Did all '69 Z/28's come with the tall rear bumper guards?

[ZLP955]

Minor difference at D is probably due to difference between mono and multi leaf spring arrangement and arch profile, and tolerance on manufacturer's tire dimensions. That's why the dimensions that are comparable across all models relating to bumper height are J and K.
I wouldn't be too quick to say the AIM is incorrect.

[X33RS]

Sure looks that way to me.  Been discussed in the past.  It's pretty obvious when you look at the numbers.

How can you have 2 cars with virtually the same tire height, yet one is lower at K while the other is lower at D.   D being the actually suspension measurement.  Just not possible. 

Lets make it easier.  2 identical cars in every way.  When both are measured at D, example 1 is lower than example 2, yet example 1 measures higher at the rocker???  Someone must have had a few beers when they hung the sheet metal on example 1.   

[ZLP955]

D is a relative measurement between two parts on the vehicle, sprung and unsprung. The measurements from the ground are what count.

[X33RS]

Actually, the D measurement is the important one.  The measurements from the ground have other variances (like tires) that affect the measurement, and even air pressures come into play.   So like I said earlier, when you have 2 cars and example 1 is lower at D than Example 2, yet example 2 is lower at K than example one, yet both have the same height tire, the math doesn't add up.   That's why people question the numbers in the AIM. 

   Frankly, If I were looking to set a 1st gen properly, I would be using the D measurement to base my cars from, then put the proper tires on it.   

[ZLP955]

We don't have to agree, but I'd rather see a discussion on what factors influence the height of a rear bumper.
If you put a jack under the front and raised the front wheels a foot off the ground, the lever effect pivoting around the rear axle would drop the rear bumper height significantly.
D would not change as it is vertically over the pivot point, the rear axle (ignoring any change of the frame rail frofile and assuming the effect of jacking did not transfer more weight to the rear) but would J and K measurements change? You bet.

My point being that other models besides the Z/28 had a very comparable rear bumper height, yet did not have mandatory V32 guards. To those who suggest the AIM trim height table must be wrong for at least several tire sizes needs more thought.

The V31 front bumper guards are very similar to the V32 guards, yet nobody has put forward a theory that these were required to make the front end bumper height meet safety standards, presumably because they weren't mandatory on any model.

I'm not sure how one could 'set' a car to those AIM dimensions anyway. I would think the table shows the tolerance on ride height, with the car built with the correct components. No doubt the line workers could spot an anomaly in ride height, and that would trigger checking the car, but the table shows where a car should sit if all was well.

[Stingr69]

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.

Post by John Hinckley.  Good enough for me.   

[ZLP955]

John's credibility was never in question. That statement has been repeated many times since. However it doesn't address the fact that other models appear to have shared the same 'reduced' ride height, yet had no V32 bumper guards mandatory. Just saying the AIM must be wrong in this regard because it doesn't fit the statement seems strange. This site is about research and discussion after all.

[ZLP955]

So perhaps another consideration should be:
What were the 'Federal bumper height regulations' in place for the 1969 model year (and even earlier, since previous 1967 and 1968 MY Z/28's also had mandatory rear guards), and what were the dimensional requirements of those?
From what I can determine, the first Federal Standards for passenger vehicle bumpers came into force in late 1972 for the 1973 MY.
NHTSA CFR 49 (Transportation) Part 581 (Bumper Standard) and FMVSS 215 (Exterior Protection) specify performance and testing requirements related to impacts in the height range of 16"-20" above the road surface. FMVSS 215 became effective in September 1972 and led to the demise of chromed bumpers in favour of resilient rubber versions.
So what national bumper height standards applied to passenger cars in the late 1960's? Were there any, or did manufacturers position bumpers to suit aesthetics and functional protection areas?

[Jon Mello]

1967 Z-28s did not have mandatory rear bumper guards. That started with the '68 Zs.

[ZLP955]

Thanks for clarifying that Jon, that was based on http://www.camaros.org/diffs67.shtml which says the '67 Z/28 had them.

[bcmiller]

A couple of things to note...

For what is it worth...
From the 1969 Camaro AMA specs, the distance listed in the GROUND CLEARANCE section for these cars in general for the height from Bumper to ground - rear is 21.2 inches for coupe and 20.8 inches for convertible.  There are also AMA specs listed for the Z28 as well, and the height from Bumper to ground - rear is listed as 21.2 inches. 

Also for what it is worth, opinions will vary on ideal tire size and "look".  Well here is a 1968 big block Camaro - with rear bumper guards - with rear tires and wheels that are not stock.  The look is about ideal in my opinion.
 

[Kelley W King]

Looks like Bryon,s type car. 468 or 496?

[69Z28-RS]

....
Also for what it is worth, opinions will vary on ideal tire size and "look".  Well here is a 1968 big block Camaro - with rear bumper guards - with rear tires and wheels that are not stock.  The look is about ideal in my opinion.
 

You're kidding???   with tires sticking outside the body by 2" or so??   

They should have radiused the wheelwells a little higher and put even larger / wider wheels on it ... and they could protrude even farther!

[Kelley W King]

cmon Gary, Are you too young to remember Day 2?

[bcmiller]

Tire/wheel combination is legal. It’s a Bill Thomas Camaro with a 396 and “two fours”.  Has original block, otherwise 496 would have been preferred. Search for it if you are bored, currently at SMT.

Sorry for the Day 2 distraction. Now back on topic.