CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[3 pedals n a stick]

I'm wondering if shorter or adjustable rear end links adjusted shorter than stock might help me to factory angle? My frs is lowered on Ohlins r/t about 1.25 with cusco LCA'S. I think that the rear sway bar may be limiting suspension travel do to the angle of the rear bar being a lot higher than stock. Going up drive ways at an angle will lift one wheel do to sway bar going beyond flexable range one link way and the other side down also on hitting switch backs on an incline during aggressive driving . Also on rear suspension compression equal on both sides the sway bar angle to high where it meets end link doesn't have full pivot motion anymore hope I'm explaining please help

[rainmonkey]

Originally Posted by CSG Mike

We run the factory rake. We'll delve into that more as we start adding aero to the car.

Hi,

I have 2 quick questions, well one might end up a lot longer...but either way:

1. What is factory rake? This is usually comparing measurements from some part of the chassis right? If I'm not mistaken, a couple inches in front of the rear wheel well, and a few inches behind the front wheel well. I'm assuming it would be measured in ratio rather than just a static measure in inches/cm.

2. How does rake affect the handling of the car and what's the magnitude of difference given say a 1/2 inch vs a 1/8 inch difference?

Thanks!

[Racecomp Engineering]

Originally Posted by rainmonkey

Hi,

I have 2 quick questions, well one might end up a lot longer...but either way:

1. What is factory rake? This is usually comparing measurements from some part of the chassis right? If I'm not mistaken, a couple inches in front of the rear wheel well, and a few inches behind the front wheel well. I'm assuming it would be measured in ratio rather than just a static measure in inches/cm.

2. How does rake affect the handling of the car and what's the magnitude of difference given say a 1/2 inch vs a 1/8 inch difference?

Thanks!

1. The quick easy way for a rake measurement is from the center of hub to edge of fender. Off the top of my head I don't know what that is stock.

However, it may be better to think of rake in terms of "roll axis." This is what you get when you draw a line from the rear roll center to the front. Harder to measure, but this is a better idea of looking at how things change.



2. A complicating factor in feeling the effects of changes in rake/ride height is changing the amount of bump travel you have. All else being equal, lowering the rear can increase understeer in a steady state corner since you have lowered the rear roll center...however if you are now sitting your rear on the bumpstops you will have some snap oversteer issues.

On the other hand, raising the rear would make the car more prone to oversteer...but COULD help you put power to the ground on exit.

Assuming you have adequate travel to work with, a 1/2 inch change in ride height can be noticeable IMO.

- Andy

[chrisl]

Originally Posted by ZDan

You don't have to worry about all that to determine when you get an inside tire lifting, and what happens to load distribution on the other three after that. The left/right and front/rear load distribution on the four contact patches is only a function of:
static weight and weight distribution
acceleration (lateral g's and longitudinal g's)
c.g. height
track
wheelbase
To further determine individual tire loads, you just need to know relative front/rear roll stiffness.

That's it. For simplicity, I talked about steady-state cornering (front/rear load distribution is same as static). You could just as easily calculate the individual wheel/tire loads for other points on the friction circle, like 0.71-g braking combined with 0.71-g cornering (trail-braking), and 0.5-g acceleration combined with .87-g cornering (lowish power/weight car accelerating out of low-speed corner).


Ah, I misunderstood what you were saying. Yes, if you tune the suspension with greater front roll stiffness for a rwd setup, the inside front will pick up sooner, but you will keep greater load on the inside rear for longer. And for a fwd setup, you dial in more rear roll stiffness, picking up the inside rear sooner, keeping more load on the inside front for longer.

Either way, once you do pick up an inside wheel, you increase the rate of loading the outside wheel and unloading the inside wheel at the opposite end of the car. It sounded to me like you were saying that when you picked up the inside front, you'd actually start to INCREASE load on the inside rear. Now I see you must have meant that if your *setup* is such that you lift the inside front first, that this keeps the inside rear loaded more. Agree!

