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Extra castor on K/L front ends
pete wood - October 18th, 2005 at 01:41 PM

I had an idea about getting some negative camber into a King and link pin front end by adding extra castor. To do this you'd need to add extra castor shims behind the lower beam. The effect is that when turning the streering wheel, the outside front wheels gets progressively more negative camber the tighter you turn. I don't have figures for this but I know the mechanics of it work from looking at pics of drift cars and from building my billycart recently.

Does anyone have any real (personal) experience of doing this?

Are there any potential pitfalls? Ie. wear or bad geometry?

VWCOOL - October 18th, 2005 at 02:03 PM

Yeah - that's a nice old trick that I use on everything. There are some drawbacks on VWs - such as reduced suspension bump stroke, especially with BJ front ends, and change in toe-in on turns

[ Edited on 18-10-2005 by VWCOOL ]

[ Edited on 18-10-2005 by VWCOOL ]

2443TT - November 7th, 2005 at 11:55 PM

You can buy castor shims pre made in two sizes. I've got a set of the thin ones spare somewhere (maybe in my toolbox). The original idea was to restore castor to "stock" after lowering the front of the car, because the rake of a lowered front end counteracts castor.

I've now got the thickest castor shims I can get which are about 7-8mm thick at the fattest point and I use longer lower beam bolts to hold the beam onto the chassis fram head. I went this way for greater straight line stability at speed. The only draw back is that its harder to turn. Not that I'd notice with 205x40x17's up front.

pete wood - November 8th, 2005 at 08:15 PM

you've still got a K/L front end right?

I just want some extra negative camber, mmm extra, I mean any would be nice, to give me a better chance of not understeering out of corners on the go pedal. Straight line speed is not so much of thing.

How much harder is it to turn?

2443TT - November 9th, 2005 at 11:11 PM

Pete, its not hard to turn at all. I wish the steering was a little more firm because that would help make the car easier to drive at speed. Especially when accelerating. Even in top gear and above 100km/h my car gets a little light in the front end. I'm still learning to deal with the surplus amount of HP that my new engine has.

The "camber" thats being referred to here isn't "real: camber. Real camber as in toeing in the top of the wheel while they are still facing forward isn't possible with a king and link beam. But by adding caster by jacking out the beam at the bottom and then turning the wheel causes the top of the wheel to be toed in slightly at the top. I'm sure it makes a little diference but you'd only notice it if you made some lap times on a circuit and then made the adjustment and tried again.

On the street is pretty pointless, well at least up here in cairns it is. I spend more time swerving around pot holes than high speed cornering.


[ Edited on 9-11-2005 by iswinkels ]

pete wood - November 10th, 2005 at 02:54 PM

lets just say that anything that will help my buggy understeer less is welcome. So I think I'll be wacking the shims I have in.

Out of a corner on the throttle, it rears up like a tail heavy tinny in a swell and does it's best to go in straight line. 21inches of rear rubber and all the weight behind the wheels tend to cause that.:o

tassupervee - November 10th, 2005 at 07:05 PM

Pete
Why buggerise around with castor shims when you can add and remove CAMBER shims?
L8tr
E

pete wood - November 10th, 2005 at 09:22 PM

ok, tell me more. are they hard to fit?

wibble - November 11th, 2005 at 09:52 PM

Dude, welcome to the world of buggies.. Understeer is part of buggy life espiecially if you (which you do) are running a powered up heart. I pretty well steer my manx with the go peddle and thats with a little 1500sp atm :smilegrin: let me know if you find a fix but :thumb

hellbugged - November 12th, 2005 at 07:09 AM

Quote:
Originally posted by tassupervee
Pete
Why buggerise around with castor shims when you can add and remove CAMBER shims?
L8tr
E


so you're talking about adjusting the link pin shim stacks to gain CAMBER, yeah? you have done this before havent you! heres my simplistic idea....

i was figuring to set it up properly by measuring the offset of the trailing arms, but on the top link pin (as a starting point) take one shim from the inside and add it to the outside stack and the opposite on the lower link pin- one shim from the outside stack and add it to the inside. the golden rule is to stick to 8 shims for each link pin tho!

pete have you got a decent sway bar on the front? any where you can adjust the front end stiffness? (shocks or height adjusters)......and you're supposed to be STUDYING!!!

