wrightcomputing

iTrader: (5)

After reading up on suspension geometry, I have noticed that like most lowered Rx8's my control arms are higher on the wheel end then on the chassis end. This is not ideal as it upsets the geometry of the suspension and will put increased pressure on the shocks and springs. I have raised my car to try an eliminate this which in turn raising the center of gravity which will also reduce the cornering ability of the Rx8.

My friend/tire guy has extended ball sockets on his Integra that lower the mounting point of the suspension which allows a bigger drop in ride height while still maintaining the correct geometry of the suspension.

Does anyone know if there are parts available for the rx8 to allow a bigger drop without ruining the geometry. With the rear being multi-link it makes it a more difficult task. If not does anyone have any input for avoiding/improving this issue?

dannobre

iTrader: (3)

There is no reason to lower the car far enough the geometry is fubarred. I have mine so that I can't go over speed bumps easily...and it is still has level control arms.

If you are tracking the car and have it too low raise it back up to where it functions properly...

The only reason to be dropped that low is for looks.....showcar or the like

You might need to look at your spring rates and bar stiffness if you feel that you are getting too much roll. I have noticed and had it confirmed by a couple of racers that did quite well with the car that a bit of body roll actually makes the car faster....

wrightcomputing

iTrader: (5)

I was lowered to about 13" (center of the wheel to the wheel arch) It is not so much the way it functions because the car still feels good. It is more when I look under the car I notice the control arm is higher on the outside.

The body roll is fine, I have stance GR+ coilovers and Hotchkis sway bars the are 3 way adjustable. I think I will raise it to about 14" and see if the car feels any faster.

I had a good look around last night and could not find any extended ball joints for the Rx8 so it is probably not an option anyway. I did find the integra ones though.

paimon.soror

iTrader: (15)

I have the same coilovers and have the same "issue". My control arms are slightly angled upward from parallel to the ground.

Could you help educate me on why this is bad?

Mr_Pieper

I remember reading one of the engineering themed articles in Sport Compact Car years ago that elaborated on why this is bad. Something about things getting really wonky after the starting point of the control arms goes beyond parallel. Maybe I'll go dig through my Rubbermaid bin full of old magazines before I get into Call of Duty land.

paimon.soror

iTrader: (15)

Are we talking bad in the sense of performance, or bad in the sense of catastrophic effects to the vehicles suspension. What i mean is...for those who are lowered for aesthetic purposes, are we slowly killing our car?

Mr_Pieper

I've found something about it wreaking havoc on cars with MacPherson style struts like the aforementioned Integra and fixing it with things like longer ball joints. Otherwise it looks like toe angles can become compromised below a ninety degree angle of the control arm and cause random toe-steer. I also see something about camber being changed incorrectly below this threshold. It is also saying that incredibly stiff springs and bushings prevent all of this from happening as the control arms do not have a chance to travel as much.

paimon.soror

iTrader: (15)

this affects both front and rear correct?

Mr_Pieper

The article I found was part four in a series from 2005. It stuck to the rear mainly but I imagine it could have the same effect. The main point was concerned with a severely lowered car going through a part of the suspension travel where toe and camber angles suddenly change in the factory geometry. These are areas the car was not meant to spent any significant amount of time and sweeping in and out of it can cause random handling changes, especially if only one wheel hits a bump without the other.

JCrane82

iTrader: (3)

The concern over this topic deals with changing the nominal suspension position out of the designed range of motion. Mazda engineers designed the suspension geometry around the stock height, and once you modify that height, you are no longer working in the range intended.

When you lower the ride height, you change the dynamic motion of the suspension, and there is a point where it negatively affects the handling characteristics. Caster, toe, and camber all are dynamic entities.


Suspension design and modifications are all compromises.

Mr_Pieper

I could have sworn that was what I was saying. Either way, lowering with stiffer springs narrows the travel. You just have to find the sweet spot where nothing is negatively affected. On a smoother area you can get away with more. Over-lowered on a back road with bumps can lead to surprises when you don't want them because the geometry beyond the height makes you car suddenly over or under-steer.

paimon.soror

iTrader: (15)

This might sound like an ignorant question, but I would be interested in knowing how one would find out where the "sweet spot" is. Now of course one could say that Mazda already found that sweet spot which is why the car was the way it was from factory....but when running newer suspension components how does this 'sweet spot' change.

