The 1973 Citroën SM coupe is a masterpiece of French engineering, known for its futuristic design and advanced hydropneumatic suspension. This system provides a magic-carpet ride but requires specialized parts that can be hard to find. If you are searching for "1973 Citroën SM coupe suspension parts for sale," you likely need to restore or maintain this unique vehicle. This guide will help you understand the suspension components, what to look for when buying, and where to source them reliably.
Understanding the 1973 Citroën SM Suspension System
The SM uses a hydropneumatic system that combines hydraulic fluid and nitrogen gas to absorb shocks and maintain ride height. Unlike conventional coil springs, the SM's suspension uses spheres and hydraulic cylinders. Knowing how it works is key to buying the right parts.
Hydropneumatic vs Conventional
In a hydropneumatic system, each wheel has a suspension sphere filled with nitrogen gas and separated from hydraulic fluid by a flexible membrane. The fluid is pressurized by a belt-driven pump, and the system automatically adjusts ride height. Spheres lose pressure over time, causing a harsh ride and sagging. Conventional suspension uses springs and shock absorbers, but the SM is entirely different. Parts for conventional cars will not work.
Common Wear Items
The most frequent issues are flat suspension spheres (loss of nitrogen), leaking hydraulic cylinders (corroded pistons or worn seals), and sticking height correctors. Rubber bushings and anti-roll bar linkages also deteriorate. When shopping for parts, focus on these high-wear components.
Key Suspension Parts for the 1973 Citroën SM
Here are the main components you will need to consider when buying suspension parts.
Spheres and Accumulators
Suspension spheres are the heart of the ride. They come in front and rear variants, and also a main accumulator sphere that stores pressure for the system. For the 1973 SM, you need correct part numbers (usually 95 627 198 or equivalent). Spheres are available new from Citroën specialists or as rebuilt units. Ensure they are pre-charged with nitrogen to the proper pressure (around 40–50 bar depending on position). Most aftermarket spheres are compatible but check the membrane material – rubber diaphragms are standard.
Height Correctors and Linkages
Height correctors are valves that adjust fluid flow to maintain ride height regardless of load. They are prone to sticking due to old fluid deposits. You can buy new correctors or rebuild kits with seals and springs. Linkages from the corrector to the suspension arms also wear; they are small but critical for proper alignment.
Hydraulic Cylinders and Seals
Each wheel has a hydraulic cylinder (actuator) that replaces a conventional shock absorber. The cylinder body and piston can corrode, especially in salt-belt states. Seals inside the cylinder leak, causing loss of pressure. You can purchase new cylinders (OEM original or aftermarket) or rebuild your existing ones with a seal kit. Rebuilding is cost-effective but requires careful disassembly and clean fluid.
Anti-Roll Bars and Bushings
The SM has front and rear anti-roll bars to reduce body roll. The rubber bushings that mount them to the chassis dry out and crack. Polyurethane replacements are available for longer life. Also, the drop links connecting the bar to the suspension can be replaced.
Wheel Bearings and Hubs
Though not strictly suspension, wheel bearings are often serviced alongside suspension work. The SM uses unique hub assemblies with integral bearings. Check for play or noise. New hubs are scarce; rebuild with quality bearings from SKF or Timken if possible.
Where to Find Suspension Parts for Sale
Finding parts for a 1973 Citroën SM is easier than you might think, thanks to a dedicated community. Here are the best sources.
Specialized Citroën Parts Suppliers
Several companies in the US and Europe focus exclusively on Citroën parts. They carry NOS (New Old Stock) and reproduction suspension components. These suppliers often have technical knowledge to help you verify fitment. Examples include Citroën Classics, Western Hemispheres, and Long Beach Citroën Spares. They sell spheres, cylinders, height correctors, and seal kits. Prices are fair for the rarity of the parts.
Online Classic Car Parts Retailers
General classic car parts websites may list some SM suspension items, but availability is limited. Use specific part numbers to search. These retailers often have used parts from parted-out cars. Be cautious with condition – ask for photos and guarantee of functionality.
Citroën Enthusiast Forums and Classifieds
Forums like the Citroën SM Club (SMClub.org) and the Citroën section of the Citroën-Visual forum have classified sections where owners sell parts. You can find used spheres that still hold pressure, rebuilt cylinders, and even entire suspension subsections. Prices are negotiable, and you can ask the seller about the part's history.
Rebuilt vs New vs Used
New parts are ideal but can be expensive and backordered. Rebuilt parts (especially spheres and cylinders) are a good compromise – they are disassembled, cleaned, and fitted with new seals and fluid. Used parts are cheapest but risky; only buy used if you can confirm they came from a working car and have no visible leaks or corrosion.
How to Choose the Right Parts
Selecting the correct suspension parts requires attention to detail.
Compatibility and Part Numbers
The 1973 SM has some differences from earlier and later models. For example, front and rear spheres have different pressures. Always verify your car's VIN or production date. A parts supplier that asks for your chassis number is reputable. Use original Citroën parts catalogs or the Smiths Service Manual to cross-reference part numbers.
Quality and OEM vs Aftermarket
OEM parts (made by Citroën or licensed suppliers) are generally best, especially for spheres and height correctors. Aftermarket parts vary: some are excellent reproductions, others are poor. Look for brands like SACHS, a known OEM supplier for Citroën hydraulics. Polyurethane bushings are fine for anti-roll bars, but avoid cheap rubber that degrades quickly. Ask suppliers about the material and warranty.
Budget Considerations
A full suspension rebuild (spheres, cylinders, height corrector, bushings) can cost $2,000–$4,000 USD in parts alone. Spheres are around $100–$200 each. Cylinders are $300–$600. You can save by rebuilding cylinders yourself with seal kits, costing about $50 per cylinder. Allocate extra for hydropneumatic fluid (LHM or equivalent).
Final Recommendation
For a 1973 Citroën SM, prioritize replacing all suspension spheres first. Flat spheres cause the most ride degradation and can damage other components. Buy new or professionally rebuilt spheres from a known Citroën specialist. Rebuild the cylinders if they leak; seal kits are widely available. Replace height corrector linkage bushings and check the corrector function. For anti-roll bar bushings, choose polyurethane for longevity. Avoid generic parts – stick to parts made for the SM.
Source parts from a mix of specialized suppliers and enthusiast forums. If you need a quick fix, use a rebuilt cylinder from a vendor with a warranty. For long-term reliability, replace rubber components with quality polyurethane. Always flush the hydraulic system with fresh LHM fluid after repairs. With proper parts and installation, your SM's suspension will again deliver the legendary smooth ride that makes this car so special.
Restoring a 1973 Citroën SM is a rewarding project. The suspension is the most critical system, and sourcing the correct parts ensures your car remains safe and enjoyable. Take your time, consult with specialists, and buy quality components. Your SM will thank you for it.