ptrhahn

iTrader: (9)

^^^

I'm not sure how geometry is a "problem" per se that needs to be solved, or how that arm helps. It doesn't change the suspension pick-up points, and the lower arm is already the one you adjust for static camber on the stock car.

That adjustment is on the inside, via a cam bolt, and the aftermarket is on the outside, so I guess theoretically you'd have two adjustments to play with... but it's still just a point-to-point length, right?

Black91n/a

With that arm you'd be changing the location of the lower pivot point relative to the upright, which changes your roll center, which almost always gets all out of whack when you lower a car a lot. What happens is that the roll center drops faster than the CG, giving you a larger roll couple and more roll overall. By raising the roll center up again using those, you could soften the suspension a little to gain you some more compliance over rough patches of the track.

Another solution that I've seen is drop spindles. They allow you to maintain the stock geometry while lowering the car for a better CG height. It won't change the roll couple, but it should improve grip overall compared to either stock height, or traditional lowering to that point.

ptrhahn

iTrader: (9)

How exactly would you be doing that? The pivot ponts are welded to the chassis and subframe. The arm just connects those points to the spindle. Does it have some sort of standoff on the outer ball joint?

Black91n/a

By using a rod end with an extended stud and spacers you can move the outer pivot relative to the upright. Note that I'm not talking about moving the inner pivot points, only the outers.

Although, with arms like that it de-couples the camber/caster and the inner pivot point locations. That way you can put the inner pivots where you want them within the stock adjustment slot range, and then adjust the camber to suit using the rod ends. Why would you want to do this? Well it'll allow you to change the camber curves a somewhat. You could also slightly alter the anti-dive and anti-squat with these by moving the attachment points up and down within the stock range. Note that without needing a cam bolt you'll have more options of places to locate the pivots, as you could make some sort of washers and put the hole wherever, then use those in place of the cam bolts. You may be able to just make them as oval washers, or you may need to weld them in place. Enlarging the stock slot might be needed in that case.

DRAGON_PERFORMANCE

Does anyone have links to aftermarket FD arms, designed for widebody cars?
Most people I have spoken to have suggested that the aero is not effective below 100mph, this seems contradictory to the Jap, hard springs and big aero ways.

Mahjik

iTrader: (1)

"Most people" just quote what other people have told them without doing any real research on their own. Obviously it depends on the design and purpose of the aero as to what speeds it will effect. Just like airplanes which have "flaps" that effect it at lower speeds, there are aero pieces which and are designed to effect cars at much lower speeds. But as in life, there is always a trade off.

Black91n/a

Just have a look at an A Mod autocross car, they've got MASSIVE wings and speeds don't really exceed 50mph or so. So yes, it all depends on the design, but to get lots of low speed downforce you'll end up with TONS of high speed drag.

The arms for those widebody cars will inevitably be custom, along with just about everything else on the cars.

eoph

But is there really a benefit to these? I dunno if the roll is really that bad for double wishbone cars, and even if it is, it can all be fixed with stiffer sway bars right? Or does it make the roll more gradual?

Black91n/a

Any time that you stiffen the car you're reducing compliance, which means that you're compromizing grip over rough patches in order to gain grip in smooth sections. So you see it's not a perfect solution.

JTurtonRX_7

I love all the good information that came out in this thread, exactly what i was looking for. Another thing im curious about is matching sway bars to your setup. When do you get stiffer sway bars and what change do they noticeably make when you are driving the car.
I should have my car back on the ground in a few weeks and im going to do some testing on it to see what needs to be adjusted next.

If its any help ill have on the new Tein HT's 18k/18k and the delrin bushing set and stock sway bars.

eoph

sway bars are also called anti roll bars, so i think u can guess what u should notice .

The thing with those arms are they are 'adjustable', meaning it would be hard balancing the front and rears together. Like where would you get the data? its not like your alignment where you could just give some specs to a shop and they would do it for you right? Also with the price tag of 1.5k..............I see lots of Honda's fixing the roll center with ball joints for a fraction of the price.

eoph

I think this sums up the benefits of adjusting the roll center pretty well.

http://www.ikeya-f.co.jp/en/product_...oot_works.html

JTurtonRX_7

yeah, ive read a million books like carol smith's tune to win. I know "how" it all works on paper, but im looking for peoples hands on findings per this application. Just like before.

Black91n/a

One thing to keep in mind, is that as you up the spring rates, the sways have a proportionally smaller effect overall than before.

Most alignment shops wouldn't know what to do with those arms, but if you go to a race shop they could probably set it all up for you, or you could just get yourself a camber/caster gauge, some toe plates and align it yourself.

JTurtonRX_7

speaking of adjusting things yourself, I could just adjust the front or rear camber going by the tick marks right. because i want to test out a bunch of different setting to see what i like.

Black91n/a

If you want to make quick adjustments between different setups at the track for testing purposes the best and fastest method to use would be to map out a bunch of different alignments at the shop and note the cam positions as well as tie rod adjustments, as a camber adjustment will change toe slightly too. This way you can just set it up per your previous notes and you won't have to fiddle with adjusting everything, it'll be a set it and go type thing.

eoph

If you raise the roll center to the center of gravity, roll decreases. but what happens if you raise it above the center of gravity?

Black91n/a

Theoretically you'd roll INTO the corner. But I don't think you EVER want to even get close to having that happen, not even close to having the roll center and the CG in the same spot.

Besides, the roll center moves around as the suspension moves, since it's based on the intersection of lines projected from the control arms.

Formula cars usually have roll centers near, or even under the pavement, but they also have much lower CG's.

It's all just a big set of compromises, the struggle is to find the best one.

eoph

ic, so it really is something you have to get some track time on to see what works best? But that could also mean that it is probably no adjustment is needed when you lower the vehicle, the extra roll actually helps, like my initial theory

Black91n/a

Suspension tuning is an incredibly complex thing, there is no cut and dry answer. It depends on a lot of things, like the track (is it bumpy or smooth), the dynamic alignment (ie does the suspension loose camber in roll, bump steer, roll steer, etc) and a lot more. Modelling can help, but in the end it needs to be proven at the track.