JCrane82

iTrader: (3)

I never disagreed with what you were saying Pieper, just wanted to add some clarity to the conversation.

When the suspension travels through rebound and jounce, the caster, camber, and toe values change. When you modify the nominal ride height, you shift that range of motion out of the "intended" range, possibly causing negatve effects to the dynamic caster, camber, and toe curves.

All suspensions are different though, and it is difficult to make blanket statements for how it affects suspensions.....especially when comparing the RX-8's fully independent front suspension to the Integra's McPhearson design.

JCrane82

iTrader: (3)

Caster, camber, and toe curves are all calculable.....IF you have adjustable coilovers (or a way to compress the suspension evenly) and a way to measure caster, camber, and toe values. For example, race teams will measure these values (or use modeling geometry to calculate) and graph the dynamic caster, camber, and toe curves for a given suspension design.

The majic "sweet spot" you talk about is purely subjective to application. An autocrosser's "sweet spot" is different than a trackday junkie's. With suspension design, there are very few universal truths that you can apply across the board. The answer is always.....it depends on your application and desired results.

paimon.soror

iTrader: (15)

Btw here is what my control arms look like in the rear with all 4 wheels planted .... now of course this means nothing without a flat edge to show the angle, but you can get an idea

j9fd3s

i'm trying to keep this as simple as possible. i haven't measured up the Rx8 yet, but i've done the integra, and the FC, the Rx8 is next on the list.

firstly the extended ball joint doesn't work on the Rx8, the Rx8's ball joint points down, instead of up like the integra. the Rx8 would require a drop spindle.

secondly, you should actually measure the camber and toe change over the suspensions travel. we have found in the integra that it basically has zero bumpsteer thru the front suspensions full travel and the camber curve is good up until the last half inch or so of travel. so basically we run it as low as we can*

if you look at cost no object cars, they will relocate arms, and do fabricated spindles and stuff (the WTCC cars were really weird)

with the Rx8 there will probably be a happy spot where you get some benefit from lowering, without loosing geometry, and still be able to go over bumps.

*on the integra the upper control arm hits the body first. if you go look at road race hondas, the shock towers will all be dented, and since its made of tin, they eventually start ripping open

wrightcomputing

iTrader: (5)

I guess the consensus is that there are no parts available to assist with the Rx8, so raising the car is currently the best option. I am going to raise my car and see how it feels. I will have no data though so the information is only as good as the next persons opinion.

JCrane82

iTrader: (3)

Remember to correct your alignment after raising. I align my own cars, so I would be happy to provide help if you are thinking of trying it yourself.

paimon.soror

iTrader: (15)

Mind taking a pic of your current geometry so we can compare mine and yours?

j9fd3s

well the ball joint on the 8 looks normal, but its inverted so a longer ball joint would move things the wrong way. the simplest way looks like a drop spindle

i just had my car aligned the other day, and the alignment does change quite a bit with ride height, so you have to realign the car once you raise it.

ultimately the better way is to pull a shock and measure the alignment change thru the suspensions travel.

oh and don't be afraid to play with it, part of having the right setup is knowing how YOUR car reacts to suspension changes, and the best way to figure that out is to try it.

TANKERG

Watch a car with hydrolics and you can see massive camber changes when going up and down

SayNoToPistons

iTrader: (8)

The "massive camber" is dependent on the suspension type also...

wrightcomputing

iTrader: (5)

Here is the front and rear suspension. I have already raised the front and inch and it's still not right.


I installed the suspension and do the alignment so I am good but thank for the heads up. I autocross about twice per month so as the tires wear down and things get added to the car I make changes to the alignment all the time.

I understand that the the extended ball joint is not an option on the Rx8 but any ideas if there is a drop spindle available? My friend google is not giving me any options.

dannobre

iTrader: (3)

You don't need a drop spindle.....put the car at the correct ride height and it will handle well if you adjust the springrate and damping...and maybe the front bar depending on your philosophy

wrightcomputing

iTrader: (5)

I will raise the rear but it is not like it is slammed. Here is a photo of the ride height.

These are my 18" wheels when, I put on 17" wheels I have a massive wheel gap. I will raise it up though and see how it drives.