Dedicated to the memory of the late Brian Archer who fulfilled his dream to re-create John Sprinzel's Sebring Sprite Coupé


Adjustable Shock Absorbers

from Peter Caldwell

My contact, and Sebring builder, in the USA, Neil Anderson, recently told me about some adjustable front and rear shock absorbers being produced by Peter Caldwell, in Madison, Wisconsin now that original Armstrong adjustable 22s are almost impossible to find. Graeme Henderson is using Caldwell's items on his Sebring Fastback, as they are now available in the UK through Peter May Engineering.
Caldwell explains: "Having been in the remanufacturing business of Armstrong lever shocks for many, many years, we have had the opportunity to rebuild a few of the original Armstrong "Adjustable 22" externally adjustable shocks. You can find examples of these in some of the original special tuning parts manuals. Armstrong had different castings made for some of these models, but did not make them available for all of their various models of shocks. Because the body is somewhat larger and had a large adjusting knob, not all cars could be fitted with the "Adjustable 22" units.
We have been able to use their same principles and apply them to a wider variety of lever shocks by employing an external and remotely mountable valve alleviating the need for new castings and fitment constraints.. The way the Adjustable 22's and our shocks work is by utilizing an extremely stiff modified main original "co-axial" valve assembly in the usual position, and providing a bypass circuit with a variable needle valve that allows adjustment of the volume of oil that passes through the co-axial main valve. (The "22" meant that Armstrong had 22 steps of adjustment.) Our valve is variable without steps, and can allow the shock to be locked solid without moving, to full, undampened movement. By machining the co-axial valve and replacing the springs with our custom made ones we succeed in providing a damping rate equivalent to full competition at 1½ turns open of a potential 5 turns.
The valve is of brass body full flow stainless steel needle construction. Connections between shock and valve are similar to brake hydraulic equipment. We've been able to test fit these on all of the models we offer to ensure accessibility and roadworthiness.
Historically, shocks become less effective as the oil heats. Our experience has been at about 20 - 25 minutes of track work, the shocks lose their dampening. After several attempts, we are now using Redline's suspension oils, and have been very pleased with the performance, especially in this application.
The modifications of the adjustable shocks are performed on our highly regarded remanufactured units. We install sleeve bearings in the bodies, install stainless shaft sleeves, and install radial lip oil seals. Pistons and bodies are selected for their proven reliability using the best combinations.
Each order is custom made so that we can consider your intended use, as well as any additional equipment you may have that would affect the mounting of the valve. We also like to know if the ride height is significantly changed as we can ensure the pistons are working in their mid-range most of the time.

For more information contact Peter Caldwell at:
World Wide Auto Parts of Madison
2517 Seiferth Rd.
Madison  WI  USA  53716-3302
US WATS (800) 362-1025
tel: (608) 223-9400 or fax (608) 223-9403

Return to top

Caldwell shock absorber
The Caldwell front and..
Henderson rear shocks ..rear shocks on Graeme's car
Caldwell FSA
Peter Caldwell's front shock absorber modified for Peter May's triangulated top link
Caldwell rear shocker
Pete Caldwell has now come up with a different valve on the rear shockers as it was difficult to reach and lock
the earlier type used.