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Steering geometry TR4A


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As we know, the tie rods out of the rack angle forward to the steering arm pivot attachments.
This is to accommodate the engine fan in front of the rack.
As I intend to delete the fan and fit a thermo fan onto the rear of the radiator, I am contemplating moving the rack forward about 20mm, together with lessening the pinion angle slightly to compensate, and lengthen the steering shaft.

Anyone care to comment.....

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Hi Melcom,

I thing the fan is not the reason for the position of the steering rack,

with the original metal fan it should be possible to move the rack 20 mm more to the front with the fan still used.

What is the benefit you hope to get, please?

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13 hours ago, Malbaby said:


As we know, the tie rods out of the rack angle forward to the steering arm pivot attachments.
This is to accommodate the engine fan in front of the rack.
As I intend to delete the fan and fit a thermo fan onto the rear of the radiator, I am contemplating moving the rack forward about 20mm, together with lessening the pinion angle slightly to compensate, and lengthen the steering shaft.

Anyone care to comment.....

My opinion would be cautious and have a very good reason for doing it.
 

Pushing the rack forward will push the wheels outwards, so you’ll need to shorten the steering arm lengths. By making them shorter you’ll probably affect the bump steer that Triumph built into the geometry. On top of that you’ve got other modifications to make. Is it worth the effort? There is no problem with the steering arms being angled forward as they are.

Kevin

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Hi Malcom,

I guess your hope is a more easy going steering?

We discussed already about an electric power steering for you....

The angled tie rods are the hypotenuse of a triangle, moving the rack le/ri changes the adjacent (effective) side le/ri probably different.

And the attachment points are moving on circles (sinus function) but are shure not on 90°  /  sin = 1,

so one will rise to 1 and and than decrease again, the other one will only decrease (faster). The hole stuff is the steering geometry.

Driving a bended road this causes (needed) the inner wheel to be angled more than the outer wheel.

Shure there will be somebody out there who can exactly tell you what to do.

As long this is not the case my advice is not to change anything on the steering geometry on "good luck".

Ciao, Marco

Edited by Z320
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Hi Kevin & Marco....thank you for your replies.

On my 4A, I have welded in a new replacement rhs steel crossmember for the rack brackets, so I have the option of welding on the original mount brackets in whatever position I choose...I'm thinking why did the factory choose to fit the steering rack where they did?...why are the tie rod arms angled forward as much as they do??

Some of the geometry of steering theory is currently beyond me.

I can understand that a change in the height of the rack would effect bump steer, but a simple [for me] explanation on what effect moving the rack slightly forward would have would be appreciated.

Marco...I am currently building an epas column using an MGF unit.

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