Cortina Based Rear Suspension

[Guest steveyb]

Hi all, just bought a Cortina based RH rolling chassis, bit tatty but mostly complete including log book, but minus engine&box.

Front and rear suspension and steering fitted is original Cortina.

Intend putting in a 2.0 ltr Sierra donor engine&box, which I already have.

 

When jacking up the rear end to strip/clean & renew bushes etc the springs fell out of top locator (an inverted and lipped square metal tray secured with four bolts to floor).

Not having a build manual I'm a bit puzzled about this set up to say the least and am assuming it's not meant to be like this.

 

The shocks are 12" closed and 20" open (centre to centre).

The springs are 12" overall length. (rating not known).

The top of shock mounting holes are spaced 21" approx apart in the underfloor rail (10 1/4" approx inboard from each rear end of mounting rail).

 

Would be very grateful for any info on these Cortina based RHs, especially any shorter shock types were tried that cured the spring drop out problem.

Also has anyone with a Cortina rear axle based RH changed the rear to coil over shocks, if so what was involved (shock rail looks a bit lightweight) and is a Panhard rod needed?

Regards Steve

Edited November 2, 2009 by SteveyB

[agent_zed]

Hi,

i've seen it written on here that a strap should be fitted to stop the axle falling too far and allowing the springs to fall out, but thats just what ive picked up on here. Even with the seirra wishbones it was suggested that when using coil overs that straps are used to stop the wishbone dropping and being stopped by the shock (presumably when jumping bridges etc ) i think the use of old timing belts was suggested as a strap.

HTH

[Guest Christine]

Hi, I don't have a problem with the springs dropping on mine, I havn't any retaining straps on it ether ? I know the previous owner had trouble with axle trap and has fitted pandard rods.

Garry

[chris n]

Hi,

First off welcome to the world of all things Robin Hood

 

The rear axle set up on a Cortina Hood is the same principle as the donor vehicle.

The rear shock-absorbers are the same used on the Cortina and are angle inwards to the middle of the car.

Robin Hood did add to the set up what they called a fifth link to stop any axle wind up that bolted to the rear bulk head and then into the top of the diff casing, but as the link was bolted in to the diff casing using a track rod ball joint it too didn't last long before it pulled out or just took the top off the diff, totaling the axle.

 

 

 

 

The way round this is to fit a pair of rear links from a mk1 micra you will need to make up a pair of mount to fit to the rear bulk head and a pair to mount to the axle. the Micra links will need to be shortened by 2 inch to sit in the right place.

I have all the info somewhere on how to do this mod

 

 

The springs set up is

 

Saloon 1600

Standard

Colour code yellow/violet

wire diameter 0.44/0.56 in (11.13/14.28mm)

free length 11.9in (302.5mm)

outer diameter 5.08in (129mm)

number of coils 7.5

 

heavy duty

Colour code blue/violet

wire diameter 0.47/0.59in (12.05/15.03mm)

free length 11.5in (291.5mm)

outer diameter 5.08in (129mm)

number of coils 7.5

 

saloon 2000

Standard

 

Colour code green/violet

wire diameter 0.47/0.57 in (11.9/14.48mm)

free length 11.2in (284.4mm)

outer diameter 5.08in (129mm)

number of coils 7.5

 

heavy duty

Colour code blue/violet

wire diameter 0.47/0.59in (12.05/15.03mm)

free length 11.5in (291.5mm)

outer diameter 5.08in (129mm)

number of coils 7.5

 

 

 

 

estate models

 

Standard

Colour code pink/violet

wire diameter 0.43/0.59 in (10.90/14.92mm)

free length 12.2in (309mm)

outer diameter 5.08in (129mm)

number of coils 7.75

 

heavy duty

Colour code yellow/green

wire diameter 0.46/0.60in (11.65/15.3mm)

free length 11.9in (301mm)

outer diameter 5.08in (129mm)

number of coils 7.75

 

Sound like the springs you have are correct for the job, I have also refitted the rear anti-roll bar which Robin Hood said was not needed I find the car handles a lot better with it on.

 

If you need any more info give me a shout and I will try to help

[Guest Tim Norman]

All this talk of Cortina based S7's and rear suspension is making me feel nostalgic for BOB Does anybody know what happed to him SRB 61X ?

 

Did hear he ad gone round the "Ring" in not too slow a time.

 

Chris, to get even better handling, your rear "top arms" should be the same length as, and parallel to, the bottom arms. But that means the forward mount being in the cab. I had that set up on Bob with a panhard rod that went under the nose of the diff and an anti roll bar on the front, from a Reliant Robin. If I can get his spiritual son, Bobson, to handle the same I will be a happy man.

[Guest steveyb]

Hi Gary, Agent zed and Chris, many thanks for info so far.

 

The idea of straps holding the rear axle up seem a bit crude, are they MOT acceptable?

 

Chris, your anti tramp set up looks very interesting.

I assume you don't have a strap fitted to stop the springs falling out, if so what shocks (closed open lengths) do you have fitted and are the tops mounted as mine are @ 21" centres in the rail?

 

I mentioned the Panhard rod (top of body one side above axle along and down to end of axle other side) as being a means to stop sideways body swing under hard cornering, fitting the Cortina anti-roll bar would probably help stiffen this, I can now also see that with a lightweight body and 2 Ltr engine the anti tramp bars will also be needed when flooring the pedal, so your plans for this would be of great help.

 

In the meanwhile after re-bushing etc, I may have to reassemble and take some measurements to determine a shorter closed/open shock length, I think the shocks already fitted are Cortina and would probably have had a higher top mounting position on the original Cortina body shell and would have bottomed before the springs lost all their compression on jacking up the rear end.

