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Checking castor and camber #617593
16/02/20 02:20 PM
16/02/20 02:20 PM
Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Richard Wood Offline OP
Talk Morgan Expert
Richard Wood  Offline OP
Talk Morgan Expert

Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Just ordered one of these relatively cheap tools described as for measuring front wheel castor and camber. Appears to be only calibrated for the latter though.

[Linked Image]

Easy enough to see how it works with an adjustable calibrated pivoting level. You set on a flat surface so that bubble reads zero then magnetically attach to brake disc to measure camber.

Less clear how it works for castor measurement though. My thoughts are as follows: Trad sliding axle suspension means that camber and castor do not vary with suspension movement so measurements can be taken with the convenience of car jacked up and wheel's removed.

Using straight ahead wheel position as a camber datum, if it were possible to move wheels through an angle of 90° then the difference measured at say brake disc would be the castor angle. This diagram on right filtched from this GoMog article makes it clearer.

[Linked Image]

Clearly this is not possible so I would propose the following: On left side turn steering to left to be at 22.5° to straight ahead, measured by large protractor. Attach tool to top of brake disc and set to zero degrees. Then move steering to right until it's again at 22.5° the other side of straight ahead and measure change in camber angle of disc through a practical range of 45° of steering movement. Double this and that's the positive castor angle [Linked Image] Repeat for right hand side.

I believe I've read somewhere that the actual stub axle is not at right angles and/or in line with kingpin pivot. Not sure if this would make a difference but above should still give castor angle if not kingpin inclination in the fore/aft plane.

Would appreciate any constructive criticism of above.


Last edited by Richard Wood; 16/02/20 03:48 PM.

Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Checking castor and camber [Re: Richard Wood] #617617
16/02/20 03:53 PM
16/02/20 03:53 PM
Joined: Apr 2017
Posts: 1,073
Staffordshire
IvorMog Offline
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IvorMog  Offline
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Posts: 1,073
Staffordshire
I've got a similar tool and I have my measurement theory although I will be happy to hear comments on my methodology.

I have assumed that the springs are sitting concentrically to the king pins, which they should be.

Then take a steel straight edge and attach the magnetised base to it.

Measure the height from the flat garage floor to the bottom of the cross head.

Jack the car up and remove wheels both sides then lower the jack gently until it gets back to the height you measured earlier. i.e. normal ride height. DON'T WORK UNDER AN UN SUPPORTED CAR

I put a block under the cross head so I simply lower it onto that or use axle stands set as close as possible to the correct height on both sides.

It's important that it's done with the car set at the same attitude it would be on the road or your castor angles will be wrong.

Then I simply put my straight edge against the back of the spring so the gauge is parallel to the car.

The angle you read of then is the castor angle.

You can do the same for kingpin inclination. Obviously at 90 degrees.

Remember this assumes the springs are concentric to the kingpins but I can't see any reason why they shouldn't be.

I nervously await the learned cognoscenti on here to debunk my theory.


Bob

1999 4/4 2 litre Zetec
Re: Checking castor and camber [Re: Richard Wood] #617627
16/02/20 04:26 PM
16/02/20 04:26 PM
Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Richard Wood Offline OP
Talk Morgan Expert
Richard Wood  Offline OP
Talk Morgan Expert

Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
FWIW can't fault that method Bob, using a level garage floor as your datum with measurements taken at normal ride height. It would give I believe, kingpin inclination in the fore/aft plane which may or not be the same as castor angle, ref my point about stub axle orientation. Out of interest what measurement did you find and was it matched each side?

I assume the kingpin inclination at 90° reference you made would be for camber measurement.


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Checking castor and camber [Re: Richard Wood] #617632
16/02/20 04:54 PM
16/02/20 04:54 PM
Joined: Apr 2017
Posts: 1,073
Staffordshire
IvorMog Offline
Has a lot to Say!
IvorMog  Offline
Has a lot to Say!

