DjGreggieP said:Looking at these is giving me bad ideas of coil over suspension for a vehicle that doesn't have an existing coil over suspension option... Which would probably be a horrible idea overall...
Make sure your shock towers can take the load if you do that. First-gen CRXs can have trouble if you pull the front torsion bars and put all the suspension loads through the shock tower.
It's installation day!
First, the thing you all want to know. Will the box fit in the trunk of an NA?
Yes.
Very convenient. I did not test the box fitment on other generations.
To make this a more typical install, I'm doing it on jackstands. Or a QuickJack, really, but that's just the equivalent of very convenient jackstands. The V8 MG is still on the lift sans V8.
Our patient is a 1990 Miata with a few modifications. It's been used to sign off on other suspension setups before, and has spent significant amounts of time on both the FM Stage 2.5 and the Fox Racing Stage 2. Recently, it's been used to test some alternate setups on that hardware. It's aligned to Supermiata specs, which means a fair bit of front camber and a fat front bar. The current suspension setup is running a high rear rate so the rear bar is disconnected. Anyhow, just your typical Miata.
There aren't any instructions with these things. That's actually on the MaXpeedingRods website. I did discover that one piece of paper (with a picture of a strut, not a shock) was mostly extolling the wonders of the new hardware but had one little tidbit that said not to adjust the spring preload as it was set to perfection at the factory. Well, that ship has sailed :) More importantly, the lock rings were not locked so there's no way to tell. From what I could tell during disassembly, they were set up with just a tiny bit of load on the springs. Just enough to keep hardware in place.
In the front, I started by setting the body length to give maximum compression travel without having any rubbing. Basically, I used my existing setup as a guide. Then I set the front spring to just barely preloaded (as it had been from the factory). This will give us our lowest possible realistic ride height, whatever that is. And unfortunately, it also means a big loss of droop travel.
Because they're shorter, they went in pretty easily. You could legitimately screw the bodies down to minimum length or drop the perch to make installation even easier (I've done this and been accused of cheating) but since I had to pull the upper control arm to get the previous suspension out, I didn't do that.
In the rear, I set the body length to be as short as possible as I'd already determined this was a problem. The NA and NB Miatas are notoriously lacking in rear compression travel. I gave the springs a random but matched amount of preload just to see where the car would end up. The rear shock body is pretty close to the lower control arm, but does not make contact. If you were going for maximum height and extending the suspension further in droop than the short body setting allows, you may have to do a little clearancing here.
And here's a problem. This car is fitted with a set of NB prototype swaybars that weren't quite dimensionally accurate, and they hit the fat body of the MaXpeedingRods. This is not really a problem of the new coilovers although none of my previous setups had this interference.
And because this is the sort of car it is, half of the intercooler plumbing needs to be removed to pull the front sway bar.
I dug into my collection of spare sway bars and came up with a factory MSM bar as a good option for the time being. This is liable to be a little oversteery with that relatively high spring rate and a little less bar than I'd prefer, but oversteer is always more fun than understeer.
Maximum droop, 14.5" front and 15.5" rear.
Dropped the car on the ground. Front ride height, 12" (hub to fender). Rear, 14". That's without rolling it around, but the QuickJack does roll the car slightly when it comes down and I'm just looking for a first round.
Back up on the QJ. I raised the front 3 turns and dropped the rear 5, which completely unloaded the rear springs but did not make them loose. This is basically minimum ride height in the rear.
12.25" front, 13.5" rear. Given these spring rates, I'm aiming for 12.5/13. The passenger's side is very slightly taller.
Added 3 (left) and 2 (right) turns in the front and pulled out 7 (left) and 5 (right) in the rear. The rear springs are now completely loose and the hardware is able to move around. The perches have decent inner collars on them so I was pretty confident everything would stay in place.
12.5" front, 13" rear. Good. Button up, call it done.
