Left side-rear suspension sub-frame locating jig. Note 1.25″ dia wooden “dowels” represent exact placement of final 1.25″ chrome moly tubing. Fixture drops at 10 degree angle to facilitate final plane of lower control arms. Entire assy bolts into frame, & consists of 3 pcs—left & right sides, & detachable center crossmember (which supports transaxle).
Photo details where upper L & R “uni-body” sections are cut (top-center of pic)—-these are anchored by super-rigid shock towers. End of 1.5″ aluminum tubing visible at center of pic represents true plane of uprights at static ride height (4.5″ G.C. with 28″ rear tire).
“Cleaned-up” rear frame rails. Note, rear structural bumper mounting “pads” left intact for eventual fulcrum attachment for tilt rear end (1 pc. CF). Also, upper L & R”uni-body” sections cut off just aft of external box-section stiffener, & weatherstrip molding lip left intact for eventual seal for rear “shell”.
More details visible of wooden rear suspension sub-frame jig. It’s this kinda “late-night engineering” that really takes the most time—you’re looking at version 3.0! In fact, when I started this project, I anticipated keeping the stock NSX suspension—even had successfully re-located OEM components aftward (see picsÂ inÂ the “chassis”Â gallery)—-only to decide the look (& non-adjustability) wasn’t up to speed (pun?).
First few pieces of Moly in place. Don’t try this at home! This is the left rear wheel well.
Early phase of cutting, bending, & fitting chrome-moly tubing to locating fixture. Note plate (marked D.S.) bolted to frame rail indexes off 3 existing bolt holes / internal frame “anchors”—that originally secured OEM rear tie-down brackets. Other 3 larger holes are for plug welds, while bottom hole acts as an anchor for chrome-moly sub frame. Because of it being outboard ofÂ the frame rail, more triangulation between plane of frame rails & lower plane of sub-frame is achieved—this keeps the lower suspension from trying to “walk” right or left.
Â The “D.S.” plate is fully welded up in this pic. Wooden locating fixture removed, & final fitting of transaxle support section (looks like a “k-member”) is positioned for weld-up.
Â Passenger-side view of same assy. Shock rocker is just sitting in its “nest” (top of pic), but isnt bolted thru actual pivot points.
Â View of inboard drivers-side rear frame rail (looking towards front of car). Entire chrome-moly assy bolts to frame rails with 7 bolts per side.
Chrome-moly rear subframe is 3 pieces. Center “k-section” un-bolts (4 bolts) & drops straight down for engine & tranny removal.
The final sub-frame, missing only final transaxle mounting plate (visible in other pics). Entire ass’y bolts into NSX frame which was modified to incorporate welded in “slugs”, each of which is fitted with steel Keenserts (like a helicoil, but much stronger & permanent).
Rear sub-frame removable center section facilitates easy engine & trans removal—only takes 8 bolts to drop entire engine & transaxle assy in about 15 minutes! (alum fixture in top of pic is not a part of car—used for holding critical dimensions during fabrication)
Latest stage of custom chrome-moly lower rear sub-frame shows the drivers side lower control arm P/U attachment points. These serrated plates are the exact same size as other 12 “billet” spacers on car, but are chrome-moly—which made the machining of the serrations a lot more difficult. Even the relatively small 1/2” x 1″ rectangular tubing/gusset is chrome-moly! (front of car towards left)
Â Drivers-side rear frame rail, all layed-out (scribed) for attaching serrated billet spacers. The upper control arm centers are marked in Sharpie (just under the “D.S.” & near left-center of pic, right over green marker) This entire section of frame rail has an extra 3/16ths aluminum plate welded to it for strength & torsional rigidity.
Upper-Rear serrated billet spacers-outboard view, again with stainless bolts-thru-slots. These become the P/U point attachments for Leading-side of rear upper control arm.
Same spacers, inboard view—lot of time spent pattern making on these gems, as rear frame rails have all sorts of irregular contours, & AREN’T Symmetrical! (RPITA)
Performing final-fit “massaging” to billet spacer to achieve near perfect fit before weld-up.(sitting at passenger side rear wheel well)
Passenger side upper rear P/U billet spacers in final weld-up (front of car is towards Right) Look closely, & you can see the “rocket-science” custom rear crossmember thru the “odd” triangle shaped hole at top of pic! (it facilitates the horizontally-opposed Penske coilovers @ rear of car).
