SPD Tuning Service

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The LEDA damper company is located in England and has a strong following in sedan racing and clubman rally circles through out Europe. They have been fitted to BTCC wining Fords, FIA Porsche Cup cars and countless fast road cars. Similar to Prodrive, LEDA has developed an Impreza shock setup based on their extensive experience. The difference is that LEDA has been asked to develop a 24 position, adjustable shock that is perfectly streetable at its lowest setting, while track worthy at its mid to firm settings.

The LEDA shock uses a spring loaded tapered needle adjuster and bleed valves in the body of the shock. At soft settings the needle valve is off its seat. Thus it has a velocity damping curve that is tuned to the Impreza chassis. Once the valve is closed down past about click 8 the needle valve is closed on its seat and the spring pressure is now increased over the seat with each additional click. The smaller, fixed bleed holes now begin to dominate the shock as it becomes harder and harder for shock load to cause the needle valve to lift off its seat.

The rebound rate is fixed in proportion to the 24 position adjustable compression rate. Rebound rates have been optimized for the known weight of the Impreza. the fairly predicable spring rates that work within various click adjustable positions. This gives a very tunable shock without the expense of independent adjusters for rebound and compression ("jounce" in English, English). This compromise  is attractive from a cost standpoint and acceptable from a technical view because the average owner can trust that LEDA has worked with the front and rear shock settings to evolve a proper balance in the rebound setting for each level of compression setting. Lap times prove this to be the case.

A gas unit is used because of its superior fade resistance (shock get hot just like brakes when racing on rough surfaces) as a special option to the coil over strut. LEDA makes these units independently adjustable for compression and rebound with the addition of a gas reservoir with a needle valve controlling the bleed of nitrogen back into the shock on rebound. For most purposes on hard road, the gas units are overkill and do not improve the results the standard LEDA units.

These are no nonsense shocks that provide the Impreza owner the tools for serious track work. LEDA has done the basic valving and setup of the shock specifically for the Impreza, and by all reports from England are spot on the money. In addition the units are affordably ($65 per corner) field rebuildable for a long life.

Send mail to mshields@spdusa.com with questions or comments about this web site.
Last modified: May 23, 2000