Drop spindle discussion
 

A fellow on a local forum has peaked my interest on drop spindles and suspension geometry. I don't understand all of it, obviously, but he has worked with the concepts quite a bit with his custom built ariel atom type car, bigger than a formula style car. I don't know for sure if he's applied his concepts to going fast that much, though. He seems fairly knowledgeable.

So my main question is why aren't drop spindles more common amongst miatas or any other regularly tracked car.

The guy states lowering the car 1inch past stock is harming the car more than helping and adding spring, camber, and a good damper isn't the correct way or doing it. Since I don't fully understand this, why wouldn't all the fast track miatas have a ''correct'' setup. Too much cost, too unreliable, reinventing the wheel, or too cumbersome?

Did a search on here, only found things about rusted stock spindles, spindles for sale, and some guy asking Emilio if he's made some yet.

My view is, I'm less concerned about all the geometry and more concerned about what setup is more reliable and faster. It's also easier and cheaper to just copy the fast guys :D

This part os true for a lot of cars however the miata's suspension geometry is less than perfect at stock ride height and gets better as you lower it. This is why you do not see this type of thing on miatas.

Dann

Very, very few racing classes allow non-OEM spindles, so the market is a bit limited. That might be changing a bit with the growing number of points-based classing systems (NASA, CASC).

That said, if/when V8 Roadsters brings a set to the market, I'll be very interested. A spindle is a part that has to be manufactured exactly right, and one that you don't ever want to fail.

I've seen one-offs made for auto-cross only cars.

I thought I stuck in ''non oem spindles aren't legal for 95 percent of classes'' in the thread lol.

I figure with an billet aluminum spindle would be nice for loss of un-sprung weight, but may not be too strong.

It'll be as strong as you make it. I'm sure we could get a race only version down to around 3 pounds. You have to get all the way up to street mod before you use non-factory spindles in solo. Of course in that class you have free reign over the entire suspension besides the pickup points on the chassis.

Something like what Driftworks does for the S-Chassis cars would probably be more affordable to the masses. Theirs are a fabricated steel weldments, so it would open up the number of facilities that could do it (once the jig is made). Might not be as light as a stock (should be similar), but it would be more durable than aluminum.

https://www.miataturbo.net/attachmen...ine=1358445089

I remember these being hugely popular in the aircooled VW world many years ago. In that context, they were attractive principally because they offered a bolt-on alternative to removing and dismantling the front torsion beam, cutting it into three pieces, and re-welding it together with adjusters in the middle. The principle problem being solved there was not a matter of geometry, but rather a complete lack of adjustability in the stock design.

I'm not intimately familiar with the 240sx, however I do know that it used MacPhearson strut suspension in the front and an odd multi-link setup in the rear. It's entirely possible that these designs are less adaptable (insofar as static ride-height adjustment and / or interference-limited travel) than the double A-Arm system found in the Miata.


What's the real problem that we are trying to solve?


In the Miata, it's entirely practical to adjust the static ride height of the vehicle at both ends through the use of adjustable coilover perches, which are quite inexpensive and require no custom fabrication. Springs are also commonly available in a variety of length and stiffness, allowing for a large degree of customization even without the use of adjustable perches.

One potential limiting factor is the "free" compression travel at low static heights; the distance between the top of the shock body and the bottom of the upper shock mount. This is particularly troublesome in the NAs, but it is easily ameliorated in any car by a combination of shorter bumpstops and either converting from NA to NB upper mounts, or in more extreme cases, the use of "raised" upper shock mounts, such as those from ISC Racing.

Additionally, many aftermarket dampers are available whose body length (from the lower eyelet to the top of the tube) is shorter than stock, which also contributes to an improvement in compression travel.

Obviously at some point you will run into interference problems other than with the shock-to-mount interface, such as from the control arms coming into contact with tie rods or other components. I don't have any hard data in front of me to demonstrate at what point exactly this become problematic, however we have a large amount of anecdotal evidence to demonstrate that even with relatively small tires, the stock suspension is capable of being adjusted downwards to the point where tire-to-fender clearance becomes the limiting factor, rather than interference at the control arms.

