As part of my restoration on my '62 Mk2 I’ve lowered the front suspension by adding spacers to the spring pan. Pretty straightforward. I’ve had concerns about getting the rear suspension lowered to match as there are limited options for how to achieve this. I’ve come up with an idea that will allow adjustment of the height of the rear axle relative to the spring mount…details below. There is likely a compromise here as by doing so it’s altering the geometry between the control arms, the axle, and where the spring mounts. I’ve mocked up how these all relate with some cardboard cutouts.
I’ve yet to cut the spring mount on the axle, but am nearing the point where I’ll do this as I have most of the parts ready.
Concept: where the spring mounts to the bracket on the axle, add a slot for the bolt holding the spring to raise and lower. Lowering the bolt/spring mount from current position will lower the car.
Drawing of the concept: Gray area is metal bracketry that will be grafted onto bracket on axle
Jig built to enable precise relocation of current mount point. After I cut off the existing mount I’ll position the new mount here to ensure proper orientation
The new bracket with slotted hole for spring mount. This will be grafted onto the bracket on the axle replacing the current hole/mount point. The threaded rod ends will go through a plate with nuts on each allowing precise adjustment.
My suspension components/geometry mockup in cardboard. Don’t have this fully sorted yet, but trying to understand the relationship between the spring mount and the axle and control arm. It’s clear that the Mk2 leaf spring extends out as it compresses, which makes the spring mount point move in a C arc (a very relaxed C). The control arm moves in an arc in the opposite direction (backwards C). This assuming the axle remains in a constant fore/aft orientation and is allowed to move vertically only. At this point I believe the slot for the
A suggestion from someone with no engineering knowledge and has no right to be here.
If you wish to lower at the rear, why not have a set of springs made that have a flatter arch/profile, slightly shorter in length to offset the shorter overall length required. Bolt on with no engineering required? Owen Springs ‘spring’ to mind.
Re-arcing and shortening the leaf spring is also an option, but doesn’t allow much fine-tuning once that’s done. What I’m trying to achieve hedges bets a bit as it would allow some easy fine-tuning of the height. My springs are original and without the car together I really have no idea how this will sit relative to the lowered front.
On the concept of adding spacers under the front of the leaf where it bolts to the body for the seesaw effect – this has been my go-to option, but I’m uncertain of how effective that would be. Ian – can you share pictures of what you’ve done if you’ve been down this path? Even this idea, however, results in changes to the original factory geometry because to achieve the same axle position (that is the axle being raised relative to the car body) the spring would not have achieved the same stretch (towards back of car) as per the original design. Meaning the seesaw will raise the axle but it will technically be in the wrong fore/aft position because the spring has not stretched.
I didn’t complete the last part of my original post due to an interruption…what I was going to state is I believe the slot for the bolt needs to be angled forwards a bit (like '/ ’ looking at it from the left hand side) to compensate for the changes in geometry. I’m not at a point where I can state that for sure…need to spend more time with the mockup.
Worst case, if this doesn’t work the original factory position is there and I can just reset to that position, albeit with some additional non-stock mods in place.
I think one of the problems with the Mk2 suspension design is that as the spring wears/sags the original geometry as designed is no longer in play…that is unless the sag (height) and stretch (fore/aft movement) happen at the same rate as the spring was original designed to arc. As the spring compresses it also elongates and if this relationship changes then the geometry as-designed is no longer in play. So if trying to fine-tune a nearly 60 year old suspension with this design will be a compromise at best…is what I’m devising a better/worse/indifferent compromise?
Before I make any cuts to the axle brackets I’ll spend some more time fine-tuning my assumptions about how the slot should be placed. As said before, I believe it should not be 100% vertical. Having it angled slightly, I believe, can compensate for the stretch (fore/aft) of the spring. Whether this will make it follow the same original arc I’m not sure, but will at least start in the same spot.
The brackets are modified off the shelf items I found online at a 4x4 shop. They’re made for mounting control arms to frames and have the same 2" inside width as the Mk2 spring bushing. I had the brackets cut and modified (slotted the holes) by a local machine shop. The washers that fit into the slots are also from this same shop and marketed as weld-on washers. I had these modified to fit into the slots and then drilled them out so the bolt can pass through.
Unfortunately it will be a while for my experiment to be proven out…as the car is still at least a year out from being back on the road.
No way Ian - I was talking about ME! - I have told you before how impressed I am with your mechanical knowledge and work. I am a dunce compared to you and was making an uninformed suggestion as to the original question. I am very sorry my poor wording / phrasing led to such a misunderstanding. With hindsight it should have read more like ‘speaking as someone with no engineering knowledge and has no right to be here I make the following suggestion…
So as to be clear, please accept my sincere apologies for the poor wording and my assurance this was not directed at you.