Fully installed, it's time for the first drive. And the right rear is making a racket. Like a loose upper shock nut. Checked everything, no loose. But looking under the car, I saw this. The hardware had indeed shifted.
Pulled the shock out again. Removed the hardware and hammered it flat. But the shock still made noise when I compressed it on the bench. The noise is inside the shock, as if it's either depressurized or low on fluid. There's no sign of leaking anywhere. I've sent a note to MaXpeedingRods to let them know, we'll see what happens there. This happens sometimes, I'd be lying if I said that every shock from any manufacturer is perfect.
For damping, they feel very soft when I exercise them on the bench. I don't have a shock dyno, but I've played with a lot of shocks and I know how much damping 391/335 springs usually want. I've set the shocks to maximum stiffness to control the springs, I'll back them off if they need it.
The roads around my house are pretty smooth, so they're not good for suspension testing. The rear did bottom out on the way out my gravel driveway. I'll drive the car more tomorrow although I won't get a chance to hit my suspension test loop until Friday. I'll just ignore the noise in the rear although the shock will not be providing any damping for small movements. I've driven shocks in this condition before so I think I can account for their behavior.
Your assessment will probably turn out to be right since these are cheap generic parts. But generally hand stroking (are we not doing phrasing anymore?) the damper pretty much only tells you gas pressure and maybe low speed bleed. Which are good to know but not necessarily indicative of overall damping force.
Agreed, but these things definitely have minimal low speed damping. Some of the shocks I've worked with couldn't be stroked by hand (phrasing!!) when set to full stiff. This soft low speed behavior will mean a little more flopping around on quick steering movements.
Sounds like MaXpeedingRods will be sending another rear shock to replace the dud.
TL:DR version of my previous report:
- minimum ride height for the front is way low, far below useable height. They can be adjusted up.
- minimum ride height for the rear is fairly tall, actually higher than a stock 1994 R package. You can adjust lower by dropping the perch, but then the hardware will be loose and you'll have to take care when lifting the car and you will lose more suspension travel.
- bad rear shock
The color scheme looks like my set of ISC coilovers...
Are these also made in Taiwan?
Color scheme is variable - you can get a whole range of options. Red, yellow, blue, silver or green for this application.
The paperwork says the factory is:
LongHuGuoJi, No.166 Xinnan Road, YuBei, ChingQing, China. I've got the phone number if anyone wants it :)
Why did you shoot for 12.5/13.0?
Because years of working on Miatas has taught me that it's a good ride height for springs in that range. Go any lower and you spend too much time on the bumpstops. This is still likely to be a problem in the rear given the decreased rear bump travel with these shocks.
Coincidentally, that's the design height of FM springs for the NA and NB :)
Given the spring rate to keep it off the bump stops, would lower be better?
No. The lower you go while keeping the spring rate constant, the more time you will spend on the stops.
If you want to go lower, you need to increase the spring rate. You CAN go lower without doing that, but you will spend more time on the bumpstops which means decreased ride quality and handling.
With the spring rate on these coilovers, that's about as low as I like to go. This is particularly true on these shocks, which have considerably less bump travel available in the rear.
If you want to slam the car, go for it. Just don't try to kid yourself that it's for anything but posing :) And on this setup, you might as well pull the rear springs and just ride on the bumpstops to go much lower. I haven't measured yet, but I suspect the rear stops are very close to being engaged at this ride height.
Please ask them if you can open up the innards and show us it's guts. Remind them it's for science and proves to the community that they have a "quality" product. 
let's face it, we want these opened up to see if we can put in a quality damping unit and make for a budget coilovers.
I assume I can do whatever I want with them once I'm done testing them. Especially this dead one, I doubt they'll want it back.
Keep in mind that no matter what guts you put inside, the travel and fundamental geometry situation will not change. Some of that comes from the upper shock mount ("top hat") design, some of it comes from the length of the shocks. Given that they're a bit of an oddball spring diameter, you're pretty much stuck with the spring rate they come with. I'd definitely run the numbers before grabbing wrenches.
