http://sp-tec.com/shop/15_33.html
http://sp-tec.com/shop/15_32.html

 

what would be the reason to run these over coilovers???

 

Lower the car, but not lower the roll center more than the CG, which is what will happen when you lower it with springs or coilovers. It'll also keep the factory geometry, which on almost any car, is less than optimal when lowered. I don't know the details of an FD suspension, but I'd immagine it works best at stock ride heights.

So at the same lowered ride height with these + coilovers vs. just coilovers, the geometry will be improved, as will the roll couple. They're probably lighter too.

 

Nice!!

 

wow sounds like a worth while mod for a track guy

 

In other words, drop the car by using this, keeping factory suspension settings and ride "confort".

i wonder how those would work for those running 20Bs since they have to get theirs moded for torque steer?

 

You've missed the point. The point is to regain some of the lost geometry on an already lowered car in order to get better performance, but you could just lower it with these and maintain comfort.

20B's have problems with bump steer, torque steer is a phenomenon that affects front drivers.

 

as i understand it the bumpsteer problem with the 20b is do to some coversion kits relocating the the rack screwing the geometry to the spindle, these will not affect that. they will however allow you to maintain a much closer to stock roll center and camber gain geometry on a lowered car....I haven't run any of the numbers but i would be curious how much of an effect the change in king pin angle would have (how much castor will this add?).

 

Bumping this from the grave..

Anyone currently making drop spindles for circuit use?

Everything I can find is drift-specific angle kits

 

It's all drift stuff for whatever reason. I've been trying to get these made for years. I can't even pay people to do it.

 

How much do you want to spend? I can have them made.

 

I can have them made in Ti or whatever we want, less expensive overseas cost. But it does seem like there is very little demand, would need to be a group buy to happen.

I’m honestly thinking they just might not be necessary. Too little clearance with 18” wheels to go low enough for the suspension to be compromised. Cost vs benefit isn’t there unless you need more angle.

Are we sure nobody is making anything at the moment? None of the drift kits are drift/circuit convertible?

 

As far as the need, it's definitely there.

Even at common lowered heights, the lower arm pivots front/rear are lower to the inside than the outside. You really don't want those to go past level, and stock they are angled the other way. The result is a roll center that's underground, and this is, in part, why you need exponentially stiffer springs when you lower it. The theoretical potential is, you could run lighter rates.

I'm working on getting the OEMs 3D scanned and drawn in CAD. Then you'd need to move the axle, probably somewhere between 1-1.5" relative to the suspension pickups, and rework some things to make them feasible for CNC.

 

Are you sure they are below ground? Have you measured and calculated it? Are you looking to do an even 1-1.5" front and rear, or know where the roll centers are and adjust the roll center inclination of the car?

 

I've not calculated it, so I can't say for certain where it is exactly, but if you look at HOW it's calculated, you can see the impact on instant center from having a lower arm that's past horizontal, so that's going to impact the roll center pretty severely.

What I'd be looking to do is enough F/R to at least get the lower arms back to horizontal at a 25" to fender lips ride height (with 285/30/18's all around).

 

Even with the inboard LCA points being a bit lower than the outboard points, it will take a lot of angle for the plane of the LCA to be below ground before the centerline of the car. Even if it intersected the ground plane at the centerline of the car, the UCA is at an even steeper angle, which would make the instant center very short, and likely still above ground. From looking at the suspension, I would be surprised if they RCs were below ground on even a fairly lowered FD.

I had all the pickup points measured with a roamer arm on an NSX and plotted the roll centers, camber and toe curves. I haven't had that itch to do it to the FD yet, but there should be a goal to achieve beyond just wanting the lower arms parallel with the ground, which is somewhat irrelevant or even not ideal depending on the rest of the suspension, the handling of the car, and what you're trying to achieve.

If you just want to do a even front-rear drop spindle by 1" or so, that would be the most conservative objective that doesn't require much analysis. The uprights are pretty simple on an FD (compared to an NSX), so designing and making 1-1.5" drop spindles, keeping factory geometry, shouldn't be that difficult.

 

Having done quite a lot of track driving, and run various setups, wheel diameters, etc., I can tell you that lowering the car is a balance between lowering the center of gravity and putting less air under the car, and the way it rolls and feels during cornering. I discovered this when I ran 275/40/17's all around, and you needed to lift the car up so they wouldn't rub. Fritz similarly ran the car higher as he favored that tire setup, and I drove his car a few times. It's noticeable. It also tracks with what I've heard from people who raced the car professionally, like Peter Farrell. For me, getting those arms back to level would be a big deal. Sure, there would be some optimization that could be done beyond that, but I think for me the work to benefit ratio there wouldn't be as good.

The rear upright is relatively easy. The front, unless you want to make it completely out of steel, needs a bolt-in stub axle. I'd looked at converting to rx8 hubs (a company that made Miata drop spindles did that), but RX8's have the ABS ring/sensor built in, and that wouldn't be compatible with OEM ABS, or the MK60 I have going in.

 

Add me to the list of interested parties...
7075 or 6061 T6 would be pretty cool.

 

Rob dahm just made some for the 3 rotor car. Hard to understand why other companies that do this for a living can't make one.

 

More like he hacked up the stock aluminum rear upright, and welded on new pickup points. I hope for his sake that the strength of those welds and the integrity of the non heat treated aluminum hold up to the forces that he is going to put them through, but it's not the best idea to weld on an upright like he did. Making a new one from scratch, whether billet, forged, or cast, would be much safer.

It's supply and demand. If there's enough demand, things get made. However, the FD market isn't huge, and the market for people to spend $800-1K per corner for billet uprights is even smaller.

 

I agree, I wouldn't trust a modified/welded upright for track use. I don't even love the extended lower ball joint stud, as that still puts your upper arm at a sharp angle.

The sunk cost is in the man hours to design them (which I've actually offered to pay people for, but my money wasn't green enough apparently). Once drawn, they're one-off made to order, and that cost is what it is. I've seen some designs for other cars that might make them cheaper to CNC, like they are a couple smaller pieces bolted together in key places so you don't need to machine from a giant billet block, but that requires more design time and thought.

If I knew how to use CAD, there would be some rad *** stuff available for FDs I can tell you that. Getting my ideas made is always the issue.

 

agree, I don’t care for the welded one, but modded knuckles are not something new.

this is what I was referring to, CAD modeled and machined. I was not referring to the modded stock piece. I’m not just fanboying over Rob, he wanted a lower car with good geometry, so he went and made stuff to do it. Now a drop spindle for an FD exists, although different brake and hub than OEM.

 

Ah, I see that on his story now. I'm glad he's making one from scratch. The welded knuckle was a bit questionable.

 

Hilarious timing, glad he’s watching my posts. Now he just needs to install those wheel covers I sent him last year 😂

I talked to Wisefab, they aren’t interested in making circuit stuff for the FD. But there’s a good chance their knuckles will work for circuit use with custom linkage arms to bring the offset back to stock vs the very widened drift stance

 

Happy Cactus Garage has a wheel speed signal convertor with some other stuff to support the Mk60/e5. I’ve got one in the mail headed my way.