Well if you plan on running autocrossing with the SCCA... you cannot change the rear LCAs in Stock (aka: Street), Street Touring or Street Prepared. You'd be bumped straight to Street Modified (which allows all SORTS of suspension and drivetrain mods, so be ready for some serious competition) or C Prepared (a place for gutted race cars on giant slicks, with some very goofy rules)
That's where our car ends up in SCCA right now - Street Modified. We ran an autocross last weekend with our local Texas Region in this very class, and it was brutal. There are some stupid fast cars in SM in many regions of the country, especially at Nationals. I've worked with 2 different winners of SM at previous Solo Nats and neither car remotely resembled a street car. I got lucky and won by a couple of tenths, but to be competitive there we would be replacing the metal hood and trunk with carbon fiber, making all bushings spherical, and doing a fully built race engine or adding a power adder like a turbo or supercharger. All of that is allowed in SM... so watch out what you wish for.
Now in SP and ST classes you can change the UPPER rear control arm, and even go to a custom spherical mount and weld/cut on the body. But the lower rear arms have to remain stock. And you can't do LCA relocation brackets, and most brands of Watts Links are illegal. Why? Well... if I explained it to you your brain may explode. There is no why in the SCCA, you just stick the car where they say it belongs this week.
Of course, as the poster boy for Whiteline, what LCA do you think I am going to recommend?
But I prefer the Whiteline adjustable LCAs with their elastomer bushings because they have held up to the abuses we've thrown at the car on track, on the street and in many autocrosses. We've put a lot of hard miles on their LCAs without a squeak or issue. Adjustable lower arms allow you to adjust for pinion angle on lowered cars and get rid of a big, pliable rubber bushing in the suspension load path, too. They do have merit.
Is it silly that solid rear axle cars cannot change the LCAs or add LCA brackets?
Of course it is! I've been asking people that are SCCA members to WRITE THOSE LETTERS (linked
here) asking for these to be allowed, for years. Whenever you lower a Mustang the suspension geometry gets all wonky, and/or there are other aspects that need to be altered at the same time, including:
- An adjustable Panhard bar or Watts Link. When the suspension is lowered the fixed length stock Panhard bar will then be too long and the axle will sit offset relative to the chassis. One tire will be closer to the fender than the other, usually by 1/2" or more. A shortened Panhard bar or a Watts Link will realign the axle to the car.
- Rear Relocation Brackets. A lowered S197 makes the rear suspension geometry all jacked up, with massive anti-squat. Lowering the rearmost pick-up point returns the LCAs to level.
- Camber plates. If you are going to the trouble of adding lowering springs, adding camber plates involves almost zero extra work. And adding negative camber saves your front tires and increases grip - it is just part of the equation.
- Adjustable rear control arm. Lowering the rear changes the pinion angle, and you need to adjust for that either at the top arm (UCA) or the bottom arms (LCAs).
Again, if you are wanting to run in the more common STX/STU or ESP classes, then don't change the lower arms. Get an adjustable upper arm to compensate for the pinion angle change on a lowered car, instead. It sucks, but thems the rules. As much as I'd love to sell you "one of everything", we will always steer people to the right parts for the classes they run, before trying to make a sale on the wrong parts.
Cheers,