I believe these are designed to correct roll center problems created when the lower control arm drops below parallel on many suspension. I've yet to take accurate measurements of our suspension so I have not done the kinematic analysis on it and cannot say for certain if this is the case with ours, but it HIGHLY likely it is.

It's not very scientific, but my thoughts are:

If none of the guys who race and put a LOT of money into their cars aren't worried about it, then neither am I. If they were a big deal, someone would already be selling them now. Or maybe Emilio does have some and isn't telling anyone, and that's his secret to going fast.

If they are a problem for d0r1ft0rs, well then maybe don't slam your car and you won't need to worry about the changes to the suspension geometry.

I'll be running modified stock spindles on my car. Just purchased a full tubular setup from a SCCA EP driver. Front spindles aren't modified just the rears.
Picture of the modified spindle:
https://www.miataturbo.net/attachmen...ine=1358453159

Yes, that is/was my take. I measured and modeled up the Miata suspension sears ago. Without changing the location of the suspension pickup points, lowering the chassis on the springs moves the roll center and instant centers to an unfavorable position (down below ground level and in, iirc). Dropping the height of the spindles by the same amount of your overall ride height drop negates that change.

Back when I measured and modeled the suspension, I paid for the software and it was kind of a PITA. I've been through several computers and computer crashes since then, and likely don't have the data anymore. That said, there is a free online tool that simplifies the process a bit. I bet if we pool our knowledge it wouldn't take much to recreate the Miata suspension here: Vehicle Suspension: Front View Online Suspension Simulator . Might be a cool tool for the community.

Going back a few years, I believe drop spindles were available from Mazda Comp(etition, now known as MazdaSpeed Motorsports) for Production / GT Miatas. They weren't cheap.

If drop spindles were allowed in Spec Miata, everyone would have them and the price (should/would) be reasonable.

The ones V8 Roadsters were working on sounded great, made with mounts for radial-mount Wilwoods, if I remember that right. Its been a couple of years since I read anything about them.

Running smaller diameter tires has the same effect as drop spindles - lowering the car without changing the geometry. However you get a smaller tire footprint - but maybe it can be made up for with a wider tire.

Yep lowering a car will lower the roll center faster than the CoG. This increases the roll couple - the amount of roll force absorbed by the springs instead of the suspension arms, and increases roll angle, all else being equal. That is where cornering forces result in an upward force at the CoG. I haven't seen numbers though. Wildo, what sort of amount of lowering started to look bad?

I was going to do it like I did the formula car. As a sketch in solid works. Works really well. Having the roll center below the ground isnt bad. IMO I like it down there because as the suspension is compressed you gain mechanical grip rather than loose it. BUT you never ever ever everever want the roll center to switch from above to below ground in any normal suspension movement. Dis is bad, it creates a discontinuity in the suspension output. Basically you loose all grip for a split second, this is why if you lower an AP1 s2k the wrong way they become spin machines.

In.

Strut suspensions develop serious camber problems when lowered by simply shortening the springs, thus explaining the popularity of drop spindles with that crowd. That's less of a problem with double wishbones.

I've had freeCAD installed for a while, thinking that I could model an entire Miata chassis, but haven't come anywhere near actually using it.

I think the issue you are referring to is mostly with MacPherson struts. I think its the angle of the LCA with the strut. Once its greater than 90* it develops a positive camber curve. I have heard some of those BMW guys run 5+* of camber to over come it, but I couldn't tell ya for sure.

We did some of this stuff with the Formula Hybrid car, but I wasn't particularly involved.

Lots of great info in this thread thus far, thanks for the responses :).

wildo mentioned that if they were common in SM, than we would see them a lot more. I don't think they keep the "spirit of the rules" as I've heard a few times about SCCA rules. That being said I think for Solo or Club Racing only Mod or Prepared classes even allow these, limiting the market.

I ganked this from a m.net thread, note this is quoting someone that quoted him(maybe he'll open this thread :D)

Emilio said-

"The camber curve of a Miata with the LCA's angled the wrong way is in the non linear part of the curve. Changing the inner or outer pickup points can fix that.

The lateral force acting on an LCA angled upward compresses the suspension instead of being fairly neutral as it is a stock ride height.