Problem is most shocks are listed by application and don't usually give open/closed measurements.

Regards Steve

[chris n]

Chris, to get even better handling, your rear "top arms" should be the same length as, and parallel to, the bottom arms. But that means the forward mount being in the cab. I had that set up on Bob with a panhard rod that went under the nose of the diff and an anti roll bar on the front, from a Reliant Robin. If I can get his spiritual son, Bobson, to handle the same I will be a happy man.

 

 

Tim, your right the top arms should be the same length as the bottom arms but after many years of playing around with the set up its now a case of if its not broke don't fix it as it all seams to work well only failed me once and that was leaving the Uxbridge show a couple of years ago on the rough road when I went down a pot hole and broke the off side link, was a bit like steer from the rear after that on the drive home

 

BTW Steve I looked out my spare rear shocks and measured them

12 1/2" closed and 20" open

so yours sound like the right ones.

[Guest steveyb]

I looked out my spare rear shocks and measured them

12 1/2" closed and 20" open

so yours sound like the right ones.

 

Hi Chris

I'm assuming your springs are 12" approx too?

How do you stop the springs falling out when jacking up the rear?

Are the top of your shock centres closer together (less than 21") giving a shorter stroke?

 

Steve

[chris n]

Hi Chris

I'm assuming your springs are 12" approx too?

How do you stop the springs falling out when jacking up the rear?

Are the top of your shock centres closer together (less than 21") giving a shorter stroke?

 

Steve

 

 

Hi Steve

I have fitted a set of spring clamps to the rear spring to lengthen them this also gives thr rear of the car a better ride height,

this may stop your spring from falling out

 

 

 

Also do you have a rubber spring seat that fits to the top of the spring and sits tight in the mounting bolted to the floor?

 

Will check on the top shock mounts next time I'm down with the car and will let you know how far apart they are.

[Guest mower man]

RE spring clamps /adjusters IMHO the ones shown have no place on a car which may be driven shall we say vigourously?OK for trailer queens and creeping cruisers but not on a sports car please Hope I havent upset any one regards mowerman

[chris n]

RE spring clamps /adjusters IMHO the ones shown have no place on a car which may be driven shall we say vigourously?OK for trailer queens and creeping cruisers but not on a sports car please Hope I havent upset any one regards mowerman

 

Photo are only an example and yes you are right they are the ones for a trailer. The ones I've have are set of Grayston Coil Spring Clamp GE7 which have a double clamp holding them to the spring.

Fitted since 93 and driven vigourously with no problems. it justs sorts out the Cortina S7 ride height

[Guest steveyb]

I have fitted a set of spring clamps to the rear spring to lengthen them this also gives thr rear of the car a better ride height,

this may stop your spring from falling out

 

Hi Chris, yes, I can see how the lengthening of the springs would keep them in, did notice them in your pic.

I would think your top shock mounting points would be the same as mine then @ 21" in that case.

 

What was going through my mind regarding the space being shorter, would of course not alter the stroke as such but would I think make them reach the end of their travel in a shorter vertical drop of the axle.

 

The spring tops have the Cortina moulded rubber insulator but as I mentioned the actual locator where they sit looks a little odd.

It's just a square of plate folded up each side held to the under floor by four bolts you can see the imprint of the rubber insulator:-

 

[chris n]

What was going through my mind regarding the space being shorter, would of course not alter the stroke as such but would I think make them reach the end of their travel in a shorter vertical drop of the axle.

 

Hi Steve , what I forgot to say is I have also fitted a pair of Spax rear shocks (PART NUMBER G005) so I can adjust the dampers rebound and bump, these are adjustable on the car without dismantling the whole set up.

 

Have you got a few photo's of the complete rear axle set up fitted to your Hood? Can not for the life of me see why you are having so much problems with it as it should just fit as it did to the Cortina.

 

 

It's just a square of plate folded up each side held to the under floor by four bolts you can see the imprint of the rubber insulator:-

 

Looks to be the same as what I have got, but the only thing I can see from your photo is that the rubber insulator on mine is a lot tighter fit in the mounting plate.

[Guest steveyb]

Hi Chris, thanks for reply, as the spring locator arrangement is much the same as yours, I presume it was a standard setup on these hoods.

 

I have all the rear end dismantled at the moment renewing the void/solid rubber bushes on the upper/lower trailing arms and axle, it is though a bog standard Cortina axle/trailing arms/shocks setup.

Of course in the actual Cortina, the shock uppers would have been anchored higher in the body

so would reach bottom before the spring compression was fully released.

 

The only problem I'm having is the one with the springs dropping out when the rear is lifted, I'm assuming this is because the shocks are too long in stroke to keep them in.

I'm not too keen on the strap idea, don't even know if it's acceptable during an Mot.

So there seem to be only two options:

1. Increase spring length.

2. Fit shorter stroke shocks

 

p.s. Also bolted on the top of the axle (between the bush mounts on upper trailing arms) is a piece of shaped angle iron with a central hole in it.

I'm beginning to wonder whether this was an axle location for that fifth link you mentioned, the link itself I don't have.

 

Steve

[megadodo]

The maximum open shock absorber length should be short enough to retain the spring in its seats. To use a retaining strap is not considered "good practice" even if it works! I'm sure the guys at Gaz would be be able to sort out a suitable pair if you give them the open and closed dimensions. I'm sure if you took a car to SVA/IVA tester thaye would fail a car that used straps to stop the sring falling out!