I raised the rear of my car (on one side to level it) using spacers. See attached. In addition to the spacers I have two spring pads (and a longer center bolt to hold them). I used grade 8 bolts all round. Frankly I was a little nervous given the potential for catastrophic failure… but have been driving happily lif this for 10 years now. I fine tuned using washers and then made up a series of simple packing shims from metal plate with two holes drilled. More stable.
One thing to consider before you head down this path. My car is still a little higher at the back than the front. I was more interested in ensuring it was level. In the end I think this rakish angle adds
My 2 cents, even less because I know nothing about Mk2 suspensions.
I’m worried about the weld. Could be wrong but it appears from the picture that you’re planning to weld two different metal thicknesses together with a butt weld. It may be hard to get good penetration on the thicker metal without destroying the thinner. Maybe adding additional thick metal to attached directly to the axle tube?
Dave – raising the ride height looks straightforward with washers/spacers…it’s the lowering of ride height that I’m trying to solve for. I plan on making the top most position in my slotted arrangement the stock ride height. If for some reason I need to raise it beyond this then your solution makes a lot of sense. Thanks for sharing this and the pictures.
Tom – yes, the welds will be of different thickness materials, but it will be a fillet joint not a butt joint. The brackets I’ve modified are 1/4" while the brackets on the axle I believe are 1/8". With a fillet joint I can more easily focus the heat of the weld into the 1/4" plate. To be clear, the axle brackets will be cut such that they weld to the plate on the top of my bracket coming in at a 90 degree angle. I’ll weld around the outside and as much of the inside as will be reachable. I may also add additional gusseting depending on how well I can execute this. I agree that welding two different thicknesses creates a challenge, but believe that the method I’ll use will help mitigate this challenge to some extent.
Ian – I like the simplicity of that concept and as I said before that’s been my go-to strategy. However, it is not without its challenges. The rear wheel will move in an arc, so by spacing the front of the spring down the wheel travels up but also travels forward or backward depending on where the wheel is in relation to the pivot point (being the middle spacer in your example). So essentially the wheel ends up in the wrong fore/aft position. Maybe it’s not enough to matter.
My concept faces the same challenge…but I’m hoping the angle of the slot will compensate for this. Will play around with it this weekend before I start cutting the axle brackets!
I’d be curious what led Jaguar to the unique design they used. It’s not an intuitive design and as the spring wears the original factory geometry is lost.
Yes I can see your point , but I am only talking about a small amount , maybe up to 3/4 20 mm ,
When I fitted GAZ adjustable shocks all around , I had them all at mid point setting , at the back it was far too much , car bounced down the road .
Maybe it would be posable to take a leaf out the spring , then fit Adjustable Coil overs .
As you can see the mounting point for the Axle is at quite a angle , could you not weld the adjustment on the bottom of the mount , so the slot was vertical , that way the spring would only move up and down
What about just using thinner front rubber buttons? All the Mk2’s I have have seen with saggy rear suspension, have been caused by the wear\compression\ deterioration of the front (0f rear suspension) rubbers. If you could source new, but thinner rubbers, you could have lower suspension with largely unaltered geometry, and a very simple system. You could "tune " the setup with different thickness and\or compound rubbers. Your system is very impressive, but too complicated by half, to coin an old phrase. Sometimes simple is best.IMO. Like your thinking, though.
Keep in mind that the control arm is also in play here, and when you move the axle vertically the control arm is pulling it forward. I’m assuming that the control arm is above the horizontal axis (if below horizontal it pushes the axle rearward) . The farther from horizontal the more front/back movement for every vertical movement of the axle.
Because of this, angling the slot by a few degrees can compensate for this, essentially by pushing the axle back so it counteracts the control arm movement. In theory I could get the axle in the exact right spot front to back given the lowering of ride height. However, the arc this will travel (this being the leaf spring mounting point to the axle bracket) will never be quite the same as original because the distance between the spring mount point and the axle centerline will be longer. That said, I think it will be close enough based on what I’ve mocked up where it won’t be material. And as I said before, the factory geometry is already lost as the springs sag/stretch and the rubber buffers wear/compress.
There is a much easier solution , just place two 2x2x 2inch paving slabs in the boot
On saying that you may only need one lol
When I took my rear springs apart , there was very little left of the rubber spacers , you can imagine as the springs move slightly , over the years they just wear away .
I made new spacers out of polycarbonate , they sit a little proud as did the rubber , plenty of waxoil , on rebuild , the springs are the Original ones ,
I too have used spacers at the front , along with uprates springs , I am quite happy with the way my car sits !
May be worth looking at the spring centre mounting plate , they tend too bend , I fitted uprated ones (red)
