cd.thomson
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| posted on 9/8/10 at 08:25 PM |
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quote:
Originally posted by locobri
One of our club members has just gone through the IVA with his GKD Legend, He'd fitted a set of springs inside the steering rack and this worked
a treat and passed that part of the test.
He's getting me a set of them to just to make sure I' get that bit right as well.
I'll post some pic's as and when I fit them
yeah that'd be great locobri, be interested to see how they work 
Craig
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nitram38
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| posted on 9/8/10 at 10:02 PM |
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Right do a search and yes, I do bang on about this.
Castor isn't just for fun!
When you drive into a corner, the feedback from the steering should be of that the wheel is trying to straighten again in your hands.
It is vital you get this right otherwise you are driving a dangerous car.
I've corrected my suspension by changing the top wishbone so that it is slightly further back than the bottom bone giving both my builds 7.5
degrees and changing the car from vague to ones that feel good out of corners.
The alternative is having to feed the steering back to straight ahead which is not only un-natural to most peoples driving but means you can't
feel the road.
Springs, toe in, toe out, tyre pressure changes all work at low speeds, but when you are recovering your car from a ditch, don't say someone
hasn't warned you.
Oh and trusting manufacturers to do this stuff? Some are still producing wishbones with no castor
[Edited on 9/8/2010 by nitram38]
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matt_claydon
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| posted on 10/8/10 at 06:32 AM |
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quote:
Originally posted by nitram38
Right do a search and yes, I do bang on about this.
Castor isn't just for fun!
When you drive into a corner, the feedback from the steering should be of that the wheel is trying to straighten again in your hands.
It is vital you get this right otherwise you are driving a dangerous car.
I've corrected my suspension by changing the top wishbone so that it is slightly further back than the bottom bone giving both my builds 7.5
degrees and changing the car from vague to ones that feel good out of corners.
The alternative is having to feed the steering back to straight ahead which is not only un-natural to most peoples driving but means you can't
feel the road.
Springs, toe in, toe out, tyre pressure changes all work at low speeds, but when you are recovering your car from a ditch, don't say someone
hasn't warned you.
Oh and trusting manufacturers to do this stuff? Some are still producing wishbones with no castor
[Edited on 9/8/2010 by nitram38]
Amen. I don't understand why people are so happy to bodge 
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PeteS2k
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| posted on 10/8/10 at 08:09 AM |
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Nothing wrong with the Rush steering geometry from a self-centring perspective. There's plenty of castor designed in (9.5 deg measured on
mine).
It's the initial stiffness (excessive pre-load) in some installed lower ball-joints that seems to cause the problems.
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cd.thomson
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| posted on 10/8/10 at 08:13 AM |
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I'm not in the slightest bit "happy" about bodging.
Craig
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PeteS2k
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| posted on 10/8/10 at 08:36 AM |
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U have U2U
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matt_claydon
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| posted on 10/8/10 at 05:45 PM |
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quote:
Originally posted by cd.thomson
I'm not in the slightest bit "happy" about bodging.
Sorry, wasn't referring to you, but to all the people who seem to advocate time and again putting valve-springs etc in the rack. I just
don't understand why after nearly 10 years, the cars are still being sold with incorrect (and to be frank, slightly dangerous) suspension
It sounds like the Dax (unlike MK et al) actually has the correct geometry anyway, in which case your problem is most likely down to a stiff rack,
column, or ball joints.
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Madinventions
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| posted on 10/8/10 at 10:23 PM |
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Just because some people fit springs etc to aid the self centering test during IVA, doesn't automatically mean their geometry is wrong. The
springs etc are a sure-fire method to overcome initial stiffness in the system and only come into play at full lock. Previous posts are completely
correct - during normal driving, it's the geometry that gives you the correct feel and safety factors. But, for the 'show a degree of
self centering from full lock' test during IVA you sometimes need some mechanical help to overcome the tightness of new steering components.
