So I've been adjusting the ride height today. I think my pinch welds must be jacked up or I'm doing something wrong here. I searched around and found a few pictures of XIDA shafts in the "optimal ride height", "Adjusting ride height is a pain", and the "Spring length..short travel" threads.

I was trying to get the "optimal" ride height of 4" front, 4.25" rear. With the front at 4", I have 1/4" left of shaft showing between the bumpstop and shock body. Rear at 4.25 gives me about 3/4" between bumpstop and shaft body. Is that really all the travel needed between the bumpstop and shock body?

Spring rates are 750/450. Splitter and GTC 200 wing. Track only car.

I went ahead and raised it back up to give it a little more travel for now. For reference about my pinch welds, with front at 4.75" I'm a little under 12" hub to fender. Rears are 4-5/8" with a little over 12" hub to fender. With the rears that high, the helper spring is almost completely compressed(on jack stands) which seems to defeat the purpose of it.

This is the reason I'm asking about the remaining travel, as it seems my height measurements are out of whack. Basically I want to go low but still have usable shock travel. Or do I need to just leave it high, then do the zip tie thing to see how much travel I'm using at my next event?

 

I never measure travel used on the car. I simply lower it until it bottoms too much or upsets the car. The car needs to be super light before you can run 4" front pinch weld heights. Try it. If it bottoms excessively or handles unpredictable, raise it 1/8" at a time until it feels right.

 

Define "super light", please. I know I'm using a lot of bump-stop and not sure if that's a bad thing.

Front shock:

Rear shock:


Not Xidas btw, you'll get my money eventually.

 

My car is definitely not super light. I'm class limited to 2338lbs. I'll lower it back down to get some of the preload out of the rear so the helper is doing something, then follow your suggestion of raising it if it feels odd.

When I first got the car the previous owner had it slammed on some 450/250 springs. First autox the car would oversteer anytime I hit the throttle. Raised the car and tightened the rear sway bar to get it manageable. Hopefully I can go a little lower than what I had it at ->

 

"I'm too effeminate to remove the glass from my doors" crew need not apply.

 

Ouch

 

The dude is only talking ---- because he's in Commiefornia and he knows that if he were in Texas I'd make a hat out of him. He is also functionally female.

 

This is what confuses me too. The helpers in most cases are completely compressed in order just to set height/preload. So why the helpers at all? $250 is an expensive way to shave some weight off (over using one long, heavier spring) or to act as a spacer.

When you read this post, emilio says you don't need helpers, but they 'do everything better'... which initially made a lot of sense 'cause you figure the helpers are doing their thing when the tire is completely unloaded. But now, i'm a bit more confused...

As far as travel/stroke is concerned, the notion of "i never measure travel" and "you need to run a super light miata" is a bit disconcerting.

 

As I understand it, they add droop travel over holes in the road. I'd love for an engineer to explain this to my cat so she can dumb it down for me.

 

Your question is predicated on a false assumption. The helpers are not "in most cases ... completely compressed".

Whenever one corner of the car is drooped beyond static ride height, the helper is fully extending the shock and helping the tire maintain contact with the ground over curbs and potholes.

Assuming you have the coilover collar adjustment range to set your ride height at the same point using both a 6" and 7" spring, using a longer spring and eliminating the helper will do nothing.

For example, let's say you have a 2000lb car with 1:1 motion ratios, 50:50 weight distribution, and perfect cornerweights. At all four corners, you have a 6" 500lb spring, and you replace it with a 7" 500lb spring. Because you have not altered the spring rate or the weight of the car, the compression of the spring does not change - you are still compressing the spring by ~1". The extra inch of height in the spring raises the car by ~1", so you can either use them to lift the car or set the collars lower to absorb the inch (basically, you can add it on the top of the spring or the bottom of the spring).

You're still only compressing the spring by 1", though, so when you droop the shock by more than 1", the spring comes off its perch, and there is no force being applied on the shock. The tire ends up floating in the air and skipping over bumps.

With the helper in place, it remains essentially compressed until the main spring is fully decompressed (this is not strictly true, but it's close enough for this example). Once the main spring is fully decompressed, the helper spring continues to press the tire down towards the road. With the helper, the tire would remain in contact with the road, which results in more traction, a smoother ride, and better sex with your significant other.

In fewer words:

 

I believe that he is saying that he is preloading the helper all the way down and effectively making it a 250$ spring spacer.
I have the same "problem" in my MSM. If I set the perches to where they only slightly compress the helper I am at about 4" pinch welds.
This is too low for me for street duty, but probably perfect for track, for which they were intended...
If I set ride height to where I want the helper is fully compressed at full droop.

Solution is FM tophat spacer and maybe the spring locator Emilio is delivering for the CS will give some extra height.

 

If the helpers always remain compressed, then you need longer springs (assuming they won't bind). Once the longer springs are in place, you can reduce the preload and uncompress the helpers, and they will actually do their job.

 

How much pressure can the helper spring actually exert, where it would aid traction on a tire that is probably already un-weighting. I don't know d*&k about suspension but trying to understand this also

Thanks!

 

On a certain small percentage of installations with taller ride heights and heavier cars with 5" rear springs, the rear helpers may never extend. For that reason we now spec a 6" rear spring as standard. Adds a bit of weight but ensures that more owners will be able to take advantage of the rear helpers. I have yet to see a front installation that doesn't extend the front helpers.

