RockShox Sid/Reba Solo Air Sid/Reba 29"/27.5"+, CSU

$337.00

In Stock

OEM replacement crown/steerer (CSU) for RockShox SID/Reba Solo Air 29"/27.5+ forks. Boost 15x110 compatible, 51mm offset, tapered alloy construction with diffusion black finish.

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Product Details

Overview & Technology

RockShox SID/Reba Solo Air CSU is the OEM crown‑steerer assembly designed specifically for SID and Reba Solo Air forks in 29" and 27.5"+ wheel configurations. Machined from forged aluminum and finished in diffusion black, this CSU integrates the tapered 1-1/8" to 1.5" steerer, a 51mm offset crown and Boost 15x110 axle interface to preserve the fork geometry and axle stiffness intended by RockShox. This replacement part retains the Solo Air spring interface and upper leg mounting points so you keep the original damping and air-spring characteristics. The aluminum construction balances stiffness, weight (0.7 lb shipping weight), and durability for trail and cross-country use while the precision machining ensures correct crown-to-leg alignment for consistent handling.

Key Features

Purpose-built fit and finish: The CSU ships in diffusion black and is finished to OEM tolerances so it mates with SID/Reba upper legs and seals without modification. The tapered steerer (1-1/8" -> 1.5") supports modern headtube standards and improves front-end stiffness. • Boost compatible 15x110 axle spacing for modern hubs and frames. • 51mm offset optimized for SID/Reba geometry — maintains trail and handling characteristics. • Aluminum construction offers high stiffness-to-weight and long-term durability. • OEM spec replacement: designed to work with Solo Air internals and original upper legs.

Fit & Compatibility

This CSU is specifically produced for RockShox SID and Reba Solo Air forks configured for 29" and 27.5"+ wheels with Boost 15x110 spacing. It features a tapered 1-1/8" to 1.5" steerer and a 51mm offset crown — verify your fork model and year against manufacturer part number 11.4018.008.409 to confirm a match. Please note: this is a crown/steerer assembly (CSU) and not a complete fork. It is intended as an OEM replacement and must be installed with the corresponding SID/Reba upper legs, seals, and Solo Air internals. If your bike uses a non-Boost axle, different offset, or a different steerer standard, this part will not be compatible.

Who This Is For

This part is aimed at mountain cyclists who already own a RockShox SID or Reba Solo Air fork and need an exact OEM replacement for a damaged or worn crown/steerer unit. It’s ideal for racers, cross‑country riders and lightweight trail riders who want to restore original handling and stiffness without replacing the entire fork. If you’re upgrading fork platforms, changing axle standards, or switching to a different offset to alter geometry, consult a mechanic; this CSU is for riders who want like‑for‑like replacement and proven RockShox performance.

Key Features

✓ OEM replacement crown/steerer for RockShox SID and Reba Solo Air forks
✓ Tapered 1-1/8" to 1.5" steerer for modern headtube compatibility
✓ Boost 15x110 axle spacing for increased front-end stiffness
✓ 51mm offset crown preserves original geometry and handling
✓ Forged/machined aluminum construction — lightweight and durable
✓ Diffusion black finish matched to OEM SID/Reba upper legs
✓ Direct fit to Solo Air internals and factory upper-leg assemblies

Product Identifiers

Vendor Item #	11.4018.008.409
UPC	710845769535

Frequently Asked Questions

Will this CSU fit my SID or Reba fork?

This crown/steerer assembly is designed for SID and Reba Solo Air forks configured for 29" or 27.5"+ with Boost 15x110 spacing and a 51mm offset. Confirm your fork’s model/year and compare part number 11.4018.008.409 to ensure compatibility before ordering.

Is the steerer pre-cut to a specific length?

No — the steerer is the OEM tapered 1-1/8" to 1.5" steerer and will require cutting to length during installation to match your headset and stem stack height. Have a qualified mechanic set the final steerer length and torque specs.

Can I use this CSU with non-Boost hubs or adapters?

This CSU is built around a Boost 15x110 axle interface. Using adapters or non‑standard conversions is not recommended as it can compromise axle stiffness and fork alignment. Use the correct axle standard for safe operation.

Do I need new seals or internals when replacing the CSU?

Seals and internals may be reused if they are in good condition, but RockShox recommends inspecting and replacing wear items (dust seals, foam rings, o‑rings) during service. If the upper legs were damaged, replace seals and inspect Solo Air internals for damage.

Can I install this myself?

Installation requires press-fit techniques, correct headset bearing preload, and precise torque settings. Unless you have the proper tools and experience, have a professional bike mechanic install the CSU to ensure safe, reliable operation.

What finish and weight should I expect?

The CSU is finished in diffusion black to match factory SID/Reba components. The shipping weight is approximately 0.7 lb; individual part weight is light thanks to the aluminum construction.

Buying Guide

When replacing a fork CSU, confirm axle standard, offset and steerer type first — these determine fit and handling. Match part numbers or consult RockShox compatibility charts to avoid cross‑model mismatches. Decide whether you need a direct OEM replacement or if a full fork upgrade is more cost‑effective. For reusing your upper legs and internals, an OEM CSU restores original geometry without the expense of a new fork; for crashes or major upgrades, consider a complete fork replacement and professional fitment.

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