Of course, it's imperative that every new build has a decent amount of time spent on it to get the geometry set correctly - it makes a
huge difference to handling and safety. Get this right first and then think about springs etc if you still need them, (and your test/retest
date is looming...)
Just my 2p's worth...
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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nitram38
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| posted on 11/8/10 at 05:15 AM |
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If you get enough castor then you shouldn't experience these stiffness issues. Often these cars have too little castor for road use coupled with
new componants. Racing cars are slightly different in that they often use a bit less.
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Madinventions
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| posted on 11/8/10 at 10:32 AM |
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But if you have too much caster then the steering can get too heavy and you can start to loose the 'feel' that we all want from our cars.
Also, the steering can tend to kick if you go over a bump, and changes to camber during cornering will also increase. As with anything, it's a
compromise and once you're past the 'safety' aspects (ie. making sure it doesn't try to spit you off the road), a lot of it is
down to personal preference - especially the differences between setting up for track days, or just for road use.
My cars is mid engined and I run about 5-6 degrees of caster and the steering is nice and light while still being positive and straight line stability
is good. I've got rubber tubing on the steering rack ends but this only ever comes into play at full lock so has no effect whatsoever during
normal driving. It just helps when parking etc.
Happy days
Ed.
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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cd.thomson
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| posted on 11/8/10 at 10:38 AM |
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Am I right in thinking correct "castor" would manifest itself with the upright sitting on a diagonal axis with the top of the upright
closer to the rear than the bottom of the upright?
Just checking my wishbones are right
[Edited on 11/8/10 by cd.thomson]
Craig
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Madinventions
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| posted on 11/8/10 at 10:53 AM |
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The top should be further back than the bottom, like this.
Ed.
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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cd.thomson
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| posted on 11/8/10 at 10:59 AM |
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cheers ed! Simple enough.
Looks to be plenty on my car, so I doubt thats an issue!
Can anyone explain what effect caster actually has? Basic physics/engineering welcome. No point building a car if I don't learn something at the
same time!
[Edited on 11/8/10 by cd.thomson]
Craig
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procomp
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| posted on 11/8/10 at 11:01 AM |
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Hi
I really can not believe that this subject is still coming up for discussion and argument . The fitment of valve springs in to the rack to aide self
centering is not accepted by the IVA. If they find out they are fitted they will fail you.
Now if you have 5 deg of castor and geometry that is in the ballpark of being what the car would require to be driven normally it will pass the IVA
without problem there should be no need to start setting the geometry up with way out settings just to induce self centering. What most are missing is
that castor dose not just give you self centering that is only a small effect of what effect it has on the geometry whilst turning.
Now the problem here is that just about every one of the main kit manufacturers have such poor control of the jigging on there chassis that if you
actually measure the castor properly you will find that they fall well short of what the manufacturers actually claim. Most only have 2-3 deg rather
than the 5 deg than they claim. Then there's the problem that the jigging from left to right is also poor so you get differences of up to 4 deg
across the car.
The claim that ball joints are too stiff is also a bit dubious. If a joint is stiff enough to stop a car with a genuine 5 deg of castor self centering
then the joint is not usable and should be discarded because manipulating it to loosen up is only going to give it a short life span or worse case
scenario damage the construction of the casing where it has been pressed over leading to it becoming possible to pull the inner ball out of the
casing.
If you do not have the required castor for your car or application as there's a difference between a CEC and a BEC you are not just lacking the
ability to have self centering ability you are lacking some of the basic geometry to control camber during cornering and with out it you will never
have a car that will handel as it should giving positive feedback and feel. Illegally bodging it through the IVA test and ignoring the fact it is not
right is also robbing you of having a car that is much more pleasurable to drive and more importantly helping you avoid situations that could lead to
an accident.
If your kit manufacturer sells you a kit stating it has X amount of castor and you build it and find you are falling short of what they have stated
and it does not allow you to legally pass the basic tests required to become road legal then you should be talking to you manufacturer and getting
them to correct the problem FOC.
