Daf 33 Steering geometry - thoughts?

[spunkymonkey]

I've been having a few thoughts over the past couple of days about the virtual lack of self-centering on Betty's steering. Now, I'm all for light and direct steering but she does take a lot of concentration to keep straight in the winds round here. There's no wander as such - just a tendency to keep going on any curve you "dial in" with the wheel until you turn it back again.

Now, from what I remember, most cars with cross-plies used to be set up with a very small, or zero, camber angle because crossplies tend to distort and create camber as you drive. Hence the much lighter effect when you fit radials.

Sure enough, the 33's (with geometry designed for the 60s and - presumably - crossplies), has a listed castor angle of 0 degrees compared to between 4 & 5 for the later models.

So, my questions are:

1) has anyone had experience of a 33 on crossplies and, if so, was there more of a centering effect than with radials?

2) Can anyone with an original workshop manual confirm if there is any adjustment available to the castor? Obviously, the Autodata book doesn't cover things like that but I thought there's just a chance that the originals would include any method there is (shimming etc) for suspension angles apart from tracking.

Thanks,

Joe

[littlebelter]

DAF official workshop manual section 7-28 to 7-31.

These pages give the routines for measuring caster (sic) and camber. The proceeddures involve lamps, swivels and graduated boards and trimming the level of the car with weights.

It goes on to say that castor (which should be zero) can be adjusted by moving the upper attachment point of the strut forwards or backwards. It does not specify which movement achieves what alteration.

Camber is adjusted by moving the upper attachment point in or out.

The method:
". . . this will necessitate elongating the bolt holes and washers must therefore be fitted and welded on completion of adjustment."

I will happily copy the pages for you but cannot do this until early next week as my scanner is hors de combat.

Regards,

Pete Hayselden.

[starider]

Hi, I, from experience would not fit x-ply,you would probably find the 33 even more lively on the steering,plus you would get less mileage from x-plys.If the geometery is properly set, it may be worth checking tyre pressures. starider.

[spunkymonkey]

Thanks for that, Pete & starider.

I wouldn't want to fit x-plies for exactly the reasons you give. But I assume they were the "norm" when the cars were designed and often a switch to radials can be improved by adding a little extra castor to correct for the different tyre characteristics.

I'd appreciate copies of the pages when you can, Pete - but sounds like a job for the spring / summer if it involves opening and welding mounts!

[daf44]

hi joe.

i had a kit car with no self centering on the steering about 12 years ago. me and my cousin tried everything we could think of with castor/camber angles with no effect.

a neighbour suggested changing the tracking so it had a few extra degrees toe in. i still don't understand quite how it worked but it was much better afterwards.

apparently a slight toe in will make almost no difference if the steering centres itself, but if it does not centre itself , then the slight toe in can give some centering effect. ?

made no sense then. still doesn't.
it did work though.

worth a try before any major work is done

let me know what happens.

paul44

might be worth a try.

[spunkymonkey]

That's certainly worth trying, Paul. An awful lot easier to put a turn on each rod end than to start opening mounts in the bodywork!

Joe

[daf44]

hi joe.

let me know what happens.

paul44

[stefan]

Toe in is what is needed not caster/camber, caster is anti dive and steering weight and camber is high speed cornering under roll, that is my understanding from a book on race and road car chassis building and modifiying.

[stefan]

I have to agree with john about elongating mounts Alot of work and I think alot of long term trouble

[daf44]

hi.
to get a slight toe in on the front wheels, all you do is lengthen the trackrods.

to give a couple of extra degrees toe in, slacken off the locknuts on the trackrod end ball joints and turn each trackrod about a quarter of a turn then do up the locknuts.

as one end of the trackrod is a left hand thread and the other a right hand thread this will lengthen the bar a bit (as long as you turn it the right way).

not sure about the 33s, but i can do this on my 44 from above in about 5 minutes.

paul44

[spunkymonkey]

Agreed if a little extra toe-in works - it's definately the first thing to try. A little extra (in fact, a little full stop) centering would be good around here with the winds we get.

As for the various settings, in terms of road cars (generally using much more conservative settings than race suspension), the main centering effect is normally provided by caster. If the wheel's contact with the ground trails behind the (extended) steering axis then the wheel will try to run straight ahead like a shopping trolley wheel. Ok, bad example with the trolleys round here

Caster also tends to increase camber in turns, effectively "leaning" the wheels into the corner, and also lifts the front of the car slightly. So the weight of the car also tries to keep the wheels ahead by naturally finding it's lowest position.

On track / race setups they tend to use toe-out, which makes the car a lot more responsive on the turn-in to corners, combined with fairly high caster angles which help counter the straight-line instability that toe-out creates. Tis all a balancing act.

