carnut169

I'm assuming that I raise the lower perch to accomplish this. My question: is it 1:1? In other words would raising the perch 1" raise the car 1"? Seems like it would also just compress the spring 1" so I'm confused about how this works to raise the car but if it does, great.

emilio700

iTrader: (3)

Motion ratio of the suspension is close to 1.5. It's actually a bit under or over depending on year, which end of car where in travel and wheel offset. I use 1.5 as a rough guide

Thread pitch is 1.5mm. One full turn makes 1.5mm difference in collar position.

So multiply preload collar distance by about 1.5.

Example:
4 turns = 6mm preload change
6mm preload change x 1.5 = 9mm. Multiply mm x .0393 to get inches

9mm x .0393" = .35"

sakana

It's not 1:1. In Fact...

"On a Miata, the front motion ratio is 0.69:1 and the rear is 0.75:1"

So for every 1" you move the front perch, the car will be raised 1/0.69 =1.45".

Similar for the rear. Read this whole article, it explains a lot about shocks in a miata.

http://www.motoiq.com/magazine_artic...a-hacksaw.aspx

edit: beaten!

2ndGearRubber

Why not just use FM shock spacers if you don't want to adjust the perches?

crashnscar

iTrader: (9)

Uhhh, what??? Why not go spend money on something else when you can just adjust what you have? Please.

Savington

iTrader: (31)

Don't think of it as compressing the spring - the weight is the same so the spring isn't going to change in compressed length. What you're effectively doing when you raise the spring perch collar is lowering the shock in relation to the spring, which pushes down on the lower control arm and raises the car up.

As shorthand, I have always gone with 3 turns = 1/4". Remember that raising one corner of the car will shift weight onto that corner from the opposite side, so even if you were to figure out the exact motion ratio the adjustments are almost never exact or perfect the first time. 3 turns actually ends up at something like 7mm, but it's more than close enough for rough adjustments before you fine tune at the end.

2ndGearRubber

If he doesn't want to pre-load the springs, or has some other reason to not want to adjust the collars up further, they would work. Or he could be in my shoes and have maxed out the collars, and still have ride height issues; thus FM spacers may be applicable.

Braineack

iTrader: (62)

If it was 1:1 yes. but it's not, the ratios have been posted, but it's closer to 1.5x.

the spring doesn't compress an extra 1", because the car moves back up 1". the spring will always be the exact same length under the car's body weight...so all you are doing is moving the point in where it rests in relation to the shock...the car sits on the springs so the position of the perches dictate the body height.

Joe Mauch

Got my Xidas on Saturday, installed on Sunday!

I ended up ordering the FM shock spacers yesterday and while I wait for those to come in tomorrow, I didn't install the 4 extra bushings on the shocks before I put them in the car, which I assume is there to raise the car. Right now, I'm running enough preload to compress the helpers half way just to not bottom out on my 1-2" drop off my driveway while I figure out how to get the car a little higher.

Where do these extra bushings go in the stack and what exactly is their purpose?

Braineack

iTrader: (62)

wtf why? shock spacers on adjustable xidas, are you serious?

just raise the god damn perches. what a waste of $70+ dollars.


what bushings are you speaking of? and why would you leave something off a world class suspension setup? why can't my fist go through my screen and into yours?

Joe Mauch

Hmmm, wouldn't adding the spacers allow me to back off the preload a bit -- allowing the helpers to expand back out and regain some droop while getting that sweet progressive spring effect by not running with helpers fully compressed all the time?

All I want is to clear my 2" drop off my driveway and not bottom out on speed bumps -- which it did until i cranked the perches up an inch as a band-aid solution. Is my logic wrong here?

Jesus, calm down. The shocks came fully assembled and I installed them that way because that's what Emilio instructed me to. I'm just curious what the extra bushings included are for and where they go. They come in a separate baggie along next to the bag of allen wrenches in the delivery box.

soviet

iTrader: (10)

Brainy there are extra 1/2" bushings that go under the top hat. They are optional and I imagine are for people that want to have stock ride height (????)

Joe even if the shocks are fully assembled you still need to set ride height for your specific car.

Braineack

iTrader: (62)

you have a slight point here, but helpers are meant to be compressed all the time, only in droop should they extend and only to keep the spring planted. If you had fully compressed tenders then that would be a different story. the helper springs are like the shock spacers for your springs if the were longer you wouldn't have to dial up back in any more preload.


I don't see raising up perches as a band-aid whatsoever so long as you have not compromised more droop then the sways even allow.

carnut169

I was also wondering what those bushings were for.

I did raise the car last night- needed to go 20 full turns in the rear to get 12.75" (from center of wheel to fender) and yes, the helper springs appear to be almost completely compressed (and now doing nothing) with the tire in the air.

May end up going 12" in front and 12.5" in the rear which would give me a *slight* amount of room left for the helpers to compress. I'll drive it 1st and see how it feels at the new height and if I get any rubbing.

If you did add the extensions the collar could be unwound quite a bit which would seem to allow for less spring compression... Guess I could just install the other set of bushings and have the same effect although removing again doen not sound all that appealing.

Where are you guys running the shocks- full stiff, soft or in the middle? I counted 12 clicks of adjustment.

carnut169

My helpers are completely compressed even with the wheel in the air- required to obtain desired ride height.

Joe Mauch

Same, except i'm not running the perches as high as to fully compress them, because i'm still on my lame 14" wheels that tuck into the fender and dont' rub. If I had my 6UL's on I would have to roll and raise the perches some more. (6UL's get on this weekend when I borrow my friends hammer)

I bought the xidas knowing the shock body is not height adjustable, and I do think cranking up the perch is a bandaid to a degree which is why I went with the FM spacers.

if Soviet is correct and the extra 1/2in bushings add height by installing them with the other bushing under the top hat, what's the real compromise?

soviet

iTrader: (10)

my helpers are completely uncompressed with wheel in air. I have poly bushings and 12.5/12.75" ride height

soviet

iTrader: (10)

lol, no you don't. Run more camber and borrow your friend's mallet.

The only place I rub is inside the shock tower and maybe the sway bar at full lock. 15x9 + NT-01

Braineack

iTrader: (62)

they were made this way on purpose, as they were sized specifically for a miata. Adjustable length shock bodies are a horrible compromise and bandaid in order to make shocks fit cross-platform while giving up bump travel.

what spring rate/length did you end up with? something doesnt sound right if you need that much preload in order to only have a 12.75" rear and a fully compressed helper in droop.

Joe Perez

iTrader: (8)

Uncompressed length and spring rate of main springs?