alistairolsen
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| posted on 17/3/08 at 11:17 AM |
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Cortina uprights- geometry issues
From what I hear the geometry on the cortina uprights is less than Ideal as regards steering self centring with far too large a scrub radius due to
the hub design.
That said, the racers manage ok, or maybe simply make do due to the rules?
How big a negative offset can you get away with and does anyone have any ideas on the ideal scrub radius (offset figure?)
cheers
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nib1980
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| posted on 17/3/08 at 11:30 AM |
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Hi
I use Cortinas on My ST and I have no concerns, have OK self centreing, not same as a road car, but still managable.
hope that helps
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britishtrident
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| posted on 17/3/08 at 11:37 AM |
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A big scrub radius isn't ideal but it isn't a major problem.
If you take away all the scrub radius you take away a lot of "feel".
A large scrub radius results in kick back through the steering, the classic case of massive scrub radius was Mk1 & MK2 Escort rally cars and also
Group 1 Capri racers which were forced to have a big scrub radius because the strut suspension layout and they did OK.
A big scrub radius tends to be tiring to drive at the limit for extended periods due to the physical effort required when the steering loads up in a
corner also the kick back through the steering wheel can be a hazard to the extend of inflicting injury on off road vehicles eg; 1st rule of
off-roading: keep your thumbs clear of the steering wheel spokes on rutted surfaces!
[Edited on 17/3/08 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Mr Whippy
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| posted on 17/3/08 at 11:41 AM |
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I don't think the cortinas upright has anything to do with that, the problem, more down to wish bone shape and over tight steering racks and not
helped with over wide low profiles.
My Falcon has cortina suspension and it has more than enough centering
[Edited on 17/3/08 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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alistairolsen
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| posted on 17/3/08 at 11:47 AM |
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if you accept the geometry of the hubs and a"normal" wheel offset in the mid 30s, run a 185/60 13 tyre and a new rack...
Has anyone tried adding morecastor to a locost chassis?
I dont mind heavy/tiring, but I want proper feel in the steering....
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RichieW
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| posted on 17/3/08 at 12:33 PM |
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Lots have people have used more castor.
They just set the top wishbnones a further 10 mm further to the rear, or as has already been mentioned use differently designed wish bones that use
the same pick up points but have the threaded part for the ball joint set further back on the wishbone.
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Johneturbo
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| posted on 17/3/08 at 12:40 PM |
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I know Mnr use escort stub axels in their cortina uprights for less scrub raduis.
Thats why my first set of hubs didn't fit!
i'm on my third set...but maybe a fourth!
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alistairolsen
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| posted on 17/3/08 at 12:41 PM |
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that sounds like a plan! I assume it feels considerably better?
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Johneturbo
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| posted on 17/3/08 at 01:00 PM |
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I'll let you know when the car is finished!
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alistairolsen
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| posted on 17/3/08 at 01:44 PM |
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one of those!
I reckon Ill stick with cortina stuff and then fiddle with geometry when its on the road!
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RazMan
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| posted on 17/3/08 at 02:13 PM |
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My 'tina setup has very little self centreing but after playing around with castor and toe it improved enough to pass SVA
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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paulf
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| posted on 17/3/08 at 02:43 PM |
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Its worth remembering that if building a book design car the top wishbone design is wrong and should have been drawn with an extra 10 or 12 mm offset
to get the 5.5degrees quoted.
Paul.
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alistairolsen
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| posted on 17/3/08 at 05:27 PM |
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offset in which direction? I assume they are handed and the balljoint tube site further back when they are on the correct wayaround?
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leto
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| posted on 17/3/08 at 06:29 PM |
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A "by the book"-locost will have a scrub of about 80mm. The Swedish amateur build approval organization is actually considering baning the
Cortina hub in future builds, because of the poor geometry.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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alistairolsen
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| posted on 17/3/08 at 07:20 PM |
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quote:
Originally posted by leto
A "by the book"-locost will have a scrub of about 80mm. The Swedish amateur build approval organization is actually considering baning the
Cortina hub in future builds, because of the poor geometry.
80mm with what wheel offset?
banning it to replace it with what?
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907
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| posted on 17/3/08 at 08:51 PM |
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My first w/b's were made to the book.
After a test drive or two I decided to remake them.
Pic below shows a jig I made with the old book one laying on top.
A big improvement.
I can now take my hands off the wheel without the car wandering which ever way the road camber takes it.
Paul G
 
Rescued attachment wb-jig-s.jpg
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leto
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| posted on 18/3/08 at 07:55 PM |
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quote:
Originally posted by alistairolsen
quote:
Originally posted by leto
A "by the book"-locost will have a scrub of about 80mm. The Swedish amateur build approval organization is actually considering baning the
Cortina hub in future builds, because of the poor geometry.
80mm with what wheel offset?
ET 41mm and 566mm roll diameter. With a KPI of 4.3 degrees you will need extreme stuff to get a decent scrub.
quote:
banning it to replace it with what?
What to replace them with isn't their problem. 
Around here uprights from Volvo 140 and Opel Asocna B are still pretty easy to find ,but the Volvo uprights wont work with 13" rims. Then there
is the Sierra upright with some geometrical trouble of it's own.
It's a little sad that the after market uprights duplicates originals with bad geometry.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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.jpg)