Why most cars designed for x-plies had either zero or negative camber is because a x-ply tends to distort in use, so the contact with the road is slightly behind the wheel centre - which creates caster itself. Radials don't give that effect so an otherwise similar car tends to have camber built in to the suspension.

If you compare the 33's - very much from the x-ply era - and 44's: The 33s are listed as 0 +/- 1/2 degree of camber and the 44's, with a very similar setup in all other respects except that radials were becoming more normal, are listed as 4 3/4 degrees. Hence my original thoughts on the matter.

The last example of this that I had contact with was an old Rover 75 of my father's. Designed for x-plies, with radials on it was lethally skittish on the road. About 2 degrees of caster added to the front suspension absolutely transformed it - it helped that Dad ran a garage with full alignment gear at the time, of course!

Unfortunately, if elongating mounts is the official way to do it, then that's the option you're stuck with if you want to try. It wouldn't actually be that critical a job. From measurement of the struts, 1/2 degree adjustment equates to moving the mount about 1/4 inch, and even out of the factory they're allowed +/- that much! For the nearly 5 degrees that a 44 runs happily with, that would mean shifting the mount about an inch and a quarter backwards - hardly high precision!

Undoubtedly a lot of work, and if a small toe change settles her down then it's a much better way to go, but if all else fails in the gales around here I'll definately be considering adding 1/2 degree or so - when it's working weather again ;D

[spunkymonkey]

If there's slight adjustment at the bottom end then even better, John. Altering mounts only came up because, as far as I could see from the Autodata diagrams, the lower end is located by a pin so I assumed there would be no movement available there. Then Pete gave a quote from the official manual that it should be adjusted at the top mount and welded washers used to "finalise" the setting, so that seemed the way to go

[littlebelter]

I agree with Bear that b*****ing about with the top mounting points should only really be neccessary after (say) body damage.

Nevertheless it is the official way of doing it (if neccessary).
I had not picked up on spunkymunkey's bit about the pins, which I now see in the Autobooks manual.

Even allowing for the fact that both the manuals leave a lot to be desired, I would have thought that one or the other of them would have stated if adjustment was intended to be possible at the lower end.

The existence of the pin does IMO confirm that no adjustment should be available at the lower end and ipso facto if "adjustment" is available at the lower end, something is wrong down there. (e.g. rust removed leaving a sloppy fit).

Admittedly you may achieve almost the same result, BUT:

If, for instance you adjust the lower end either forward or aft on one side, then you are upsetting the geometry to some extent and giving one wheel a slight lead or lag against it's partner.

Adjusting at the top would not do this to any significant extent.

That's my after dinner red wine reasoning.

I agree with "44" - try the toe-in first!

Regards,

Pete H.

[spunkymonkey]

Nov 24, 2008 20:05:03 GMT littlebelter said:

I agree with Bear that b*****ing about with the top mounting points should only really be neccessary after (say) body damage.

I also agree in general. In fact I'd go a little further and say that, generally, camber and caster shouldn't normally need adjusting anyway except after damage because it shouldn't vary if there's no damage.

In this case, though, I'm not looking at restoring the factory setting - rather modifying them slightly to allow for the difference in tyre characteristics between "then and now".

A little extra toe is definately the first thing to try though - the less deviation from original (and work) the better!!

Would still like to see those pages when you get your scanner sorted, though, Pete

[daf44]

hi there.

regarding the bottom ball joint bracket adjustment, there should not be ANY movement on the pin in to the bottom leaf spring.

this "pin" is about 3/8" diameter and is a snug fit into a hole in the bottom leaf spring to hold it steady and stop movement.
the bracket over the 2 leaf springs does NOT clamp the springs tight to allow for movement of the upper leaf as the suspension moves up and down.

movement on the pin will affect the steering geometry, and clamping the leaf springs tight will put massive strain on the upper spring.

i agree with little belter that ANY movement on this pin should be considered as something wrong.

paul44

[spunkymonkey]

Well, used the sunshine today to dial in an extra millimetre or so of toe-in and she seems a little more stable. It's hard to tell for sure because, along with the sunshine, the 50mph winds we've been having have disappeared! No doubt they'll be back soon enough.....

[spunkymonkey]

Learnt a lesson today. Well, a couple really.

The first one - which I'm a little embarrassed by cos I should have known it anyway - is always start with the basics

The second - which, again, I should have at least considered - is never assume someone else's work is right (especially on an old car they're not used to!!!). Checked the tyre pressures today, having had the new tyres fitted recently, and I guess no-one told the tyre centre that Dafs don't run with modern pressures.

Instead of the regulation 20/24 PSI front / rear (and presumably in the absence of a data sheet for it) they'd set pretty standard "modern" pressures of 30/30 PSI. No wonder it felt light!!!!! ;D