Two-Stage Stack Spring

Integra’s Two-Stage Stack Spring Kit is typically used on the right front of
Dirt Late Model cars. Its use allows the car to initiate movement by starting with a softer
spring, then eventually hitting a “stack nut” and utilizing a
pre-determined stiffer spring. Adjustment is made by changing the “gap” that is between the
“stack nut” and the slider.

Stack spring examples are for demonstration purposes. Each track may require a specific
combination and stacker nut “gap” for your particular chassis and racing surface.

Stack Spring Configuration

Pictorial description of our Stack Spring Configuration

rate progression of 2 stacked springs USING A 4" (600 lb.) AND 8" (700 LB.) SPRING
no stacker nut		with stacker nut
Displacement In Inches	Wheel Load Lbs./Inch	*1" gap travel rate Lbs./Inch	*3/4" gap travel rate Lbs./Inch	*1/2" gap travel rate Lbs./Inch
Ride Height	500	500	500	500
1"	847	847	847	924
2"	1199	1267	1425	1587
3"	1637	1905	2073	2243

*Gap between stack nut and slider (see illustration 1-A)

rate progression of 2 stacked springs USING A 4" (350 lb.) AND 8" (700 LB.) SPRING
no stacker nut		with stacker nut
Displacement In Inches	Wheel Load Lbs./Inch	*1" gap travel rate Lbs./Inch	*3/4" gap travel rate Lbs./Inch	*1/2" gap travel rate Lbs./Inch
Ride Height	500	500	500	500
1"	774	774	774	861
2"	1135	1210	1365	1554
3"	1755	1854	2037	2200

• All examples are starting 18" eye to eye measurement on shock and spring and simulate car at ride height, giving you an accurate starting point on wheel load.
• Testing conducted using an Integra RF IDA Shock with 50 PSI gas pressure.

STACK SPRING RATE CONVERSION CHART

4" Spring and 8" Spring in Series

8" LONG x 2.5" I.D. SPRING

4" LONG x
2.5" I.D.
SPRING

	400	450	500	550	600	650	700
350	186	196	205	213	221	227	233
400	200	211	222	231	240	247	254
600	240	257	272	286	300	312	323

Dual Stage
Stack SPring Kit
#310-30550

*All rate values in lbs/in

	400	450	500	550	600	650	700
350	186	196	205	213	221	227	233
400	200	211	222	231	240	247	254
600	240	257	272	286	300	312	323

	400	450	500	550	600	650	700
350	186	196	205	213	221	227	233
400	200	211	222	231	240	247	254
600	240	257	272	286	300	312	323

	400	450	500	550	600	650	700
350	186	196	205	213	221	227	233
400	200	211	222	231	240	247	254
600	240	257	272	286	300	312	323