[Healeys] BN2 Caster Angle

Thu Jan 7 05:47:54 MST 2021

Sound right to me Chris.

M

On Thu., Jan. 7, 2021, 4:35 a.m. Chris Dimmock, <austin.healey at gmail.com>
wrote:

> 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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