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Caster- how much?


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#1 luvemfast

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Posted 15 March 2013 - 10:33 AM

I know that camber and caster are generally expressed in degrees.
But, how does it equate in millimeters?

The LCA's are adjustable. But my caster rods will be at a fixed length.

How far in mm's are people moving their front wheels forward?
Many thanks

#2 nizm0zed

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Posted 15 March 2013 - 11:43 AM

how far in mm's from what fixed measurement point?
And is that measurement point the same on everyone's car? once you take into account manufacturing tolerances? accident damage?
40 years of wear and tear?
Its also assuming that your car is 100% true and square to begin with.


#3 luvemfast

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Posted 15 March 2013 - 12:09 PM

I understand everyone's set-up is going to be different.
Last time the alignment was done, the caster was pretty much, spot on identical.


#4 NZeder

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Posted 15 March 2013 - 12:12 PM

As much caster as you can physically get is what we do - ie adjustable rods and push the wheel as far forward as you can go without hitting guards etc then pull back if you must to match the other side.

"Caster Makes You Faster" so get as much as you can - I have seen people modify guards to get more ;) just remember your car has power steering so lots of caster will not require popeye to park the car as it might with a 240z/260z.

#5 DAZDA

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Posted 15 March 2013 - 02:47 PM

I had a go a 'start point' wheel alignment here;

http://www.viczcar.c...pic,7422.0.html

#6 620Z

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Posted 15 March 2013 - 03:10 PM

Yeah we put as much caster on my Zed as possible with out hitting the front guards. Car seemed to handle better but much heavier steering which I put up with for years. But since putting in the power steering in not a problem now. Plus when the body on my car was done I modified, or cut the front guards out a smidgen so I can get another 10mm of caster now. I have been to lazy to move it. But will one day.
Go for it Simon. 15mm should be OK. See how that goes first up. Maybe put in some adjustable rods. Remember always think ahead and do things once.  :D

#7 luvemfast

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Posted 15 March 2013 - 06:07 PM

Well. I've started off with 15mm off the caster.
When the LCA's are pushed out, the caster will move forwards some more.
So overall, will be close to 20mm

#8 Riceburner

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Posted 15 March 2013 - 06:10 PM

So what would 15mm be in degrees?

How did you set it up to ensure you got 15mm? Can you measure the distance between the front and rear hubs on each side and then extend both by 10-15mm making sure they are both the same?

#9 luvemfast

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Posted 15 March 2013 - 06:12 PM

So what would 15mm be in degrees?

I've got that data on CAD at work. But would be about 1.25-1.5 degrees.
20mm will be about 1.5 degrees.
Extra.
From memory.

#10 luvemfast

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Posted 19 March 2013 - 12:27 PM

Well.
It appears that 15mm shorter is too much  :(
Adding 3° camber automatically changes the caster and now there are issues with the tyres rubbing on the front spoiler.  :'(
So will make some mods and get it aligned again.....

#11 luvemfast

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Posted 20 March 2013 - 09:00 AM

After removing, changing, dropping and checking clearance many times............
I ended up with 2mm more on the caster rod! Not less at all.  ???

Given that the 280ZX has the caster rods towards the front and inwards. Whenever you push the camber out, the caster is already arcing towards the front of the car.

So if you put 3° of neg camber on, use std caster rods!

#12 Riceburner

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Posted 16 April 2013 - 10:54 PM

May as well continue on with this thread. I'm contemplating adjusting my suspension in the search for more corner speed. I have 3.5deg of neg camber, zero toe in and stock'ish' caster. I already have little to no clearance to the gnose, but I have urethane offset strut tops fitted that give 1 deg neg camber.

I had an idea I could rotate these towards the back to give caster without losing clearance to the gnose? giving me 2.5neg camber, 1deg more neg castor than current stock'ish' setup. I have adjustable castor rods but these are at stock length due to clearance issue.

Thoughts?

#13 luvemfast

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Posted 16 April 2013 - 11:08 PM

That works in theory.
But is losing neg camber, as a trade for more caster going to give you more corner speed?
As the saying goes......
"Caster is faster"

#14 Roberto

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Posted 16 April 2013 - 11:17 PM

You need toe in. This will help straight line stability as well as cornering. 2 to 5 mm is factory recommendation.
Also, are you willing to trim your front spoiler and utilise the adjustable caster rods?


#15 dat2kman

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Posted 17 April 2013 - 12:03 AM

Simon, you have forward facing castor rods in the ZX?
To increase the castor, put the rod into a lathe, and machine the shoulder, where the big washer is up against, back, say 15mm, you can add washers as packers if car frame is uneven.
In the root of the shoulder, turn it with a bit of radius, so there is no sharp internal corner, to become a stress riser, ie break.
Change nothing else at all, get a before and after wheel align, with adjustments for same toe.
The 15 mm will then tell you what degree castor you gained.

On Dato 1600's we used to run a LC-LJ Torana rod, fully adjustable, and straight bolt in

5 degrees is a good amount.

#16 Riceburner

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Posted 17 April 2013 - 09:35 AM

That works in theory.
But is losing neg camber, as a trade for more caster going to give you more corner speed?
As the saying goes......
"Caster is faster"


My understanding was the more caster you have the less neg camber you will need. I noticed at the nats I seem to be running a lot more than others. Gerhard was running -2deg, Gordon's looked about the same(-2) or even less but he has different tyre size.

You need toe in. This will help straight line stability as well as cornering. 2 to 5 mm is factory recommendation.
Also, are you willing to trim your front spoiler and utilise the adjustable caster rods?


Thanks, I'll aim for 2mm toe in then. I've already cut 20mm off each side to get good clearance, I can't really cut off anymore. I used the adjustable rods to get equal caster on both sides.

#17 Riceburner

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Posted 17 April 2013 - 10:44 PM

I found some more info. http://www.racecartu...com/03/205.html

My strut tops shouls allow for an extra 1deg of caster, the added caster should give .5deg of camber too which will get me back to 3deg. The caster change should give me a bigger tyre contact patch while cornering=more grip. The trade off is it will reduce stability, I guess thats due to quicker turn in? It will also unload the rear inside tyre, so I'll disconnect the rear sway bar to compensate. Thoughts?

#18 Riceburner

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Posted 19 April 2013 - 10:16 PM

I found some more info. http://www.racecartu...com/03/205.html

My strut tops shouls allow for an extra 1deg of caster, the added caster should give .5deg of camber too which will get me back to 3deg. The caster change should give me a bigger tyre contact patch while cornering=more grip. The trade off is it will reduce stability, I guess thats due to quicker turn in? It will also unload the rear inside tyre, so I'll disconnect the rear sway bar to compensate. Thoughts?


I'm gonna give this a try tomorrow. I'll give it a test at Phillip Island on sunday, if it's no good I can change back at the track.

#19 zr240

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Posted 20 April 2013 - 08:08 AM

Great post guys :)

What does everyone use to measure caster?

Good luck at the island this weekend Gareth

Ash

#20 redrbzed

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Posted 20 April 2013 - 02:35 PM


I'm running -4 camber on the front, 3.5 caster and zero toe.
On the rear -3 camber, 1mm toe in.




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