S Type to series 3 rear suspension?

[malky1965]

Hi, I need a rear IRS for a series 3 and I have got the chance of a 1966 3.8 S Type which I know is a 54cm track width the same as a series 3 but apart from diff ratios does anyone know if driveshafts, wishbones, radius arms, calipers and cage are the same.
Thanks
Malcolm

[PeterCrespin]

Not the cage as it has different fittings (no compensator linkage etc) but it could be adapted.

If the track is the same I'd guess the main bits are, but the calipers may not be. 68 could be around the time they switched to the Girling one piece used on the S2/S3 though. I have a complete earlier S-type IRS in the barn which I think has Dunlop separate piston rear calipers. It is intended for a Realm D-type some time so if anyone wants to shoot Series 3 measurements at me I can see if the S-type parts are the same. It's not particularly something I'd want to drag all the way to the USA so if someone wants to pay me what it cost for the whole LSD rear assembly plus vented disc front suspension lumps then you can collect it all.

Pete

[vee12eman]

Hi Pete, Malcolm,

I can't help with actual knowledge of the S type/ E-type suspension differences, however, I have just dropped the Suspension of my Early Series III (again!) so it is currently on the floor and I can take measurements as Pete has suggested - thing is Pete, I don't know which measurements you need. If you let me know what to measure, I can do it; I presume you mean mounting points, but are there any other measurements you need for accurate comparison?

Let me know, the suspension should be on the floor until Sunday at least, but I will put it back as soon as I can 'cos I want to go out and drive it again!

Regards,

[malky1965]

Hi Simon & Pete, Thanks for your reply, I would presume the most important measurements would be the length of the wishbone and the length of the driveshaft, some close up pictures would be helpfull to compare S Type to E Type S3

My email is malky1965@aol.com for anyone who has close up pictures of either IRS

Many thanks
Malcolm

[MarekH]

Dear Malcolm,
If you can take some pictures of your s type setup, then you can use a photoshop type product to superimpose them onto my s3 pics which can be found at
http://www.jag-lovers.org/snaps/snap_vi ... 1287747435

That should give you an idea about the cage width/fit.

kind regards
Marek

[PeterCrespin]

I don't think cage width is an issue for an S3/S-type comparison (famous last words). I think wishbones/halfshafts, as described. No need to dig down into the IRS to measure the halfshafts as they will follow the wishbones to preserve parallelism. I will measure the easyily accessed wishbone tube by hooking the tape over the inboard end where the forging ends close to the disc and reading at the edge where the tube disappears into the outer fulcrum forging.

Additionally, I will run the tape along the flat top of the cage just to clarify that is the same. Should get a chance this weekend but if I forget, nudge me.

Pete

[malky1965]

I have found this link with an exploded view of all the parts but im not good with photoshop type software but maybe the sizes could be superimposed on to the parts to show exactly where points were measured from if anyone has that knowlege,

Thanks for your time and help Pete,


http://xkedata.com/pdf/irs.pdf

[vee12eman]

Hi Again,

Here are some measurements:

From mounting point to mounting point, across the car (the studs which protrude downwards from the cage mount rubbers; 883mm or 34 1/2 inches.

The length of the wishbone central main tube (not including the "C" shaped ends which link to the cage at one end and the upright at the other); 343mm or 13 1/2 inches.

Measuring from the centre of the diff input, diagonally to the wheel flanges; LH side is 705mm (29 1/2 inches); RH side; 700mm 27 1/2 inches).

Across the flat portion of the cage ( front edge) is 800mm (31 1/2 inches) and the handbrake is central on the front face.

All measurements are taken with a simple tape measure so are not precisely accurate but are as close as I could manage.

Hope this helps, if you need more measurements ask quickly as the unit will be going back on very soon.

Regards,

[malky1965]

Hi Simon, Thanks for the measurments, we shall compare them when Peter has got time to measure the S Type Axle he has,

Thanks
Malk

[PeterCrespin]

Here are the S-type numbers next to Simon's, as far as I was able to interpret them:

"From mounting point to mounting point, across the car (the studs which protrude downwards from the cage mount rubbers; 883mm or 34 1/2 inches."

