Triumph Sports Cars

engine swaps and other performance upgrades, plus "factory" V8s (Stag and TR8)

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malbaby
malcolm baker

(10 posts)

Registered:
08/25/2017 05:56PM

Main British Car:
TR6 Steering Rack Position.
Posted by: malbaby
Date: February 07, 2022 04:30PM

Hi Guys...
As we know the tie rods angle forward from the rack to the tie rod/steering arm ball joints.
I currently have a bare rack mount cross member with the welded on brackets removed, I am thinking of moving the factory steering rack forward about 20mm, maintaining the same height.
Apart from altering the steering column and tie rods lengths, can anyone advise as to if this would be detrimental to the steering geometry, or would it be a slight improvement.
The proposal should not create bump steer as the rack height remains the same.
.


88v8
Ivor Duarte
Gloucestershire UK
(1054 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: TR6 Steering Rack Position.
Posted by: 88v8
Date: February 13, 2022 05:05AM

Don't recall from my own departed TR6, but if the rack height is such that the drag links are horizontal when the suspension is at rest with the car fully loaded, moving the rack fore and aft will have no effect on bump,

However, if there is a height difference, moving the rack so that the drag links need to be shorter, will exacerbate whatever bump steer already exists.

Ivor


BWA


(345 posts)

Registered:
04/13/2010 08:13PM

Main British Car:
Re: TR6 Steering Rack Position.
Posted by: BWA
Date: February 16, 2022 03:31PM

When you move the rack forward you are making the angle between the ends of the rack and the arms on the spindles more extreme.
The less this angle is the more direct the steering response will be when you turn the steering wheel.
As this angle gets more extreme the steering response gets less.
Just draw a simple diagram and you will see what I mean.
If the rack is moved a small amount it may not make much of a difference.

Cheers
Byron
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88v8
Ivor Duarte
Gloucestershire UK
(1054 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: TR6 Steering Rack Position.
Posted by: 88v8
Date: February 18, 2022 03:57AM

When you move the rack forward you are making the angle between the ends of the rack and the arms on the spindles more extreme.
That's true.
But in this case the rack is to the rear of the steering arms.... 'the tie rods angle forward from the rack to the tie rod/steering arm ball joints'.... so by moving the rack forwards the angle will become less extreme and so the steering will become a little more direct.

Which of course makes it even more important to pay attention to bump steer, because the combination of a more direct rack and bump steer would not be much fun.

Ivor


malbaby
malcolm baker

(10 posts)

Registered:
08/25/2017 05:56PM

Main British Car:
Re: TR6 Steering Rack Position.
Posted by: malbaby
Date: February 21, 2022 04:08PM

Thanks guys....
Ivor, the rack on a TR5/6 is slightly forward of the steering arm ball joints.
The TR4A rack is about 75mm back from the TR5/6 position, and is in a better position for the "Ackerman" principle to apply.


88v8
Ivor Duarte
Gloucestershire UK
(1054 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: TR6 Steering Rack Position.
Posted by: 88v8
Date: February 22, 2022 05:28AM

Slightly forward. Oh, OK.
From your first post I got the opposite impression.

In that case moving it further forward will just make the steering a little bit 'slower' but won't worsen any bump steer.

On my TR6 I didn't notice any bump steer, just tramlining from the oversize tyres.:}

Ivor


malbaby
malcolm baker

(10 posts)

Registered:
08/25/2017 05:56PM

Main British Car:
Re: TR6 Steering Rack Position.
Posted by: malbaby
Date: February 26, 2022 05:04PM

Can anyone advise on how to find the ideal rack height in relation to ride height...theoretically.
Does the "Instant Centre" method work?....or not... because the rack/tierod pivot point is not inline with the inner upper and lower control arm pivot points.



88v8
Ivor Duarte
Gloucestershire UK
(1054 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: TR6 Steering Rack Position.
Posted by: 88v8
Date: February 27, 2022 04:26AM

Instant centre... is a label for a geometric function of the suspension, so yes.
Set the angle of the tie rods to align them so they intersect the IC point.

If you parse the factory setup you will likely find that this is how it is.

Ivor


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