suspension questions

[Stig]

I think the key thing here must be the change in camber with roll. I've always understood that a front anti-roll bar would generally increase understeer by putting more load on the front tyres, but if it controls the camber and keeps the tyres in better contact it could actually reduce understeer. I guess you won't find out for sure without trying it, but if anyone else has experience they can share then please do!

(I'm sure there are some professionals who know the best setup but as that's their bread & butter it's hardly fair to ask them to comment )

[Peetee]

I've always understood that a front anti-roll bar would generally increase understeer by putting more load on the front tyres, but if it controls the camber and keeps the tyres in better contact it could actually reduce understeer

that's a very important point. A cars passive suspension geometry is set up to provide the best handling in motion. vehicles with soft suspension will have different passive camber settings to those with hard. As the vehicle tilts during cornering the effective camber angle will differ because of the lean of the vehicle and also the compression of the suspension. Most systems - Macpherson struts for example - do not allow perfectly vertical compression of the uprights.

[Cam]

It is a fact of physics that the softer the suspension the more the grip will be, all other things being equal.

Presumably you mean due to there being little 'bounce' in a soft system as opposed to a 'hard' system. BUT as we know, that principle is for an ideal system. If (as in the Minor's case) the system is sub-optimal then hardening the suspension can lead to the tyre surface being in contact with the road surface more uniformly due to less geometry change upon weight transfer. The ideal system of course would induce more negative camber on the side that needs it under cornering so that the % of tyre contact with the road remains as high as possible.

On the other hand a very low suspension which is very stiff will slide a lot. The compromise (and this word comes up all the time with suspension design) is somewhere in between.

Exactly. The old 'trade-off'. This is why the people that put huge tyres with low compliance on a car with hard suspension suffer the 'crossply effect' and end up skittering all over the place as the contact area starts to lift under hard cornering.

What nobody can argue with is what each person prefers, that is a personal preference.

Indeed. There is also a lot to be said for driver skill too. A skilled driver will do far better in a poorer handling car than an unskilled driver in a well set-up car. Especially if there is a sharp breakaway limit which is quite common in well set-up cars. This often takes inexperienced drivers by surprise!

All my experience with standard Minors and modified Minor suspension show that when pushed hard a Minor will understeer. A front anti roll bar will make this worse.

Unless of course you fit a bigger engine, then you find that it oversteers. The trick though is to balance them out.

Suspension is a complicated business.

It certainly can be!

[Willie]

As I understand it a front anti-roll bar reduces the 'lean' on cornering which
translates into less roll on the tyres so that more of the tread remains in
contact with the road. This makes it harder to turn from the straightahead
position which means increased understeer, an added bonus being that, since
the front wheels are now linked together by the roll bar there is less reaction
when one wheel hits a pot hole so the overall ride is 'calmer' I have read and
my own results agree with the statement that, for some reason this increased
understeer does not happen when the anti-roll bar is fitted to a standard
Minor. Indeed I find it much more pleasant to drive and no longer have to
wrestle with the wheel round roundabouts. I have no idea why the Minor
defies the normal reaction in this way, perhaps someone could explain. My
57' car is now bog standard except for the front roll bar and the fact that I
have fitted 5 leaf rear springs instead of the original 7 leaf as I value my teeth!

[Innovator]

You have to read my replys carefully, especially the parts "all other things being equal" and "camber control"


Fitting a front ARB can reduce understeer if the suspension without has very poor camber control and the ARB keeps the tyre more upright.

Suspension Basics.

The following is the basis of most of my points in a very basic form.

4 equally loaded tyres will give more grip than if the car is on 2 wheels. This is because the coeficcent of friction of tyres does not double with twice the load.

Therefore we want all the tyres to be equally loaded.

Stiff suspension will load the outer tyres more that a soft suspension. If you struggle with this concept take it to extremes. If the suspension is rock solid and the body rolls a small amount the inner tyre is unloaded. With soft suspension the tyre will stay in contact with the ground longer.

The above is the basis of and over and understeer. You alter the stiffness at one end relative to te other to alter the wieght transfer at one end so increasing or decreasing the grip. This is why you require a torsionally stiff chassis because you are try to make each end of the car work differently.

I hope theabove very simplified explanation helps.

John



John

[Peetee]

I have no idea why the Minor
defies the normal reaction in this way, perhaps someone could explain

My best guess is this:
The Minor has a roughly 50/50 weight distribution but there is more weight forward of the front axle than there is weight behind the rear axle. As a result the car doesn't roll evenly and as cornering forces increase, proportionally more load is applied to the front wheel than the rear. The front corner of the car 'dives' and the rear inside corner 'lifts'.
This puts the front wheel at a less than ideal angle, the tyre rolls and the car understeers.
Much has been said about the perils of fitting the B-series engine with regard to understeer because it has to sit slightly forward. When you bear in mind that most of the A-series engine is forward of the front axle anyway it's likely that understeer is inevitable if you drive the car hard enough.

