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  • Rulebook frustrations - front suspension - back to the drawing board
  • Post author
    Joel Grannas

Rulebook frustrations - front suspension - back to the drawing board

UPDATE: Thanks to Jason Miller and the WCF Tech crew I am approved to run. I think they realized that we are just trying to make spindle mounts work with the oddball location strut towers on the MKIV supra.

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So, I have been really happy with how everything was going with project H-Pattern. Doug at Precision chassis has been doing some amazing work for me on this machine. The one part of this car that I was more excited about than really any other part was the front end and front suspension setup.

I have never done a spindle mount setup on a car previously, so this was something I was extremely excited about. For this car, I was going to spindle mounts, along with a really trick front suspension setup. This would allow easier engine serviceability, take out weight, and allow the use of a common domestic style front suspension rather than the awkard angle OEM style struts.

But, after some pictures were posted, questions were raised about the legality of my front suspension. After review by some tech officials and sanctioning people it has been deemed not legal to fit into the class I normally run at World Cup Finals.

A lot of time and money has been put into this front end setup, and it looks like now we have to go back to the drawing board in order to make the top of the strut bolt "pass through" the stock strut tower location. Basically you can not change the angle of the strut, even if using the stock mounting location. This is extremely limiting when it comes to the Supra, as the front suspension angle leans in, and will not allow you to ever run a spindle or aftermarket front strut because the shock tower location is just too far inward. See pictures below of the angle of the stock front suspension, versus what is required for a spindle type setup.

Here is the stock front suspension angle:

MKIV Supra Front Strut angle

Factory MKIV Supra shock tower location. Notice how far inward they sit:

supra shock tower location

Here is a mustang shock tower location... Notice how outward they sit, and the suspension angle that comes with that. No issues.

mustang notchback shock tower location

Here is how a spindle mount setup looks when mounted to the supra. Notice how there is not much available inward angle in these, and there is no way to get the strut top over to fit the strut tower mounting points. In the mustang picture above you can see how this would put some cars at a disadvantage.

Spindle mount suspension Grannas Racing MKIV Supra

So here is what was designed in order to run a spindle mount setup. The front mounting location is used, with a bracket moving outward to meet the top of the strut.

Grannas Racing supra front suspension

Because of the stress caused on those three bolts by the strut outward, bracing was added into the front bars to keep it from bending the stock shock tower sheetmetal.

MKIV Supra front strut relocation bracket Grannas Racing

So, let's talk about legality... and how ridiculous this rule really is. So in these rules you can not change where the top of the strut sits. It apparently it has to bolt directly into the shock area, with the top of the strut in the shock tower area. Keep in mind, THIS IS FRONT SUSPENSION!!! This is not greatly effecting the performance of the car like something with would by changing geometry of the rear suspension. This is not changing the wheelbase, not changing the track width, not changing the forward/back location of the strut, it is only extending the shock tower mount location outward to meet the strut. These same rules will allow a rear wheel drive IRS car to bolt in a solid axle rear suspension setup, which totally change the car, yet won't let something simple like this pass. It is really unbelievable.

Grannas Racing Supra spindle mount front suspension

So, now what? All of this work basically will be scrapped. Because, in order to run a stock style front strut setup I have to go back to a factory style front subframe with a control arm that holds the strut. This was all pretty much done, very little to do yet as far as the front goes, but now this is a major setback in timeline. I have so much other stuff to do, and money to spend elsewhere in order to have this car ready to race this year, and this just throws a giant wrench in all those plans.

It is just really frustrating... all of the great benefits like allowing the area under the engine pan to be open for easy serviceability of the engine, usings a common drag rack/pinion, and lightweight components goes out the window with this change. Notice in the above picture how nothing is under the motor, that sure would have been nice for checking bearings.

So, unless something changes... Here is the eventual plan. We will be building a stock replacement tubular front subframe, which will allow the use of all the stock suspension up front, and will have to go back to using stock front spindles, arms, and run a suspension with the stock suspension angle. I could go to some other aftermarket front spindle, and do a "one-off" setup for this car... but I might as well make this a bonus to the supra community, and try and make a "bolt-in" Supra product out of this. Which will also allow me to recoup some of the money lost on all this mess. So Grannas Racing will now have a tubular front subframe now to match the rear one we already built. This front subframe will allow use of all the stock arms, and have a really nice front suspension package to match the back.

-Joel

  • Post author
    Joel Grannas