SPD Tuning Service

Page down for detailed information. Suggestions, comments and questions are always welcome.

Mr. Wilfred Eibach, president of Eibach Springs, Germany has personally arranged for the Impreza spring kits now available in the US. Everyone should know that we owe him personal thanks. And special thanks to everyone at Eibach USA for the help in making this possible, as well..

The SPD Eibach/Germany Sport Spring kit is designed for the many Impreza owners who really want a better setup than stock, yet do not want the expense of Prodrive Eibach/Bilstein suspension. The spring kit is about 10% firmer than the RS and about 20% firmer than the standard Impreza. The kit is designed to be used with stock Impreza struts, although the RS struts or WRX struts will give higher performance. The ride remains very smooth on most surfaces, especially with stock or RS struts. There is a noticeable increase in stiffness only on larger bumps and, of course IN THE CORNERS!

The big question for many is how much does it lower the car. (And more on this at the end of the article.) The chassis is lowered by only about 18mm or 3/4 inch. There is a very good reason for this, so please read on. The stock strut length does not permit the ride to go any lower, if the car is going to have great handling. If the spring were to set to any lower ride height, the car would always be hitting the bump stops of the strut, upsetting the balance of the chassis. Not Good!

Eibach engineers have set the ride height and the spring characteristics so that the stock strut length and bump stop system is used to the best advantage, where the bump stop is "part of " the spring design. Under normal conditions the springs do all the work, and only on severe bumps do the heavy rubber bump stops come into play to stiffen the effective spring rate at full spring compression. This is as it was designed by Subaru engineers, and the Eibach springs keep this important design feature of the suspension. Remember this when some company offers you a 1.5 inch or 2.0 inch drop suspension - Unless the struts are shorter, the springs will never work properly. In fact, the Prodrive kit's struts are 20mm and the LEDA struts 35mm shorter than the standard strut for just this reason.

The Eibach Sport kit shows a much more controlled balance into corners and higher cornering potential. We recommend the use of the SPD Tuning Service 18mm rear bar. The 18mm bar gives very good results, so please follow our recommendations. See the remaining <Technical Information><Suspension> sections for details about 18mm and 20mm anti roll bars.  The car is very quick to turn with the 20mm bar when you turn under heavy deceleration, a condition known as trailing throttle oversteer. A manual transmission is a must and you must also be experienced enough to remember to get out of the brakes for a moment to settle the car. If you have done it, fine, if in doubt - use the 18mm bar.

This brings us to the the issue of tires. The stock and RS tires just lay down and die with this spring kit, so in order to improve your handling, good tires are needed as well. It is also an opportunity to lower the ride height a bit more and take advantage of the improved acceleration that smaller diameter tires will give.

The "official" SPD Tuning service tire is the Toyo Proxes, but there are other good tires out there. Use a 205/55-15, a 205/50-16 or a 215/40-17 to lower the car another 1/2 inch and make the suspension work 5 times better than stock passenger car tires.

When the standard is fitted with the larger rear bar, Eibach Sport springs, AGX or up-rated shocks and great tires, the car is a solid performer. For the RS owner, the larger rear bar is a surprising improvement to the car, while keeping to a reasonable budget or for the purpose of finding out what kind of a difference these changes make without spending several hundred dollars.

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