Antnicuk
|
| posted on 21/9/09 at 01:02 PM |
|
|
How do I measure Castor ???
I am looking to give my car a little more castor. I have rose jointed the front suspension (which is inboard with a rocker arm) so i can move the
lower wishbone forward to increase it. (its 3.5 at the moment)
I just wondered how much movement on the wishbone will give me about 5 or 6 degrees castor and how do i measure it?
Also, apart from self centering, what does more castor do to the steering?
[Edited on 21-9-09 by Antnicuk]
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
|
|
|
|
|
blakep82
|
| posted on 21/9/09 at 01:04 PM |
|
|
castor is the angle from the top to bottom ball joint, measured against vertical.
hope that makes enough sense, without drawing it out lol
edit, this should help
[Edited on 21/9/09 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
nick205
|
| posted on 21/9/09 at 01:09 PM |
|
|
One method of measuring is to hang a plumb line from the top outer ball joint (upright removed) down past the lower ball joint then measure against a
large set square using trig to calculate the angle.
Increasing the castor will affect the dynamic camber change on turns and possibly the dynamic toe in/out on turns. I'm guessing these effects
will be greater when moving the lower bone rather then the top bone as the uprights steering arm/TRE will move forward/backward to a greater degree.
Might pay to re-check you static toe settings after you've move the bones.
If you know both sides are set the same to start with, might be simplest to move both lower bones by the same increment (1 washer?) and road test to
see how it feels.
[Edited on 21/9/09 by nick205]
|
|
|
phelpsa
|
| posted on 21/9/09 at 01:09 PM |
|
|
I wouldn't worry too much about measuring it, just adjust and try it until it feels right to you.
Castor will make the steering heavier especially at low speeds as it's lifting the car a little while turning the wheels. It can make it appear
to have more 'feel' but that's really just the extra self centering you're feeling. It also changes the camber while steering
so giving more neg camber on the outside wheel while turning in, giving better grip theoretically.
This is just theory and in the real world you may not feel the same effects...
|
|
|
blakep82
|
| posted on 21/9/09 at 01:10 PM |
|
|
i'm not sure if you'll be able to get as much as 5 degrees without new brackets, but push the top wishbones all the way back, bottom all
the way forward, you might just about manage it
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
Antnicuk
|
| posted on 21/9/09 at 01:32 PM |
|
|
Hi, Thanks for that, i understand that bit but i mean how do i actually physically measure it?
Its difficult to get a digital spirit level (what i normally use) up against the upright which is not straight.
edit as its been answered now, thanks.
I have about 10mm of movement available, will that give he extra 1.5 degrees?
[Edited on 21-9-09 by Antnicuk]
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
|
|
|
nick205
|
| posted on 21/9/09 at 02:04 PM |
|
|
You should be able to work that out roughly by measuring the distance between the top and bottom ball joints then draw a right angle triangle with
that distance as one side of the right angle and your 10mm as the other side. Join the two lines to form a triangle and then measure the angle at the
long pointy end. That will give you the max. adjustment you're going to get then you can fiddle around and work out the change in dgrees per mm
of adjustment.
As above though it's probably more important to make sure both sides remain the same and you can get back accurately to your current setting.
Then just adjust a liitle/test in increments.
The proof is in the fell, not the number as they say.
[Edited on 21/9/09 by nick205]
|
|
|
Daddylonglegs
|
| posted on 21/9/09 at 02:50 PM |
|
|
Another way similar to nick205's, but without having to remove the upright is shown by Mark Allanson
here
God bless inginuity 
HTH
JB
It looks like the Midget is winning at the moment......
|
|
|
rusty nuts
|
| posted on 21/9/09 at 06:28 PM |
|
|
Been a while since I measured castor but IIRC you need to put the front of the car on turntables , attach castor gauge and zero then turn 20 degrees
left using the turntable to measure angle turned, take a measurement then turn right 20 degrees (40 in total) take a measurement which should give you
the total castor. If?? I can find it I have a Dunlop instruction sheet which may be of use
|
|
|
.jpg)