Passenger side Front frame rail showing areas to be strengthened, and / or augmented in prep for upper control arm pick-up attachment points. Large black marker “bullets” are reference points for drilling 1/8th alum. stiffener plate—for plug welds, which helps spread any loading across entire section of OEM “crumple-zone”. (see pic below)
Passenger side front frame rail after 3 different stiffeners / spacers have been welded in place. (lots of “cypherin” on that frame rail!)
Front lower suspension pick-up crossmember—before any machining (just laying on top of frame rails). Â See final config. in pics below.
Â 58 pieces of precision machined aluminum—all of which will become the one-of-a-kind “driver adjustable front camber” front suspension. Note also front crossmember,which has undergone serious hand machinig (Makita with cut-off wheel) since other pic taken right after initial weld-up.
Front lower-suspension crossmember in final prep for installation / weld-up in frame. Note solid inserts inside tubing (near end) will have steering rack clamp-holes bored before installation. The Woodward rack that bolts to crossmember is the same config as used in the Saleen S-7R, which had to incorporate beefier “hydraulics” because of 4000 lbs of frontal downforce generated at top speed!
Various front & rear control arm pick-up attachment points. The bolts in the slots are stainless, & allow for rasing or lowering pick-up point by a total of 1.5″ at all 4 corners ( to adjust roll centers, and/or ride height & camber geometry. I “borrowed” this idea from the Pratt & Miller GT Corvettes.
These spacers weld to re-inforced sections of frame. There are 6 of these, 4 are upper control arm pick-up attachment points at rear, 2 are uppers at trailing P/U at frame front.
Upper-front frame bracket before installation–note serrations to facilitate P/U adjustability
This view highlights how bracket design spans significant cross-section of frame–also where it will weld over already welded up frame stiffener (no more “crumple” zone). FYI, both front & rear of car incorporate CF/Kevlar attenuators for crash load absorption (they didn’t have THAT technology back when the NSX was engineered!) Black tape on firewall covers the 3 holes & locating studs for Tilton clutch & brake cylinders.
View of driver’s side front frame rail & relative position of upper control arm pick-up attachment point (leading edge of control arm) Also visible are the shock-rocker fulcrum bosses (just left of bracket in pic)
Lower front suspension components at start of fab—note beefiness! OEM NSX suspension pieces are works of art, but a little fragile for serious road racing, especially with much larger wheel & tire combos & “race” rubber.
Lower front suspension pieces a little farther along in the fab process. Note fixture (2 round steel tubing pieces) purposely locates the components NOT parallel, but with an included angle of 3 degrees—which begs a rather scientific discussion on anti-squat, anti-dive geometry
Individual assy going thru stress relieving–after a total of 19 lightening holes were bored. Note massive steel workbench is PERFECTLY flat & level!
Latest development in the front crossmember is the solid aluminum spacer welded inside the rectangular cross-section (visible @ near end) which provides extra strength for the P.S. Rack clamps to attach to. Notice the “rack clamp holes” are already milled (not drilled) thru at both ends—-before crossmember gets final weld-up between frame rails. Big Thanks to Tony Woodward for the education on design / configuration considerations for ultimate performance! FACTOID: final power steering will have 3 different “map” positions for cockpit adjustability of assist ratio!
Drivers side front frame rail upper control arm pick-up points positioned for weld up. Also visible; special crossmember that facilitates horizontally-opposed Penske coilovers & “shock-rocker” fulcrum tabs welded to top of frame rail. Also visible is 3″ hole thru-frame for Woodward Power Steering rack & pinion—the rubber bellows (dust boot), actually protrude thru the frame rails, but not the rack housing.(front of car towards right)
Final weld-up of all frame bracketry.(drivers side front frame rail–black tape covers 3 holes for Tilton brake & clutch cylinders)
Drivers side front frame rail top view, after weld-up.(front of car towards right)
Drivers side front frame rail outboard view after weld-up. Notice the two 3/8ths stainless bolts protruding thru the slots in serrated plates. This is method of attaching billet “break-away” P/U brackets @ all 4 corners of the car. Also provides 1.5″ total up & down adjustment of the P/U centers, for dialing-in anti-squat / dive, & roll-center geometry. (For those in Rio Linda, means incredibly tuneable suspension for different track conditions & tire / wheel combos) front of car towards left.
