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After a decent drive at speed I’ve decided I will definitely have to dial in some negative caster.


FB ute fixer upper, EK van on rotisserie

Errol62 wrote:After a decent drive at speed I’ve decided I will definitely have to dial in some negative caster.


FB ute fixer upper, EK van on rotisserie

How does that help on these old buses Clay?


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Think about riding your old pushbike with no hands Rob. It would track straight and you could turn by leaning into corners. Try this on a modern trail type bike with a more upright head stem. Much harder to ride no hands and you can come a cropper in an instant. The tilt on the head stem equates to negative caster.

Having the top pivot behind the bottom one makes the contact patch of the tyre sit behind the axis so any attempt to turn the tyre off line, it gets dragged back straight by a side loading vector component. So it want to follow the path of least resistance and go straight. This makes for steady straight ahead driving with increased steering force required to turn in to bends. Downside is heavier steering at slow speeds.


FB ute fixer upper, EK van on rotisserie

(Just read your reply. You have the sign of the caster angle backwards. The tilt on the head stem of a pushbike is equivalent to positive caster, not negative.)

My 2 cents':

Negative caster is a bad idea. The gain is a little less steering effort when cornering. But with negative caster come more understeer, less self-centring action of the steering, plus toe-out on bump, making the car wander under brakes.

George Roberts (whom we have to thank for the HQ's steering and handling) prescribed negative caster for the HTs, just after he arrived at Holden. Story goes that the Holden dealers in the know reset the front suspension angles on HTs to the HK specifications, because they steered and handled so badly.

(So, dial in a reasonable amount of positive caster by all means. The best way to do this with an HR front suspension is to remove shims from the front stack. Doing this has minimal effect on the camber and toe-in. And my remarks earlier about negative camber were in jest. Zero to -1/2 degree camber works well with radial tyres.)

Rob

Thanks Rob,
Always had a problem with sign conventions in maths. I will remove some from front stack and add to rear stack I think which is probably how I had it before the expert set it up. In the past I have found more camber evens up my front tyre wear. Otherwise they tend to wear on the outside.

Will probably need to re adjust toe as well.


FB ute fixer upper, EK van on rotisserie

Thanks Clay and Rob - I’m getting used to having to adjust the toyota settings as they scrub tyres on front from day one - I tend yo favour a more aggressive set up for the cruiser do it gets around things better and they straighten up pretty well anyway but the EK is still a mystery


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Hey mate go and see Brett at southern steering and suspension at seaford... he is the guru... just go talk to him and you will understand what I mean... I would never take anything anywhere ever again


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Cheers Glen will see if he can fit me in.

Woke early dumped oil changed filter ready to run the 44km in to work this morning. Reversed out pulled on handbrake and headlights went out. Released handbrake and came on again. Engaged and off again. No coming back on this time. Fiddling around under the dash I could get the occasional flicker, and could hear bimetal spring points closing briefly. Think there is a short under there somewhere. Time to instal Blacky's new switch and check the pressure on the glovebox extinguisher.

FB ute driver, EK van project

The little switch on the end of the handbrake sounds like the culprit - either that or the handbrake mech or cable is pulling something out of connection - I have a similar issue with my door courtesy light switches from races - one broke so had to disconnect it and of course that stuffs the indicators - need to install the fancy ones I bought.
don't let the magic smoke out.

Errol62 wrote: ↑Wed Jun 02, 2021 7:30 am Cheers Glen will see if he can fit me in.

Woke early dumped oil changed filter ready to run the 44km in to work this morning. Reversed out pulled on handbrake and headlights went out. Released handbrake and came on again. Engaged and off again. No coming back on this time. Fiddling around under the dash I could get the occasional flicker, and could hear bimetal spring points closing briefly. Think there is a short under there somewhere. Time to instal Blacky's new switch and check the pressure on the glovebox extinguisher.

FB ute driver, EK van project

gledge wrote:Hey mate go and see Brett at southern steering and suspension at seaford... he is the guru... just go talk to him and you will understand what I mean... I would never take anything anywhere ever again


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Booked out 6 weeks but very helpful and informative.

FB ute driver, EK van project

Patrick's diagram is a very useful aid.
To which I will add -

Uneven caster makes the car pull to one side. Then the outside of the front tyre on the side the car pulls to, shows feathered wear. Remedy: increase the caster on the side the car pulls toward (or decrease caster on the side the car pulls away from). A very slight pull to the right on a level road is OK, because most highways are cambered.

The only reliable way of measuring toe-in is to chalk-mark the front tyres, put the car on the ground, roll forward a yard or so, and measure the chalk marks front and rear. I've had a couple of front wheel alignments done where the toe-in was nowhere near correct, because it was not measured in a rolling condition.

If your camber is positive, set the toe-in to the more positive limit. If your camber is zero or negative, set the toe-in closer to (or even) zero. You can find the optimum setting quickly by road feel. If the car feels "wandery" at straight ahead, increase the toe-in slightly.

If the steering wheel is angled at straight ahead, correct the condition by equal and opposite adjustments of the tie rods, once all the other angles are set correctly.

Frequent cross-winds will cause front tyre wear that looks the same as under-inflation. This is more a Humpy problem.

Rob

ardiesse wrote: ↑Wed Jun 02, 2021 12:48 pmThe only reliable way of measuring toe-in is to chalk-mark the front tyres, put the car on the ground, roll forward a yard or so, and measure the chalk marks front and rear. I've had a couple of front wheel alignments done where the toe-in was nowhere near correct, because it was not measured in a rolling condition.

Remind me to show you the Servex M500 toe-in gauge I have stashed away. A spring-loaded pole is placed between the tyres, with a dangling chain used to set the pole height. Roll the car until the bar is on the other side of the wheel, chain again touching the floor. Small pointer shows the toe-in. Came from a garage located in town that had been in operation in the '20s - '70s.

Cheers,
Harv

Holds a straight line nicely at 60kmh no hands on the wheel. I’m confident he has things even. I will check the toe before I make any adjustments, and after of course. Just a bit light and twitchy at 110.

The list grows.
Wheel align
Light switch
Inside passenger door handle


FB ute fixer upper, EK van on rotisserie

Did your front wheel aligner note down the numbers? I would aim for something like zero camber, 1 - 2 degrees positive caster, and 1 - 2 mm toe-in. If you say "light and twitchy" at speed, I'd suspect that you need a little more toe-in; possibly bring the camber back to zero if it's negative; and maybe more caster is needed.

A twelfth of a turn on each tie-rod tube (use the nuts as guides), and see if the steering feel improves.

Rob