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Author: Subject: Bump steer and steering rack selection
John Bonnett

posted on 27/6/20 at 06:53 PM Reply With Quote
Bump steer and steering rack selection

Some advice please.

My understanding is that the track rod pivot point should fall on an imaginary line drawn between the top and lower wishbone pick up points. So first of all is that correct?

If so, it would be necessary to select a rack with the track rod pivot points at the correct distance apart rather than the dimension of track rod centre to track rod centre.

Steering rack selection. Is there anywhere that gives a list of racks with their dimensions?

Thank you for your help.

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mark chandler

posted on 27/6/20 at 07:21 PM Reply With Quote
That is correct, to get rid of bump steer I shortened an escort rack, both the internals between the knuckles and the casing.
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gremlin1234

posted on 27/6/20 at 07:34 PM Reply With Quote
yea I know its 3 1/2 years ago, but
https://www.locostbuilders.co.uk/viewthread.php?tid=207116

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John Bonnett

posted on 27/6/20 at 07:45 PM Reply With Quote
Okay, I was correct about the position of the track rod pivot points relating to bump steer but I'll need to source a rack that puts them in the right place. Is there a table of rack dimensions or any source that would help in finding a suitable one?
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GManScot

posted on 27/6/20 at 09:34 PM Reply With Quote
G15 Build/bump Steer

Hi john

Are you trying to cure bump steer on the G15?


Tom

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John Bonnett

posted on 28/6/20 at 07:03 AM Reply With Quote
quote:
Originally posted by GManScot
Hi john

Are you trying to cure bump steer on the G15?


Tom



I'm sorry for any misunderstanding. Bump steer is not the problem here, it is sourcing a suitable steering rack that will put the track rod joints where they are needed to be on an imaginary line drawn between the upper and lower wishbone pivots.

So if I can rephrase the question. Is there somewhere a list of steering racks with their dimensions? The rack sits in front of the axle.

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Sam_68

posted on 28/6/20 at 08:28 AM Reply With Quote
quote:
Originally posted by John Bonnett
Is there somewhere a list of steering racks with their dimensions?


The short answer is no.

As Mark suggests, above, the easier solution is to work out what rack length you need (bearing in mind that there is usually some flexibility, as you can move the rack up or down a little to suit), then modify an existing rack, it's not a hugely difficult job.

Rack manufacturers like Titan will make one to whatever dimensions you want, of course, but that won't be a 'Locost' solution.

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John Bonnett

posted on 28/6/20 at 08:33 AM Reply With Quote
quote:
Originally posted by Sam_68
quote:
Originally posted by John Bonnett
Is there somewhere a list of steering racks with their dimensions?


The short answer is no.

As Mark suggests, above, the easier solution is to work out what rack length you need (bearing in mind that there is usually some flexibility, as you can move the rack up or down a little to suit), then modify an existing rack, it's not a hugely difficult job.

Rack manufacturers like Titan will make one to whatever dimensions you want, of course, but that won't be a 'Locost' solution.



No surprise but thank you. I have managed to find out the dimensions of an 80s Cortina rack which has the track rod joints 5 inches wider than an Escort which is similar to the Kitten. They are available new and might just do the job.

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GManScot

posted on 28/6/20 at 08:52 AM Reply With Quote
Bump steer and steering rackselection

Last time I was looking for a steering rack a friend of mine suggested contacting Dermot Healy who apparently can be found on uphill racers forum and is very knowledgeable in this area
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christim

posted on 12/8/20 at 02:12 PM Reply With Quote
I've always wondered....anyone have any idea why the books introduced the problem of bump steer? (or at least why the Haynes Roadster book didn't correct the problem)

There seems two easy ways to sort bump steer that the original designs could have incorporated (jack up the rack mount to a suitable height so the pivots are in line with the wishbone pivot lines, OR design a slightly wider front end so the wishbone brackets are the correct distance apart)

Sure people may want to use different racks which will introduce the problem and that's fair enough, but why say in the book 'use an escort rack' but then not design the car's front suspension around that rack?

Maybe i'm missing something?





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pigeondave

posted on 13/8/20 at 01:22 PM Reply With Quote
I've always liked this explanation on how to measure it here
https://youtu.be/LO07qmJ9zkk

This is what a friend had to do to his Fury to all but eliminate it (pic wont load) basically bit of inch box under rack mounts and then drilled the new holes further back also. So it was raise and push back.



He tried to run toe out for better turn in, but what with is going toe out in bump made the car crap.
All better due to the above.

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tims31

posted on 14/8/20 at 10:33 AM Reply With Quote
quote:
Originally posted by pigeondave
I've always liked this explanation on how to measure it here
https://youtu.be/LO07qmJ9zkk

This is what a friend had to do to his Fury to all but eliminate it (pic wont load) basically bit of inch box under rack mounts and then drilled the new holes further back also. So it was raise and push back.



He tried to run toe out for better turn in, but what with is going toe out in bump made the car crap.
All better due to the above.


I'd be interested in the picture of that if you can email it to me. I'll U2u you. Thanks





Build: http://www.martinsfurybuild.co.uk/

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pigeondave

posted on 14/8/20 at 10:44 AM Reply With Quote
quote:
Originally posted by tims31


I'd be interested in the picture of that if you can email it to me. I'll U2u you. Thanks


done did

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tims31

posted on 14/8/20 at 10:55 AM Reply With Quote
quote:
Originally posted by pigeondave
quote:
Originally posted by tims31


I'd be interested in the picture of that if you can email it to me. I'll U2u you. Thanks


done did


Got that, thanks





Build: http://www.martinsfurybuild.co.uk/

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