The CG is lowered by an amount proportionate to the change in ride height. The roll centers are lowered non-proportionately to ride height. The (sic) lowers roll resistance.

The two latter issues both require additional spring rate to combat the change in suspension geomtery compressing the suspension more for a given lateral acceleration than at stock ride height. Address the roll center issue and we could all run lower spring rates with the same roll stiffness and lower (optimize) bounce frequency. Both of which would increase mechanical grip.

That Miatas are freakishly fast without the geometry fix is a testament to the soundness of the basic car's design and big tires. Watch a nationally competitive DP roadracing Miata on a fast track though, and you will see what more is available with better suspension geometry."



So I started looking through NASA TT rules and someone correct me on this if I'm wrong but I couldn't find it specifically listed under points nor no-point mods.

"16) Relocation of front suspension mounting points +6
17) Relocation of rear suspension mounting points +6"

I don't think these too rules apply to the spindle mounting to the control arm, but the CAs to the f/r sub-frame? If it does apply, 12 points is A LOT and that's why you don't see them in NASA much, either.

Sorry, I don't remember the specifics, and I don't want to spread wrong information.

What I do remember is that at track/race car ride heights (I was running SCCA ITA at the time, more similar to SM than EP or GT), that 1-2" drop spindles would have been beneficial (on paper).

I'm not a suspension engineer (or engineer of any sort), and went through that process and read as much as I could for a few months during that time, in an effort to broaden my understanding of suspension dynamics. Some of it stuck, but like high school, I have forgotten more than I remember.

Cliff notes:

If you're not 4+ seconds under the Spec Miata track record you don't even need to begin to worry about this.

DUH

These would be beneficial for track cars and street cars.
You would be lower and your suspension will continue to function properly. Many race cars have drop spindles on them. It make simple sense.

Which ones? Any miata specific?

For most of the mere mortals on this forum, the classes that they auto-x, TT, or race in either forbid drop spindles (SCCA) or punish those who decide to use them (NASA through their points system).

While there are certain classes that may allow them, those classes (EP, FP? ST3?, Mod classes in Auto-x?) are fairly high buck cars that very few people on this forum play with.

The reality remains that you can (and most do) build a miata to handle beautifully and competently without them. That's not to say they wouldn't be beneficial, for either street or track car.

Don't the '94R outer tie rods also help the suspension geometry on lowered cars? Most people choose not to run those because they are too expensive. I'd have to imagine those tie rods are lot cheaper then a set of custom drop spindles.

+1. Not sure if NASA ST penalizes you, but PT definitely does. You can make a Miata on stock spindles and control arms handle better than 99.95% of cars.

Apples and oranges. The outer tie rods alleviate bumpsteer induced by excessive lowering. A properly designed drop spindle would account for this and allow you to run standard tie rod ends without worrying about it.

I know they are apples and oranges. That's why I used the ambiguous statement: "don't they help suspension geometry on lowered cars".

My point is, if 95% of the people on this board aren't willing to spend the $250 (or however much those tie rods are) for the tie rods, why would they want a set of $600-800++ custom drop spindles.

I also don't know about the NASA ST rules, I imagine there's someone on this board who would know though...

:party:

1. I bet more people run LE/R tie rod ends than you think
2. You can get similar benefit by shimming the steering rack up
3. I would bet that custom drop spindles on all 4 corners are significantly more than $800. Think double that.

:party:

ST allows relocation of suspension mounting points in all classes with no penalty.

It depends on how much demand for them there is if there was demand for a few thousand you could almost justify casting them and likely get it down to around $800. If you were going to make a welded up set for yourself, after making jigs (you're going to want to make jigs for this), and having a shop do finish machining to the weldment (you're going to need this) I could see it coming out to around a grand. Now if you have access to CNC machines and want to make them out of aluminum billet, depeding on how big they are, you could do it for about 400 on all corners + whatever the spindles (the actual steel shaft that the bearing runs on in the front) are going to cost. But if you're at that level, you're making your own hubs and are going to run a completely different bearing setup, likely with a bearing similar to the miata rears on the front and hubs that look like the rears in the front. Man I wish I had the time and money to do this right now. Might have to re-apply to school for a part time MBA and do it one class at a time just to keep access to the shop, haha.

