Stock rear shock question

[EMS]

Semantics, Rick. when I was talking about "damping" I was referring to what Honda calls the "Spring Adjuster" on the bottom of the shock. This is the only adjustment the 79 and 80 shock have in common. Changing that, will change the length of the shock.

[NobleHops]

So you misspoke, no big deal. Damping is damping, spring preload is different. That’s not semantics, that’s the wrong term, describing something different. Adjusting the ramped collar that adjusts preload does NOT “change the length of the shock”. It will lengthen the as-installed length of the shock when loaded. Adding more spring preload will raise the rear of the bike for a nominal load by reducing the amount that the bike is “sagging” under load.

“Sag” is a term that many people struggle to understand. Sag refers to how much a shock is compressing under load, as compared to its fully unloaded condition, meaning “rear wheel is off the ground”. There is only one correct sag (spring/preload setup) for a given bike and load, one where the shock is 1/3 of the way through its total travel, when loaded. For riders within a nominal 160-220 lb range that is usually attainable using the stock preload adjustments on the bike. When it isn’t attainable, a spring swap is what’s needed to get the suspension working properly.

Too little sag means that the bike is too lightly loaded for the spring, which will result in a rougher ride. You WANT the rear wheel to travel over a bump, to give the damper the opportunity to do its things and reduce the oscillations that would occur without it. If the spring is too strong, the shock won’t travel.

Too much sag means the bike is too heavily loaded for the spring resulting in very little travel in reserve to absorb and dampen those bumps, turning you and your heinie into the reserve damper.

Artie, Dave, spring condition would not affect the as-measured eye-to-eye length of an uninstalled (or fully extended on the centerstand) shock, unless the spring is so sacked that it has play at minimum preload on the ramped collar. All shocks have some degree of spring preload (on the order of 10mm) when manufactured, to prevent the spring rattling around. Or, if you prefer, the spring is already pushing the shock to maximum length, when unloaded.

Happy to answer any suspension setup questions, as a guy that sold shock and fork products for 6 years.

[Rick Pope]

Does the '79 American version have a damping adjuster, as EMS implied above? I thought spring preload was the only adjustment that year. I'd go look, but my stock shocks fell off years ago. But the picture Mike posted above doesn't show damping.

[EMS]

. Adjusting the ramped collar that adjusts preload does NOT “change the length of the shock”.

Nils:
If you take an uninstalled shock and adjust the spring pre-load, the overall length of the shock will change. I just did that.
Figure that you compress or release the spring and there is no hold on the upper eye, the length of the shock will move.
I am sorry for the term confusion, but it seemed it was clear what I meant as the spring adjuster is the only adjustment the 79 and 80 shock have in common. One other thing, if you look closely at the pictures, you will see that the lower part of the shocks, under the springs are not the same length. Partially compensated by a different spring length, but still resulting in an overall different length.
And yes, Rick, the US shock does not have an upper damping adjustment. As we have determined, it was a misleading description.
The European 79 model had the fully adjustable shock as the 1980. Why they did that for US and Canadian bikes, I have no idea.

[NobleHops]

Mike:
The only reason that an uninstalled shock would change it’s eye-to-eye length as a result of adjusting preload would be if the spring was so worn out that it had lost more than 10mm or more of its nominal free length, and was sitting on your shelf in this condition when you tested this. And you can confirm this if you like by removing all preload with the ramped collar and un-sticking the spring from the collar and you will find that it is rattling around because it has lost free length and is shot.

To be clear: ALL shock absorbers with integral springs have a minimum amount of spring preload, regardless of the preload setting. An uninstalled shock will be the same length on your shelf regardless of any spring preload setting it may have, unless it has a roached spring, as above.

The ONLY EXCEPTION to this is sometimes found in high-end shocks or racing shocks that have an additional adjustment for ride height, which is simply a thread and locknut setup on one end that allows the overall length of the shock to be adjusted to change the attitude of the bike.

[EMS]

I am not really sure what's going on, but in any case: I am sorry for slipping with the terminology and causing this deviation, which may be educational but did not help the original question. And that was, "What is the difference in length between a 79 and an 80 shock". Short answer, the 80 shock is slightly longer.

[Rick Pope]

What's going on, is that some of us are learning. This is not a bad thing. Thanks to all for the lessons and clarification.

[jnnngs]

ah, maybe a typo then. You put 350mm for the '79.

Paul, your typo comment prompted me to go back and look again at the shocks and what made me put up the numbers. I had to make sure the shocks were on the same damping setting. There is indeed a difference - smaller than I originally stated - between the two types. It is difficult to really assess what the "as new" conditions of a 40 year old used part actually was. Especially as the springs -like all springs - do set with age and use.

That's not a CBX FVQ shock - it's for a CB900 / CB750. Not sure it makes a difference!

[EMS]

Paul: Not sure what you are looking at, but the FVQ came off a 1980 CBX. Why don't you post a picture of what you have for a 1980CBX (or Euro 79Z for that matter)

[jnnngs]

Paul: Not sure what you are looking at, but the FVQ came off a 1980 CBX. Why don't you post a picture of what you have for a 1980CBX (or Euro 79Z for that matter)

See attached picture for differences between CB900F (and 750F) and the CBX shocks. Euro '79 and all '80 shocks are the same.

Screenshot 2022-12-06 120453.png