1600hf rear axle

[spyder]

I thought some of you more experienced Fulvia fanatics may know the answer to this one

Is the rear Axle in a 1600HF different to a 1.3 Axle?

I know the 1600HF has negative camber wishbones on the front, but is there any difference in the rear of the car?

Any answers greatly appreciated

Regards

[ncundy]

On S2's the axles are the same, on S1's there are 4 different part numbers but the only difference I have ever seen and am aware about is that the 1.6 HF axles (don't think it was fitted to the others) had aluminium end castings saving something like 5.5 kg.

Geometrically they are all the same.

[1,6 HF]

My understand's essentially the same as Neil's--the geometry's the same regardless of series or part number.

[Old Man Wattsy]

On S2's the axles are the same, on S1's there are 4 different part numbers but the only difference I have ever seen and am aware about is that the 1.6 HF axles (don't think it was fitted to the others) had aluminium end castings saving something like 5.5 kg.
Is this why some 1.6HF axles have '818.540' painted on them to ensure the correct axle is on the car?

[ncundy]

Probably, although they also have a serial number plate - and a magnet gives the game away :)

[1,6 HF]

Is this why some 1.6HF axles have '818.540' painted on them to ensure the correct axle is on the car?

I'd say that's right. A number of components that looked otherwise identical had type numbers stencilled on to reduce confusion on the factory floor. My car still has a faint "818.540" stencil on the left-side rear leaf spring.

[spyder]

Thank you for the information Guys

You always come up trumps!

[riczag]

The HF has a wider rear track than the 1300s (1355mm cf 1280mm).
I think that most or even all of this accounted for in the different wheel design (which is further offset) but if it is not all accounted for in the wheel design, then there would be some slight difference in axle length.

[spyder]

Thanks Riczag

So excluding the 14" Chromodora`s, would you know how many millmetres difference there would be in the length between 1600 & 1300 Series 2 Axles?

[lancialulu]

Do you mean wider (ultimate pedant!)?

If S2 1600HF then I dont think so. The Tav55 does not identify a different axle or hub.

Tim

[1,6 HF]

The HF has a wider rear track than the 1300s (1355mm cf 1280mm).
I think that most or even all of this accounted for in the different wheel design (which is further offset) but if it is not all accounted for in the wheel design, then there would be some slight difference in axle length.

This is interesting theoretical speculation, but the length of the axle itself is the same.

[riczag]

Tim

I understand the point you make about part numbers, but the fact remains that the rear track of the S2 HF is some 75 mm wider than the 1.3S2.

75 mm is just under 3 inches (to be precise some 2.9528 inches). The question is how is this extra track width obtained? There are only three ways of increasing the track, viz a wider (longer length) axle, the same axle but with a spacer fitted between hub and wheeel, or a wheel with wider off-set. We know that there is no spacer and therefore the wider track has been achieved by either a wider (ie., longer length) axle or by the 6 inch cromodoras having a greater off-set than the 4 1/2 inch steel wheels.

I no longer have any S2 steel wheels and therefore cannot measure the off-set (ie., the distance between the inner edge of the plate that abuts the disc cum drum hub) and the ouuter rim. If it was not so cold, I would measure the off-set of the 6 inch cromodora.

Without doing any measurement, I am somewhat sceptical that the off-set of the 6 inch cromodora is almost 1 1/2 inches more (ie., half of the extra 2.9528 inches from wheel to wheel), although co-incidentally this is nearly all the extra width size of the two rims. It would mean that the entire extra width was in off-set.

Further the front track of the S2 HF is 1390 mm whereas that of the 1.3S2 is 1300 mm. This is a difference of 90mm or 3.5433 inches. If one speculates that the entire extra track at the rear (ie., 75mm) is due to the off-set of the 6 inch cromodoras, this means that 75 mm of the extra front track must be accounted for by the wheels such that the chasis change at the from end is just 15mm (ie., 90mm - 75mm). This would mean that (in the absence of a spacer at the gear box or different front hub design or simply packing out the spline into the front hub) the S2HF's drive shafts would be 7.5mm longer (being half of the 15mmm difference) than the 1.3S2's drive shafts. Does anyone know the difference in length between the drive shafts on the two models?

[lancialulu]

The front track of HfvCoupe is tricky to unpick with neg camber wishbones being of different length.
The rear axle absolutely the same - see Tav 49A for coupe HF Sport the axle part number 1304917 is same as Tav 55.

My HF literature indicates the rear track for an HF with Chromadoras is 1335mm not 1355 as per UK driver handbook.

The hand book has a few oddities and I would suspect 1335 is the more accurate and would support the difference of 2 x the difference of 6J-4.5J wheels. We know that Chromdoras have clearance issues with ordinary coupe bodies....