And to fact check myself, a set of two drop spindles for a truck from belltech ranges between 200 and 420 depending on the truck and the drop. So it might actually be possible for someone to come out with a set for $800 for 4.

?The LE tie rod ends are $46.84 each from Mazda. Not that expensive.

Bob

SCCA Solo Rules for Street Modified.

E. Suspension components are unrestricted as long as they use the
original attachment points. For the purposes of this rule, “suspension”
is defined as any item that is designed to move when a wheel
is deflected vertically. This includes shocks/struts, control arms,
steering knuckles, uprights, etc., but not tie rods, steering racks, and
subframes. In addition, shock absorber/strut upper mounts are to be
considered suspension components.

You can use drop spindles. Can't move your rack. The LE tie rod ends are acceptable as they were available as an option.

Bob

16.1.F allows you to move the rack.

Driftworks drop spindles for the S-chassis run around $2500 a set (but they are coming from the UK). I can't remember who makes some in the States, but i think they were a fraction cheaper.

What about how Modified Mag did to correct the geometry (2000 Honda S2000 - Adjustable Geometry, Optimum Handling - Project S2K - Modified Magazine) but on the miata it would have to be the K-member and the rear suspension cage. If V8 Roadsters built something to correct or make a better geometry I would be in!

I agree with what is being said here. I know the stock ones can be made to handle very well.
I also wasnt taking budget or classes into account. That is my mistake. Most of my experience with race cars is more of an unlimited situation.

If most classes cant have them and stock are doing what they need too $1000-$3000 definitely doesnt seem feasible.

More like $1400 or so.

PBM is making forged knuckles, and Era-1 makes cast spindles. Lots of options these days, though it seems like 240 owners are bigger brokedicks with every passing week.

Roll center in a 240 goes to hell pretty fast in the front (thanks mac struts) and I know in my 240 it was a huge benefit when I added correction. The other beauty of spindles is that you can shorter the steering pick up to quicken the steering. I'm at 2.25 turns lock-to-lock now, and I love it. Makes the miata rack feel slow ;)

You also forgot to take into account how cheap we all are. :giggle:

There's a company in Japan that makes them

SP-TEC
https://www.miataturbo.net/attachmen...ine=1358988096

People aren't buying anything close to Xidas in 240land, let alone drop spindles.

Though with more and more people taking their drifting srsly, the market is opening up. No impact on the grassroots level stuff, though.

For the miata I don't see much utility just b/c the susp works so well. 240s take a lot of money to work well.

They cost 677/thing I dont know if that is per pair or for a single.

677 per pair but you still have to pay for shipping.

What are the suspension measurements, I'm 1200 miles away from my car and can't do the measurements. upper cont arm center bushing to center bushing, center to center on the spindle, lower control arm center to center and for the inner K-member.

Danny George Racing has come out with designs for drop spindles, with intent to produce them.

Danny George - Drop Spindles

And yes, Danny George is a drifter.

Early stages here. But all the feedback is welcomed. This is a big project with a lot of costs involved so making them as universal for everyone can make it a smart decision to go forward.

Emilio mentioned adding in camber of -1 degree front. Putting +.5 rear. That pretty common thoughts? For drift we will have enough adjustment to not be affected by that.

Drop spindles have been popular with the truck crowd for a long time. I have a Tacoma and there is a fabricator on the Customtacos forum that builds them using your stock spindles for $450 a pair. I'm actually looking into a set for mine to correct the geometry I ended up with on the truck after adding coilovers. I had no clue anyone had tried this for the Miata, although like Savington said, I doubt it's necessary for the Miata.

The issue with putting drop spindles into production is simply that few can really use them in competition legally. The guys running street don't care. That leaves a few HPDE guys that actually believe they'll spend $2000 to reconfigure their suspension. They won't. If we are able to get two sets, they'll be on run on a NASA ST2 car: turbo 270-360whp, big wings, 10" slicks, road racing.

Camber
The potential market for them is small IMO. That said, I want a set. Current state of the art in track Miata suspension tuning with radials is -2.8 to about -4° front camber and -2.2 to about -3.2° rear. On most Miatas with low ride heights, we run out of toe adjustment and sometimes have to run a bit more negative camber than we really want. In front, the NA chassis struggles to get to -2.8° at the ideal ride height. So a bit more front and a bit less rear camber would be nice.

