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.