Classic cars forum & vehicle restoration.
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OuBallie
Joined: 02 Mar 2013 Posts: 225 Location: South Norfolk next to Suffolk
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Posted: Wed May 17, 2017 4:57 pm Post subject: Wheel tracking |
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This thought provoking article appeared in the Morris Minor magazine.
Geoff - Progress on the Austin. _________________ Too many hobbies, not enough time!
1935 Austin Seven Ruby ARQ
1957 Austin A35 2-door
1967 Morris Minor 2-door
2007 Fiat Doblò MultiJet (It carries the spares etc)
Model Engineering |
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Farmer John
Joined: 18 Feb 2010 Posts: 181 Location: Manawatu NZ
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Posted: Thu May 18, 2017 3:16 am Post subject: Wheel tracking |
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Hello Geoff. Sorry but I will have to start at the beginning. If you bowl one of your Austin wheels along on a smooth surface you will notice that to have the wheel go straight it will need to be perfectly upright. Actually the circle prescribed by any part of the tread will be vertical to your British earth. (Just realised a tyre is better, no weight offset)
Bowl it and let it go. When it gets to the end of the run two things will occur at the same time. The wheel will lean and the previously straight path will become an arc. Just as it starts to lean you might see that it is at the same angle as the camber of your car, and it is then off on an arc which will eventually end in a small circle. When Herbert added positive camber to your Austin, that put the front wheels on divergent trajectories, so he pointed them in a bit by an amount we know as toe-in. So toe-in is the result of a calculation to make the front wheels track parallel. It is actually calculated.
Now consider this. If your steering is so flimsy that simply driving it along causes it to bend out of shape, then what will happen when you really haul on the wheel when parking? Hit a pothole at 100kph and you become an interested passenger. So, no, toe-in is not to compensate for weak steering parts.
There was a time when there was nothing but cross plies, well almost nothing, Pierre was making them and French cars would wear them. The French cars we serviced at the time did not differentiate between radial and cross-ply toe-in setting.
Looking at negative camber and toe-in or toe-out will show the same correlation, check Morris1100 or Standard10.
All this is general only, there are exceptions, the notion of bendy steering parts is what needs correcting.
John |
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mikeC

Joined: 31 Jul 2009 Posts: 1808 Location: Market Warsop, Nottinghamshire
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Posted: Thu May 18, 2017 8:31 am Post subject: |
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In the 'sixties it was quite common for family cars to be supplied as standard on cross-plies, with radial tyres as an option - to my certain knowledge radials were an option on Heralds (and Spitfires) and Imps; neither Triumph nor Hillman quoted different tracking settings for the different tyre constructions. _________________ in the garage: 1938 Talbot Ten Airline
Recently departed: 1953 Lancia Appia, 1931 Austin Seven, 1967 Singer Chamois, 1914 Saxon, 1930 Morris Cowley, 1936 BSA Scout, 1958 Lancia Appia coupe, 1922 Star 11.9 ... the list goes on! |
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1763 Location: Above the snow line in old Monmouthshire
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Posted: Thu May 18, 2017 11:55 am Post subject: Re: Wheel tracking |
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Farmer John wrote: |
All this is general only, there are exceptions, the notion of bendy steering parts is what needs correcting.
John |
I agree that steering parts don't (or at least shouldn't) bend, but don't forget that any steering system has a certain amount of free play in its various joints. It starts out as just a working clearance, minimal yes but still there, but then of course the various parts gradually wear and increase the amount of play. This wear can add up to quite a lot before it begins to impact on the safety or even driveability of the vehicle. |
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Farmer John
Joined: 18 Feb 2010 Posts: 181 Location: Manawatu NZ
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Posted: Thu May 18, 2017 9:57 pm Post subject: Wheel tracking |
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Hi Geoff, just found time to finish this.
When you are presented with an Austin for wheel alignment these are the first three steps. They are "must do".
Set tyre pressures
Set vehicle height
Check all suspension and steering for wear.
Any wear must be rectified before aligning. Bear in mind that parts may have free play but still be within manufacturers specs. That is fine. There are bottom outers that allow up to 0.040" lift, axle bearings with 0.003" end-float and these would look and feel loose yet still within spec.
Whatever has been happening to the car, jacking testing etc., the vehicle must, another "must do", have rolled forward a few yards ( 5 for me) before any measuring is done. This puts the right load, the right "set" on all the components.
Toe-in is measured at the front of the wheels and then rolled forward half a turn so that the gauge is reading on the same spots on the tyres when the rear is measured. Using the same spot eliminates any error from misshapen tyres or wheels.
John |
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Penguin45

Joined: 28 Jul 2014 Posts: 384 Location: Padiham
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Posted: Fri May 19, 2017 12:24 am Post subject: |
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Oddly enough the 'Crab (never sold on crossplies) has 1/8" toe-in.
P45. _________________ '67 Wolseley MkI 18/85, '70 Austin MkII 1800 The Landcrab Forum. |
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