Caliper mounts
There is room for the Dynapro 4 pot radial mount caliper in front. My thought is that it would be nice to have the spindles built with radial posts up front and 5.25" lug mounts in back to start. The make adapters for OEM caliper that bolt onto those. Just about anyone that's allowed to or can afford to run the drop spindles will want radial mount DP4s and either a 2 pot superlite DL4 in back.

Dampers
One think never mentioned in these discussions is that the coilovers will either need spacers or be lengthened to retain the same bump travel. Ideally, one would redesign a damper with a longer body and shaft to gain droop travel. If I ever get my hands on a set of drop spindles, I'll have set of longer stroke Xida doubles built to go with them.

Hubs
Stock hubs aren't big enough. We need to run a press in sealed bearing that's 2.5x the size of what we have now and retain the 4x100 PCD.

I'd prefer Cr-Mo construction, perhaps 4130 plate. Much better fatigue life over any 1000 series mild steel. There will be guys running these at 160+ mph on road courses, turning at nearly 2G.

my .02

I am interested in the development as are a couple more auto-x'ers.

I'm concerned about fitment on the 13x10s with a 1.5" drop spindle. I'll have to go measure how close things are now. In auto-x, you'll find most Miata that could run a drop spindle legally(Super Street Mod and D/X Prepared) either run 13" or 15"s, usually about 10" wide.

Strength would be key. I've seen control arms that fine for road racers bend when used in autox.

Maybe even integrated brake duct inlets?

I think the conclusion you have drawn is erroneous. If the arms you saw were bent by an autocrosser in a normal run (no contact), they were not "fine" for a road racer. It might only indicate that the road racers in question ran (won?) road races with wobbly control arms.

I can't recall any car to car contact, 1.5g compression during 1.9g lateral loads (banking), 100mph 6" kerb hits in autocross. No offense intended. But yeah, I agree that any potential spindle intended for motorsport use on a Miata needs to be at least as strong as the OEM piece with a progressive failure mode.

I personally know of 3 sets of Miata tubular control arms(from two popular sources one of which is very popular among the Road Race crowd) that were bent on their first event in a Autocross SSM Miata. It is more than common to see sustained g loads over 1.6g on a flat surface with peaks even higher.

I just went and looked at the data from the East course at Nationals this year. On a 58 second run my car spent 29.05 seconds loaded up over 1.25g with one segment loaded up at 1.5g for over 6.25 second and 14 instances where the car went from pulling 1.2 or more g turning one direction then immediately pulling that amount the opposite direction. I am of the opinion with the AutoX failures I have seen were more related to the rapid loading / unloading than ultimate force(Think of a paper clip bending back and forth)

Just my opinion...but what the hell do I know.

At ACS my relatively slow by autocross standards PTC car sees a sustained 1.8G in T1-2 for about 10 seconds every lap of a 35 minute sprint race. About 5 minutes of turning with the right front 800# spring fully compressed. In the Thunderhill 25 hours, T2 is also about 9s long x 700 laps x 1.55G. So maybe an hours worth at 1.5G, in one day of racing. This is not counting the 700x the RF catches air then bottoms completely over T5.

Autocrossers don't hit kerbs, unless they're crashing. A road racer will rack up a few thousand kerb hits a year, not to mention chucking off track into the dirt a few times. Ever notice the big tire donuts on the doors, krinkled fenders and black smudges on the lips of the wheels on road racers? I can'r recall ever seeing an autocrosser with more than cone smudges.

You will never convince me that autocrossing is harder on suspension components than road racing. Again no offense, but there is just no comparison.

This isn't a pissing contest. I was merely pointing out that I personally know of three sets of tubular control arms(again from manufacturers that sell these parts on a regular basis to road racers) that bent at their FIRST Autocross event AND offering my opinion as to why it happened.

*Didn't mean to start a thread drift but what the ....

I think the control arms "might" be fine for road racers. I surely didnt mean to imply auto-x was harder than road racing. I'll make no speculation on the life span in road racing. Perhaps in the realm of road racing contact, either wall or other car, happens before the fatigue life failure happens.

