Improving handling

[JonE]

I'd sort those rear springs before you do anything else. The angle of the front WILL be right if there is no wear/distortion in your standard components from nosepiece through spring to axle and kingpin, surely? You can get a bit of an estimate by just drawing the degrees - slice of cake - on a bit of paper and looking at it in relation to the axle line viewed side on.

Springs... as its a light car, I'm interested in people like Ian's thoughts on the right spec to use, as the standard flattish sports springs (Nippy and the like) are probably having to cope with greater weight. (I'm wondering same with Speedex. The existing ones look very flat but very thin. Do we get like for like, or...)

[stuartu]

Paul, the simplest way I have found of measuring castor (not camber) angle is to use a digital inclinometer like this

https://www.ebay.co.uk/itm/113955392731

You can zero it by putting it on a straight length of timber lying next to the car then sit it on top of the stub axle (probably remove the screwed brass cap first) and it will tell you the answer.

It may not be 100% accurate but it's cheap, easy, quick and will certainly give you a clue if things are wildly wrong.

I suppose you could use it for camber as well if you really wanted to but let's not complicate matters.

Regards,

Stuart

[Ian Williams]

Jon this is a special and unfortunately not a particularly well conceived one either from the evidence of Paul's previous posts, if the springs have been flattened without consideration of steering geometry the castor will almost certainly be wrong. Getting into spring rate's involves numerous other factors, chassis stiffness, weight of the car etc, I am not a suspension expert but there are books and calculations should you wish to study the subject. However I have found through trial and error that fitting soft rides on a relatively standard chassis with just side rail boxing detrimental to corner speed, stiffening the springs and dampers helped my case enormously. That said it was not so great on the road where the surface was not as smooth as on a circuit and would skip across bumps in corners, slackening the dampers off again helped in this situation. Personally I feel that Austin were not far wrong in context of the time with the Ulster chassis, it would be my starting point on a vintage style special as weights would be similar.

[Bob Culver]

For a rough check with car on level ground, the facings of the axle where large radius rod nut sits represents the castor angle. may work off nut face or can undo nut one at a time and if the radius rod not twisted or untwisted in the process castor will alter little. With a level and perhaps a square the gradient  (1 in whatever as a fraction) can be established and the angle from sine or tangent table 2 deg .035, 4 deg .07 6 deg .105. Drills can be used as packers to obtain level.
The walls of the radius rods should be vertical but on the pre Girling cars with just the single big nut the rods can be twisted to some extent with a large Crescent or somesuch to provide some adjustment.

[Paul Nott]

Hi
Not sure what you mean by flatter springs as far as I know the front spring is not of the type fitted to a Nippy, it's a standard A7 front spring as are the rears. One thing I have noticed is the O/S radius arm is slightly twisted, this was slackened when changing the brass ball cup and plate rivets with bolts.

[Ivor Hawkins]

Hi Paul , yes it sounds like your caster angle is out and that will have a dramatic effect on your handling, so much so that any irregularity in the road will feel as if you are about to fly over the nearest hedge.

As Bob pointed out, twisting the radius arms will alter the caster angle, therefore you need to set the ca4 up flat and level and maybe using the inclinometer mentioned earlier get the axle tilted backwards and those kingpins aligned to about 9 degrees I think it is and the handling will be transformed.

[Hugh Barnes]

Not wishing to complicate things but it should be pointed out that the radius arms are handed and it not unheard of for them to be fitted incorrectly. In fact, for many years (it subsequently turned out) one of the best Austin 7 mechanics I know (knew, sadly no longer with us) had a pair of left handed ones fitted to one of his cars.. It's very easy for the uninitiated to make a simple mistake when fitting and if all else fails, that might be worth examining..

[bobthompson]

You can get a Protractor App for free on your phone and that can measure the castor too.

[Ian Williams]

Paul if your car is on standard high chassis springs it will handle like a high chassis car and my earlier comments are somewhat irrelevant. You may be able to improve matters if castor is incorrect but you will simply have to get used to the tendency for it to bump steer from the rear as all standard sprung A7's do.

[Paul Nott]

Thanks for all your advise, plan to replace from tyres ,refit radius arm and check castor.
Will report back when completed.
Many thanks