Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Fitting Crosshead and setting castor

For those following my Plus 8 rebuild exploits, you'll know that I'm at the stage where I now have to refit the crosshead.

I'll be setting the castor at 6 degrees as that's what the majority have said it needs to be, however, I'm unsure if that's 6 degrees against a flat/horizontal chassis, or when it would be on its wheels, on the ground and with rake built in.

I've had conflicting info and the two measurements are very different, so any help would be appreciated.
Thanks!

Since positive caster angle relates to how far the extended steering (kingpin in the case of a Morgan) axis is in front of contact patch of tyres, I would say its best measured with wheels on.

More info here

Thanks Richard.

I tend to agree. I'll set the chassis up on the axle stands so that it has the same degree of rake as if it were on its wheels and then set the Crosshead in place at 6 degrees from that position, rather than on a horizontal chassis.

As you say, castor angles normally relate to the angle of the kingpin against the vertical angle of the stub axle or tyre contact patch.

I think the rake of the chassis will change whether it is loaded or not. Also the weight of the body tub , fuel tank/fuel etc will make a difference.

The factory spec used to be 4 Degrees , but the set up was pretty crude (very little evidence of a jig in the early days) and most seemed to come out around 2 +/-

At my last rebuild (some years ago now!) we set the castor at 6 Deg with the chassis level on axle stands. Quite tricky to measure precisely once the suspension is all built up and the car on its wheels , but I seem to remember the result being about 5+/-. The car tracked well and I was pleased with the result.

Slight thread drift but above has got me thinking.

It seems that many new owners comment on the lack of feel and maybe self centering action of the steering. Certainly the case with my Roadster although it corners well. I don't have my handbook to hand but wonder what the caster angle actually is anyway, furthermore what options there are to change it.

Given the modest caster mentioned above and what the OP was aiming for I wonder how much benefit in steering feel would be available with increased caster.

Richard

Changing the caster angle is possible , but not without some bravery. You have to bend the tubes of the frame front ever so slightly to get more angle. From memory the top needs to move "back" and the bottom one "forward" . But as you will be aware this is not a job for the faint hearted , a degree or so too many and stand a chance of weakening the frame front.

I think the "dead ahead" feeling is also related to the rack and pinion steering used. My old +4 with a box was great straight ahead, I always felt the R & P on my +8 was more vague, and this feeling was increased when I discarded the damper blades in favour of steering bearings. However there was an upside , my wife was much happier with driving the car as she felt the steering was much "easier" to manage.

Thanks Andy, might be worth just checking just what camber caster I have first.

I do feel spoilt by our modern Mini Cooper Clubman. The steering is high geared with heavy self centering action but the electric assistance gives accurate steering with minimum input despite the 225 tyres. Sort of the best of both worlds allowing you to seemingly just think it round corners. Only negative is the FWD torque steer.

Although both corner well the Morgan's steering feel couldn't be more different.

I wonder if this is a time to also visit the "ride Height" issue. I would probably use 205 R15 tires to fill the fender well so My Morgan does not look like it has roller skate wheels. But R 15's are not available. I have also tried to use the Suplex Kit to lower the ride height but I run out of shock travel. I know of other +8's that have used this technique to adjust ride height. Something to think about. However it does make this job more complicated.

Culminator, scroll down to the excellent comprehensive post by Andy (MOG 615) in this thread - about half way down.

As a post script to Andy's excellent article. I subsequently bought the restoration project from Edgar 1969 4/4.

The crosshead was quite easily the worst I have ever seen. One bottom tube had cracked in the usual place and had been badly repaired, the sheet steel pressing was paper thin from corrosion and had various stress cracks. Terry Foxen made me a new one and aligned it to the chassis

Arwyn