Â New front crossmember being positioned for weld-up
Â 3″ aluminum tubing finishes hole-thru-frame, & intersects crossmember to spread crossmember structural weld cross-section to both the inside, & outside edges of frame rails. Yellow item is a bubble level to index to chassis’ Â level status.
Â View from under drivers-side frame rail just prior to welding. Lower radiator support is at left side of pic. Notice 3″ aluminum tube is fit to finish-weld to frame rail stiffener, which is already welded in place.
Â After weld-up (including next 2 pics)
Â Notice how 3″ tube welds to crossmember, as well as frame rail.
Â Weld-up complete.
Â Top-Secret lower front suspension piece—to be explained after patent approved!
This is a close-up of “break-away” control arm pick-up attachment bracket. Rod end of control arm fits inside center “well” with 1/2″ thru-bolt. Buttonheads are 3/8″ stainless.
Lower front suspension “bridge” (from 2 pics above) after holes chamfered, & “fences” welded on serrated sections—cleaner, but still not finished!
Left-rear upright (from wheel flange view)–notice “webbed” billet design promotes maximum brake cooling.
Top view (L. rear upright)–tape indicates almost 4″ of total wheel bearing “spread”–OEM NSX piece is 2″!Â Notice also hub is “pin drive” for center-lock wheels. Foil is to protect CF from extreme rotor heat. Wheel bearing diameters & overall spread are more suited to 13″ x 18″ wheel with 13″ x 28″ tires that we are running!
Inboard view of Left rear upright–axle shaft splines are visible inside center “stub”Â hole. Billet “ear” peeking out from left side of CF brake ducting is for toe-link attachment.
Left front upright from wheel flange view—actually a little “meatier” than rear because of the need to “sink” extra heat & loading (weight transfer) generated by front rotors, compared to rear rotors.
Front upright also features generous wheel bearing “spread” @ about 3.75″–also incorporates pin-drive hubs. (this is actually bottom view).
Inboard view ofÂ L. front upright—notice monoball at top for upper control arm attachment (bolts on), shimming allows fine-tuning of “scrub-radius”—also “dual” duct inlets, to facilitate extra cooling.
Original OEM NSX all aluminum right rear upright & control arms areÂ very light weight, & elegant design—for anything OEM,—not really designed for racing however in terms of bearing sizes, spread, & brake cooling.Â Note the recess in center of upright is for wheel bearing hub & drive flange (next 3 pics),—Not very deep!
Steel wheel bearing hub & drive flange—-compact size = low weight, but. . . . . .
the hub assy (lower cast piece) has the inner & outer wheel bearings literally butting up to each other, for a total overall bearing spread of 2″ (half the spread of our newly-fabbed custom rear upright, 7 pics back)—remember; this configuration was designed in ’89 or ’90—for a 16″ x 8″ wheel with an 8.5″ wide tire. The engineers probably break out into hives every time they see a “street-racer” NSX with 10″ x 19″ wheels & 11″ wide tires—-wheel bearings will fail—NOT a pretty sight!
Stock NSXÂ right rear upright configuration, still probably the most sophisticated suspension ever incorporated into a production automobile—-BTW, I still have all 4 corners of NSX suspension in excellent cond—-if you know anyone.
Rear control arm designs; Latest, greatest, hi-tech CAD output on garage floor—the result of many hours of data-point plotting using a plumb-bob, level, tape measure, &Â framing square! Look closely, & you can see the “third-dimension” notations in the form of vertical measurements (from ground-level)Â to each attachment point.
Front control arm designs (same method as rear, in caption above). Note the monoball receptaclesÂ at theÂ outer ends of upper & lower control armsÂ (bottom center of pic)Â do not line up vertically with each other. The resultant vertical line which intersects the two reflects 3 degrees of camber, & 6 degrees of caster, as fabricated! Â The outboard end of the upper control arm (blue rounded-triangle in pic) is vertically serrated, and is adjustableÂ for an additional 4 degrees of caster fore or aft. (as-in 2 degrees to 10 degrees total).
All 8 control arms, 4 still in the “home-made” jigs. The 2 jigs in the center facilitate control arms whose pivot-centers are not in the same plane as the upper & lower connection points on the uprights. Note also that the lower control arms are “beefier” 1.25″ x .095″ wall chrome moly. The uppers are 1″ x .120″ wall, & are fairly small in overall configuration because of very tight space requirements to tuck all of the CF brake ducting inside the wheel, as well as the fact the front wheels turn thru a total 4o degree sweep—-so clearance between arm & inside edge of wheel @ “full-lock” is critical.