Remember that the two advantages of coilovers are the ability to set ride height/cornerweight and the ability to use generic springs. These coilovers have some problems with the ride height and can't use generic springs unless you have access to an unusual size.
My question earlier was a bit poorly written
Given proper shocks and travel and rates (a perfect world) what is the idea height for the suspension geometry? Whats the sweet spot? Is it still 12.5/13? Or lower? Or higher?
Ah, I get what you were asking.
Race cars are usually interested in CoG height, street cars are interested in ground clearance, hard parkers are interested in oil pan to ground contact. Then you run enough spring rate to stay off the stops most of the time.
In reply to Keith Tanner :
So, pretty much anywhere in the range of12-13.5 for street and autocross id the sweet spot? (I know this is a threadjack. Justvwent 750/450 springs on my challenge nb and trying to get a ballpark height)
you're running an alternate engine in that :) If it was a four cylinder and I had access to the full range of travel, I'd be willing to go lower but ground clearance would definitely have to be taken into consideration. 12.5/13 (you usually want the rear about 1/2" higher than the front) is a pretty solid all-around height.
Dusterbd13-michael said:In reply to Keith Tanner :
So, pretty much anywhere in the range of12-13.5 for street and autocross id the sweet spot? (I know this is a threadjack. Justvwent 750/450 springs on my challenge nb and trying to get a ballpark height)
When I ran 800/500 XIDAs on my NA, my pinch welds weren't beat up so I used the 949 alignment setup.
4.5"/5" pinch weld heights front and rear, something like -3.3° camber in front, -0.5° less than that in the rear.
FuzzWuzzy said:The color scheme looks like my set of ISC coilovers...
Are these also made in Taiwan?
Most likely, along with KSport and a number of other cheap brands with flashy colors. As well as many of the knock off/cheap enthusiast wheels are all SE Asian.
z31maniac said:Dusterbd13-michael said:In reply to Keith Tanner :
So, pretty much anywhere in the range of12-13.5 for street and autocross id the sweet spot? (I know this is a threadjack. Justvwent 750/450 springs on my challenge nb and trying to get a ballpark height)
When I ran 800/500 XIDAs on my NA, my pinch welds weren't beat up so I used the 949 alignment setup.
4.5"/5" pinch weld heights front and rear, something like -3.3° camber in front, -0.5° less than that in the rear.
The problem with using pinch weld heights is that it assumes a specific tire diameter and pressure. My test car is currently on 195/55-15s so my pinch weld heights would be different than most other Miatas. It's good for comparing ground clearance numbers but you'll find the travel range will change. If I were setting the car up on hub stands, they would be different again. Mazda uses the hub-to-fender height in their documentation.
z31maniac said:FuzzWuzzy said:The color scheme looks like my set of ISC coilovers...
Are these also made in Taiwan?Most likely, along with KSport and a number of other cheap brands with flashy colors. As well as many of the knock off/cheap enthusiast wheels are all SE Asian.
Psst! I posted the address of the factory, not Taiwan. ;)
So I have access to shock dynos for my day job. I can ask for permission to do some benchmarking on these and see what any damping adjustments do. It would require them to be shipped to MI though.
In reply to PMRacing :
That sounds great. I love how much effort we put into bottom rung parts for the sake of science.
Someone else is paying for the shipping in that case. I've already given up most of a day off to install and troubleshoot these things. I am not going out of pocket just to satisfy someone else's idle curiosity.
What matters at the end of the day is how they work, which is why I'm willing to put them on a car and drive the car.
In reply to Keith Tanner :
Yeah I almost posted the same thing after I asked if you had a dyno. I have the ability to dyno them and check the springs. But while I'm curious I'm not curious enough to pay for shipping and assumed you wouldn't be that interested in it either.
I'm in for $10 towards shipping them for science
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