QuiCKSHiFT / GT42R,

In the context of the original question regarding travel, correct, I do not typically measure travel. This was done during the development phase of the Xidas. No real need to do it on a regular basis now. We simply lower it until it bottoms then bring it back up 1/8" or so. Not terribly complicated or difficult to identify.

Regarding ride height and weight, I would hope that's self explanatory? Lower is faster. If the car is heavy enough, it will need really high rate springs to keep from bottoming at 4" front. Again, those with 5" rear springs (your set has 6" rears) may run out of spring length if the car is towards the heavy end of things. I define "heavy" as OEM weight + roll bar. Yes, I tend to assume every has lightened their car, sorry!

I'm anxious to hear how your set works or your monster FE3 powered car. Come to think of it, I just want to see the engine bay. In for pics.

tomiboy,

 

Based on your cars with the XIDA's, could you describe, very roughly, how much bump travel you have?
Or more generally even, the rears have 4" stroke for instance, how much bump-to-droop is that split up between?

 

Stroke (not travel) is 103mm front, 120mm rear. Damper body lengths, stops and mounts are configured to allow a 225/45/15 on our 9" wheel to hit the front shock tower bulge with about 5-10mm interference with -3° camber. This overlap was designed in to allow a bit more bump travel with narrower 205's on 8" wheels. Our enduro cars all have polished tubs and a nice wedge of rubber under there.

A friend with a national championship winning CSP car has actually worn through the tub in the front shock tower from the 275 A6's rubbing (Penske's IRC). Knarly, but fast.

On a Miata at 4" with the 225/45 on our 9" combo, almost all the stroke is used
up with sag, very little bump travel left. At rest, there is usually only 10mm or so left before the stop is engaged up front. On paper that sounds shaky. On track, it drowns in win soup.

Those running 13" wheels will just run out of stroke, then control arm articulation, then tire room.

 

Remember this?

If my rear spring is fully decompressed with a very slight pre-load, would dropping the perch and adding the helper do anything? I can't though because the perch will hit the half-shaft. Non-Xida fail.

 

re: I have yet to see a front installation that doesn't extend the front helpers.
Yes, I realize in the case of the front, that isn't an issue. I should have been more clear, I was mostly speaking about the rear damper. My mistake

re: In the context of the original question regarding travel, correct, I do not typically measure travel.

I realize this is largely how you tune the car to go fast around the track. But the OP was asking about travel, and your answer kind of just blew it off. I'm asking again because I'm trying to get a better understanding of the design considerations made when developing a damper body as specifically tuned as this one, a fresh blank slate design no less.

re: Regarding ride height and weight Lower is faster lighter is faster,
This too i know, and I also understand how those things play into building a genuinely fast miata, ala, 949 supermiata. That in conjuction with these specially tuned xidas im sure makes it very impressive indeed. I'm simply trying to consider the implications and future spring rate and length adjustments I might be doing to fine tune my setup, as its a bit overweight, bit front heavy, lots of aero, etc,

re: I'm anxious to hear how your set works or your monster FE3 powered car. Come to think of it, I just want to see the engine bay. In for pics.

I'm confident my xida's will blow me away, and are modular enough that they will last to whatever extent I continue to build the car out. At the moment, I've only assembled them and mocked them up in order to check for rear axle clearance, until I get the upper spring perch thing sorted. I started spinning some 4.5" aluminum stock on the lathe today, so I think pretty soon I'll have a pretty good solution for that, and be setting up and testing the xida's out in no time. If you're calling me out for pics though, it will have remain PM.

edit: just read your most recent reply emilio, and that was very insightful in regards to my post here, thank you!

 

That's kind of why spring length in rear is tricky. For most cars, a 6" and helper will just clear the half shaft and allow the helpers to extend. If the car is too light, running really low so requires almost no preload, the 6" springs allow the perches to hit the halftshaft. Few cars are that light and low, hence the switch to 6" rears for regular production.

GT42R,

I might recommend something like we do with the adjustable length "JDM" style coilovers like Flex, et.al. Pulls the springs out and check stroke/tire clearance on the car withe tire/wheel mounted. You can get and idea of how much bump stop you need for your particular tire/wheel combo. Naturally, I have to find a happy medium somewhere with damper assembly length to try to optimize tire room for the widest range of users. To get that last tiny bit of bump stroke from the damper, mock it up with a tire and no spring.

You'll see how little room there is for control arm articulation and tire clearance just before the bump stop engages. What amazed me when we first tested the really low ride heights was how little bump travel you could set up for and still have it soak up big hits.

They will spend a fair amount of time in the stops but that's mere millimeters away from the control arm articulation limits. IOW, more bump travel would be pointless.

The flip side of that is if one wanta less bump travel and more static ride height. Many daily driver, rarely (never) raced set ups want near OEM ride heights. That's what the extra spacer we send, is for. Several ways to make the assembly longer. The spring seats you and Joe are making will slightly lengthen the assembly and reduce bump travel. Unless you are running really small tires, that's OK though as the way we ship them leaves you with a few unused mm of useful bump travel anyway.

In short, custom tune your particular install to squeak the last bit of useful bump travel from it.

 

Looking at the Xida Clubsports vs the Xida S it appears the NB top mounts of the Club Sports provide more travel than the AST Mono Ball hats of the Xida S in the front by about an inch.

The rear hats are taller and do not appear to be as travel limited. Maybe on the super low cars you can run the rear style AST top hat in the front?