[minor_hickup]

according to a book i have somewhere, having soft independant suspension at the front was used on bigger cars from the 20's to stop the wheels shimming and became convention. Im sure ill be corrected but maybe the answer

[Cam]

Thanks for taking the time to explain, John.

So basically you are saying that stiffening the suspension will cause it to handle worse than if it's left standard?

[rayofleamington]

So basically you are saying that stiffening the suspension will cause it to handle worse than if it's left standard?

''all things being equal" is the key in John's comments as far as I can see ;-)

My understanding of it, including John''s comments is:
The standard minor is fairly soft at the front, and has very limited travel at the rear. This gives pretty limited handling as
1) it doesn't take much to unload the inside rear wheel.
2) the front camber control (when the body rolls) is far from ideal for agressive driving.

Therefore stiffer front suspension and/or an ARB will give an improvement but that is only because it compensates for other limitations.
If the rear suspension had the same travel as the front, and if the front had better camber control then ARB's and stiffer suspension wouldn't give the same benefit.

[Packedup]

Are people talking about grip, or handling?

As far as I know, handling is how well the driver can feel what the car is doing, whereas grip is purely the amount of friction between rubber and road.

I had an Uno once - I'd say the handling as awful, but the grip was actually very good.

[dp]

I used to have a 2cv and that was a bit of an eye opener handling wise. seemed to defy the laws of physics, the body leaning over to what seemed like 45 degrees but still keeping all four skinny (125 x 15) wheels firmly planted.

[Kevin]

Would it be possible to fit upright dampers without the towers that go into the boot?

Well I have teles fitted at the rear using a similar method to that shown in the technical tips manual without the need for the floor mounted or wing mounted parts, admittedley they are still at an angle but they work fine for me as locally as we have a lot of mountainous sleeping policeman, and I have found it a great improvement over the standard levers at the rear mainly in the comfort department rather than the performance stakes and consider it a real benefit, if you want more info send me a PM as I think I still have some photo`s at home, if not I can soon take some more if interested.

[Innovator]

If I was to tweak Minor suspension to give good grip and handling this is what I would do. It is based on my experiences with my van which had Minor front suspension and a live axle with 5 links. It handled well (not just me saying this and was refined)

This would be my starting point and I can not garrentee that it will work without tuning once it is put together.

Front: Lower 1 spline, cut the top bump stop down by about 20mm, fit the biggest tele dampers I could fit in (I have had damper fade with small tele dampers), fit soft poly bushes (not hard plastic), 1 deg negative camber and (this may surprise) at least 100% uprated torsion bars.

However the torsion bars are dependant on the type of driving and roads. I tend to drive on bumpy back roads and need the increased spring rate to prevent bottoming out. If smooth roads were mainly used then Marina bars will do.

Rear: The main thing at the rear is to get as much suspension travel as possible. It is a compromise between lowering and reducing travel. If I was very keen I would modify the chassis / body to increase axle movement. Then run the softest springs you can so you are not hitting the bumpstops all the time. Dampers would be upright either in the inner wings or inboard. Leaf springs will do with a panhard rod. Otherwise a 5 link and coilovers.

Now to go against everything I have said previosly, I may fit a very weak front ADJUSTABLE anti roll bar because this is the easiest way to tweak the understeer over steer, but this would be decided upon by testing. I would definitly not fit a rear ARB.

My van was pretty balanced with excellent rough road handling and ride without a front ARB. It had twice the spring rate on the front and 170lb per inch springs at the rear.

I would also get as much weight from the front of the car to the rear especially the battery. Any other weight I would get low.

John

PS Writing all this is making me want to put together another saloon!

[Innovator]

DP. A 2 CV is a good example. The skinny tyres are a lot more tolerant of extreme camber angles so can tolerate lots of roll. If the tyres were fat and square profile then it would be a different matter.

John

[Matt]

This is probably me being thick, but how do you make an ARB adjustable?

[Innovator]

To make an ARB adjustable you have to alter the leverage or mechanical advantage. The normal way is to have links between the suspension and ARB which slide along the ARB altering the leverage. Holes in the ARB are another method. However on my latest Minor moving the drop link 25mm (1") along the bar altered the handling from being far too oversteery to far to understeery. So I favour the sliding links.
Look here for some pictures:

http://www.beardmorebros.co.uk/website% ... t_2003.htm

John

[Matt]

ahh! ok

[chrisd87]

Is it possible to fit parabolic springs to a moggy rear end? It's a very popular mod for old landies, as it gives much better comfort and handling. Also I'm sure I read somewhere that the late Itals had parabolic springs - do these fit?

[Matt]

You can get them for spridgets.... im not sure if they would fit tho