Product Overview
The DNM AO39RC is a high-performance bicycle rear shock absorber designed for mountain bikes. It features a dual-chamber air system, adjustable rebound damping, and a 3-stage lockout mechanism to adapt to various riding conditions.
Image: The DNM AO39RC shock absorber available in three different lengths.
Key Features
- Dual-Chamber Design: Primary and secondary air chambers work in coordination for enhanced damping performance.
- Rebound Adjustment: Allows fine-tuning of the shock's return speed.
- 3-Stage Lockout: Provides distinct modes for climbing, trail riding, and descending.
- Material: Constructed from durable and lightweight aluminum alloy.
Image: Visual representation of the AO39RC's main features.
Setup and Installation
1. Installation
It is recommended that installation be performed by a qualified bicycle mechanic. Ensure the correct length and travel shock absorber is selected for your bicycle frame. The shock absorber is available in 165mm, 190mm, and 200mm lengths, with corresponding travel of 35mm, 50mm, and 55mm respectively. The bushing dimensions are 8mm and 24mm.
Image: Dimensional diagram of the AO39RC shock absorber, indicating length, travel, and bushing measurements.
2. Air Pressure Adjustment
The AO39RC features a dual-chamber air system. Proper air pressure is crucial for optimal performance and rider comfort. Use a high-pressure shock pump to adjust the air pressure.
- Main Air Chamber: Adjust this first to set the sag (the amount the suspension compresses under the rider's weight).
- Negative Air Chamber: Adjust this to fine-tune the initial sensitivity and small bump compliance.
Attention: The maximum air pressure should not exceed 275 PSI. Ensure that the main chamber pressure is always greater than or equal to the negative chamber pressure.
Image: Detail of the air valve, emphasizing the maximum air pressure limit of 275 PSI and the relationship between main and negative chamber pressures.
Image: Illustration of the dual-chamber design, showing how primary and secondary air chambers enhance damping performance, with a graph comparing shock absorption with and without the shock absorber.
Operating the Shock Absorber
The AO39RC offers several adjustments to optimize your riding experience.
Image: Labeled diagram of the shock absorber's core functions, including adjustment points.
1. 3-Stage Lockout
The lockout switch allows you to quickly change the shock's compression damping to suit different terrains:
- Lockout Status: Ideal for road cycling or smooth climbs, minimizing suspension movement for maximum pedaling efficiency.
- Semi-Lockout Status: A mid-position offering optimal performance for light off-road use or undulating terrain.
- Open Status: Fully open setting, excelling on rough terrain and technical trails, providing maximum shock absorption.
Image: Visual guide to the 3-stage lockout switch and its corresponding statuses.
2. Rebound Adjustment
The rebound adjustment knob controls the speed at which the shock absorber extends after compression. Adjusting this is crucial for maintaining tire contact with the ground and preventing bucking.
- Clockwise (S): Slower Rebound. Use for widely spaced, high-intensity impacts to prevent the shock from extending too quickly.
- Counterclockwise (F): Faster Rebound. Use for closely spaced obstacles with low impact intensity, allowing the shock to recover quickly for successive bumps.
Image: Detailed explanation of the rebound adjustment, showing the effect of clockwise (Slower) and counterclockwise (Faster) turns.
Maintenance
- Cleaning: After each ride, especially in dirty or wet conditions, clean the shock absorber with mild soap and water. Avoid high-pressure washers directly on seals.
- Air Pressure Check: Regularly check and adjust the air pressure in both chambers using a shock pump. Pressure can fluctuate with temperature changes.
- Seal Inspection: Periodically inspect the seals for any signs of wear, cracking, or leakage. Worn seals can lead to air loss and reduced performance.
- Lubrication: Keep the exposed shaft clean and lightly lubricated with a suspension-specific lubricant.
- Professional Servicing: For internal maintenance, seal replacement, or complex issues, it is recommended to seek professional servicing from a qualified technician.
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Loss of Air Pressure | Worn seals, damaged valve core, improper valve cap. | Check valve core for tightness. Inspect seals for damage. Replace worn seals or valve core. Ensure valve cap is securely fastened. |
| Poor Damping Performance | Incorrect air pressure, improper rebound setting, internal damage. | Adjust air pressure to recommended sag. Adjust rebound setting. If issues persist, seek professional service. |
| Lockout Not Functioning | Internal mechanism issue, low air pressure. | Check air pressure. If the lockout lever moves but has no effect, professional service is required. |
| Unusual Noises (e.g., squishing, knocking) | Low oil level, air in damping system, loose mounting hardware. | Check mounting bolts for tightness. If noises persist, it may indicate internal issues requiring professional service. |
Specifications
| Attribute | Value |
|---|---|
| Brand | DNM |
| Model Number | AO39RC |
| Material | Aluminum/Alloy |
| Use | Mountain Bikes |
| Length Options | 165mm, 190mm, 200mm |
| Travel Options | 35mm (for 165mm), 50mm (for 190mm), 55mm (for 200mm) |
| Weight (incl. 24mm bushing) | 165mm: ~293g, 190mm: ~315g, 200mm: ~324g |
| Max Air Pressure | 275 PSI (Main chamber pressure > Negative chamber pressure) |
| Features | Dual-Chamber Design, Rebound Adjustment, 3-Stage Lockout |
User Tips
- Sag Setting: Proper sag is critical for suspension performance. Consult your bike manufacturer's recommendations or general guidelines (typically 25-35% of total travel for trail/enduro, less for XC).
- Shock Pump: Always use a dedicated high-pressure shock pump for adjusting air pressure. Standard tire pumps are not suitable.
- Spare Parts: Consider checking with the seller or manufacturer for the availability of spare parts, such as seal kits, for future maintenance.
- Break-in Period: New shocks may require a short break-in period (a few rides) for seals to fully seat and damping to become consistent.
Warranty and Support
For warranty claims, technical support, or inquiries regarding spare parts, please contact the seller or the manufacturer directly. Keep your purchase receipt as proof of purchase.