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Just an update, we've ran ~2 hours combined at a track day, 7 hours of an enduro, and another 6 the next day with no issues so far. I'm not saying they're perfect or ideal, but I thought I'd report. Again I'm not really sure what I'm looking for though.
You're looking for catastrophic failure, dude. The OEM arm limits rotational movement of the spindle by limiting fore-aft movement of the top half of the spindle. The OEM arm is a dogbone design which will not deflect substantially in the fore-aft direction. You have taken the OEM arm, which does this job with arguably marginal effectiveness, and replaced it with an arm which is not in any way designed to do the same job. The spindle is free to rotate fore/aft with absolutely no restriction aside from what is offered by the lower control arm and the RLCAO bolt. Every time you are on throttle, the axle twists the hub, the hub twists the tire, the tire twists against the ground and tries to roll itself forward, and that rotational force applies an enormous twisting force on the RLCAO bolt, the lower control arm, and the lower spindle attachment points. Those parts were never designed to endure such a twisting force.
These arms are ******* awful and anyone with even a modicum of knowledge of mechanical system design can see that. The fact that you continue to champion these is really odd to me.
I don't even know what the purpose is. I have never experienced an issue with inadequate camber settings in the back of the car. I think the adjusters in Rover are set dead center of their range for 2.5deg. I know Spec Miatas want more, but they are weird and with proper spring rate they shouldn't need as much camber.
The only advantage of these arms is to be able to easily make camber adjustment without affecting toe. Of course that advantage is not worth the issues these introduce.
I think we can all agree getting rid of the compliance in the upper arm is a good thing but doing that without introducing bind is tough since the knickle will be located at a different point front to rear depending on what toe setting you're running. This is the reason I built my custom adjustable A-arms for the rear, no bind and little to no compliance and I get the ability to adjust camber without even pulling a wheel.
IMHO the best way to change the camber adjustment range in the rear (certainly the cheapest) is to use offset delrin bushings with stock arms. I know SadFab makes them for the front, don't know that I've seen them for the rear although I can't imagine it would be any harder to make them.
Or, you know, a rod that isnt threaded in the center - you know, because magical metallurgical properties of the blue coating isn't actually going to prevent the threads from digging into the sleeve it sits in.
Stop attacking a color idiots. It just designates a different metal, you two are the first humans I've heard of who can tell apart two different mild steels from their...smell? The way they look at you?
Stop attacking a color idiots. It just designates a different metal, you two are the first humans I've heard of who can tell apart two different mild steels from their...smell? The way they look at you?
I spoke with SPL this morning and they have agreed to issue me a refund for the replacement parts I purchased (blue threaded rod and aluminum bushings). They also mentioned my car is the only car that's had this issue.
I would throw those arms in the garbage and run away. The ONE arm in a Miata suspension system that needs to be more robust than the factory arm is the rear upper due to twisting force. The ONE arm I changed immediately when I added the LFX was to put in a V8R tubular rear upper arm because it solves exactly that issue - the camber adjustment is just an extra perk, the primary reason for replacing that arm is to minimize twisting. That SPL arm is far, far, far worse than a factory arm in that crucial department. I wouldn't run it on a bone stock car.
04-23-2018, 11:07 PM
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