Joined: Apr 2017
Posts: 1,073
Staffordshire
Castor angle and kingpin inclination will not be the same.

The fore and aft measurement is castor angle and the side to side measurement is kingpin inclination.

My measurements from memory were not the same side to side (surprise) and I think I had castor angles between 4 & 5 degrees and kingpin inclinations between 2 & 3 degrees.

I do need to re-check my numbers though as I'm working from memory but they are close to the handbook numbers for my car.

The variation in kingpin inclination angles mean I have about 1/2 degree negative camber on one side and 1/2 degree positive camber on the other.

The stub axle is machined at about 92 degrees to the kingpin (nominally as I have no way of checking that accurately) hence the camber angle is directly controlled (in the straight ahead position) by the kingpin inclination.

Be very interested in your findings.

Last edited by IvorMog; 16/02/20 05:12 PM.

Bob

1999 4/4 2 litre Zetec
Re: Checking castor and camber [Re: Richard Wood] #617634
16/02/20 04:58 PM
16/02/20 04:58 PM
Joined: Apr 2017
Posts: 1,073
Staffordshire
IvorMog Offline
Has a lot to Say!
IvorMog  Offline
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Joined: Apr 2017
Posts: 1,073
Staffordshire
Originally Posted by Richard Wood


I assume the kingpin inclination at 90° reference you made would be for camber measurement.


No that is for kingpin inclination angle which is not the same as camber angle. The camber angle is in effect the angle you would get if you put the gauge on the brake disc with the wheels accurately in the straight ahead position.

Last edited by IvorMog; 16/02/20 05:00 PM.

Bob

1999 4/4 2 litre Zetec
Re: Checking castor and camber [Re: Richard Wood] #617637
16/02/20 05:13 PM
16/02/20 05:13 PM
Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Richard Wood Offline OP
Talk Morgan Expert
Richard Wood  Offline OP
Talk Morgan Expert

Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Thanks Bob. That has confirmed my suspicions re stub axle to kingpin orientation. What info I've gleaned is that castor should be between 3 and 5° so yours sounds good. I'm hoping my method will give a measurement at the axle which is all I'm interested in.


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Checking castor and camber [Re: Richard Wood] #617676
16/02/20 08:10 PM
16/02/20 08:10 PM
Joined: Apr 2017
Posts: 1,073
Staffordshire
IvorMog Offline
Has a lot to Say!
IvorMog  Offline
Has a lot to Say!

Joined: Apr 2017
Posts: 1,073
Staffordshire
Richard

BTW I prefer to use a digital inclinometer such as this from Ebay. There are cheaper ones but I know the Laser brand so that's what I opted for.

Inclinometer


Bob

1999 4/4 2 litre Zetec
Re: Checking castor and camber [Re: Richard Wood] #617678
16/02/20 08:36 PM
16/02/20 08:36 PM
Joined: Feb 2010
Posts: 776
S
SimonH Offline
Talk Morgan Regular
SimonH  Offline
Talk Morgan Regular
S

Joined: Feb 2010
Posts: 776
Ideally castor would be around 6 degrees
Camber about 0.5 negative for the road

Kpi varies from stub axle to stub axle, I measured three in the workshop last week, and got from 3 to 5 degrees....

Scrub offset also varies between axles, as does Ackerman ...

Each car is always going to be entirely individual

Oh, and the cross head flexes with static load , and more so in cornering...
About 0.25-0.5 degrees under the static load and about double that under dynamic loads
But that all depends on vintage of the car also
Most of the time the cross head isn’t even symmetrical across the car...

Simon @ Sifab.co.uk

Re: Checking castor and camber [Re: Richard Wood] #617699
16/02/20 10:44 PM
16/02/20 10:44 PM
Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Richard Wood Offline OP
Talk Morgan Expert
Richard Wood  Offline OP
Talk Morgan Expert

Joined: Feb 2016
Posts: 2,397
East Harling, Norfolk UK
Many thanks Simon.


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom

Moderated by  Aeroman, Simon 

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