My cage still has the rubbers attached so I measured from stud/nut to stud/nut on the forward pair but got 960 mm. I assume we were measuring the same thing but that's a big difference. Probably reflects the wider-spaced chassis rails on the saloon?

"The length of the wishbone central main tube (not including the "C" shaped ends which link to the cage at one end and the upright at the other); 343mm or 13 1/2 inches."

The S-type ones were identical at 343 mm, allowing for rust. Ergo, the half shafts will be the same as the S3 too.

"Measuring from the centre of the diff input, diagonally to the wheel flanges; LH side is 705mm (29 1/2 inches); RH side; 700mm 27 1/2 inches)."

This is a very odd measurement to do since the flanges are about 10mm thick (measured to front ot rear edge?) and the diff input shaft centreline is hard to measure in a straight line from the hubs because the tap
e or ruler ends up 10-15 mm in front of the shaft if one is to avoid a bent tape. Moreover, the diff input is deliberately off-centre by much more than 5 mm surely? My measurements (remember the wishbones are the same) were 740 LH / 705 RH. Actually, looking at Simon's numbers there IS something worng as his Imperial and metric numbers don't compute, although I haven't done the maths.

"Across the flat portion of the cage ( front edge) is 800mm (31 1/2 inches) and the handbrake is central on the front face."

The S-type cage was 830 mm measured across the rear face at the top where the flat upper surface adjoins. The corners are somewhat rounded in the vertical plane, making precise edge definition suspect, but there seems to be too big a difference for it to be measuring error. However, if the cage upper rear is only 30 mm wider, how come the front monut attachments are the best part of 80 mm further apart? Maybe I should have measured the rear pair of Metaliastik mount studs, but the way the IRS is stacked aakes that tricky.

So the diff will be the same size, as will the halfshafts and wishbones, but the cage for an E-type seems narrower as well as having different handbrake mounts. I do have a SWB cage lying in another place so I will measure the same mount and face distances, just ot satisfy myself and remove all doubt, as I assume all E-type cages are the same width.

Pete

[vee12eman]

Hi again,

I will check my measurements once again, they were taken late at night with me lying on my back in some cases. I agree that some of the measurements were likely to be innaccurate, due to curvature etc and yes, the diagonal measurement is an odd one to take, but it seemed likely that this would be a good way to cross reference the two units. Perhaps I will be able to take a photo and illustrate exactly where I am taking measurements from. For reference, I measured as best I could, trom the outer face of the flange to the centre of the diff input shaft, understanding this would be innaccurate as the tape measure would really have to bend to accomodate this, but knowing that this would be the same for anyone comparing measurements (also, diagonals are a very good way of checking not only linear measurements, but overall geometry). It seems unlikely the two units would differ only by a few mm, especially given Lyons' propensity to use common parts wherever possible, this was just a way of confirming the basic similarity (or otherwise) of the units' geometry.

Futher, I apologise that I made a typo; I think the left diagonal measurement from flange to diff nut centre should be 750mm, not 705mm, the imperial figures were correctly typed. Again, I will check this when the unit is in front of me.

I will check again when I get back home later today and see if I have made any glaring errors - could you suggest any other measurements I could take to help further? You'll need to let me know fairly quickly - the IRS is still on the floor but should definitely go back in over the weekend as all the work on it is now complete.

Regards,

[PeterCrespin]

Not suggesting any error other than a typo, because a 2 inch difference doesn't correspond to a 5 mm difference. 50 mm would be right, as you suggest.

The wishbone measure confirms the 'guts' of the IRS from an S-type will transfer to a Series 3 E-type cage. Once the wishbones/half shafts are confirmed identical - which we have done - the diff is known to be the same for all so that's all we need for the mechanical bits IMHO.

The cage would make sense to be model-specific, since although LWB and SWB E-types have the same chassis rail spacing, there's no reason any other model would. Once you alter the chassis rails, you'd expect the cage would alter to suit.

[malky1965]

Hi Peter / Simon,

I really appreciate the two of you going to the trouble to take and cross refference measurements for me, as I said I can get an S Type rear Axle at a reasonable price but if I was to mention E Type the price would jump considerably and thats if I could find one,

Once again
many thanks

Malcolm