Front suspension/alignment question

[tjb0274]

Now that the obvious things are sorted in the Ricciardi suspension (TA bushes, caster arm bushes & ball joints, shock travel, etc), the road holding is back to about where it should be.

I'm still not happy with the feel of the car, though. Bear in mind that until recently I hadn't driven it for several years, and not at speed for longer than that, but I never really felt that confident in what the car was going to do next.

Driving it again now, I think at least part of that is that the steering seems to get very heavy when turning into corners at speed. Thinking about it, that seems odd, because the steering is very light around town - going lock to lock at parking speeds is a breeze. That seems counter-intuitive - I would have expected the steering to lighten up at speed, unless I was still braking hard at turn-in, which I'm not. It's a very, very long time since I drove my GTV, but I don't remember it behaving like this. Of course, maybe I've just got soft driving modern cars with speed-sensitive PS.... 

So, firstly, am I on crack, or does this sound odd?  And secondly, any suggestions on whereabouts in the front geometry to look for explanations? Also any tips on checking geometry "at home" would be welcome - I suspect it's a bit late to book the car in for an alignment check before xmas!

The bulk of the front end is stock 105, but it uses a 116 rack instead of the standard steering box. I'm not sure what that means in terms of steering arms, etc.

[Barry Edmunds]

First suggestion would be to get a full wheel alignment done to check that the front wheels are both pointing the same direction. What about tyre pressures? tyre brand? tyre sizes?
Location of steering rack and how it lines up with the font end? You may have to consider the whole front end geometry.
I would also suggest having a talk to Bill Prowse to see if he has encountered the same issues with his car and or to Hugh Harrison who has a lot of experience setting up "new" cars. Let Hugh drive the car and get his input.
You could flounder around for ages and still not get it right.

[cjheath]

Sounds like you have a lot of caster. Hugh likes significant caster on a 105 "because they seem to turn in better", but it does make the steering heavier. Look at where your top arms join the crossmember - if they're almost touching the rear of the opening you're set up for larger caster.

[tjb0274]

Thanks for the replies :-)

Hugh had driven the car, although probably not at a speed where this would be apparent. I assume he set the caster after replacing the caster arm bushes - I'll check and see What he set it to.

I thought about caster, but assumed it would make the steering heavy at slow speeds as well?

To be honest, after recently discovering that the rear suspension had been incorrectly assembled, presumably from new, and that I in company with two different respected Alfa workshops had managed not to notice over the years, has me nervous that there might be something similar at the front. I remember curing some handling problems in a frend's Datto 1600 many years ago when I discovered that the tie rods were installed upside down and on the opposite side...

Edit: If I can find a level floor, I can manage roughly checking camber with an inclinometer (got one on my phone) and an improvised straight edge. Toe should be a straightforward measurement with a tape measure. I *think* I've worked out a way of checking castor by measuring the vertical and horizontal (front->rear) distances between the upper and lower ball joints - the inverse tan of (horiz/vert) should be the castor angle. Unfortunately the small horizontal distance (in the order of 10mm I suspect) means that the margin of error will be something like 0.1-0.2 degrees for every millimetre out on that axis, so it may not be useful if I can't get an accurate measurement. Anyone got suggestions for a better way of measuring castor?

[tjb0274]

Barry was spot on - turned out to be tyre pressures. I couldn't find my gauge when I was putting the new wheels on, and relied on the servo's gauge, which must have been out.

Pumped them all up to 32psi and everything's fine - in fact the car is now fantastic