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When we set out to explore the coilover needs of Slingshot, we had the benefit of being able to observe a variety of types having already been implemented in the Slingshot marketplace. Further, we had high-quality information from some select members of our Turbo Posse, our group of hardcore Hahn Turbo Slingshot owners. These advantages are not insubstantial, and led to us choosing the QA1 line of high-performance coilover replacements.
We’ve used QA1 in a variety of other applications over the years, from drag racing to street rods to circle track, so we had a good foundation to work from. The company is a proven leader in the market, and undoubtedly could provide quality product at an achievable price. As an American manufacturer ourselves, we also greatly enjoyed that the QA1 product we chose is also American-made. That scores a lot of points with us! But that was just one of many strong reasons we chose QA1.
The first challenge was to determine the best-suited combination of parts from the vast offerings of QA1. As QA1 does not do Slingshot-specific coilovers, one must understand how to address all of the variables that define the differences among the hundreds of different universal part numbers they offer. Enter: Turbo Posse! With a strong assist from these aggressive customers who had researched the QA1 product and adapted, tested and refined until the best combination was found, we had a great blueprint. Now we just had to make it something anyone could install themselves, with zero research or mods to the Slingshot needed, just order up and you get the perfect recipe, in direct bolt-on form.
Therein lay the second and final challenge: make this well-researched, well-proven coilover alternative that was gaining popularity among uber-enthusiasts into an absolute bolt-in, making it no longer a “universal” part that requires its own adaptation to fit Slingshot. That’s where Hahn RaceCraft came in strong, as I developed the parts to do just that. Whereas previous installations of QA1 Sphericals on Slingshot had required chassis drilling, shimming and other parts required, now we’ve made these a direct bolt-in. Swapping out the fronts is as easy as this: jack up the vehicle, remove the two easy-to access coilover bolts, remove stock coilover, put Hahn/QA1 Coilover in its place, and reinstall the bolts. Done. Might take all of five minutes for both if a beer were also involved. The rear unit is just as easy, with some plastic panels that have to be removed and replaced to gain decent access.
These Hahn/QA1 Spherical Coilovers come to you fully assembled and rough-preset to a starting ride height. They are of the Spherical mounting bearing variety, which we’ll learn more about in a moment. We offer these sets in both single adjustable (combined compression and rebound damping adjustment) and double-adjustable (discrete separate compression and rebound damping) adjustment types. Every set is also completely adjustable for ride height as well, with spring rates carefully chosen to be an ideal compromise of stiffness versus comfort for street and track use. We even include the needed spanner wrenches to perform your ride-height adjustments. We’d like to think that, with the help of the Turbo Posse, we’ve all managed to really nail it in this now completely bolt-in solution.
Now, as if thousands of miles of testimonial love from the Turbo Posse isn’t enough to seal the deal on just how well QA1 works on Slingshot, allow me to also add my own impressed self. The Hahn SST Turbo SL upon which we engineered the prototype bolt-on Hahn/QA1 Spherical installation also benefited from a new set of performance BFGoodrich Sport Comp tires, which were installed on the stock wheels.
The transformation was simply stunning. We lowered the SL about ¾” to 1”, did some local street testing that dropped all jaws, and then sent it to the best place to gather even more data: the race track. On a track day at the Florida International Rally and Motorsports (FIRM) complex, the SL just smoked around the 1.6 mile road course. Riding shotgun was the track instructor, who is like a force of nature at the FIRM, adding great skills and insights to all who are fortunate to come in contact with him at this fun, effective facility. A veteran road racer of no small caliber himself, he has been continually impressed by the Slingshots we have all brought to the facility. This time though, it was personal, with him in the machine for hours of direct exposure as he trained and refined the driving skills of our eager customer. The verdict was one of complete agreement that properly set up, a Slingshot can hold its own with any production performance car on their track, as well as also hang tough with many pure racing machines! He was nothing short of blown away by how competently the machine handled this challenging course.
That racing stance!
On the street, the capability is no less apparent. I was astounded at the difference. This Slingshot just dares you to throw it into a corner, then laughs at you for being so timid, prodding you to push harder next time. Slingshot’s chassis has a lot to offer if you are of a mind to seek it. I am 100% sold on the fact that the stock “coilovers” (really little more than just shock absorbers with spring seats welded on) have no business on this machine if one wishes to explore its handling capabilities in any detail. That is all. It’s just that cut and dried. You can’t have the kind of fun this machine can provide in handling prowess unless those stock concessions-to-the-bean-counters are permanently deleted from your beloved SS. Toss them in a box somewhere in the deepest recesses of your shop-world, for you will never seek them again.
The Argument for Spherical Ends
Spherical ends on our coilovers create an improvement over flexible poly (rubber) ends in two primarily significant ways: precision of response, and reduction in friction. Let’s touch on each.
