Simple Camber Question

[mjmghdm]

If non-zero cambers make shoulder wear of tyre (as Fig.), Why many of famous car manufacturers choose a non-zero (almost larg negative) camber for their front (or rear) wheels?
If you tell me they compensate it by toe-in (for example), I'll ask you how?
thanks.

 

[GregLocock]

1a) The outer wheel, in a corner, experiences a large inward drag at the contact pitch. This tends to rotate the inside lip of the CP upwards and inwards. Static camber gives you some 'presentation' of the CP to account for this.

1b) As the vehicle rolls it generates negative camber on the outer wheel. In practice you can't include enough camber gain, especially on rear wheels, partly because this is closely linked to RCH. So you dial in some static camber to help compensate for lack of camber gain.

2)How?

Cos we're clever.






Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[cibachrome]

It is a bad assumption that a tire at zero camber produces zero lateral force, aligning moment and overturning moment. This assumes zero slip conditions, too. The Famous Car Manufacturing Companies (FCM) take these tire properties into consideration when choosing static and dynamic alignment specifications, especially for addresing steering lead/pull and max. lateral acceleration issues. In fact, these force and moment offset properties are usually part of a tire construction specification document.

 

[mjmghdm]

Hey;Thanks,But; I know these necessities of negative (static) camber.
<Maybe I ought to list a "What I know" at each thread!>

My essential question is:
Is shoulder wear a penalty for these tires (aging)? (If not, ...Why...Please...)
And do they use this appreciable negative static camber with a solution for their shoulder wear?

 

[GregLocock]

Adding toe-in can help to reduce the shoulder wear associated with negative camber. It wouldn't exactly amaze me to see toe of -.05 to -.2 times the static camber setting.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Yawing]

Shouldnt you add toe out with neg camber not toe in? The toe out balances the camber thrust so with the steering heading straight ahead the net lateral force is less giving less drag and wear.

For a radial I think it is about 1:10 ratio toe angle versus camber angle in terms of lateral force.

 

[GregLocock]

No

The differential wear on the tire from camber and toe is to do with which part of the tire is working hard (the obvious shoulder), not the thrust.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.