limits tire pressure to 45–65 psi. For most XC riders, we recommend starting around 30-35 psi for mountain bike tires, but the rim's hookless bead requires ETRTO-compliant tubeless tires. Always check the tire manufacturer's recommended pressure range for the specific tire width, and adjust based on rider weight and terrain. The 28mm inner width supports 2.1–2.4" tires, which typically perform best at lower pressures for traction and comfort.

What tire sizes are compatible with this rim?

The 28mm inner width is optimized for tires between 2.1" and 2.4" (53–61mm). This range ensures a rounder tire profile and improved cornering traction. Using tires outside this range may affect performance or risk pinch flats. Always use tubeless tires that meet ETRTO hookless standards.

How much weight can I save compared to an alloy rim?

The rim comes in three weight grades: Standard (375±15g), Superlight (330±10g), and Ultralight (300±10g). Compared to a typical alloy MTB rim of similar width (which often weighs 450-550g), you can save 75–200g per rim, significantly reducing rotational weight. This translates to faster acceleration and easier climbing. The Ultralight option offers the most savings but with reduced impact tolerance.

What custom build options are available?

Spoke hole diameter (standard 4.5mm), valve hole (6.5mm), assembly hole (7.5mm), and nipple direction (left 5° / right 7°) can be configured to suit your wheelbuilder and hub. The ERD is 592mm, so you can calculate spoke lengths precisely. It is recommended to have an experienced wheelbuilder with carbon rim handling experience.

How do I maintain and inspect the rim?

Regularly check for cracks, delamination, or impact damage, especially after hard rides. Clean the rim with mild soap and water; avoid harsh solvents. Torque spoke nipples to the recommended tension (greater than 300kg rating). Ensure the tubeless sealant is refreshed every 3-6 months. The rim is rated for riders up to 100kg when built to specification, so exceeding that could void the warranty.

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