[ Edited on 11-11-05 by dumone ]

pete wood - November 13th, 2005 at 02:02 PM

Quote:
Originally posted by wibble
Dude, welcome to the world of buggies.. Understeer is part of buggy life espiecially if you (which you do) are running a powered up heart. I pretty well steer my manx with the go peddle and thats with a little 1500sp atm :smilegrin:


Yeah I know. But anything I can do to minimise this is good as far I can see. And let me tell you it understeers alright.

Dumone,
I do have dual adjusters in my front end, but no sway bar. I took that off to get a bit more movement offroad. I have one set of castor shims I am planning to put on. The front shocks are quite soft.

At the moment, the car is a bit of a handfull round corners. I mostly drive it like a granny though but when I have a squirt it can get interesting. Coming off alot of throttle while in a corner serious unsettles the car. Which is a bit hair raising.:crazy:

So if there is a way to help that It would be great.

P.s. I am taking a quick break from study that's all ;)

hellbugged - November 13th, 2005 at 04:56 PM

you have raised it, yeah?

pete wood - November 13th, 2005 at 05:17 PM

course :smilegrin:

tassupervee - November 14th, 2005 at 05:11 AM

Quote:
Originally posted by dumone

so you're talking about adjusting the link pin shim stacks to gain CAMBER, yeah?


Yes

Quote:
Originally posted by dumone

You have done this before havent you!.


Errrr...yes.

BTW Pete

It helps to have some worn LP bushes if you want much more camber over stock.
After that, you will have to make some off-set bushes as as you substitute more and more camber shims, the pins will eventually bind up and stiction will become a drama.

You can also bend the top chicken legs but this is a pretty hit and miss affair and requires it to be done with the aid of a wheel aligner and plenty of patience and the same drama of the bushes jamming up is still there.
Have fun.
E

VWCOOL - November 14th, 2005 at 09:31 AM

lol - the more worn, the better

hellbugged - November 18th, 2005 at 09:53 PM

hey pete! you should be studying!
o.k i have been studying and this is what i learnt about caster.

as usual "the factory" got it right. caster is the angle that the king pins lean back (at the top). caster (3-4 degrees) was built in to add enough driving load thru the king pin to hold it steady enough at speed but excess caster would result in a heavy wheel at low speed.

so if the caster is removed through modification or bent frame horns etc, you would experience an "over reacting" steering feel.small corrections at speed on the highway seem to go on endlessly, bouncing from one side of the lane to the other, wind and uneven road surfaces causing the same effect. the faster you go, the more the wind pressure pushes down on the front, and the worse it gets
as you loose even more caster.

the caster in the king pin was built in alignment with the front end beams, so as the arms are raised up towards the beam (lowering), the caster is lost and so is the nice feedback the caster returns through the steering wheel.

how to restore caster? add wedges under the bottom beam of the front end! this will bring the bottom of the king pin forward, thus re-creating the caster that is present on stock set up V.W's. high speeds of drag racers should even add two wedges and have up to 6 degrees of caster.


so what does this all mean for you Pete? i suspect raising the front would add caster? so you may not need those caster wedges after all and at this stage we are all pretty sure they won't help your understeer issues...........

.....can i have them? i think i have just convinced myself i have caster issues in my bug!:P



[ Edited on 18-11-05 by dumone ]

[ Edited on 18-11-05 by dumone ]

[ Edited on 19-11-05 by dumone ]

pete wood - November 19th, 2005 at 03:39 PM

Get your own dude, I think I'm gonna wack mine in anyway.

I have a mate who's into rallying and he reckons all the guys driving datto 1600s wind so much extra castor into the front end that the front wheels nearly touch the front edge of the guard. As you say, makes turn in at low speeds a lot heavier, but the car is totally stable at speed. Also increases the wheelbase of the car very slightly making the car even more stable in a straight line and moving the centre of gravity of the engine back just a fraction for their front mount motors. He also said that newer cars have heaps more castor than older ones and generally get round the heaviness at low speed coz they have powersteering anyway.

So I figure, the buggy is already light in the front so a bit more weight in the steering won't make a lot of difference to me.