Spherical bearing on left vs. poly bushing on right
Precision of Response
Consider for a moment how your coilover’s shock absorbing (damping) assembly works. It uses a calibrated resistance to movement in order to dampen spring oscillations. This damping resistance is also adjustable in performance upgrade coilovers. It is expressed in two directions of travel: Compression occurs when the wheel goes up and compresses the coilover, such as when we hit a bump. Rebound next occurs when the spring pushes back, when the coilover un-compresses as the wheel returns to its normal ride height position.
In high-performance use, we prize having adjustability to this damping resistance. Such adjustability enables us to optimize the suspension behavior of the machine to suit the vehicle’s chassis combination, road surface and driver. A further advantage is that we can have multiple personalities for the vehicle, such as one for hard track, one for cushy cruising…all available at the twist of a knob.
Now imagine what this coilover does when the suspension is suddenly compressed, like from a bump in the road. If it has poly or rubber bushings, the resistance to movement in the coilover (created by both spring pressure and damping rate) causes those bushings to deflect or compress, to the extent that the coilover itself does not begin to compress until the bushings have both first compressed at both top and bottom. This causes a time lag in the coilover’s response to suspension movement, but more…we also have a momentary stored energy in these now-compressed flexible poly or rubber bushings. As those bushings transfer this energy back into the coilover, our prized damping valving is again momentarily confused.
Our hybrid filled nylon/steel spherical bearing allows precise, low-friction movement without the looseness and harsh shock transfer associated with pure steel spherical bearings
Friction Restricts Movement
Poly bushings have another shortcoming for high-performance applications: they do not pivot as freely as spherical bearings. During suspension movement, the coilover needs to pivot at each end as angles change. Poly bushings resist this pivoting action to a degree, as their internal friction is considerably higher than spherical; the “breakaway torque” required for initiation of movement is higher. The smallest bumps won’t even overcome this friction sufficiently to allow any suspension movement. Not so with spherical bearings, which present negligible resistance to pivoting thanks to internal friction that is but a fraction of poly. The difference in suspension “feel” is significant. The tires simply feel more precisely engaged with the road…because they are, and it is evident in both handling prowess and feedback to driver.
Poly bushings dampen coilover valving response and create excessive friction
There is an excellent method to eliminate these variables, and to achieve precise, accurate synchronization of coilover to suspension movement: our hybrid nylon/steel spherical bearings. Spherical bearings do not compress and release like poly or rubber, and thus ensure that our high-performance coilover is getting the most, and the most accurate, information on actual suspension behavior.
Spherical bearings clearly dominate poly bushings in these aspects, both in design concept as well as in practice. To say you can feel the difference is actually an understatement. It’s just that evident. It’s like the difference between your bare fingertips and wearing gloves. When you need precision, when you need to feel the nuances, you don’t wear thick gloves…and neither should your performance machine if you want to get the most out of it.
You will never be so confident in both your Slingshot’s as well as your own capabilities as when you move up to this level of precise, sensitive connection to the road. Now the handling limit will be much more clearly defined, as well as higher than ever before, with none of that vagueness or unpredictability that can leave a troubling stain. You’ll feel more relaxed and more empowered in practically every road condition.
But aren’t spherical bearings harsh for regular use? While there is definitely a firmer feel to them, using them on just the coilovers does not make the machine “race-car stiff”. Further, our nylon/steel hybrid bearing does provide a modicum of cushion. Meanwhile, the machine still benefits from stock rubber isolation bushings where the control arms pivot on the chassis, so there is still adequate cushioning available. Your Slingshot will still be very street-friendly over bumps and in general with our hybrid spherical coilovers. Further, your coilovers’ adjustable nature allows you to fine-tune the suspension strength to what best suits you.
But what the spherical bearings WILL do is to completely synchronize the coilover’s behavior to the actual machine’s behavior, with none of the lag, vagueness or friction of poly. When we invest in quality coilovers, the best thing we can do to fully exploit that exquisite, fully-adjustable damping potential is to not confuse it with squishy, sticky poly bushings!
Double Adjustable standard; adjustable for both ride height and damping. Springs included. Contains three pre-assembled, bolt-in coilover assemblies; two front and one rear. 100% bolt-in ready, two bolts per coilover and done. Features 18-position combined compression/rebound damping adjustment. Pre-adjusted to stock height, we also include a spanner wrench set for your own ride height refinements, for which you can go either lower or higher.
Triple Adjustable: Independently adjustable for height, compression damping, and rebound damping. For the hardcore handling junkie, we present no fewer than 324 valving options, with 18 positions of compression adjustment and 18 positions of rebound adjustment. There are no jumps in adjustment range when adjusting between any two clicks. Each adjustment has been carefully defined to provide the ideal force curve to maximize performance. When too much adjustment is just enough!
Triple Adjustable Option: add $300
Spring seat bearing assembly
Spring Seat Bearings Installed: If you like to play about with ride height a fair amount, these precision roller thrust bearings make life a lot easier. They reside between the spring and the spanner nuts, and allow you to adjust ride height without galling or binding under pressure. We’ll even hand-pack them with grease for the smoothest operation and longest life.
Spring Bearings Option: add $50
Thanks for your time!
-Bill Hahn Jr.
Learn more about QA1’s suspension technology here: