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Old 18-02-2018   #1
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128 front suspension variants

Hi there, strange long winded question coming up regarding 128 variants.

My 128 sedan is a mongrel of Uno Turbo, X19, Tipo, Strada and 128...

I have Strada 105TC front hub carriers (steering knuckle) on my 128 which are part number 7535184 (one side) this is so I can have the big bearings in the hub for equal length driveshafts. This hub carrier is the exact same one as used on 'modern' 128's from 1979 onward. I've also got the front arms from a Strada which have the bigger bolt hole to attach to the chassis but so far as I can see are the same otherwise.

What I want to know is...

What other differences are there (if any) that anyone knows of, to accept the 7535184 hub carrier on the 128 chassis? Does anyone know if the mounting points changed? Or if the steering rack is different (along with a change of tierods). Or wheel alignment different?

Reason for asking is...

I have found my inside wheel turns further than it needs to and tends to 'skip' a bit, plus the car is a little more understeery too which I want gone. Let me know if you know. Thanks!
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Last edited by myte128; 18-02-2018 at 02:16. Reason: Adding tags
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Old 18-02-2018   #2
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Re: 128 front suspension variants

Did you change front hub carriers on both sides or just one side?
If just one side, can you measure the steering arm length?

As you probably already know, the inside wheel always turn through a greater steering angle in order to avoid tyre scrubbing (check out Ackerman angle if you want more info in this), so I'm assuming that this inner wheel steering angle is now excessive?

Can you check if steering rack is centralised? i.e. with steering wheel set straight ahead, have you got equal amount of turning left and right?

If rack isn't centralised, you'll have unequal length track rods lengths in order to get the tracking set correct in the wheel straight ahead position but on turns you'll get more steering lock in one direction (left or right) which might be the problem you're now experiencing. The cure would be to centralise the rack, reposition steering wheel on splines to straight ahead, then set track rod lengths to get the correct toe-out figure.

Can you check 'toe-out on turns' ?

Idt a different steering rack would make any difference to your problem.

Re - understeer on a 128. These cars tended to sit up in the air a bit and iirc correctly ran with positive camber on the front. I sometimes elongated the upper hole in the strut to hub carrier attachment in order to get some negative camber. This helped a lot with turn-in/understeer but easy does it if choosing this option, a little filing on this hole has a big effect on camber - first time I did this , I ended up with iirc 6 degrees of negative camber!!! So take it easy with the file or rotary burr etc. !

AL.
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Last edited by F123C; 18-02-2018 at 10:04.
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Old 19-02-2018   #3
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Re: 128 front suspension variants

Thanks for the reply Al. They were all good points. Answers below.

Both carriers changed, On full lock (both ways)there is a metal on metal graunch noise from the inside wheel area and I suspect it is the cv joint getting turned beyond it's capabilities.
Yes, ackerman looks to be out of whack because the arms are longer and in towards the middle of the car more. Hence the request for further info on whether other things were done to the chassis perhaps.
steering rack removed and rejuvenated, centralised and wheel alignment done 1mm toe in each side(at home, I'm yet to get to the man).
I have coilovers and adjustable camber plates, sitting at around -1.6degrees.
There's not a lot left standard on this car and this is my one area of concern.
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Old 19-02-2018   #4
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Re: 128 front suspension variants

CV joint - yes, might be being swivelled too much. If you feel like removing the cv boot ( Yeah, I know, not my favourite job either!) you might find contact marks on the driveshaft where it's catching on the inside of the cv body.

Another thing to watch out for if you change the hub carriers but not the track control arms (bottom suspension arms) is the cv joint being incorrectly positioned in relation to the steering swivel points.
If you imagine a line dropped vertically from the centre of the top strut mounting down through the centre of the bottom balljoint, this line should pass through the centre of the cv inner lobe body on the driveshaft. (hard to check!)

But it's certainly possible for the cv joint to be turned too far if the steering arms are longer (potentially more steering lock/angle).

Can you do a rough check at home of the amount of steering lock you're getting at the moment. E.g. make a mark on the ground with the wheel pointing straight ahead, then make another mark with the wheel at full lock, roll car back and try to measure the angle with whatever you have to hand. (Idk what equipment you have available? but even a cheap protractor would do, or you could use trigonometry if you know this?).

My suspicion is that the longer steering arms on the different hub carriers are turning the wheels too far, causing the inside wheel to turn too far and possibly also causing the cv joint to be turned through too great an angle resulting in the noise you mention.

Longer steering arms are good as they give you slightly? quicker steering at the expense of a slightly? heavier feel. But they also mean that the track rods from the steering rack are now operating at a different angle to the rack and are moving through a slightly bigger arc. I suppose, ideally the steering rack should be moved back by the same amount that the new steering arms are longer than the originals but I'm probably just splitting hairs here. There's usually plenty of reserve swivel movement built into the track rods inner joints (under the steering rack boots).

But it might be worth limiting the amount of steering lock now available to prevent cv joint problems and possible wheel fouling. Some cars have lock limiters somewhere on the hub carrier, some others have it built into the steering rack. You might be able to incorporate something here or add to whatever is present?

Wheel alignment - 'Tracking'. It's a long time since I worked on a 128, but I seem to recall that the front tracking was set 'toed-out' rather than toe-in.
Also that there was some strange procedure to be followed before checking/setting to the factory figures - certain weights to be in the car in LF,RF and rear. I.e. the factory figures weren't for the car unladen (as nearly all other car figures are usually for). Iirc, in the Fiat Dealership I worked for, we used to set the front tracking unladen at approx 1.0 - 1.5mm toed-out?

The thinking at the time was that the front wheels on a fwd would tend to toe-in when power was applied to pull the car forward, so were set to toe-out statically, on rwd cars the front wheels would tend to toe-out as they were pushed forward so they were set to toe-in.

Wheel camber? 1.6 degrees negative? Sounds like quite a lot, how does it drive like this, any problems with straight line stability/wander? Just curious.

AL.
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Old 20-02-2018   #5
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Re: 128 front suspension variants

I can certainly give the measurements a try on the garage floor however my eye-crometre has measured it as being out of whack.

I used to have toe out but torque steer was a bit, shall we say... wild. So I stuck it on no toe and it calmed down a bit. I changed to equal length driveshafts and different carriers and found I needed toe in to try and align the wheels whilst turning. I am seriously thinking about limiting the steering but the turning circle is pretty bad already.

Steering arms; I would have thought a longer arm on the carrier will give you slower steering as it needs to turn through a longer radius. And less heavy steering because more leverage...

-1.6 camber is ok, steering is a little vague just off centre but strong self centering in a bend. I thought I should try and get some more caster but I have run out of adjustment on the sway bar.
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Old 20-02-2018   #6
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Re: 128 front suspension variants

Re:- The effects of longer steering arms.

Apology Time.... Yes, you're quite right that longer steering arms give slower and lighter steering. (my bad, I was thinking of the effect of a longer Pitman arm on a steering box!...). So maybe disregard my suggestion to reduce steering lock until you've been able to measure it!

Re:- Increasing Caster angle. Is there any adjustment for Caster on the Camber adjustment plate? (which I assume is at the strut top mounting?) Or else you might gring back the step on the sway bar to allow the track control arm to move further forward to increase the Caster to more positive, but I'm not sure how much the TCA can swivel on it's inner mounting bush?. If you have wider wheels/tyres fitted, there's already quite a lot of self-aligning torque from the tyres alone, this increases with rim negative offset (i.e. outboard from the hub mounting face). Maybe actually decreasing the Caster angle might help? (Easy enough to try out temporarily, just slot some washers, loosen the sway bar to TCA mounting, pull the TCA rearwards and pop the washers in).

I remember the 128 had a tendency to lift at the front/squat at the rear under acceleration, particularly noticeable, for some reason, on the later 128. (which was sold over here as the 128 Nuevo? Nova?circa 1976> and had plastic bumpers instead of chrome bumpers). When the front lifts, the wheels drop, camber tends to go towards positive, tracking can change and grip is reduced. It's hard to prevent this lift but maybe you can stiffen the rear spring rate to reduce squat.

AL.
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Last edited by F123C; 21-02-2018 at 00:55.
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Old 21-02-2018   #7
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Re: 128 front suspension variants

I think i'll get the alignment done properly and check the caster before I get carried away with grinding the sway bar... No adjustment in the top plates, just camber.

3 leaf spring in the back already and the coilovers at the front are very stiff so there's not a lot of droop.

After all of this good talk I'm still none the wiser on how these hub carrier upright things are on the more modern 128's, unless of course my alignment is way out of whack. I have new bushes for the back so I'll stick them in and get the alignment done. I shall come back with findings.
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