Correct Front Coil Spring Tape Decals for 1969 Z/28 RS

[jmcbeth]

I noticed that Rick's First Generation catalog has a different front coil spring tag listed for the 1969 base Z/28 (#3955720 "YF") and the Z/28 RS (#3955722 "YM"). Jerry's book doesn't list different numbers. Can anyone confirm the different number for the RS model? Was there actually a different coil spring for the RS? If so, why?

Thanks,

jmcbeth 

[Mark]

There was about 8 different front springs available.  The spring used depended on the weight over the front and rear axles which inturn depended on the options the car had.  The RS option added something like 22 lbs to the front of the car, so stiffer springs were needed, but other options could have added or removed weight from the front or rear of the car resulting in the car using anyone of the available springs.  Each car is going to be different.

[jmcbeth]

Mark,

Fascinating! Thanks for the info. I had no idea it was that complex. I am surprised  that  the tension in the springs was that sensitive to the weight distribution.

John

[JohnZ]

Springs got complicated in 1969 due to federal bumper height regulations; the primary impact point of the bumpers (both front and rear) had to be within a height "window" relative to the ground, regardless of style or options, so the springs were selected by an Engineering computer program that determined front and rear weights based on each car's specs and selected the appropriate springs for those weights. That's why Z/28's all got the "tall" V32 rear bumper guards due to their reduced rear ride height dimensions.

[jdv69z]

My 69 RS/Z28 has power steering, and uses spring coded "EY"

Jimmy V.

[Mark]

According to the 69 spring chart, the YF spring is the base spring for all weight additions to the front end from 0 to 68 pounds.  The EY spring is used for weights from 69 to 148 pounds, and the YH was used for all weights above 148 pounds.  The rear spring was always a BM spring for all weight additions or deletions.  There is no HD suspension springs available for Z28s.

So your choices just got easier.  The RS option adds 23 lbs to the front and takes 2 lbs off the rear.

Typical Z28 options weights are:

M20 +11 lb  front +5 rear
D55  +8 front +4 rear
D80 -1 front +6 rear
J50 +9 front +2 rear
N10 +3 front +26 rear
N40 +30 front 0 rear
U63 +6 front +3 rear
U69 +7 front +3 rear
U79 +5 front +2 rear
V01 +7 front -1 rear
V31 +5 front -1 rear
V32 -1 front +5 rear
VE3 -6 front +1 rear
Z22 23 front -2 rear
Z28 3 front +33 rear

I don't think you could get to a set of YH springs unless you had a Z28 with just about every option made on it.

[jmcbeth]

Ok,

I audited my options, added up the weights of each and came up with an increased front end weight of 81 lbs, placing me squarely in the EY range, just like Jimmy V. This confirms that the current tags (YF) are the wrong ones for the car.

Thanks! I continue to be blown away by the quality of people and posts on this site.

[william]

Spring tags were not always visible. On my last 69 and our 67 Z/28 the springs had been installed with the tags at the top.