It is of course still preferable to keep all four on the ground, but if you have enough grip you will start to pick up an inside wheel given a track width, c.g. height, and grip levels. On just about any halfway decently set up fwd car (even totally stock) you will pick up the inside rear on corner entry due to massive static front weight bias and near-1g braking combined with some cornering load.
On a rwd car with decent power/weight and weight distribution and setup, it is also possible to lift an inside front accelerating out of a low-speed corner (my 255hp 240Z did this).

Given limitations on c.g. location and track width, you sacrifice a bit of ultimate cornering grip to get better drive out of the corners. On a 60/40 - 70/30 FF car, you use rear roll stiffness to keep the inside front planted for corner exit. On a 50/50-60/40 FR car, you dial in a lot of front roll stiffness to keep the inside rear loaded.

I know this post is a couple months old, but I remembered it while watching a Chris Harris vid on youtube today, and it's a cool video...

Older 911s with sticky tires and a good track setup will lift an inside front tire all the time, sometimes pretty high off the ground. You can see it really clearly at about 3:15 and 8:50 (and I'm sure a couple other spots) in this video:

[ame]http://youtu.be/QOAXHR3grlY[/ame]

[solidONE]

So what is the main contributor, besides the tires, to the inside wheel lifting? Thick swaybar?

[Racecomp Engineering]

thick swaybar, stiff springs.

[autobrz]

I'm curious about the top hats that add bump travel. Are the shocks okay with working at essentially higher ride height (how the shock sees itself) than it was designed to do? No one seems to have this concern but I figured it's good to get confirmation.

[solidONE]

Okay.. So my question is on caster angles for the 86. I've read some good feed back from folks who have increase caster by 1 to .5 degrees on this car from the factory setting with good results via camber/castor plates or offset bushings.

How does increasing castor improve handing characteristics in terms of grip and feel?

Would it increase cornering speeds or transitional response or both or neither? Will it likely result in faster lap times?

[Racecomp Engineering]

Originally Posted by autobrz

I'm curious about the top hats that add bump travel. Are the shocks okay with working at essentially higher ride height (how the shock sees itself) than it was designed to do? No one seems to have this concern but I figured it's good to get confirmation.

Yes, the shocks will be okay in almost all situations. You shouldn't be running coilovers at max-height...that would be a problem...but if you want that ride height then don't run lowering camber plates.

Even with a mild drop, lowering camber plates will be fine.

- Andy

[Racecomp Engineering]

Originally Posted by solidONE

Okay.. So my question is on caster angles for the 86. I've read some good feed back from folks who have increase caster by 1 to .5 degrees on this car from the factory setting with good results via camber/castor plates or offset bushings.

How does increasing castor improve handing characteristics in terms of grip and feel?

Would it increase cornering speeds or transitional response or both or neither? Will it likely result in faster lap times?

Wepeel has a good thread on this...stand by while I dig.

- Andy

[Racecomp Engineering]

Here you go:
http://www.ft86club.com/forums/showt...ghlight=caster

- Andy

[vanetix]

Hey guys,

Couple questions - What would you recommend for camber in the front of the car? Lots of folks say bolts, but frankly bolts seem like a hack to me. If I went with top mounts what is the preferred front top mounts for a Tarmac 0 setup, and will I need to change the rear top mounts?

Thanks!

[Racecomp Engineering]

Do you know how much camber you want? If it's a lot, say more than -2.5, then you'll want plates. We're still able to get well over -2 with just bolts on Tarmac 0 and Tarmac 2 with stock top mounts, but some other set-ups you'll be stuck with less.

Advantage to stock top mounts is no noise ever and slightly better ride so if that's important to you than it's worth sticking with them. Higher quality camber plates will be quiet if installed correctly but may ride a tiny bit harsher. You do lose the rubber though and get slightly quicker response.

Most camber plates out there work with our Tarmac coilovers. Vorshlag and HVT work well. It looks like there may be a few coming from other manufacturers soon. We can work out a package if you're interested.

Not too much need to change rear top mounts from stock...I'd do it on a car that is pretty track focused but the gains aren't huge.

- Andy

[CSG Mike]

Ok, I have some catching up to do. I'll be back...