14 replies to this topic

[malc_west]

So Ive brought a mini Austin 1988 with a twin carb 1.3 metro engine in and I'm looking to sort the handling out. The rear wheels appear to camber the wrong way or at best have no camber at all the back end is skittish so would adding camber help fix this? Theres also a fair amount of roll so I'm guessing lower stiffer suspension is the way forward?

[RooBoonix]

I found this quote from another post, it's Coopermans info and it's exactly what I'm following for my Mini. There is plenty of info out there with a quick search, this post is handy as it lays it all out for you.

 

The suspension settings are quite critical on the classic Mini, especially the rear settings.

 

Whether or not your rear brackets are adjustable will be easy to see. If they have adjustment there will be small fittings for screw adjustment. if the brackets are plain faced, then they are not adjustable, but can be set more correctly.

 

The ideal settings for a 'not quite so slow road Mini' are generally as follows:

 

Front;  0.5 to 1.5 degree negative camber, which can be achieved with either different lower arms or offset lower arm inner bushes.

3 to 3.5 degrees caster which can be achieved with adjustable tie-bars.

1mm to 2 mm toe-out

 

Rear:  zero to 0,5 degrees negative camber

1 mm to 2 mm toe-in

This can be achieved either with adjustable brackets or by filing the hole in the bracket forwards and/or upwards until the correct settings are achieved, then welding on a large washer to maintain the settings. If there is too much toe-in on the rear the brackets need to be shimmed away from the sub-frame mating face.

 

Accurate measurements are critical. When done both road-holding and handling will be much improved.

 

Set the car to standard ride height, not lowered for best overall performance on the normal roads.

 

Note that these settings do not necessarily apply with the 13" wheels/175 section width tyres when the camber for the front should be no more than 1 degree neg maximum and 0.25 degrees neg on the rear camber.

 

Edited by RooBoonix, 12 June 2018 - 07:53 PM.

[malc_west]

Thanks mate

[Cooperman]

I think you actually mean 'road-holding' rather than 'handling'.

The two are completely different.

Road-holding is the amount of 'G-force the car can generate when cornering and is a measure of the speed the car will safely negotiate a corner.

Handling is the way the car responds to the basic dynamic inputs of power/torque, braking and steering. Good handling = good predictability.

To give an example, my Cooper 'S' has superb handling, even on 'knobby' forest/gravel tyres, but with these tyres on dry tarmac the road-holding is poor.

Thus it is possible to have superb handling but poor road-holding or poor handling with good road-holding.

A well set-up car will have both good road-holding and very predictable handling.

[malc_west]

Na I race karts I understand the difference, my issue is handling as in the back end is skittish and it wallows slightly which makes turn in delayed. Grip or road holding in general is OK. But I do have a question on the advice, people talk about the difference in geometry giving different "feels" with out stating what to change (as in camber,castor or toe in) and at which end to make the car feel loose or pointy or what ever. For instance I like a pointy car that's direct on turn in but the back is slightly loose in a predictable manner of course
Thanks

[GraemeC]

The back will get looser the if you run less toe-in.  Parallel is probably as far as you'd want to push it on a road car and you need to be confident in driving it like that as it will step out when it goes light.

[malc_west]

So what's camber on the rear alter then mate? And how do I get the front to be more precise and less delayed

[Alex_B]

Toe out on the front will help turn in, as well as less toe in at the rear if you like a looser back end.

Camber is more down to maintaining a contact patch rather than changing the feel, it’s a compromise between straight line grip and grip whilst higher speed cornering. More negative camber will mean better contact patch whilst under cornering loads but less grip in a straight line where as less negative camber will have the opposite effect. I run about -0.5 degrees on the back of mine and -1.5 degrees on the front and it feels pretty good in all situations on the road.

[malc_west]

Ok mate that's clearer, what's castor then

[Cooperman]

It does sound like insufficient toe-in on the rear, possibly with slight positive rear-wheel camber.

For a road car the rear needs between 1.5 mm to 3 mm toe-in with zero to -1.5 degs neg. camber.

As above, on the front, with 10" or 12" wheels a caster of 2.75 degs to 3.5 degs seems to work well combined with 1 degree to 1.5 degrees negative, Offset inner lower arm bushes are available to enable one to 'dial-in' the final setting, although normal 1.5 deg neg fixed length arms seem to work well. That's what I have on my 'S' with 10" wheels and it works very well.

[GraemeC]

Caster affect how quickly the wheels return to the straight ahead position.  Too little and the front end will wander, too much and it's very difficult to make the car 'break away' from carrying on in a straight line.

[Spider]

Ok mate that's clearer, what's castor then

 

Good question and it seems one that's not often well appreciated.

 

Cooperman and Graeme have cover some of it, however there's one extra 'trick' caster has.

 

With Caster, as the a wheel that's on the outside is steered in to a corner, it adds more negative camber to that wheel, so the tighter you turn in, (if set up right), the more grip you can get from that wheel.

 

It is this feature that allows me to set my wheel for zero camber, thus giving best possible grip for accelerating and braking (though that changes with attitude) and yet get good 'negative camber' type grip when cornering.

 

It also improves tyre life.

[malc_west]

Ok so a best of both worlds job then, how do you go about achieving that is it something you buy and fit? Or a way off setting up?

[Bat]

 

I found this quote from another post, it's Coopermans info and it's exactly what I'm following for my Mini. There is plenty of info out there with a quick search, this post is handy as it lays it all out for you.

 

 

3 to 3.5 degrees caster which can be achieved with adjustable tie-bars.

 

 

 

Cheers 

[racingbob]

here's how I experienced not enough toe out on rear round Silverstone back in 70's in mini 7 long sweeper bend wouldn't turn in properly. all other settings been done. changed it to 1/16 toe in next time was fine