Rear suspension alignment - car wanders

[JohnFol]

Morning all, over last few months I've had all the suspension bushes replaced and had new rear shocks fitted (by Lancia garages I hasten to add). I noticed the back of the car "wanders" even at slow speed, and I get tyre screech at very low speeds on roundabouts. Gut feeling is it's geometry so just had 4-wheel alignment done and it's clear the rear was out. That said, driving home and the issues are worse, i.e. tyre screech on straight at 20mph, car cannot hold a straight line.

Garage claim they cannot set camber as their computerised system doesn't have the specification. Even if I could supply it, they cannot set the values as it's all computerised.

Not sure where to go from here so any ideas, or garage recommendation near Reading who can diagnose suspension issues most appreciated



Car is '79 spider

[JohnFol]

I'm reliably informed by the lovely chaps at Beenham Auto it's the beam. My guess is they will be hard to come by and probably as fragile.

Does anyone know of a source before I go the RSJ route?

[squiglyzigly]

I’m confused with some of this. Claiming its ‘the beam’?
What does that mean? The rear cross-member? If so they are not very stiff pieces from the factory but they don’t really need to be. But what is supposed to be wrong with yours to be causing such severe problems as screeching tyres at low speed. Is it snapped?
Even if it was a little bent, with the measurements you have it’s not going to cause screeching at low speed.

Cheers
Ian

[JohnFol]

Thanks Ian, intend to agree if all 4 corners are pointing all the same way, then where is the real issue. They fitted the rear dampers and commented the "beam" had some movement so today's comment is based on previous visit rather than inspection. So to be fair to them, it's the best guess until I can get it booked in

As for "beam", it's the bit all the suspension bits are bolted to so yes, cross member is a name I'm more familiar with.

[peteracs]

Hi John

Looking at your figures, it implies toe in at the front and toe out at the rear, pretty sure that the Haynes setting is toe out at the front and toe in at the rear? This is what I normally set the car to and never had an issue.

I do not know the value in minutes, just the value in mm based on 14 inch wheels, so cannot comment on the actual values. I could of course work it out….. will look to do so.

Anyone else care to correct me?

[peteracs]

Also just noticed you seem to have (if I am reading this correct) the camber changing between the two before and after which given you have no real adjustment on is interesting and implies all wheels are at negative camber?

As with previous comment, not sure what on the rear cross member can be affecting it as essentially just two bolt holes?

One thing to check is if any of those rear suspension arms are bent which is not uncommon.

Peter

[WestonE]

Hi John

The Beam description has me puzzled. Perhaps they mean the Rear anti-roll bar which on late Spiders can be moved in its U clamps affecting rear camber and set back (wheel base). I would look hard at all bushes and look for bent items as part of your strategy. Front wishbones bend far too easily as do the rear long links often thanks to poor jack use.

I fitted 4 adjustable rear links on mine to give more control over camber and toe at the rear. A very similar rear link design is used on Integrale. It may even be usable as a replacement although I have never checked the lengths.

Eric 

[peteracs]

Hi

Just checked Haynes and rear camber is quoted as -30 minutes +- 20 minutes and front is +40 minutes to 1 degree 20 minutes. So looks like your camber is out as per diagram and I was correct on toe out for front wheels and toe in on rear. Your diagram shows different tolerances to Haynes for toe values.

Peter

[peteracs]

Hi Eric

Good point about the rear anti roll bar being adjustable on its attachment to the hub.

Peter

[peteracs]

Hi John

One last question (promise) are you running standard spacer at the front wheels and no spacer at the back as per original?

Peter

[JohnFol]

No spacers have been added or removed.

All bushes replaced, a couple of bent bars straighten, new rear shocks... I'm reasonably confident with the diagnosis as if all 4 wheel were "straight" and fixed securely then I can't see what else it could be other than something flexing.

Rear wheel does look off vertical and I'll get a picture posted.

[peteracs]

Hi John

I still think you have the rear end setup wrong, ie it should toe in not out. Your original setup was way too much toe in at 1 degree, ideally should be around the 15 minutes by my quick calculation which sort of agrees with the chart, but as a toe in not out.

Peter

[Clifford]

Under the rear seats inside,  is  a cross beam that is welded to the sides and the floor.  This hasn't rusted through has it, because that will allow the car to flex on the move rather than keep it rigid as all of the suspension set up (sway bar etc.) underneath then would be flexing wouldn't it?
C

[JohnFol]

I'll have a look under the rear seats this weekend. I'm sure at least 1 wheel is pointing in the wrong direction so I might have a go at adjusting toe myself to make it more drivable (as opposed to not drivable)
Tyres lack date codes and are 185/65 so booked in Monday to get new tyres of original spec and revisit the alignment.

[JohnFol]

Odd angle but this is me standing by rear nearside wheel looking down. My camera has a level in it so I know this was taken directly above and flat.

The spirit level is horizontal and touching each side of the wheel (tyre not rim). Red line is a good approximation of being parallel to the side of the car. 15 minutes toe in? I think not

[peteracs]

Hi John

Hmmmm…. Very little wonder the car is so erratic.

If you fancy a bit of home diy, you could use the string method of setting the car up. I did it for mine and it drives faultlessly and hence not at the vagaries of a company you do not know. Once you then know it can be setup to work then you could have it double checked.

PM me if you need any help doing it, pretty straight forward to do.

Peter

[squiglyzigly]

Evening John
I’m not disputing your findings but. . . . You cannot setup or assess suspension angles by using the bodywork or other visual markers. It’s ‘very’ deceptive.
I have my own geometry setup equipment and have been tinkering with geometry on fwd Betas for 3 decades. I also calibrate my tracking/caster/camber equipment every time I use it.
Whilst I think it reasonable to question the reliability of the measurements you have been given, I think thorough visual checks under the car are the best place to start before you start moving tracking that allegedly isn’t far out.
As Peter has mentioned, the rear tracking needs to toe-in. Having said that, a little toe-out will not cause the car to ‘drift’. It will cause a fair amount of ‘lift-off oversteer’ when close to the limit but you won’t feel any noticeable unusual behaviour when driving sensibly.

Good luck
Ian

[JohnFol]

Progress. Took it to another tyre place who confirmed tracking is way out. Also confirmed one of the (new) bushes in the cross member is/has failed. Also confirmed slight flex in cross member.

If anyone is interested I took a quick video but not sure how to post as it's 21Mb

Decided to bite the bullet and remove cross member, get it shot blasted and strengthen. What could possibly go wrong?

[peteracs]

Hi John

Post the vid on YouTube and link to it here.

Glad you have had your thoughts confirmed. I am guessing that it is one of the rear arms which are a sort of U shaped one which do look quite fragile compared to the earlier tubular ones?

Hopefully they will sort you out and get it to the point of driving ok.

Peter

[JohnFol]

https://youtu.be/a_V3CAKxOxo

2 things to look for.

1) back right arm movement
2) cross member rocking

Hoping a refit / new bush solves 1) and unsure about 2) until I remove it