Good handling at 50-60mm drop?

[Racecomp Engineering]

Here's an example where the shock isn't even mounted on the LCA:



- Andy

[diss7]

Appreciate your input.

Looks like the LCA does need to be treated as per the UCA in my diagram above.

I'll keep the diagram, but edit the post to indicate that it's not accurate.

[Captain Snooze]

Slightly off topic but related. It is a bit of a misnomer calling it a roll center. It would be more accurate to call it an instantaneous roll point. That is, that point can move around, off center line too, depending what the suspension is doing at the time.

[Racecomp Engineering]

A lot of people are moving away from kinematic roll centers anyway and using force based roll centers and force application points (FAPs). The KRC is a good effective first look for most of us though especially in a simplified static condition.

- Andy

[diss7]

Would I be right in stating that if you are going to the trouble of adjusting the pivot points, it would be worth doing the math and actually targeting a specific roll centre point?

Google tells me that the COG is 460mm, that'll obvioulsy be from the road. So mine would be 405mm. I know my track is 6mm more than stock when I run my track wheels. So those two points are known, and the only variable left is the arm angles.

Would also need to measure the exact location of the pivot points as the lines need to go through the pivot points you're keeping, and will then show you where the other two pivots points need to be modified to.

I wonder if these measurements are already known, or there is a shop drawing or similar of the subframe. It would be fairly easy to code a programme like the wheel/tyre type calculators. You just enter your ride height, wheel/tyre/offset information, target roll centre height, and it shows the info needed to achieve that.

[diss7]

So I raised the car up today. 15mm front and rear, upto about 35f 40r. I didn't think I'd notice a difference, but around the twisties I defintely did.

I'm going to raise it up another 10-15mm when I get the time. I need to swap the sway end links to raise a bit more. Interested to see if its better again, more than where I'm at atm.

It doesn't look as good. But I enjoy driving the car 10x more than just looking at it.

[s2d4]

so it's been over a week, have you had your car aligned yet?

[diss7]

Originally Posted by s2d4

so it's been over a week, have you had your car aligned yet?

Yes, got one earlier in the week. Now I need another.

I'll prob try raising a little more first. Also my whiteline bushings will hoopoe fully arrive this week, will put them in first before next alignment.

[s2d4]

Originally Posted by diss7

Yes, got one earlier in the week. Now I need another.

I'll prob try raising a little more first. Also my whiteline bushings will hoopoe fully arrive this week, will put them in first before next alignment.

You may find that around the 25-30mm mark to be more to your liking.

[wparsons]

Originally Posted by diss7

and the only variable left is the arm angles.

Slight clarification, it's not the arm angle it's the angle formed by a straight line between the inboard and outboard pivots.

I'm sure you get it, just clarifying for anyone else reading.

[Moto-P]

Originally Posted by diss7

What makes me disappoint, is how badly the car now handles when given a workout. Taking it around roads I'm can really hammer on, it's noticeably worse. I do have some parts coming to correct what I am hoping is causing these problems, but I'm really surprised at how different the car is behaving.

Is it possible to correct what riding at this height causes?

To quote myself from the post I left in the RSR review thread...

I'm not trying to have the best or fastest car, I'm prepared to lose some handling from an optimal setup to run this height, but I'd like that to be only a small concession, not the massive concession I feel this setup has made.

I'd really like to clarify a couple of things.

The Black-i is a STREET specification coil over system, which is designed to satisfy the users who are into the fashionable trend of lowering a car extensively for the visual and stylistic elements. On an Scion FRS/Subaru BRZ/Toyota 86 siblings, like most other cars, do have very inherent issued that is outside of the shocks and struts, such as dynamic and static alignment going excessively out of performance oriented parameters.
And one should ALWAYS know going in, that ANY suspension drop that is as excessive as over 40mm in ride height, and modified with shocks and springs only, is going to have decreased levels of performance. This is because the suspension arms, various alignment links, sheer space under the wheel housing, and other factors will reach a point where the ideal requirements are not met. The Black-i are designed for those who will ignore or further modify on his/her own, about the performance aspect, as there are some enthusiasts, who simply want a very visually stunning car, that can be driven comfortably on the public roads.
That being said, the highest setting of the Black-i is near 40mm, so at this height that is closer to normal, the Black-i does retain the vehicle's alignment quite well, and can serve as normal suspension, though it isn't the primary role for this... The Black-i was designed for people who just wants to go lower than this. Which is why the spec starts at 40mm below to a whopping 55~80mm below, which at maximum drop, is in a territory of requiring cutting and welding, and lots of suspension arm modifications too in various places.