This all down to the very basic simple use of the jigs during construction whether that be on the chassis or the actual wishbones if they can not
control the accuracies then quite frankly they should not be trying to produce the product and take your money.
Cheers Matt
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cd.thomson
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| posted on 11/8/10 at 11:14 AM |
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Cheers procomp,
I'd just like to say, from my standpoint, now that I've been informed of the issues by very knowledgable people like yourself and nitram
(amongst others) I want to do everything I can to check the geometry is setup as well as it can be in a home garage.
I've cast a glance over my caster on both front wheels and its definitely 5 degrees plus, more like 7-8.
Craig
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40inches
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| posted on 11/8/10 at 01:28 PM |
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OK! I'll add some fuel to the fire.
As Procomp says, if the IVA tester finds anything fitted to the rack to aid self centering, you will have a fail.
The steering on my Indy was very tight, I disconnected everything one step at a time, starting with the steering column, and ended up with the rack,
an MK shortened Sierra item, having no lubrication whatsoever I fitted a grease nipple on the centre section and gave it large with the grease gun,
can now spin the steering wheel with my index finger With the car on stands.
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cd.thomson
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| posted on 12/8/10 at 06:56 PM |
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ill post this here rather than make a new thread (unless noone is reading!).
When sorting the geometry is there a specific order of things to do?
Should tracking come last/first etc?
Cheers guys, going to get stuck in tomorrow
Craig
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procomp
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| posted on 12/8/10 at 07:00 PM |
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Hi
Castor if adjusting.
camber
tracking
Assuming it's just the basics your setting up. IE not looking at bump steer etc.
Cheers Matt
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cd.thomson
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| posted on 12/8/10 at 07:04 PM |
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thanks for all the help in this thread matt, much appreciated
Craig
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procomp
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| posted on 12/8/10 at 07:23 PM |
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Hi
I missed the obvious first step. Set RIDE HEIGHT. Ideally as it would be with driver on board.
Cheers Matt
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Mark Allanson
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| posted on 12/8/10 at 07:56 PM |
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really basic checks - this is how the wishbones should look
 
Anotated castor
A simple and cheap test of your castor using basic tools like this
 
castor 1
and from above should look like this
 
castor 2
You should have 22mm difference if using book suspension with Cortina knuckles
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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cd.thomson
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| posted on 13/8/10 at 05:27 PM |
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after spending a few hours twizzling track rods am I right in concluding that I can't accurately set up my tracking (toe-in/out) at home? I need
some sort of two wheel alignment gizmo?
My manual says I need to do tracking/camber/tracking because its not possible to accurately set camber if your toe-in/out is wrong?
[Edited on 13/8/10 by cd.thomson]
Craig
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interestedparty
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| posted on 13/8/10 at 05:49 PM |
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You can do tracking pretty accurately at home, and all four wheels too.
What you need is a flat, reasonably level surface, four axle stands or similar, some good quality string and a decent 600mm steel rule and lots of
patience and carefulness.
Adjust the height of the stands so that where you tie the string to them is the same height as the hubs
basically you need to get a taut string line either side of the car, then move them about until they are parallel, AND so the car is centrelined
between them (do that by maing sure that the distance from each hub to the line is the same, but remember that the back axle might be different width
to the front.
When it's all set up, you can measure from the front of each rim at string height to the string, and then the rear of each rim, and that will
tell you whether your wheels are lined up properly or not.
The more careful you are, the more accurate
And remember to re-check the string placement each and every time you trip over the strings 
[Edited on 13/8/10 by interestedparty]
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
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cd.thomson
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| posted on 15/8/10 at 04:29 PM |
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found at least one part of the problem.
My lower ball joints are immovable .
Can just about get them to shift with a few whacks of a hammer but thats about it..
Craig
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David Jenkins
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| posted on 15/8/10 at 07:24 PM |
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quote:
Originally posted by cd.thomson
found at least one part of the problem.
My lower ball joints are immovable .
Can just about get them to shift with a few whacks of a hammer but thats about it..
That's not going to help with the self-centring...
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