How much castor?

[greenamex2]

I have a front engined RWD 840Kg Saloon that works best with about 4 degrees of negative camber when used with genuine list 1a road tyres (actually Toyo T1-R's).

How much castor should it run?

I have seen recommendations like as much as possible, twice the camber etc.

And is it castor or caster?

I have never tested it before as the suspension design precluded adding any more, but with the aid of a round file and half an hour I will soon be in a position fiddle.

[richard_sykes]

Castor or caster, are both correct.

[Cameron Winton]

Denis - I believe Castor is a trade off between steering effort, self centering & Camber change lock to lock. ie, less castor, easier to steer but more positive camber as the steering position moves from dead centre. I have heard of WRC cars running wild levels of castor (8 degrees?) which is down to the fact that they run at the extremes of steering lock. They run power steering so load isn't a problem.
I have heard of escorts running around 4 degrees castor with 2.5 degrees neg camber.

[Al Weyman]

As cameron says more for self centering and I would'nt have thought a lot of camber would make much difference on a RWD car. Maybe a front or four wheel drive may benifit y helping keep it in a straight line under power. I always run my cars more or less stock.

[Tim Falce]

Don't forget that changing the caster will alter the camber when the steering is turned.
Any increase in positive caster will cause the outside wheel to gain negative camber, while the inside wheel would gain positive camber in a turn.

[greenamex2]

That's what I am after!

[graham bahr]

using more caster will give most of the benifits of more negative camber, but without the stright line stability probs that lots of camber causes, id does make the steering heavier with a greter self centring effect.

ok its on slicks, but my beemer runs 2.25 degrees front camber and 10 degrees castor

[coln72]

On my early Corolla (RWD approx 800kg) I am running as much castor as the standard adjustment allows and the crossmember is modified to give approx 2 degrees neg. camber. Steering sucks at low speeds - it is almost impossible to steer while pushing the car - but once underway you dont notice it. The benefits outway the problems though.

[Al Weyman]

Are the effects on negetive camber increase the same on double wishbone suspension like my 2nd gen car or is it confined to just McPhearson strut type suspensions?

[greenamex2]

All suspension designs that have some form of 'King Pin Inclination' built into them, which is just about all of them.

I feel an practical experiment coming on, I suspect my car is LOSING negative camber as the wheel is turning, at least through part of it's range.

I will just have to build up some arm muscle!

[greenamex2]

graham - 10 degrees!!!! I take it your car has power steering.

[R59]

Are you feeling strong Denis - come and try the Belmont. 9.5" slicks on the front, 400lb of Chevy V8 sitting on the suspension, currently set with over 10deg caster.

Heeeeaaaaavvvyyyyyy!

Like Coln72 said - OK once you're up and running, which is where it's important.

Rob.

[Al Weyman]

Why not just run power steering? I tried without it and no good I find I can drive quicker with it.

[greenamex2]

Sounds a bit like an Ultima, and that has the Chevy V8 at the right end!

Anything above walking pace and it was like driving a Fiesta. Anything below it felt like the power steering it doesn't have had failed. The other memory of the car (it had a standard ZZ4) was commenting to the Ultima person how cleanly it pulled away, to which he replied, "it's even better when you use first rather than third".

What sort of camber do you expect to run?

[greenamex2]

1.6 Corolla's don't have power steering and I can't be bothered to try and retrofit it. I also couldn't bare the thought of my hard earned BHP and weight loss being frittered away with such frivolities!

Gerry's power steering went once at Lydden Hill of all places. He looked a broken man when he got out of the car!

[Al Weyman]

No you can't drive these camaros without power steering they are just too heavy up front. I tried it in the lighter black car but it felt doughy and unresponsive and hard work. The GM has good power steering acually and is not over light especially at speed and feels quite good for a steering box system. I am running around 3 degrees camber but could easy adjust more in and may have to if I can't stop these tyre edges messing up. I will see how it fares on Saturday with a few tweeks I have made.

[graham bahr]

Originally Posted by Denis Bassom

graham - 10 degrees!!!! I take it your car has power steering.

NO,

its a bit heavy at walking speed but above that its fine and has plenty of feel.

its actually a PAS rack on there to get a quicker ratio. if you junk all the hydralics a non working PAS system is only a little heavier than manual steering, unlike a normal power steering system which has failed which goes almost solid

[Hitech]

It must be remembered that significant castor, particularly with offset steering, will result in major weight transfer to the inside wheel in cornering. This is why it is so difficult to turn these cars in the paddock, and why they become easier to steer on the track when the weight transfer to the ouside wheel is shared more evenly with the inside wheel. Karts use much of this principal to run so effectively without diffs, and it can be a useful chassis tuner, particularly with stiffly sprung single seaters in slow corners. If you lift the front of your car off the road and measure the amount of rise and fall of each front wheel as you move the steering from lock to lock you will see what I mean.
Phil

[Goran Malmberg]

Originally Posted by Denis Bassom

I have a front engined RWD 840Kg Saloon that works best with about 4 degrees of negative camber when used with genuine list 1a road tyres (actually Toyo T1-R's).

How much castor should it run?

Sorry if I am repeating what any other has already said, dont have the power to read the whole tread.
The caster angle should be a function of hte SAI angle in use. As SAI creates positive camber when wheel is turned, compensation has to be made by incresing the caster. By the finger and thumb, 7 degre SAI (at zero camber) takes 5-7 degree of caster to be back to zero.
Goran Malmberg

[Al Weyman]

Interesting thread this, I will look into this further in the close season, maybe why my front wheels seem to tuck under and mince the tyres despite a large visable amount of static negetive camber.

[greenamex2]

Sorry Goran, you've gone over my head again.

What is SAI?

[dtype38]

He means King Pin Inclination (I asked the same question in the "Suspension from scratch" thread.

Sort of sideways castor

[marcush.]

well....caster will help you more in the tight corners ,as the outside negative camber increases with stearing angle as well as you gain positive camber on the inside.
The story with heavy steering ,i don´t buy it unless you´re well over 12 ° .
You might be able to getaway with less static camber when using lots of caster,wich help traction and braking.you might as well pick up some bumpsteer when implementing lots of caster without lookin at your rackposition.
this all leads to the aspects of offset positive or negative of the kin pin axis and the caster trail or lead ....all contributing to steering effort,self centering,pullin into the corner ,feel , feedback.
And don´t forget deflection as well.You will never be at the static angles dynamically.

[greenamex2]

It's tight corners I have a problem. I'm RWD and the FWD boys are all over me in them.

Fortunately the ONLY thing Toyota designed properly on my suspension/steering in the rack position. My car CAN'T suffer from bump steer.

I'll get me Dad to measure the KPI/SAI and see where we are.

[graham bahr]

is it on the turn in or mid corner that they have the advanage?