Steering rack narrowing..
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  1. #1
    Official RnS Addict Magman's Avatar
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    Steering rack narrowing..

    Another first for me!

    I need to narrow my MG Midget rack by about 70mm. The thing is I really want to narrow it 50mm/20mm instead of 35mm/35mm.

    As I know nothing about this stuff I'd like to know if there are any potential issues with narrowing one side more than the other apart from the obvious reduction in turning circle?

    Thanks in advance for any suggestions you all may have..

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    Off the Xmas card list kapri's Avatar
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    Do the inner pivots still line up correctly with upper and lower instersect points of inner arms fulcrum points when narrowed like that ? I take it you are offest narrowing to move the steering housing over for clearance ?

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    Official RnS Addict Magman's Avatar
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    Quote Originally Posted by kapri View Post
    Do the inner pivots still line up correctly with upper and lower instersect points of inner arms fulcrum points when narrowed like that ? I take it you are offest narrowing to move the steering housing over for clearance ?
    That took s few reads to work out but, yes, it all still lines up as it's in a flat plane from each track rod end, through the inner fulcrum points and the main body of the rack through to the opposing track rod end.
    You're right, it's just to move the steering housing over to clear the chassis rail as well as narrow the rack.

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    Off the Xmas card list kapri's Avatar
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    Just to make sure we ARE on the same page, check out this link for what I'm rabbiting on about

    http://www.uk-hotrods.co.uk/v2/tech/...g/steering.php

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    Official RnS Addict Magman's Avatar
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    Hmm, interesting reading.

    I've got 90% of it right, even down to castor angles (8.2deg per side) but the bit that worries me slightly is the last paragraph in red that says track rod ends should be of equal length on rack and pinion.

    Now, as that's in the wheel alignment section I'm not sure if it means that setting the tracking should be done by equal adjustments on both side of the car irrespective of track rod lengths or that they should actually physically be of equal length from inner pivot to the end of the track rod on both sides.

    I need to tack some measurements to make sure I've got the bump steer bit right.

    Cheers for that link Kapri, it cuts out a lot of the myth, bull**** and hearsay that I keep getting told about steering maths.

  8. #6
    Off the Xmas card list kapri's Avatar
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    Geoff that wrote the article is a good friend and excellent car builder , Berpop and Thamesy ( now Shortys Shaker ) Fordson were his builds. Everyone that has owned Thamesy has commented on its go kart handling properties !

    The UK Hotrods tech section holds basic articles on most aspects of rodding to cut though the b/s to the basics and myself and Geoff wrote individual articles on stuff and also some collaborations.

    Both on the track rod ends, they would end up equal length if the pivots intersect in the correct place. You should adjust track rods neds equally to keep the pinion in the centre of the rack in the straight ahead position and ensure equal turns ,from centred, to each lock.

    By shortening one side more than the other you will end up with more lock one side than the other but as it's a one off installation ytrue if in acar that was steering box to start off with as they tend to have restricted lock to start with. It's possible that , unless it's a purpose built chassis , the tyres would touch the chassis before the rack ran out of travel.

    That amount of caster is quite 'strong' on an IFS . Usual figures are .5- 1.5 on Mac struts, 1.5- 3.0 on IFS and 5-9 on a beam front end. The more you dial in the straighter it runs but the steering effect increases ..LOTS

    Depends what the installation is primarily used for . Many chassis'; that are built for drag racing with Mac struts use in the region of 7 degrees but that's because straight line stability is the main concern as there are no corners on strips.

    cheers
    Kev
    Last edited by kapri; 09-07-2009 at 07:22.

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