[Healeys] BN2 Caster Angle

Thu Jan 7 02:35:01 MST 2021

Michael
You’re adding in a new variable. 
“King pin inclination to contact patch ratio” 
And that is a handling killer. 
You ALWAYS want the Imaginary line following your kingpin To hit the road at the centre of your tyre. Always. No known exceptions in a rear wheel drive car. 
Doesn’t matter if the tyres are 12 inches wide or 4 inches wide - centre of the tyre. 
Sage logic always says you widen a wheel inwards. Never huge offset outwards. 
Camber is adjustable by various means 
- bending shock arms 
- offset top trunions 
- Offset bottom trunions 
- shorter top shock arms 
Etc. 
Caster- well that’s harder. Lots harder to change. 
Castor - You need to move your top shock location, AND move your bottom wishbone location on the chassis. 
It needs to “tilt”
On a “jaunty angle” 
No. I’m too busy / google it. 
Camber is easy. Castor requires a shitload more cutting and welding. 
Perfection is 8 degrees negative at  20 degrees turn in for those seeking the ultimate answer, And that means castor at 20 degrees turn in plus static camber = 8 
Best
Chris

> On 7 Jan 2021, at 6:10 am, Michael Salter <michaelsalter at gmail.com> wrote:
> 
> 
> Re: Still wondering how adjusting camber, for instance--zero camber is recommended (newer cars have slightly neg. camber)--for the radial tires most of us run is a hazard (assuming it's done properly). 
> I would have completely agreed with you Bob until I started doing some basic designing of front suspension systems. 
> Although changing the camber may seem like a small thing you would be surprised at how much a small adjustment in any of the suspension angles of dimensions affects other things including "kingpin offset" and "bump steer" each of which can have a profound effect on ride and handling.
> As an example I have a Mitsubishi 3000 GT VR4. This car has 4 wheel steering but I don't think that is relevant. 
> When I bought it fancy alloy replacement wheels had been installed. These wheels moved the front tyre contact patch outboard around 1.5 cm. 
> The car was absolutely horrendous to drive with profound torque steer upon the application of full throttle (320 BHP), appalling "tram tracking" and incredible tyre wear.  
> I had another 3000 GT come in for service and as a test fitted the wheels off that car onto mine. The transformation was absolutely unbelievable; both the handling problems vanished completely.  
> I almost managed to talk the owner of the other 3000 into swapping his regular wheels for my fancy alloys but just couldn't do it and came clean by letting him drive my car with the alloy wheels back on.
> Small changes can have VERY LARGE consequences.
> M
> 
>> On Wed, Jan 6, 2021 at 11:22 AM Bob Spidell <bspidell at comcast.net> wrote:
>> That's odd; the bearings should be immersed in grease (although I've wondered how well greasing the top trunnion works, as a lot gets squished out).
>> 
>> I installed the Torrington bearings on my BJ8 years ago; I thought steering effort was reduced a bit (but I think part of it was confirmation bias). Agree that it would make more sense to install them on the bottom, load-bearing, trunnion.
>> 
>> Bob
>> 
>> ps. Still wondering how adjusting camber, for instance--zero camber is recommended (newer cars have slightly neg. camber)--for the radial tires most of us run is a hazard (assuming it's done properly).
>> 
>> 
>> On 1/6/2021 7:34 AM, Michael Salter wrote:
>>> I installed a couple of sets of those many years ago. Unfortunately the bearings were made from carbon steel not stainless and they rusted up after about 1 year. 
>>> Hopefully the manufacturers now make them from stainless andor brass.
>>> 
>>> M
>>> 
>>> On Wed, Jan 6, 2021 at 9:49 AM Bluehealey <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> 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> 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 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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