Now that being said, so why are Black-i available then? If all it does is decrease performance?
It is because it isn't catered to the folks who want ultimate performance or normal functionality. It is catered to those who love the hot rod sled, the lowered to the max look, just as there are those who love to set cars up on airbags, or cut and hack a truck to drop a body or put gull-wing doors on the cars. There is nothing wrong with choosing to do that, and Black-i are designed for those who go beyond the normal parameters to have that look, the stance, and to help people who do this, to find the best possible ride on such goals that have very limited suspension stroke, and out of spec dynamic alignment, to have the most decent ride so it is at least useful still, as a street car. It is designed as a capable tool and part to handle a drop that is bolt-on street-able spec, at 40~45mm or so and still be a comfortable street car with stunning looks. And just like Sports-i, the track-ready sibling that can take to the performance edges, this Black-i is designed to go beyond that for those who want to delve further into styling edges, by further going into that realm by fabricating arms, hammering and cutting, and fabricating their own rides to extremes in style in the very different world of custom-cars, and if one fancies, correcting all of the inherent alignment issues even at this height with highly extensive mods in other areas, to actually make it handle at ridiculous height too, as seen in some of the highly modified D1 cars with rails just skimming the ground... But, as for simple bolt-on, one must always be aware that there are critical parameters which can't be overcome simply by installing coil-overs, and with that in mind, if Black-i is the only component being used, there are limits to what can be done.

So please don't make any assumptions whatsoever that the Black-i is good for any motorsports activity. It isn't designed for that at all. It is a good product for the enthusiasts and builders who build show cars, and enjoy a road car that is extremely low, and willing to live with limitations inherent to stock chassis components, or do much more to the cars to make things work.


The Sports-i is designed around a very different principle... I have optimized the Sports-i to be a very capable road vehicle, with road manners, communication, tactile response, and overall performance. This is why the Sports-i with different specifications of piston length, valve rates, spring rates, and geared to perform on road comfortably and has the upper ceiling to accommodate track uses, and optional rates to take it even more towards motorsports oriented uses.


These two coilover systems are VERY different in goals and targeted intended use.
As such, the mentions and promotions, accolades should never overlap for the two very distinct products, as they aim to do very different things to a very different types of enthusiasts.

While the mono-tube patented design is very capable and ideal for use in all of RSR's products, and is the type of design RSR takes pride in building in-house. The settings, and application designs are very different for each product goal, and each vehicle applications. And while other suspension makers might mention otherwise, and sell you a single product that can do it all.

As a outside consultant, and assistant R&D engineer for RS-R, I feel that all-mighty, do-it-all suspension is all smoke and mirrors of marketing by others and is only possible on Alladdin's Magic Carpet.
For the rest of us, we simply cater to a very focused and well-informed audience, with goals that are pin-point and realistic.
This is why we have two very distinct coil-over lineup for the FT86 and other cars. So that each can do the job it was intended very well, and not claim be the magic solution that will cover true track performance, and be a stunning rod-sled.


Now, many of the replies given to you by folks chiming in on this thread are very helpful for you in taking it further and improving things that are inherent issued OTHER than just shocks and springs, to make improvements at your intended ride-height, and I think it's great that there are smaller firms who car intent on making low-volume parts and tools to make changes that are more drastic, and truly useful in making your car more customized and individualistic. I think the more you develop this car, you will understand more that the RS-R Black-i is an excellent coil-over system that will simply keep up and cater to your needs, as you delve more and more into getting things more dialed in with items that overcome inherent issues of arms, frame, body and alignment at extreme drop levels.

[Moto-P]

Lots of talk about correction of roll-center, and specific line-item alignment specs.
When you understand the relationship of this dynamic alignment (alignment not just in static state but across the swing-arc of the full suspension in stroke, and in steering...), you will start to truly improve handling by finding directions, and ways to modify things accordingly. It is a complex science of geometry and physics, of loads and motion.

I'd also like to mention that with roll-center adjustment, you also need to start working on solutions for steering ackerman, toe links, upper arm re-positioning, caster corrections, and also making room to go for a deeper drop by hammering, cutting, and fabricating tunnels and making space to allow more tire clearance... Because the Black-i is that nice, and it will accommodate things quite well to these extreme drop-mod projects.

And each time you go further in correcting inherent chassis/body issues for a specific project, the more handling and precision you will gain back for such extremely lowered cars.

[Dephective]

Aside from all the roll center talk, I do hope you aren't running on the stock tires. I'm at about 2" drop, which is equivalent to ~50mm, and until I finally got a chance to wrap my RPF1's with rubber, I was miserable. It was like driving on an iced over lake. Front push, then sudden snap oversteer. Got some new rubber and all was fixed after some dampening tuning to compensate for the stickier rubber.

Not that your roll center isn't off, it's great that you are taking steps to correct this, but some things are often overlooked. You might have already upgraded the rubber, in which case, ignore my comment, heh.

Edit: I forgot to mention, I attribute this to the stiffer spring rates asking the hard stockers to handle a level of grip that far exceeds their ability.

[diss7]

Originally Posted by Dephective

Aside from all the roll center talk, I do hope you aren't running on the stock tires. I'm at about 2" drop, which is equivalent to ~50mm, and until I finally got a chance to wrap my RPF1's with rubber, I was miserable. It was like driving on an iced over lake. Front push, then sudden snap oversteer. Got some new rubber and all was fixed after some dampening tuning to compensate for the stickier rubber.

Not that your roll center isn't off, it's great that you are taking steps to correct this, but some things are often overlooked. You might have already upgraded the rubber, in which case, ignore my comment, heh.

Edit: I forgot to mention, I attribute this to the stiffer spring rates asking the hard stockers to handle a level of grip that far exceeds their ability.

Fair comment. But I use semi slicks on the track, and nitto Invos on the street. Tyre compound is not the issue.