Hi guys - I finally pulled the trigger on the rear adjustable upper control arms when they went on sale at FM (https://www.flyinmiata.com/rear-upper-control-arms.html). I abuse (I hit/jump curbs too much...) and tow dolly my exocet to the track so I've got camber locks on all 4 corners so I don't have to deal with slipping - problem with them is they're not exactly easy to fine adjust. You're at the mercy of the teeth's distance - and when I get them close I just lock them in. I'm in love with the concept of easily adjust JUST the camber (not worrying about the toe/steering alignment/etc) , but the only front arms I see that do this are "TruHart" - a brand I'm not familiar with. They come with a 5 year warranty on control arms and are made in the US of A according to the details on the site.
https://www.carid.com/truhart/a-arms.html?urlId=276002
Has anyone used them? Anyone have a better OTS solution?
The toe still changes with these arms to the same amount as with any other method of camber change. Sorry to say there is no way using the original spindle and steering arm that fails to change the toe when you change the camber.
I'm not sure I follow - I was assuming it was similar to the rear where FM states: "So you can adjust your camber quickly and easily without affecting toe" since you're just moving the top of the spindle inward and the bottom is locked in space.
Why would the toe change when moving the symmetrical upper control arm ball joint inwards? Is it not actually on the centerline as it appears?
I’m not very familiar with Miatas in general but afaik they’re dual A arm. If you change the camber from the upper ball joint only the toe must change as long as it’s controlled by a tie rod. It might be minimal or not important but it will change. Someone correct me if I’m wrong but that’s what’s I’m seeing in my head.
Edit: I googled the rear suspension. It looks like toe is controlled by the lower A arm so camber change does not affect toe. For the front because the distance between the upper ball joints at the knuckle is decreased when camber is added the two knuckles effectively move close together at every point between the upper and lower ball joints. If the tie rods remain the same length they will push out the knuckles relative to their mounting location. IE toe out if the rack is in front of the knuckles, toe in if the rack in behind.
Again, this might not matter much but there will be a small change.
In reply to spandak :
I think I see what you guys are getting at, I wonder how negligible the toe shift would be? The front is much easier to adjust the toe than the rear, but still not something I look forward to doing.
spandak said:
I’m not very familiar with Miatas in general but afaik they’re dual A arm. If you change the camber from the upper ball joint only the toe must change as long as it’s controlled by a tie rod. It might be minimal or not important but it will change. Someone correct me if I’m wrong but that’s what’s I’m seeing in my head.
Edit: I googled the rear suspension. It looks like toe is controlled by the lower A arm so camber change does not affect toe. For the front because the distance between the upper ball joints at the knuckle is decreased when camber is added the two knuckles effectively move close together at every point between the upper and lower ball joints. If the tie rods remain the same length they will push out the knuckles relative to their mounting location. IE toe out if the rack is in front of the knuckles, toe in if the rack in behind.
Again, this might not matter much but there will be a small change.
I appreciate the extra effort! It makes sense now, I'm curious how big of a delta it will make - I have paco alignment stands, but it's still one of my least favorite jobs to try and fight the toe vs camber vs the track. And anytime I unlock my camber locks I know I have a full afternoon of frustration to follow :)
Hmmm, I just looked at his site and it doesn’t look like Paco is selling front control arms. I saw some prototypes he did a few years ago, you might reach out and see if he has any sitting around. If enough people want them, I’m sure they’d go into production.
The ELBJs usually do the job most people need so maybe he decided against duplicating effort.
In reply to KyAllroad (Jeremy) :
Hmmm, I'll shoot them a line.
In other news, got the rear control arms yesterday and these things are the bomb.