My cage is built to auto-x rules. To say I'm not going to 10/10ths when I take the auto-x car on the track would be an understatement. I'm sure my car would shed an endless array of parts if required to run 30 minutes solid.

Go to SCCA National races (road race runoffs or the solo final) where production class Miatas are running and you'll see Miatas with drop spindles.
The price is over $4000 though.
You might see inverted shocks, etc. too ;)

You must have missed the part where in the next couple sentences I talked about the classes that allow them such as EProd or FProd or ST2-3. My point was that most people on this forum can't afford to build an EProd miata.

And to be honest, I have never seen a miata with drop spindles at an SCCA National. Mostly because I don't walk around the paddock at SCCA nationals checking out miatas, I'm too busy prepping and racing my own car... :giggle:

But yes, I wouldn't be surprised to see drop spindles and inverted shocks on Prather's car, doesn't really apply to the HPDE-ers on this site.

:vash2:

If someone for some strange reason would start with (or aim for) a different damper than Xidas the longer space for the damper setup can be seen as a plus.

As for cost, what is free (it just takes time, someones quality time)?
If you sink 10k in the engine, 4k on the dampers, consume 5 set of tires per year, why would custom spindles/upright be an impossibility?
Bolt-on for everyone with a idot-prof instructions and available OTS in five colors, no way.
One-offs designed and manufactured while trading other services, why not (if you think it would give some edge).

Another reason you might want to run drop spindles.

Combine them with bigger diameter wheels and tires and tubbed inner fenders.

FWIW, 4130 plate will be garbage in fatigue compared to mild steel unless you go back and re-heat treat the whole thing after welding.

Yes, it needs to be annealed, either with a torch or in a heat treat oven.

At what level does it need to go vs stop
At for overall cost. At the price point already it is slim markets.

There is only a few cars that are 4x100. Typically lighter cars. The MR2 hub I got looks pretty good. There are a few others but this was everything we needed. 5 lug would screw everything up.

Are the autox guys all using 13" wheels? Figured that 275/15 would be the new big deal. I dont have 13's to test with. Can wilwoods even fit in there ?

We can kinda do anything but putting them further into the price category of expensive and more niche with 5 lug hubs(want bigger bearings?) puts if out of the ease to make and sell.

The fast cars on DOT tires run 15's. But once you get into true slicks from a quick peak on avon's site looks like you can get radials in 13" or 15" in appropriate miata diameters up to 290wide, and it looks like hoosier FA slicks come in 12" wide in both 13" and 15" wheels. So it could go either way, and I dont know what they're actually running.

Sports car GT tires 23.5 diameter for 16" wheels Goodyear or hoosier in widths from 10" to 13"

I question though if the 25.5”diameter GT sport car tires could be faster if you designed the suspension around them like a GT1/2 car.

Images of a 275/35/15 A6 Hoosier Versus A 23.5X11R16 Hoosier Radial Slick.
https://www.miataturbo.net/attachmen...d-p1010007-jpg
https://www.miataturbo.net/attachmen...d-p1010005-jpg

For autox, anyone in an NA/NB required to run DOT tires will likely be using the 275/35s. Not much else fits easily without some major surgery.

D Prepared Miata will mostly be in 13" or 15" wheels. Weight is king and the available tires in the 20-23" diameter range provide enough grip for the power. My car lost over 40lbs going from 275/35 on a 15x10 to the FA 20x9.5x13 on 13x10.

My car is in X Prepared. I look towards D/E Mod cars for tire selection. The fast cars there tend to run the 13" Formula Atlantic tires. The power (goals) and weight of my car are not too far off the required levels of a competitive E Mod. The no longer made R110 Goodyears were magical.

I'd imagine an F Prepared car would probably do pretty well with the above 16" slick. There is enough weight to make the harder compounds available there work.

I think a 1.5" drop spindle on some 21.5x10-15 Avons would be pretty epic. I'd think I'd need a skid plate installed to avoid damaging the pan.

Just another data point, a LS2 autocross/weekend toy NB bent one of those V8Roadsters arms running 225/45/15 RS3s at an autox earlier last year. No contact with curbs, etc. V8R replaced it for free, but it's not very confidence inspiring.