Shoutout to the SCCA for adding a major national-level Solo event at our official test track, the Florida International Rally & Motorsport Park in Keystone Heights, Florida. Wait, what? It’s in three weeks? Man the wrenches!
Our original plan was to install and sort a new suspension in our 1991 Toyota MR2 Turbo before the mid-March event that usually kicks off …
I'm going to go out on a limb here and guess that a following installment will involve the Wilhelm geometry kit. It looks pretty nice. I wish someone made something as comprehensive for the Mk1, but all I can find are the T3 RCAs.
So part of the reason for the increased rates is to offset the increased leverage for the roll center change?
Matt B (fs) said:I'm going to go out on a limb here and guess that a following installment will involve the Wilhelm geometry kit. It looks pretty nice. I wish someone made something as comprehensive for the Mk1, but all I can find are the T3 RCAs.
Yeah, did we foreshadow that well enough?
In reply to z31maniac :
Yeah, if you;re just building a fun street car, you can get awa with lowering and just bumping spring rates a bit to compensate. For something you want to be able to properly tune, though, correcting the roll centers will be necessary. UPS guy is on the way with those solutions :)
In reply to JG Pasterjak :
As soon as I saw their name it was clear. 
I wasn't aware of that they did that level of modeling though. Cool stuff. Looking forward to seeing the same graphs with their kit installed.
This kind of thing makes me think if I were a smarter man I'd switch to a Mk2, but I just can't seem to quit my doorstop.
That looks a lot like SusProg3D!
Subbed. Keenly interested.
These charts make me happy. I've been meaning to 'manually cycle' the rear suspension on one of my cars on the alignment rack to try and diagnose some weirdness.
It's pretty funny that the net effect of the front and rear toe changes is the car doesn't want to go where you point it. How wonderful lol.
Audi and VW's have the same issue with their strut suspension, the cure is installing "ball joint extenders" 
Typ85 said:Audi and VW's have the same issue with their strut suspension, the cure is installing "ball joint extenders"
Yep. We have a similar solution on teh way from Wilhelm. Hopefully his powder coater gets around to them soon so he can get them to us in time for the Pro Solo.
In reply to Matt B (fs) :
At the risk of stealing some of the thunder from one of JG's future articles, the rest of my analysis is on my website: https://wilhelmraceworks.com/suspension-analysis
I can't comment on the toe curves without modeling it, but the camber curves are likely very similar on the MKI, and all of the same improvements will apply.
In reply to Alex_W :
At least go ahead and make the link work :)
https://wilhelmraceworks.com/suspension-analysis
But, yeah, we'll be leveraging a lot of the hard work Alex has already put in during our build and sharing a lot of his findings. I'm really excited to drive on the stuff soon. I'm hoping to get at least a quick test day in before the Pro Solo, but more likely than that I'll be experiencing everything for the first time at the February Pro. Which, honestly, is fine. I'm obviously really familiar with the FIRM and how the surface behaves, and every autocross there is basically a variation of the same theme, so of all the places to sample a new car that's probably the least risky for me.
Ugh, now I have to go finish installing that rear swaybar, because I just realized like five minutes ago that the entire rear subframe has to come down a bit to get it in place. Y TOYOTA?!?!
In reply to Alex_W :
Pretty impressive improvements! I started to wonder why someone would choose the standard top mounts over the extreme until I saw what they did to the toe curves.
Question - I assume you want the tie-rod spacers to match the height of your RCAs to keep the geometry as close as possible to stock or did you make adjustments? On a related note, I have to wonder if changing the relationship between the ball joints and tie-rods could actually help the front and rear-ends to act the say way rather than have mirrored toe curves. Even stock it seems like they're fighting each other. You might not want to mess with the rear for stability under acceleration, but if there was a way to make the front toe behave more like the rear (toe-in under compression) without the wild swing we see when tie-rod spacers are absent. This would lead to a toe-out condition in the front under straight line acceleration, but seems like a benefit under at least steady-state cornering. I could be imagining this thought-exercise incorrectly though. Is there something I'm missing?
Aleeeeeeeeex, Y-U-No pander to the hare-brained ideas of someone who's mk2 suspension geometry correction research entails reading your site? 
