suspension setting
Turbo Mini Forums

this has not been clearly explained ,
so could someone talk about suspension settings.
ie: heigh ; castor ; camber; tires ; tires pressure....

regards
fab

Edit: Moved

Edited by AlexB on 7th Mar, 2004.

nobody?

This is a huge topic! That?s probably why no one has had a crack... I'll start the ball rolling.

Ride height:
The reasons for lowering it are simple... to improve the handle by lowering the roll centre. The roll centre is the point (or axis) about which the car moves, much like an airplanes centre of gravity. Buy lowering this point you reduce the amount the car naturally rolls.

Lowering is normally a good thing for handleing, but like most things too much can be a bad thing. Ideally you do not want to make the bottom arms sit horizontally to the road at rest.

Camber:

Camber is the measurement of how much the wheel leans in or at the top of the wheel compared to the bottom. Negative camber improves cornering buy keeping the tyre in contact with the ground better. If you imagine leaning a tyre over, and it didn?t deform, you?d end up loading up one edge more than the other.

When you lower a mini you gain negative camber? so the only real way to sort it out is to get fully adjustable bottom arms so you can set it correctly. I lowered my mini originally about 3 inches and ended up with about 1 degree of negative camber using std bottom arms.

Castor:

Castor is controlled by the tie bars and effects the way the car steers. When you turn the steering wheel the two wheels do not turn through the same number of degrees, the inside wheel HAS to form a tighter circle than the outside wheel. Without it, the tyres would have to scrub in order to get round. The effect you feel as a driver is that the castor changes how much the steering likes to self-centre.

Tracking:

This is much more important than most people think? particularly on the rear! This effects the way the car handles messily? too much toe in and the car is completely un-drivable, utterly over-steering at every opportunity for example!

Just for completeness, tracking is the direction the tyres point in their rotation direction. If you stand at the front of the car, toe in sees the two tyres pointing towards each other and toe out makes them point away.

Tyre pressures:

This is a good way of trimming the handleing of your car once the basics are set. I typically raise the rear pressures as I like the car to be a bit ?back endy?. More pressure at the front would counter this or induce under steer. There are limits to how far you can take this of course, you don?t want the tyre to roll so far you drive on the side walls! I typically adjust the pressure until I can see ware across the whole tyre and then play with pressures a psi at a time up to about 4-5psi in total either way to find what I like!

That'll do for now!

Alex

AlexF

thanks Alex! for the pointings , about tire pressure it will help, about the others things i was understanding them , but sure it will be a usefull post
I wasn't enough precise on my questin so this the precision,
the car heigh is as the driveshafts are parallel to the ground, Dave,
the engine is a turbo powered unit ( about 110 hps)
my friend had ordered a full adjustable front and rear set up with ball joint at the front
I know that on my roadycar :
front was 2? neg on the front, 1:8 toe out and 5? of castor,
rear was 1/16 toe in 1? neg
and this was about good for the road handling carracteristic,
my friend's car will be used for track in the middle of april with50:50 driving for him and me, the tires will be 0.32R and I 'm looking for more specific track adjustements, (iemore camber?; more castor? more toe, less or more tire pressure?
I will not have the time before the track to adjust these , so I ask for some commun numbers
regads
fab
ps: about tires I'm using 32psi on the front and a little less on the rear on the road

i would really like to know how low is too low :(

i have just finished my mini and i want to go as low as posible :)

'I swear to use the Boost, The whole Boost'
'And nothing but the Boost..... So help me God'

Too low is easy to answer...

at the front there must a space between the front bump stop and the upper arm... note the suspension settles loads and often leaves you in contact!

At the rear, the rear arches are often the limit. Check that the rear brake hose doesn't get trapped by the radius arm thou!

Alex

AlexF

for the front end somes are setting their mini to the bump stop line as it seem to still work and increase the cone spring rate on some race cars, but I would stay away from this and i experienced low car and hard setted spax, ouchhhhh my back is reminding this.

running on the bump stops is not suspension... its not even incresing spring rate... its just bypassing the cones.

not good!

alex

AlexF

Few other points to think about.

Ride height - This will also change the roll centres of the suspension. So you may get greater camber change for a given amount of vertial suspension travel. Also can have an effect on bump steer.

Think about the rake of the car. The angle from front to rear and the effects it can have.

Camber - Good way to check if you have good camber angle to measure your tyre temp spread across the tread. Setting really depends on what you are doing with the car.

Caster - This is the kingpin angle from verticle when looking at the car from the side. Imagine a line drawn between the two ball joints on your hub assembley. The top one sits further towards the rear of the car. This angle gives rise to the self centering nature of your steering. The result of castor is that the true bottom of the tyre is not on the road, as the steering is turned the tyre rolls onto either side of the tyre a little, this effectively puts more weight on this part of the tyre. the steering self centres as the weight of the car tries to make it run on the flat of the tyre and spread the weight over the tread as evenly as possible. Take a look at what happens on a go kart when you turn the steering, you will see the front end lift up.

Alex you got castor mixed up with ackerman. You dont allways want to have the inside wheel turn at a tighter angle either. Changing this can really help change a car from high speed under / oversteer. Playing with this can effectively give you toe in sometimes and toe out at others throughout the arc of the wheels.

been trawling old thread?!

I'd forgotten this one completely, its 16 months old!

Alex

AlexF

Coincidently I bookmarked this the other day as something to go back and have a look at when i finally get mine on the road. No idea who the guy is or if he knows his stuff, seems to make sense though. http://www.minispecial.com/technical/showa...e.asp?article=1