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Wednesday, February 06, 2008

Sprung

Front spring specs from the factory data book
Click on the image to enlarge it

In this part of my suspension “mini-series” a few words concerning springs.

First, naturally enough the front. The table here shows a range of six different specifications and a couple of observations are worth making. First notice that the Fanalone had the same front spring fitted as the SI 1200 and 1300, 1300S and 1300 Sports. Second, notice the special spring fitted only to 1200 and 1300HFs (818-140 and 340). This spring is flatter and softer than any of the others, so if you have one of these, my advice is don’t break it, as they are hardly likely to be found in your local breaker’s yard!

Not much to add about the front spring: after all they are a pain to change and as the list shows, practical choice is limited. If you do want to change one, take the greatest care as they are installed with considerable pre-load and are perfectly capable of taking your arm off. You have been warned!

Rear spring specs from the factory data book
Click on the image to enlarge it

Turning to the rear, there are just five types. This time the Fanalone shares only with the SI 1200 and 1300 Zagatos (Sports) – the 1200 Zagato 818-132 gets mentioned here – and once again the early HFs have the flattest and softest springs, reflecting no doubt the reduced weight of these types.

Rear springs do corrode badly: this tendency is not helped by the plastic interleaving fitted. I have frequently rebuilt rear springs and since the plastic is usually shredded – and even if it isn’t – I discard it. I remove all the rust and if I had an industrial polishing machine I would polish all the leaves too, just like old Bugattis and Grand Prix cars. I then apply grease and Waxoyl. The simple buckle clamps (two per spring) I fix very tightly and weld up afterwards, this keeps the spring aligned and in good order.

For those who wish to lower the rear there are two approaches. First one can invert one of the leaves, usually the third counting from the bottom. Alternatively an additional leaf – a third or longer fourth - may be added at the top again inverted, which has the effect of both lowering and stiffening the rear. To do this you will need a longer centre clamp bolt, but a 6mm cap screw works perfectly.

Finally, Fulvia springs do sag and sometimes break (as do front ones sometimes). Some of the modern spring makers’ ideas of replacements are frankly laughable. I once was given an SII sedan fitted with replacement rear springs. Instead of six thin leaves they had four thick ones. The car’s ride was very hard on my liver and of course on the chassis too!

À bientôt

8 comments:

William said...

If I study the tabel for the front spring I do see 818-132 (1200 Sport) mentioned in the same box as the 1300 sport. A question regarding 'free'lenght. Have you ever had a leafspring on your workbench were the 'free' height came near to the data tabel? The springs I have measured came close to 18cm instead of about 13 to 14cm. And they were coming from a 40 yera old car wich stood probably lower than when it was new. I doubt the data in the table very much.
Regarding the softer 1200 and 1300HF front springs and to be carefull with them. All springs sag over time. Wich means they get softer (weaker). Old normal coupé springs might become 1200HF spec over time!
The works method of lowering the rear I never understood. You claim like the works that the spring gets lower and stiffer. I think it becomes lower and softer. the inverted leaf is completely deformed against its natural curved shape. This means it tries very hard to get its shape back. Thus trying to flatten the other leafs. Just when the car is pushed in its springs the inverted leaf can relax. I hope my non native english tonque is not causing confusion here.
I have done this 'works' mod on my car and the car is lower but most definately softer. I wonder how things went back then with a full 80 litre tank, a spare and a big tool kit in the back!

Paul said...

Thanks again William for taking the time to comment. I must have been rather pre-occupied when I wrote this little piece: I have corrected the error. I found the inverted leaf worked very well on my car but I used a seventh leaf. I have not tried the other mod as described in Carlo Stella's book. If it makes the car softer then the full tank (90 litres I thought) and all the rest would be most wheelspin-inducing!

William said...

Never thought of it but my car has a lot of wheelspin. In the wet I can spin the wheels till third gear and its only a 1200! Can that be caused by weak rear springs?

Paul said...

Very much so William, especially if the back is low. It's a question of weight transfer. Stiffer rear springs will resist transfer better.

skywalker said...

Hi Paul,

Any comments on bump stops at rear?

I think fanalone had differnt shape with spacer blocks?

My car sits low at the rear to such an extent that rear tyres can rub bodywork - 185/70R13's fitted. Weak springs?

Paul said...

Hello Skywalker, which Fulvia do you have - a Fanalone?

If as I suspect you do, then I would say that you do have a rear spring problem as I wrote, they do sag. Another possibility is a broken leaf, I once had this on one of my cars. When at Evo Engineering, I did fix this sort of problem for somebody: I simply added an extra leaf, a cheap and "dirty" solution

Anonymous said...

Thanks Paul,

Mine is fast road/race 1600 and sits at a lowish height at rear anyway. But even on both sides. What would be the effect of taller bump stops?

Wouldn't evenness imply either just weak springs or both sides having broken leaves? Where in UK do you recommend or is it better to order a set of std ones from the likes of cavalito?

Best

Luke Skywalker

Paul said...

Changing the bump stops will only affect the behaviour in bump: it will not change the overall characteristics.

I would either rebuild the springs, perhaps using an extra leaf, or I would buy from Cavalitto - I have yet to see a good English spring!

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