Project Viper GTS: Part 10 – EMI Racing Toe Stiffener
This Gen 2 toe link failed at COTA with the owner claiming he did not hit any of the curbs.  While Erik ensures the factory aluminum knuckle is safe with no documented statistical failures, and that it’s simply “a bit under-engineered for the loads going through them when the car is pushed harder than a typically driven street car”, he does acknowledge that if you subject anything to repeated bending stressors (which we know the aluminum knuckle does) it will eventually weaken and break like a wire coat hanger.

While it is extremely unlikely to have the aluminum toe arm snap off from normal track use, let’s put some things into perspective.  It has been measured that the aluminum toe arm is repeatedly flexing 0.25” per side during cornering on a road course or during drag racing.  Metal will eventually weaken and break after repeated bending stressors.  Many crashed Vipers have broken rear knuckles at the toe arm.

Now I am far from suggesting that the toe arms is going to snap and cause you to crash, but I will make the claim that due to the weakness and “under-engineering” of the arm, there is an increased chance of the arm failing after repeated hitting of aggressive curbing on a racetrack, hitting a curb on the street (it’s rare to find a Viper who hit a curb with the arm intact since they usually break before bending the toe link), or spinning off the track sideways in the dirt.

Since the arm is constantly flexing, it slowly weakens over time, and aggressive FIA curbing would likely increase this fatigue. Bracing the toe arm is really important to reduce this bending, weakening, and toe deflection.  It will also strengthen the arm and reduce the chance of it braking from curbing or an off-track excursion.

To install our Toe Stiffeners, we entrust our Viper to our friends at RareFab in Boynton Beach, FL for their meticulous attention to detail and ability to do anything from an oil change to a custom fabricated turbo system or engine swap.

There’s always something different every time I stop by RareFab.  From exotics like a Lamborghini Huracan getting a custom header-back exhaust, to imports like a 5-speed converted SC400 with a custom turbo kit developed by RareFab, to AWD euros and plenty of Hot Rods.  People from all walks of life trust RareFab with their cars due to Will’s excellent craftsmanship, honesty, and well-rounded knowledge.
The first step to installing the EMI Racing Toe Stiffeners is to remove the rear wheel and admire the Lotus Elise-sized rear caliper (yes the rear caliper is sourced from the rear caliper of an Elise).
We can see the steel rear toe link here attached to the aluminum knuckle.

23 comments

  1. Great article! Any chance you could place a link up top as to where to get the stiffeners? They sound necessary and I’d love to buy them for my GTS as well. Thanks!

  2. Wow; kind of concerning that the stock uprights were that marginal. The brace seems to take care of things but I guess it highlights stuff that didn’t get caught in the design stage.

    … I swear, every time I see a new update in this series come up I start checking ebay.

  3. You brought it to a shop for a 2 bolt nothing comes off bolt on????
    Should we all start bribing Dave Coleman and Eric Hsu to write again?

    Miatabusa………………

    1. He doesn’t wrench, but he can wheel better than any of the aforementioned names. Can relay what effects the setup changes made better than most and that is more signal and less noise.

      1. Billy can wrench and he is pretty damn good. I have seen him do it. Why do some of you feel that you have to pick this article apart in such a dumb sniveling way? Wouldn’t you rather have the car on a lift with good photography rather than some weird angles and lighting on jack stands?

    2. I would rather take better photos of the install on a lift and give credit to a friend and owner of a great shop than to show how cool I am for working out of my home garage with jackstands and a small, 10 gallon air compressor tank.

  4. Hey Billy, I know exactly what you are feeling from damper testing I did with a certain company as a consultant a few years back. I was able to get rid of most of it through spring rate and damper tuning but some was still there. Now I know what was the issue. If we had these, I bet I could have backed off on some stuff and gotten more mechanical grip. I was really impressed by how well the Viper did on the track. Pounding really hard in the Arizona summer heat and no heat, tire or brake issues. When we were done, the car was a sweetheart to drive too. Tamed the bobbing and twichyness and went a few seconds a lap faster to boot. We tested and developed settings with Pirelli and Michelin slicks as well as the OEM tires.

    1. I would say no since quite a bit of the load is torsional. Square section tubing is stiffer in straight bending though. It is also about 20% heavier for equivalent strength.

  5. Just curious how does one measure/find out on the toe deflection. I can understand what a driver feels when it deflects but how did you measure to amount that was deflected?

    I’m always fascinated by this. Keep up the great work/articles guys.

  6. I’m assuming you’re measuring this after a session or doing a tear down to see if if the part/knuckle has deformed.

    I can’t imagine you’re using that with a camera pointed at the whole dial jig whilst it’s on track. Haha

    1. I believe Erik had the chassis on a kinematics rig and loaded the suspension to measure the deflection and/or had strain gauges & potentiometers on a car to measure the deflection.

      This deflection is due to a lack of stiffness. This deflection is also (thankfully) lower than the yield point of the arm, at which it has been known to snap and not just deform.

  7. I was not aware that aluminum could bend so much, so often, without breaking more easily than it does.

    I’ve seen one or two similar products for Miatas (ND in particular), the front knuckle of which weighs like 2.x pounds. I’ve never heard of any breaking, but… has anyone else?

  8. Great write up and wow… I knew the rear toe was an issue but never considered the upright. Makes perfect sense and I’m sold on Eriks solution. Attempting to contact him now, if only to save my uprights before I get more wild in my 99 GTS.

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