This view shows the design of “caster-adjustable” upper-front control arm (third from left). TheÂ two 3/8ths bolts are welded Mil-Spec 12-pt fasteners (strongest available), & the triangle-shaped “clevis” is machined out of 4130 chrome moly billet, including vertical serrationsÂ on the back side, as is the back-up plate which is welded to the CM tubing. The “clevis” accepts a monoball which is integral to the upper portion of the front upright (see upright pic 8 pics back).
Close-up of upper front control arm reveals a lot ofÂ “unusual” angles between the “spuds”(where the spherical rod-ends screw in), the plane of the clevis, & the plane of ground level (represented by wood). The reason for all of this “voodo geometry” is so the caster angle can be maintained even when camber angle is adjusted dramatically pos. or neg.!
Lower rear control arm view shows detail of lower push-rod mount (channel-like piece with the 4 “humps”). This was fabricated from 3 laser-cut pcs. of .125″ CM, plus 8 CM washers—11 pcs. total, x 4 corners, for a total of 44 pcs. of metal for precision weld-up. (super-size this pic to get an idea of the TIG artistry here) The next pic details the procedure.
Aluminum bar stock was machined to exact width so final spacing on bracket is a perfect fit for the “high-misalignment” rod-ends that are part of the push-rod, (which actuates the shock-rocker on frame rail—which actuates the shock). The allen bolts are used to secure the 8 washers (actually precision-machined CM shims—to hold a tight tolerance on the i.d.) during weld-up.
The UPPER control arms attach to the chassis via a billet aluminum “pick-up”, which is serrated on back to allow for a total of 1.5″ adjustment up & down (to “dial-in” roll centers). Notice the use of urethane bushings in the exploded-view above. This concept brought howls—even proclamations of Blasphemy, from my fabricator community! After all, EVERYONE knows you don’t want “compliance” in a race car suspension component—right?!! Not so fast all you keepers of the conventional wisdom! The urethane in question is super-hard, & the dimensions of the billet receptacle are such that there is a “designed-in” PRE-LOAD—-the rod end can not be inserted without the aid of a special tool (designed by me, of course), which SPREADS the opening (i.e.,compresses the urethane bushings) so there is clearance for the width of the ball (in the rod end). The end result is a mount where the compliance would only be a few thousandths—BUT, think about the harmonics-dampening aspect of the piece! Yes, I designed the entire suspension to have vibration / harmonics dampening capability!—WHY?Â Â Most of my fabricator friends are used to working on steel-chassis’d race cars—-but the NSX is an all ALUMINUM tub & frame-rail design. I didn’t want the inherant suspension harmonics / shock loads to result in a “wave effect” that would, over the long-haul, weaken every critical weld / bonded component in the NSX. SO—we’ll see!—if it doesn’t work, I can always replace the urethane with Delrin.
Another “not-so-obvious” feature of this design is that these “pick-ups” are attached to the frame using two 3/8ths STAINLESS Â bolts, which aren’t as strong (especially shear strength) as conventional wisdom would mandate. The goal is to have the “pick-ups” shear off the frame in the event of a car-mangling incident. Better than mangling the frame or all of the “critical-geometry” attachment points!
Custom spresder tool spreads steel bushings (tapered face) approx .035″, which compresses the inboard urethane bushings so that rod end can be inserted between the steel bushings’ inner face.
Trick was to drill all 16 of the steel bushings in exactly the right place for spreader to work (had to build a drill jig).
Trial- fitting the Penske coiloversÂ (F.L.)Â so they clear the brake & clutch master cylinders. Precise measurements are taken for a spacer that will fit between upper rod end on shock, & coil spring “retaining collar”. Note remote shock reservoir is only taped into a hypothetical position for final body profile mock-up.
This view (F.L.)Â illustrates why a “coil spring spacer” will be fabbed—to keep the retaining collar away from the brake & clutch cylinders!
Trial-fitting L.R. Penske coilover—also will need a custom spacer to fit between spring retaing collar & shock rod end (to clear chassis where shock shaft protrudes thru to outboard-mounted rocker). Note also remote shock reservoir “tyed” in hypothetical location on still-to-be-welded-in rectangular aluminum tubing crossmember. (it has to have our URL water-jet cut into it yet)
Close-up reveals why a spacer must be fabbed to allow clearance between spring retainer collar & inside edge of chassis.
Like this—final assembly will be with silicone. Â A different length spacer is required for Front than Rear. (wanted to keep all 4 shocks exactly the same O.A. length, to lessen the cost of Â “spares pkg.”)
Close-up of above pic.
Custom step-bushings are made from an extra hi-strength Delrin compound, & serve to further insulate entire chassis from shock absorber & suspension component harmonics (ocillations).
Delrin step-bushings are .375″ i.d. x .500″ o.d. and result in an installed width of 1″—which just happens to be the dimension all of the shock attachment points (frame & rockers) were fabbed to! These also allow the use of smaller (think lighter) hardware @ every point a shock attaches! (maybe I should sell these to Penske?)
Rear shock-bridge (note 2 shock attachment holes @ top-ctr. are .375″, as discussed in previous pics)Â will also support an adjustable-blade ARB system, which will locate in the 2 freshly-bored holes in photo. The system incorporates twin gear-driven shafts, which will reside in nylon-bushed, aluminum tubes, yet to be welded into shock-bridge in the 2 large holes above centerline. The shafts will “cradle” ARB blades (in bronze bushing-photo below), which rotate in-sync thru 90 degrees of “soft vs. hard”. Morse cable attaches to a bellcrank on blade (not in pic), and is cockpit controlled by a Genesis Systems multi-position ARB levers (Genesis is really Irv Hoerr Racing from old trans am days!).
Shaft on left will have matching profiled spur gear welded. Both shafts will have matching profiled spur gears at threaded end— the gears are keyed to shafts, not welded—so assy can be installed from back-side of shock-bridge.
Final configuration before weld-in into rear shock-bridge. Note bores in CM tubing at left (with zirks) were made AFTER the tubing was welded to the shaft (which is really tubing, 1″ x .188 wall)
View as seen from rear inside “trunk” looking towards engine bay.
Blade on left is heat-treated 4130, while blade on right is Titanium. Notice the larger cross-section at base of Ti blade. These insert in Bronze bushing in photo above. Bushing is “lube-grooved”, & a grease zirk installs in small tapped hole.
Again, notice “beefier” cross-section on the Ti blade—-the metal is more flexible than the chrome moly!
These spur gears have a 105 mm pitch diameter, hence the 105 mm shaft spacing on the 2 shock-bridge holesÂ 6 pics back. The one with the hub & keyways bolts on to the front end of shaft (engine-bay side of shock-bridge). The one that is hubless welds on to the backÂ end of shaft , which is the end that cradles the ARB blades.
Amazing what a water jet can do!—these are made of stainless steel!
Center section of “trailing” front crossmember.
A lot of work for something relatively simple! (Note extra weld metal inside).
Right & Left sides to “trailing” front crossmember—formed out of 2″ x 4″ rectangular aluminum tubing.
Notice extra weld-metal on inside seams—so outside edges could be smoothed up—again, a LOT of work for a component that wont even be visible unless you crawl under the car!
Final config. before welding to underside of tub—approximately where the OEM rack & pinion used to be.
BIG brakes!—-also very light-weight because they’re CARBON
Notice how AP Racing puts the part # right on the edge of rotor to avoid confusion between sizes & compounds at the track.
Very LARGE caliper assy. with major piston bore cooling design.
Mounting holes are 210 mm’s O.C.—Note also titanium pistons with gas pressure-relief holes.
Assembly on LeftÂ front hub (front hubs use only 4 drive-pins). Wheels have 12 holes!
This is L.F. upright & brake assy. Notice monoball (lower-center of pic) is bolted-on to upright, which allows for shimming—which changes scrub radius.
This is a FRONT wheel—18″ x 11.5″Â VERY light @ 17 lbs.Â 10 oz. (magnesium)
Same wheel with all of the suspension & brake components “stuffed” in.
View from backside illustrates how entire upright & brake assy. fits totally inside the wheel, lower “monopost” is visible at bottom of upright, & secures in monoball, which is installed in outboard end of lower control arms.(detail about 30 pics back).
L.F. upper control arm, attached to monoball on upright. (top-ctr. of pic)
Special design of outboard control arm “clevis” allows for plus or minus 7 degrees of caster adjustment—WITHOUT affecting camber! Close-up reveals vertical serrations on clevis (just to left of welded bolt). These clevis’ were machined from solid 4130 billet bar stock!