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Spitfire suspension overhaul


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I've finally got around to putting some work back into the spitfire.  I've cracked on with replacing all the frond end suspension bushes with polybushes, and replaced the springs too .  I was relived that everything wen't smoothly, with the exception of one lower fork bolt which was in the wrong way and needed to be cut out.  I think it must have been put in before the strut tower.

 The dampers look in ok condition (they are KYB units) and upgrading is out of budget for the time being.  Is there anything else I should consider checking/doing whilst I'm at it?

If you are of a weak disposition you should probably look away as there are some images of slightly sketchy bush pressing techniques below, and various parts in need of paint.

 

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IMG_20210509_095825788.jpg

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Bush removal doesn't look too sketchy to me! Personally I did spend a long time de-rusting everything, experimenting with electrolysis (back in the heady days of the first lockdown).

While you're in that area, have you examined the vertical links? Any rust pitting on at the top of the threaded part, or significant play in the trunnion? Stub axles and front wheel bearings too - I changed my stubs but had issues with poor quality parts. There's a thread somewhere I can dig out if useful. 

Also maybe look at the ball joints and track-rod ends if you haven't already. 

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Thanks Pete,  I checked the wheel bearings and stub axles and replaced one about 0 miles 6 years ago, so hopefully they are still ok.  Trunnions seem to be ok, again inspected a while back, but no play and no corrosion.  I agree that I really should have cleaned and painted the general area, but I've had issues with mental spec. creep snowballing the job into something unmanageable, so I made the decision to just get on with the essentials!

I'm hoping to get it back on the road to drive it and regain the connection, before getting back into making it look nice and give it lasting protection from the elements.  There's also some garage sorting and shed building on the horizon which will make cleaning and painting easier.

Ball joints and track rod ends look ok, ARB drop links are looking a little tired but there doesn't seem to be any play so they might get replaced once I've got it back on the road if they knock.

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  • 2 weeks later...

So I got to the rear spring.  The plan was to refurbish the spare I have then swap over with the existing.  I have finally got around to checking and they are visually fairly different.

Can someone with more knowledge than I let me know what I have?

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Thanks John, that's extremely helpful.  From my best guess on measuring leaf thicknesses they are both mk4/ 1500 springs, but two different designs.  As the shocks are not standard I'm going to chose to believe that the rear has been overhauled at some point, that the "spare" spring is the original and the one on the car is a pattern part.

I suspect the proper thing to do will be to try and measure the spring stiffness of both and use the stiffer one.  My train of thought being that the stiffer in bump/squat the less camber change which is what I want, and the wing spring nature means leaf spring stiffness should not affect rear roll too much.

Unfortunately I can't get the spring out without the car in the garage, and can't easily move it with the spring out so it's a job of many steps.

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3 hours ago, egret said:

Unfortunately I can't get the spring out without the car in the garage, and can't easily move it with the spring out so it's a job of many steps

Yes I remember it being a massive pain the @rse of a job! One of those with a 'point of no return' which resulted in a very late night before I could roll the car back inside...

You could measure the unladen height of them as well as trying to gauge stiffness. Much easier to fit a lowering block (if needed) before you put the spring in!

 

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I expect it is possible but I found it challenging! Maybe its easier with the driveshafts on, can't remember exactly what I struggled with apart from the spring being heavy and awkward when you're trying to hold and manoeuvre it from one end. Curvature of a brand new spring might have made it awkward, and I distinctly remember thinking I should have taken both drive shafts off. But perhaps that would have made it harder. 

 

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I've done a few without any real drama, same as Roger.  Just make sure you have plenty of room on the side you are withdrawing the spring.  it's no fun starting the job in a single garage and realising your mistake half way through!  :wallbash:

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2 hours ago, andymcp said:

I've done a few without any real drama, same as Roger.  Just make sure you have plenty of room on the side you are withdrawing the spring.  it's no fun starting the job in a single garage and realising your mistake half way through!  :wallbash:

This...... you need about half the width of the car again......

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1 hour ago, Nick Jones said:

This...... you need about half the width of the car again......

Hello All

               If it is an attached garage just knock a brick out into the Hall/Kitchen etc HaHa 

But not to the outside as that would let the cold and rain in!!!!!

Roger

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8 minutes ago, RedRooster said:

I did mine before I fitted the body tub, guess that doesn't help you much.

RR

I'd love to be in a position to remove the tub to replace it and do all the other tub off type jobs which would be great to do, but unfortunately don't have the time or resources for that sort of project at the moment.

 

1 hour ago, rogerguzzi said:

Hello All

               If it is an attached garage just knock a brick out into the Hall/Kitchen etc HaHa 

But not to the outside as that would let the cold and rain in!!!!!

Roger

Don't tempt me!!!

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8 hours ago, rogerguzzi said:

Hello

         I am pretty sure I changed mine by jacking up and disconneting shockabsorbers and spring eye bolts.

Then just release it from the differential.

I as sure the Wsm tells you how!

Roger

Roger is right with this. The swing spring is slightly easier to swap that the fixed one as it's flatter.

While also an excellent idea I suspect successful implementation would depend on a number of external factors :blink:

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7 hours ago, rogerguzzi said:

Hello All

               If it is an attached garage just knock a brick out into the Hall/Kitchen etc HaHa 

But not to the outside as that would let the cold and rain in!!!!!

Roger

I’d go for knocking a brick out of the outside wall, can easily stuff an old towel in the hole or around the spring in the hole!

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  • 6 months later...

This is still slowly progressing as I've been distracted with various other aspects of the car (exhaust, ignition, and inlet manifolds are all in-progress projects...) and run out of time and funds a couple of times!

As the aim it to overhaul the spring, I've been thinking about the inter-leaf button thickness/height.  Given I'm making these there is scope to change their shape.  I have the drawings from the dutch website (http://www.triumphspitfire.nl/rearspringpads.html 8mm thick) so know how thick they should be, but started to think about these things last night.

  1. Would increasing the button thickness pre-load the leaves more and increase stiffness? 
  2. Would this even be a good thing?  Given it's a swing spring it shouldn't affect roll much, but would more stiffness at the back be beneficial after increasing the spring rate at the front?

I can't seem me realistically ever changing the buttons to thicker/thinner ones, so feels risky to actually do this.  Plus I will never really get any useful data telling people if what was done was sensible, so I should probably stick with the known figures. However I feel it might be an interesting conversation with the minds here.

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Thicker buttons won't change the rate of the spring. That is down to the leaves. 

What they will affect is the static height of the spring and hence the ride hight. But with the same rate.

The other thing they can do depending on the material usedis to affect the hysteresis of the spring - essentially how much effort it takes to start the leaves moving. The freer the movement the more supple and less jerky the ride. And the better the roadholding.

The other thing I found trying to fit nylon buttons in place of the rubber ones on a swing spring was that I couldn't compress the leaves enough to get them to fit in the spring box.

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Ah ok, I'd assumed some the leaves were not loaded up from the static position.

I've got a bar of UHMWPE which I think should be a good compromise for not deforming under extended compression, low friction and general strength.

Thanks for the heads up on spring compression.

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I made a couple of sets of the buttons for a local friend out of nylon bar stock to the drawing in the link.

I don’t remember getting any feedback, but maybe he’s not fitted them yet.

As Colin says, it won’t affect the rate, but it should improve the arch and thus raise ride height.

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I've put on some custom springs from DFaulkner on the front, so I'm expecting to have to put a lowering block in at some point, but given the buttons will change the height, I'll wait until they are in and settled then I'll look at lowering blocks to level out the ride height.

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