Tim

[ncundy]

The increase in rear track is 55 (not 75mm ?), the offset on my wheels is about 54mm (edited to say 24mm - all fingers and thumbs :) ) . I'm sure standard ones are substantially less - hence going to 13" wheels. The "book" says the dimension across the outside faces of the axle is 1246mm - if you've got a spare 1600 measure and compare. The toe in is different; but that is because of the 13" wheels.

As Tim says the additional increase at the from comes form the -ve camber, but that makes no difference to driveshaft length as the centre point hardly changes.

[Old Man Wattsy]

The rear track width difference is all in the offset and not in the axle length as can be shown by using the ET (offset) from www.alma.it (http://www.alma.it).
Series 2 4.5"x J14" steel wheels have an ET of 50.5mm
Series 2 6"x J14" Cromodora wheels have an ET of 23mm.
Twice the difference in ET is 55mm which is the same as Neil etc have quoted.

[Old Man Wattsy]

Tim
I no longer have any S2 steel wheels and therefore cannot measure the off-set (ie., the distance between the inner edge of the plate that abuts the disc cum drum hub) and the ouuter rim.

Not quite. The ET (offset) is measured from the hub mounting surface to the centreline of the wheel as shown in this diagram:
3661

[riczag]

Not quite. The ET (offset) is measured from the hub mounting surface to the centreline of the wheel as shown in this diagram:
3661

Whilst I am not 100% certain on this point, I am not sure that I agree with you. If you imagine, the wheel centre (ie., the part of the wheel where the wheel studs are) running along the centre line, the wheel would have greater off-set in the sense that the track of the car would be increased and yet on your measurement, it would have zero off-set (since it is running along the centre line in your diagram). Now imagine the centre of the wheel being positioned even further left of the centre line (perhaps almost upon the second from left line), the track of the car would be widened even more (and on your version, it would have negative off-set which is presumable classed in-set). I therefore consider that a more representative description of off-set is the distance between wheel centre (the part that abuts the hub) and the outter rim (the second most right hand line)

[riczag]

Neil

I can quite accept that there may be an error in the UK handbook (and I have not sought to cross reference elsewhere) and that the increase in track may be only 55mm.
I do not know whether there are any slight differences between the design of the 13 and 14 inch wheels, but we are talking about the 14 inch wheel fitted to the S2HF rather than the 13 inch wheel fitted to the S1.
If Wattsy is right that the wheel centre on the Cromodoras is some 27.5mm further inwards towards the centre line of the wheel (when compared to the 4 1/2 steel wheels) then the additional track width of 55 mm is all explained by the design of the Cromodora wheels.

[1,6 HF]

...
If Wattsy is right that the wheel centre on the Cromodoras is some 27.5mm further inwards towards the centre line of the wheel (when compared to the 4 1/2 steel wheels) then the additional track width of 55 mm is all explained by the design of the Cromodora wheels.

...which would make sense, given that the axles are all the same length.

[DJ]

...I therefore consider that a more representative description of off-set is the distance between wheel centre (the part that abuts the hub) and the outter rim (the second most right hand line)

While I know essentially nothing about Fulvias, I have done a lot of research on wheels and can say that Wattsy's description of offset is correct. Standard offset as specified by manufacturers is the measurement from the center (hub) face to the wheel center line.

[1,6 HF]

While I know essentially nothing about Fulvias, I have done a lot of research on wheels and can say that Wattsy's description of offset is correct. Standard offset as specified by manufacturers is the measurement from the center (hub) face to the wheel center line.

That's exactly right. Offset is the dimension that the centerline of the wheel is offset from the hub face. If the wheel centerline is inboard of the hub, that's negative offset; if the wheel centerline is offset outboard, it's positive offset.

And we're dealing with Fulvias, here. Generally, with FWD you want negative offset because of its effects on scrub radius. Negative scrub radius is more stable, and moving negative with the wheel offset is the same as moving negative on the scrub radius.

[Fulvia-hf]

Hi Neale,
A slightly late reply to your earlier remark concerning rear axle material specs. Many S1 Fulvias not being fanalones had the cast alloy Hub carriers. To my knowledge all 1st series exept saloons and normal 1200 cc coupes and 1200cc zagatos could be found with alloy ends. Definately all Hfs (1200, 1300 and 1600 )had alloy castings and all 1300 S1 Zagatos. Few normal coupes had them. the weight saving is remarkable but the corrosion resistance is not. The flat surface were the leafsprings rest on can crumble away to nothing as I have seen many times on north european Fulvias.

[ncundy]

Yes, I didn't know that but I recently got hold of a 1.3S axle with alloy ends :)

You live and learn!

I haven't seen the top corroded but I have seen one a few years back where corrosion had caused the end itself to split where the beam axle sits inside it.

[Fulvia-hf]

That still does not explain the different partnumbers in the partsbook. I know of several people who fitted non fanalone steel/alloy mixed axles without ill effect.
I know all non fanalone axles with alloy ends have partnumber 818.140 indicating they were first used on the 1200Hf. Same story as the 1300 cilinderhead which has casting 818.140.