If you want to at least mitigate the "loose spring" issue, you can find a way to ziptie the springs to the top mount so they have the shock body to guide them back to the bottom perches if they ever are rattling loose in there.

In practice, when I asked Ground Control about "loose springs", they said it wasn't really an issue.

It's nice to see 949 and SD "crossing streams" in here.

To clarify, there are two different types of flat wound secondary springs; Tender and Helper.

That's a tender. Doesn't do anything to change wheel rate. Only job is to keep spring from rattling.

The Xida uses a 150 in/lb helper for example, which is about the same rate as the OEM front springs. It works to keep the tire planted at full extension where the much higher rate main springs runs out of stroke. Tender's are inexpensive, Helpers not so much.

Its like an allstar team.

OK so here's some confusion into the mix.

I've always understood:
helper = flat wire coil <10 lb/in to keep springs seated
tender = trapezoidal wire coil within normal rate range for creating your own dual / progressive rate suspension profile.

And from Eibach's website:

Semantics fail.

Yeah I guess so. Oops. Anyway, the important things is to understand there are two distinctly different functions with the auxiliary springs mentioned in this thread.

If you have 7 inches of spring and compare a 550# 7 inch spring to a 5 inch 550# spring with a 2 inch tender, which works better, why?

Better?

Just different. One stack will be a progressive rate through part of it's stroke, the other will be linear rate all the way through. You decide what will work best for your application. The stack will actually have a step in the rate, softer at first then stepping to a higher rate when the short helper goes to block height.

Hyperco FAQ and formula to calculate different combinations.

I agree. A bit surprising, but it is nice to see.

One reason is that Bernie isn't the type of guy to slam 949/AST/or FM in order to sell a set of revalves. And he doesn't seem to be the kind of guy to make people wait 6 months or a year to get a set.

Or maybe it's two companies with a "fresh" business philosophy where they understand what they're selling because they developed it, and also can play in the same sand-box.

And Emilio's enough of a gentlemen that he's welcomed Bernie to the forum and hasn't had the poor taste to hawk his wares on Bernie's thread. But luv fest aside, both of these fellows are experts in their field and it's great to have them spend their valuable and very limited time answering our questions. Thanks, fellows!

True, I've read enough threads where a vendor tried to talk smack about another vendor's product to try to get a sale. Emilio and FM know what it's like to be on the receiving end of that deal.

This thread is packed full of info and I've read every word of it.

Im ever so curious about the differences between the double and triple adjustable xidas. What kind of things can you adjust with the triples that the doubles can't.

Also, Berni or Emilio, have you thought about writing a book? lol

My understanding is that the double adjust the compression and rebound independently.

Triples separate low and high speed compression adjustments. Two concentric knobs on the remotes.

I'd say that VERY FEW people need triples.

Emilio, is there a reason why AST decided to increase compression and rebound together on the singles? Would rebound only have been less expensive to manufacture?

Cost wasn't a consideration in the case of the Xida-S. Adjusting both together is pretty standard for single adjustable monotubes. One can set up an SA monotube to adjust rebound only, with virtually no effect on compression. OTS Koni Sport/Race are like this I believe. The specific adjustment range and values of comp/rebound on the CS & S were my decision. The Tein Flex (twin tube) and MonoFlex (monotube) I had done a lot of experimenting with changed compression a bit with the rebound adjuster and I found it very useful when revalving. For the Xida's each click affects comp but we kept the bulk of the comp value and knee shape change towards the last few clicks near full stiff.

Let's break things down on compression and rebound to understand it a little better.

When you compress a spring, energy is being stored by the spring. When the spring extends, energy is being released.

The purpose of a shock is to absorb energy, and in return, control resonant frequencies.

The reason a shock needs less compression than rebound is because during compression you have energy going into the spring, and on rebound you have energy being released by the spring along, with the resonance.

A stiffer spring does not absorb more energy. Why? Because you are not transferring more weight. The weight of the car is the same no matter what spring is in the car. So, since you are not storing more energy, you store the same amount faster/shorter distance. On the other end, you are also releasing the energy faster with a stiffer spring. The reason for more rebound.

This is why when you go up on spring rate you also go up on rebound, and down on compression.