Having trouble going straight

[julianm]

I did a couple of hundred miles over the weekend - the first time I took the car out on a motorway - and it was great apart from that the bloody thing wouldn't go straight! I constantly had to adjust the steering as the car would move left and right. I imagine this has been the case since I bought the car, but now it has become quite obvious at motorway speeds.

Has anyone else had that? Any ideas for the most likely cause?

 

[pauljmcnulty]

944s are very sensitive to alignment, when did it last have a proper set-up? Tyre pressures all ok? Are they standard wheels?

Could be wear in the steering or suspension as well.

 

[DivineE]

As above but just to add that the Limited Slip Diff (if you have one) can 'apparently' do this when it begins to wear. I've not experienced it myself but would 'guess' it's due to the clutch plates inside the diff slipping slightly and then gripping again causing it to pull in the direction of the wheel with most drive for a moment. You can get them re-furbished if this is the case. I'm sure there are many but Hartech are the one I know of.

 

[homesea]

Do you have 17" or bigger wheels? If so check the condition of the rear bush on the front wishbones. If this is worn you will get the shopping trolley experience.
Try replacing them with the 968 part.

 

[mik_ok]

Sounds like tramlining?

Link to my experience - which may be of help?


(edit to note that I see SuperMarv is viewing this thread at this point in time - hopefully he didn't notice I Barry'd my link 1st time round..... private joke [] ) []

 

[julianm]

OKay, I forgot to mention anything about the car. It's an '83 944 with brand new Toyo T1Rs on the standard 15" wheels.

I don't know when it has had proper wheel alignment last, but I thought that can't have such a significant effect. Went to the garage yesterday and the guys had a quick look - suspension looks OK, but there seems to be slight play in the steering rod knuckles. (Apparently the bottom one is close to the exhaust and the heat can cause oil to evaporate and lead to wear.) Not sure if that's the only thing that's loose though!

One questions that Google can't help me with - what's a castor mount?!

 

[zcacogp]

Julian,

944's are very sensitive to geometry. If you have play in the steering knuckle mounts then I'll bet you have found the problem. Not difficult or expensive to change, but get a full geo afterwards and you'll struggle to believe it's the same car.

Castor mount is the rearmost mount of the front wishbone. 944's had squishy ones with lots of rubber in them, which gets even squishier over time as the rubber perishes. 968's had ones with much less rubber in them, and are retrofittable. Cost the thick end of £100 but worth every single penny. They have been discussed on here a couple of times in the last week so search is your friend.

Is it me or have there been a lot of threads about geometry and castor mounts recently? Worth someone writing an FAQ? Sorry McNulters, what was that cough? Are you suggesting that I should do it? Typical. 944 register secretary for PCGB and he gets other people to do his dirty work for him ... [:'(] (I haven't the foggiest what the agreed meaning of that smiley is but I like the colour of it.)


Oli.

 

[edh]

I would put money on the alignment - maybe the wheels are toeing out? My first 924S drove like that when I picked it up.

The rear mount on the lower suspension arm is the caster mount - it allows for some adjustment where it bolts to the body. This has the effect of increasing / decreasing caster, and will also affect your other suspension settings. The original mounts had large rubber bushes - these can wear over time & can get very loose. The later (968) style mounts were better.

 

[Diver944]

I don't now much about the eraly cars on steel wishbones like yours but I'm pretty certain you can't fit the 968 caster mount to those models (someone else can help e out here if I'm wrong)

A proper 4 wheel geometry alignment is king with these cars. Everything is adjustable caster, camber and toe angle unlike most mainstream cars which can only adjust the toe angle. Unfortunately hitting a kerb or pothole heavily can quickly drag the alignment out of place and we all know what our roads are like []

If anyone is keen to get the best out of the fantastic handling of these cars you really need to get a proper alignment every year.

 

[graham.webb]

My S2 wandered a bit when I first got it....my indie suggested that the steering column UJ had too much play. Replaced that and it was greatly improved...about £70 as I recall. It sits next to the exhaust manifold so leads a hard life and the heat causes the rubber to degrade, apparently.

A further improvement gained when other bushes were replaced...perhaps confirms comments above about bushing in general. I haven't had my geometry checked yet but I bet that improves things too.

 

[julianm]

Thanks guys. I will replace the steering rod and get the wheels aligned and see if that sorts it. Will report back

 

[mik_ok]

Alignment does tracking only.

You really want them to look at tracking, camber & castor. Should be approx 1hr labour at your local friendly Indie to set all these.

(edit - that was for front end only - 4wheel alignment will obviously take longer / cost more).

 

[Super_Marv]

(edit to note that I see SuperMarv is viewing this thread at this point in time - hopefully he didn't notice I Barry'd my link 1st time round..... private joke [] ) []

Damn - I missed that opportunity!

I agree with what you wrote in your original post - IME tired dampers, old tyres and poor geometry can all individually lead to tramlining.

 

[zcacogp]

ORIGINAL: mik_ok

Alignment does tracking only.

You really want them to look at tracking, camber & castor. Should be approx 1hr labour at your local friendly Indie to set all these.

(edit - that was for front end only - 4wheel alignment will obviously take longer / cost more).

Actually, full geo is not something done by many indies, unless they are big ones which have invested heavily in kit: a full geo needs some moderately specialist stuff, which doesn't come cheap.

I'd be taking it to a known chassis specialist, preferably one which is known to be good with (or at least has experience with) 944's. (Which is what I know my local Indie does - subcontracts the work to a local place and charges a small premium on top.)


Oli.

 

[julianm]

Well, happy to say that the guys at Tower Porsche changed the rod and did alignment and it's all fixed now. Only downside is that I don't know if it was the rod or the alignment!

 

[zcacogp]

Jon at Tower doesn't do alignment himself. He subs it out, but always refuses to tell me where to ... !

Glad that all is well now. Tower is good.


Oli.