Going to buy a set of Progressive 412's and I'm trying to decide what length to go with. I believe the stock shocks on a Nightster are 11". I'm wondering if I shoudl go to 11.5" or 12" to get a little more comfortable ride as I ride two-up with my wife occasionally - our total combined weight is about 380#. I don't mind going up in length, but I don't want a huge change in bike height - is a 1" increase in shock length directly proportionate to the height change in the bike?

 

No. Because the shocks are mounted at an angle, not straight up and down, the rear height increase will only be around 2/3 of the shock length increase. A 1.5" longer shock will increase the height about 1.0".

FYI on the Progressive 412's. Because of the increased travel, the 12.5" and longer shocks use a different (better) spring rate than the 12" and shorter shocks do. The longer shocks (>=12.5) will give you a smoother ride.

 

^^^ Good points ^^^ However, be aware that a 1" increase in shock length looks and feels like a pretty significant lift. In other words, to me it feels like more than just a 1" lift. You would think that as little as a 1/2" difference would barely be noticed, but you'll feel the difference. A 1.5" increase would make a huge difference in looks & feel.

 

Riding 2 up on a Nightster is something that I've got some real world input on. I'd get the 12.5's. You'll definitely appreciate the extra travel even on solo trips. I'm currently running 1200R 13.5 with a 1" DK lowering block. My lady and I are about 340 an I've still felt it bottom out 2 up. But solo is absolutely awesome. Be prepared to hate your forks when you upgrade the back. I've been planning on throwing a 3/4 inch spacer in the top of my forks springs to bring them up and add preload to stop bottoming out. Haven't done it yet but will happen soon.

 

In went with the 11.5" I wish I had gone with 12"s after awhile. So what ever you are thinking add a half inch.

 

If you go with 12.5" do you have to do anything to the front end to level it out?

 

Wish I would have seen this 2 months ago before I bought my 11" 412's. So, I'll throw my 2 cents in, hope it helps.
Solo, I'm not a big fan of what I paid for. Yes they are smoother and feel more stable in corners than the stock shocks did. They did take most of the hard back jarring hits out, but will still bottom out. I've ridden on every preload setting and ended up staying at the 2nd one up. I'm barely 170lbs, plus leather bags, maybe 5lbs in junk, a 2up seat and detachable low sissy bar.
Now with a girl on the back, I find these shocks worth the money. They really seem to work better with more weight on them actually, and I've ridden 2-up with the shocks on the 2nd, and 3rd settings. I think on the 3rd setting they felt the best, even with my heaviest of female friends( I don't know her weight, and am terrible at guessing a females weight), maybe 150-160lbs?.
I really wish I would have gone up in shock length, even just 1/2in. I feel like chock travel would make the difference in my opinion of them.
Good luck with what you decide!

 

Why spend $200+ on progressives when you can go with a road king or streetglide shock for a fraction of the cost and get more adjustability and a Cadillac ride?

 

Both front and rear stock suspension tend to be soft and sag too much, so yes, it is a good idea to level things at the front. On my SuperLow I found my forks were sagging about 2/3rds of total travel, leaving me only 1/3rd, little more than an inch, to ride on. Those numbers should be the other way around!

What I did was replace the stock springs with Race Tech single rate springs, to match my weight, and set the sag correct. That way the bike rides about an inch higher at the front, where it should have been out the factory gate. I have 13" shocks and it sits about right - more a Super-not-so-Low!

 

I went with 13.5" Progressive 440s and Progressive fork springs, I used the fork spring spacers at their full 3" length. The stock shocks were 11.75", in my mind I hit the perfect combo. With the 440s in their softest position I marked the inside flute on the adjuster with a dot of black epoxy paint.. I am 5' 9" and weigh 196 at the moment. I run the adjusters 3 turns firmer from minimum. The front is .75" higher than stock and the rear?