[Healeys] BN2 Caster Angle

Wed Jan 6 08:39:27 MST 2021

Hi Fred.

You are not the first person that I have encountered with this confusion. It is usually held by those that are very familiar with pre-war cars and beam axles. In those cars the steering/stub axle is captured between fixed top & bottom ‘ears’ on the end of the beam.  The weight of the car bears down through the top ear onto the swivel axle. All fairly obvious.

In the case of our cars, with top and bottom wishbones, the weight of the car is carried on the spring and bottom wishbone. The wheel and stub axle is bearing upwards, LIFTING the car through the top trunnion using the kingpin as a pull-rod to the bottom wishbone and spring.

The whole front end is sat on those two Oilite bronze thrust washers. Any reduction in friction here pays dividends – especially in a 6-cylinder car with even more weight over the wheels.

Maybe others can come up with a clearer explanation.

Cheers.

AlanB

From: Fred Wescoe <fredwescoe at gmail.com> 
Sent: 06 January 2021 15:14
To: Bluehealey <bluehealey at gmail.com>
Cc: Team.net <lawrence.swift at gmail.com>; Ahealey help <healeys at autox.team.net>
Subject: Re: [Healeys] BN2 Caster Angle

Listers,

I have looked at these top trunnion bearing kits over the years and considered installing them.  However, I simply cannot get my head wrapped around why replacing bearings at the top of the kingpin would reduce the weight of the car and improve steering.  It seems to me that all the weight of the car is pressed against the bottom of the kingpin.  To me, it seems replacing the top bearing would have no effect on the steering effort.  Can someone explain in simple language why this kit would work?

Thanks, mystified,

Fred

66 BJ8

On Wed, Jan 6, 2021 at 9:49 AM Bluehealey <bluehealey at gmail.com <mailto:bluehealey at gmail.com> > wrote:

These are the ones.

https://www.ahspares.co.uk/austin-healey/big-healey/suspension-front/top-trunnion-bearing-kit-pair.aspx

Well worth doing.

The other often overlooked source of heavy steering is the Steering Idler. It is rarely lubricated, has no real reservoir for oil, and a poor seal at the bottom. I suggest releasing the ball joints that connect to the drop arm to check it for stiffness. Complete removal of the idler isn’t a difficult job and is the best way to clean and lubricate.

The caster is pretty good on these cars (the initial design was good). Camber could go from positive to negative to be more compatible with radial tyres. Also check and minimise toe-in. This has a radical impact on steering feel when wrong (in either direction).

If after all that you still have problems, then go for the caster changes you have in mind and tell us about your findings. The Team may learn something.

The only other aspect that seems to vary from car to car is bump steer. Some can be horrible on fast bumpies and others are on rails.  I’ve never seen a decent treatise on dealing with this on our Big Healeys.
Have fun.

Alan - from my iPad

On 6 Jan 2021, at 13:35, Team.net <lawrence.swift at gmail.com <mailto:lawrence.swift at gmail.com> > wrote:

When I rebuilt the front end on my BT7, I had the trust bearings at the top of the kingpin replaced with bearings - made a huge difference in the ease of steering.

On Jan 5, 2021, at 10:36 AM, Bob Spidell <bspidell at comcast.net <mailto:bspidell at comcast.net> > wrote:

re: "The other two are factory fixed and too dangerous to play with or maintain...even if Kilmartin makes the parts"

How so?

On 1/4/2021 9:40 PM, gradea1 at charter.net <mailto:gradea1 at charter.net>  wrote:

I'm with the philosophy "set the toe and let 'er blow" The 1/16-1/8" toe-in is most important for proper tire wear.  The other two are factory fixed and too dangerous to play with or maintain...even if Kilmartin makes the parts. Hank

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