In reply to Matt B (fs) :
Sorry, I didn't see this till you mentioned in in the comment on the other article!
You want the tie rod spacing to *mostly* match the RCA, but you can certainly play with this a little to change the toe curve. I somewhat do this already, with the rear tie rod bracket for example. By rotating the bracket in and up the tie rod is shortened, but the pivot is also raised by maybe 1/4". The front is easier, you can buy 5/8 dia bump steer spacers for less than a dollar each and make adjustments that way.
They may be pointing opposite directions, but they are both working towards the same goal (roll understeer). On the front toe out in compression and toe in on rebound causes the wheels to point towards the outside of the corner, so the car turns a little bit less than you would expect for the amount of steering input applied. On the rear toe in on compression and toe out on rebound points the wheel towards the inside of the corner, so the rear doesn't try so hard to pass you on the outside.
On my car I have always just tried to set the front to minimze bump steer and have been pretty happy with the result. The rear is tougher to fine tune, but less toe change vs stock has certainly been a big improvement in my experience. On your MKI you have the advantage that Toyota gave you a vertical tie rod stud in the rear, so you can replace it with a stud and rod end just like the front and dial in bump steer exactly as you want. I'm having to create a complete custom knuckle for the MKII to accomplish that (and some other stuff of course).
Oh, and on the top mounts, the main reason to choose standard over extreme is if you don't want to drill holes in the chassis to access a shock adjuster, or don't want to / aren't able to potentially modify the coilovers to get rid of excess camber (slot the brackets). The extreme top mounts do effect the toe curve a bit, but as I mentioned above that's easy to adjust out provided you are running them with my geometry kit, and even if you don't bother, the resulting toe curve is still not unreasonable.
In reply to Alex_W :
No worries - it's not like you have an engineering and fabrication business to run or anything!
First of all, thanks for the explanation.
Gotcha on the extreme top mounts. I didn't realize there were chassis mods needed for installation. Sounds like the benefits outweigh the negative effects on the toe curve when used with the geometry kit.
As far as the opposite toe curves - to your point I imagine the effect of the front toe-out under compression is mitigated because the wheels are already turned many more degrees than whatever the bump-steer is doing. If I can get a setup like this cobbled together for my Mk1 I'll probably experiment anyway. It would be interesting to see what toe-in under compression does to tire temps and turn-in.
Cool article; I once had an MR2 and while it was fun I didn't particularly like the way the car turned in, now I know why.
In reply to Tom1200 :
Curious - was it a Mk2 like the one in the article? Never had that complaint with my Mk1.
In reply to Matt B (fs) :
Mine was a Mk1. I can't remember which one of the posts explained the difference between the Mk2 and the Mk1 and after reading it it clicked as to why I prefer Miatas.
Yeah I could see that. The Miata has an objectively better double wishbone setup, plus they're lighter. I've just never been excited about them like the MR2 for whatever reason. I blame it on being a child of the eighties.
We raced MR2s and the best suspension setup we found was lowering springs and bilstein or koni struts. Never really cared about corner weight. The other MUCH more important suspension mod was to reinforce the trailing rods in the suspension. We would box them and stitch weld it using either two pieces of angle or a piece of square tube steel with one side cut out so it slip over the rod. We found that these rods bent (and would stay bent) under continual heavy loads constantly changing the suspension geometry. They were also the first failure point with any contact of things like curbs or even the smallest wheel to wheel or wheel to wall contact. Once fixed it totally changes the cars suspension.
In reply to dean1484 :
Interesting. I assume you discovered this by the perma-bent rods? What model year(s)?
Typ85 said:Audi and VW's have the same issue with their strut suspension, the cure is installing "ball joint extenders"
Somehow, the companies that used to make these no longer make them.
Curious, isn't it?
Pete. (l33t FS) said:Typ85 said:Audi and VW's have the same issue with their strut suspension, the cure is installing "ball joint extenders"
Somehow, the companies that used to make these no longer make them.
Curious, isn't it?
because the demand went away as the market shrank to those that have them and use them and those that no longer own/drive those cars.
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