I'm after a particular rear suspension geometry. I want arms and axles level at 25mm ride height, instead of arms rising towards the wheel at straight bones stance. Does anyone know a car with such geometry?

I have that geometry in the Kyosho ZX5 but would prefer a 2wd buggy.

The reason is I want to test the boundaries of roll center migration and jacking forces.

The arms are "level" when the inner hinge pin and outer hinge pin are the exact same height from the ground. The actual shape of the arm itself doesn't matter. It would be nice if companies just went back to straight rear arms to make things easier.

Fred, I enjoy all the posts of yours I find on rc forums. I'm going to give this method a go on my buggy and see the difference. I imagine it will help a lot. I see you're from Houston. I live a couple hours away in Louisiana, but I have been to Club RC a few times to race. I don't know if you race there or not, but if I run across you, it'd be cool to pick your brain a bit.

I'm going to try to get out there more this year. We'll see. I'm pretty busy. I've only been there twice this year so far and it's been without a car each time since I was just passing by.

Thanks for the correction.

It's not about shape, it's about pick up points, specially the lower hub point. Most of them angle the arm up and you always end up with low roll center (the TLR cars suffer more from this...).

I remember where I saw the adjustable rear hubs, the JRX Pro a2025 hubs! Do you have the JRX Fred?

Most, if not all 2wd cars are going to have this. It's not just about the roll center, it's also about the bones relationship with the drivecup. By having the bone and arm not parallel the bone will slide in and out of the drivecup more, giving more rear traction. 4wd cars don't need as much help getting traction so you usually won't see as much difference in angle.
A good example of this was when people were raising the transmission on the 22 to get more dogbone bind.

I have several JRX's and a bin full of those rear hubs. Those hubs are used on my dirt oval kit.

Precisely, I want to have less dog bone bind. I can create more traction by other means. About the 22, it was the most unbalanced car I've ever drove, spring and roll distribution wise. Didn't help most didn't knew what to do in this situation and the bandaids were common.

Have you ever tried the lower hub hole while trying to keep camber gain the same, if yes can you give input about the change?

When running 2.2 wheels, I only use the lower holes. When running older 2" wheels, I used the upper holes. The camber link also moves on the inside to keep the equivalent location. By doing this I can keep the chassis the same height from the ground at the same arm angle orientation. Basically, the roll center and ride heights can be made the same with different size wheels.
What I like about the rear end geometry of that car is that when using the lower holes, at arms level (they are straight arms, which helps), I am also at driveshafts level and I set camber links level at this point as well. The links will just be shorter than the arm length pin to pin distance.

Team Associated's suspension geometry goes back to the B3 for production but to the 89 and 91 IFMAR cars for concept. Those concept cars used RC10 rear hubs which placed the driveshaft low towards the hinge pins, much like the upper hole on the JRX hubs. Why were they so low? The simple answer is that they had to be back then. The car originally came with 1.6" rear wheels. The diff gear is going to be a certain size and will need a certain amount of room which will dictate where the driveshaft height is. Put those together and you've got the driveshaft angle. Incidentally, the original 6 gear box had a lower driveshaft height than the stealth did. As they evolved the gearbox design to use a slightly larger diff gear, they lowered the bottom of the gearbox into a hole in the chassis to give clearance while maintaining that driveshaft height.

As wheel sized increased, the rest of the geometry was never really dealt with and their modern cars are descendants of that old geometry. Our Raborn rear arms for the RC10 were typically also used with our rear hubs which were essentially Losi copies and they worked far better. That's why I have a bin full of them. You run the lower hole with the 2.2 wheels, putting the axle closer to parallel with the arms and fixing the roll center location. This is especially important when running lower ride heights.

What I'd really like to do on my B44 is to make a new rear arm that is totally straight without the upward bend at the hub. Then make a new hub that extends down to it, lowering the outer hinge pin location. This would fix the roll center for high grip tracks where low ride heights are used. I doubt I'll ever do it but I truly hate the back of that car.

Thanks for the input, really appreciate it.
You have the talent to design 3D parts, if you make the rear hubs and arms for the B5 they are somewhat compatible with the B44. And there's market for them as more and more racers demand lower ride heights so why not? The same can be said about the front and with 4(front and rear uprights/hubs) little parts you could create a real low rider that can have a huge advantage in high grip tracks.

Something I find really ridiculous is with people running the LRC blocks on the rear arms, like on the Durangos, lowering their mounting height by a couple of mm. If you are on high grip where you want a low ride height, this is only going to make things worse. Run an HRC block instead. Save the LRC for tracks that demand more droop and higher ride heights.

Exactly. This also happens with on road TC, people think low rc is always better and then mask the unbalance with springs causing further handling issues.
All the cars I've messed with had one or other issue, 1/8th buggies are a tick better but still pretty much in dire need of a balanced setup. My TLR22 setup is completely opposite of what you see around, stock springs were so far off they were borderline unusable in both rear and mid motor configurations. I haven't run the B5 yet but something tells me it's also very unbalanced.

Just started at the beginning and done with the first 10 pages. This information sure needs to be compiled into a guide at some point. I can tell you that I accidentally have been using suspension balance on all my cars for years doing the push down and watch both ends method, but have completely missed the harmonic balancing segment. Can't wait to try it on my buggy and SCT. Lots more reading to follow.

Keep in mind that the beginning of the thread was something like 5 years ago. That was right before big bore shocks came out along with their wide assortment of springs. What I had at the time was associated standard bores and their narrow range of springs. I could only obtain balance through shock mounting points. The information is a bit outdated.

Would it be possible for you to write down the actual steps in your guide in a new thread? This thread is out of bounds kind of and trying to read up 141 paggs is too daunting to let new guys in (and me). Especially when you point out that some of the info is outdated it makes it even harder. If you make the first post in a new thread and then keep it updated as the reference post, all the following posts would be discussions around the concept.
I do find your conclusions on the subject very very interesting and the scientific approach is something that I believe in strongly. We just need the concepts layed out in an updated and proper guide. Please?