bigrich
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| posted on 6/6/08 at 10:02 PM |
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Symptoms of excess castor
Well i know that little castor affects self centring, BUT what would excess caster do to the handling of a 7esque car using sierra hubs.
Opinions please guys, is too much a bad thing.
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A pint for the gent and a white wine/fruit based drink for the lady. Those are the rules
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nitram38
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| posted on 6/6/08 at 10:18 PM |
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Excessive tyre wear, heavy steering, trys to resist your turning from anything other than straight ahead
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SkinnyG
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| posted on 7/6/08 at 03:53 AM |
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Castor does not wear tires; camber and toe do.
The Lethal Locost
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worX
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| posted on 7/6/08 at 05:39 AM |
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Hi Rich,
It would just simply have the opposite effect of not having enough ie hard to steer off centre.
"Our" cars could get away with a great deal of castor and not be a pain to drive so unless you're gonna go crazy, I wouldn't
worry about going too much...
If you want to learn about it properly, one of the books I bought last year actually covers it quite well:
How to Make Your Car Handle by Fred Puhn
There is actually one on ebay at the moment
HERE
and on Amazon HERE
But if you just want to read about Castor and no other handling improvements then I'd happily scan that chapter for you!
It is a good book to have on the shelf though and if the ebay one doesn't go crazy you should get it!
Cheers,
Steve
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big_wasa
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| posted on 7/6/08 at 07:25 AM |
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I doubt you would be able to go to far without binding on the drag-lincs, bottom ball joints and track rod ends.
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Dusty
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| posted on 7/6/08 at 11:37 AM |
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Excessive castor also has an effect in rotating the hub carrier. This raises or lowers the end of the steering arm (depending on wether they are
forward or rearward facing) and thus raises or lowers the outer end of the track rod and alters its arc of travel with suspension movement. This will
introduce a change in bump steer requiring alteration in rack mounting height to neutralise.
Agree it will increase self centering possibly to the point of making the steering very heavy particularly at low speeds. No effect on tyre wear.
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Maradona
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| posted on 7/6/08 at 02:07 PM |
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Drive with much castor, is like ride a chopper bike (tipically Harley Davison) you can ride whitout hands,
Diego,
The locost builder from Argentina
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MustangSix
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| posted on 10/6/08 at 04:24 PM |
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More is not necessarily better. Ever push a shopping cart with a wobbly wheel? That's excess caster at work. The wheel will attempt to flop
side to side and you get a low speed oscillation (death wobble).
BTW, please school me here. In American English CASTOR is a bean from which a vile oil is produced and CASTER is the the angular displacement from
the vertical axis of a wheel. Is this yet another language/spelling disconnect between our respective sides of the pond? 
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loggyboy
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| posted on 10/6/08 at 04:52 PM |
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quote:
Originally posted by SkinnyG
Castor does not wear tires; camber and toe do.
Of course it does. Its best to imagine it in an extreme case to visualise its effects. Imagine a severe caster of 45 degrees, when the wheel turns you
will be lifting it onto one of its edges, thus causing more wear on that edge.
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MikeRJ
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| posted on 10/6/08 at 06:34 PM |
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quote:
Originally posted by MustangSix
BTW, please school me here. In American English CASTOR is a bean from which a vile oil is produced and CASTER is the the angular displacement from
the vertical axis of a wheel. Is this yet another language/spelling disconnect between our respective sides of the pond?
The Oxford English Dictionary suggests 'castor' is simply an alternative
spelling of 'caster'.
Personaly I've always known the suspension setting (and the vile tasting laxative/wonderfull smelling race oil) as 'castor', but I
can't pretend to have the greatest spelling skills.
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mad-butcher
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| posted on 10/6/08 at 07:06 PM |
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another good book, but definitely not bed time reading is competition car suspension by Alan Staniforth
Tony
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britishtrident
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| posted on 10/6/08 at 09:00 PM |
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Caster dosen't actually give self-centering.
What actually will do is try to align the wheels with the direction of travel --- think about what happens in a cross wind situation.
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loggyboy
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| posted on 10/6/08 at 10:04 PM |
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quote:
Originally posted by britishtrident
Caster dosen't actually give self-centering.
What actually will do is try to align the wheels with the direction of travel --- think about what happens in a cross wind situation.
Yes, Castor will infact detract from self centering as it will want to rock/tip the wheels over.
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procomp
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| posted on 11/6/08 at 07:09 AM |
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HI the most i have found that can be used ( with the sierra uprights ) without introducing unwanted symptoms is 7.5 Degrees. But this will depend on
the whole setup of your front suspension and your car in general.
Cheers Matt
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Syd Bridge
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| posted on 11/6/08 at 09:45 AM |
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quote:
Originally posted by britishtrident
Caster dosen't actually give self-centering.
What actually will do is try to align the wheels with the direction of travel --- think about what happens in a cross wind situation.
And how do you equate that deep insight (probably taken from Wikipedia or another forum??) with cornering? Does castor keep the car going in a circle?
NO!
The offset of the contact patch from the effective kingpin line causes a moment arm about the kingpin line, which causes the wheels to want to keep
going straight.
The more the offset(castor) the more the moment. Felt as force at the steering wheel.
If you want to see big castor, look at 911's. especially the early examples. 10 degrees plus from the factory.
In a crosswind, a little of the steering correction is for castor induced side loads from the wind, but the majority is to counteract side loading
from wind pressure, felt on all wheels, and pushing the car as a whole across the path of travel.
The shopping cart analogy is not really applicable. What shopping carts have is known as 'trail'. Similar effect to castor, but not the
same. Some cars are actually built with both.
Cheers,
Syd.
[Edited on 11/6/08 by Syd Bridge]
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britishtrident
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| posted on 12/6/08 at 10:00 AM |
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quote:
Originally posted by Syd Bridge
quote:
Originally posted by britishtrident
Caster dosen't actually give self-centering.
What actually will do is try to align the wheels with the direction of travel --- think about what happens in a cross wind situation.
And how do you equate that deep insight (probably taken from Wikipedia or another forum??) with cornering? Does castor keep the car going in a circle?
NO!
The offset of the contact patch from the effective kingpin line causes a moment arm about the kingpin line, which causes the wheels to want to keep
going straight.
The more the offset(castor) the more the moment. Felt as force at the steering wheel.
If you want to see big castor, look at 911's. especially the early examples. 10 degrees plus from the factory.
In a crosswind, a little of the steering correction is for castor induced side loads from the wind, but the majority is to counteract side loading
from wind pressure, felt on all wheels, and pushing the car as a whole across the path of travel.
The shopping cart analogy is not really applicable. What shopping carts have is known as 'trail'. Similar effect to castor, but not the
same. Some cars are actually built with both.
Cheers,
Syd.
[Edited on 11/6/08 by Syd Bridge]
No caster tends to align the wheels with direction of motion --- which is not always the direction the vehicle is pointing .
That insight came from a youth spent working on running and racing cars with by even the standards of those days a lot of caster (istr +11 or +12
degrees)---- a good example is the Hillman Imp poor cross wind stability many due to the positions of the centre of pressure and cg. However
when caught in a cross wind the steering would align with direction in which the the front of the car was being blown.
[Edited on 12/6/08 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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