Front spring change
- Thread starter BBLongman
- Start date
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New Member
It's pretty difficult without fitting the springs to the car, even if they are the same length, the loads on each spring will be slightly different and make the heights different on each side.
Now, if we knew the exact ratio of ride height to spring compression, then you could fit them, measure the difference and know exactly how much shim to fit.
I'm sure Mr York should be able to tell us the ratio.
Of course it all changes when you sit in the drivers seat. :roll:
Now, if we knew the exact ratio of ride height to spring compression, then you could fit them, measure the difference and know exactly how much shim to fit.
I'm sure Mr York should be able to tell us the ratio.
Of course it all changes when you sit in the drivers seat. :roll:
theshadeoflordstokes
New Member
This is a job which I wanted to do but was inhibited by the well reported difficulty. This is how the professionals do it!!..............
Last Friday I took on the dreaded spring change on my 1968 Series 1 3500 with Colin Gould at Kingsdown Classics.
The whole job was done on my car in one day.
The process went as follows:
Put the car on the hydraulic ramp.
Remove doors, bonnet, wings, knee bins and wheels and disconnect track rods, top ball joint, anti roll bar and upper links.
Disconnect shock absorbers.
This is the interesting part - remove the 4 bolts holding the rocker arm to the bulkhead (later cars have studs) and as an earlier contributor put it, "Let nature take its course".
The result was that the spring and rocker arm fell to the floor - no great drama, just fell to the floor.
In retrospect, the reason should be fairly apparent - with no load on the spring and the shock absorber removed, the length of the spring is almost the same as the free length so there is very little energy still stored in the spring.
Next, with the assembly on the floor replace the bolts with studs - don't even think about re-using bolts, it is just too difficult to line up the assemby at the re-assemby stage.
Do any other appropriate jobs at this stage eg, replace the dome bushes, bump stops etc.
Loosely assemble the new spring and pivot and with an assistant, offer up the assembly to the bulkhead - then use a body jack braced within the wheel arch between the back of the bumper mounting and the rocker arm to push the rocker arm towards the bulkhead. One person pumping the hydraulics and the other aligning the bolts with the holes in the bulkhead. Again there are no huge forces here, you are taking the spring from a length of 16 inches to about 14 inches which represents a load of about 80kg and the natural contours of the 2 brace positions on the body and rocker arm make the possibility of slippage remote.
With the studs in place secure the assembly with new nuts.
Next, re-attach the top ball joint and track rods.
Place a prop underneath the vertical strut and lower the car onto the prop - this will load the spring further until you are able to line up the shock absorber mountings. Secure the shock absorber.
From this point it is straightforward reassemby of which any self-respecting PROC member will be capable.
So to summarise you need the following;
An hydraulic ramp.
A mate.
A body jack.
A prop.
So would I do this job in my garage?........now that I have seen it done I probably would. It isn't as scary as you might think but you do need some specialist tools.
Incidentally, if you think I am understating the dangers of messing with suspension springs I suggest you do some research on Hookes Law and make some load and dispacement measurements.
The secret is that you are loading the spring in stages; the first is to jack the spring into position, it doesn't take much force to do this and once it is secured against the bulkhead it can't go anywhere. The second stage is to load the spring to get the shock absorber in place - if you don't get this right the vertical arm could slip but the spring still won't break loose.
After this you are home and dry.
I hope this contribution may help others contemplating this job.
Last Friday I took on the dreaded spring change on my 1968 Series 1 3500 with Colin Gould at Kingsdown Classics.
The whole job was done on my car in one day.
The process went as follows:
Put the car on the hydraulic ramp.
Remove doors, bonnet, wings, knee bins and wheels and disconnect track rods, top ball joint, anti roll bar and upper links.
Disconnect shock absorbers.
This is the interesting part - remove the 4 bolts holding the rocker arm to the bulkhead (later cars have studs) and as an earlier contributor put it, "Let nature take its course".
The result was that the spring and rocker arm fell to the floor - no great drama, just fell to the floor.
In retrospect, the reason should be fairly apparent - with no load on the spring and the shock absorber removed, the length of the spring is almost the same as the free length so there is very little energy still stored in the spring.
Next, with the assembly on the floor replace the bolts with studs - don't even think about re-using bolts, it is just too difficult to line up the assemby at the re-assemby stage.
Do any other appropriate jobs at this stage eg, replace the dome bushes, bump stops etc.
Loosely assemble the new spring and pivot and with an assistant, offer up the assembly to the bulkhead - then use a body jack braced within the wheel arch between the back of the bumper mounting and the rocker arm to push the rocker arm towards the bulkhead. One person pumping the hydraulics and the other aligning the bolts with the holes in the bulkhead. Again there are no huge forces here, you are taking the spring from a length of 16 inches to about 14 inches which represents a load of about 80kg and the natural contours of the 2 brace positions on the body and rocker arm make the possibility of slippage remote.
With the studs in place secure the assembly with new nuts.
Next, re-attach the top ball joint and track rods.
Place a prop underneath the vertical strut and lower the car onto the prop - this will load the spring further until you are able to line up the shock absorber mountings. Secure the shock absorber.
From this point it is straightforward reassemby of which any self-respecting PROC member will be capable.
So to summarise you need the following;
An hydraulic ramp.
A mate.
A body jack.
A prop.
So would I do this job in my garage?........now that I have seen it done I probably would. It isn't as scary as you might think but you do need some specialist tools.
Incidentally, if you think I am understating the dangers of messing with suspension springs I suggest you do some research on Hookes Law and make some load and dispacement measurements.
The secret is that you are loading the spring in stages; the first is to jack the spring into position, it doesn't take much force to do this and once it is secured against the bulkhead it can't go anywhere. The second stage is to load the spring to get the shock absorber in place - if you don't get this right the vertical arm could slip but the spring still won't break loose.
After this you are home and dry.
I hope this contribution may help others contemplating this job.
theshadeoflordstokes
New Member
The bushes looked a bit ratty at the edges but it seems that they very rarely fail. I was also told that while the outer bushes aren't too difficult the inner bushes are a swine to do - even for the professionals. So I left them all alone.
During the job I also put new shockers on, changed the rubber domes for polybush, replaced the idler arm (which had a little play) as well as changing the springs for standard JRW units and the overall result has been well worth it.
The car sits level at the front, is a little bit higher than previously and feels very smooth on the road.
During the job I also put new shockers on, changed the rubber domes for polybush, replaced the idler arm (which had a little play) as well as changing the springs for standard JRW units and the overall result has been well worth it.
The car sits level at the front, is a little bit higher than previously and feels very smooth on the road.
It's interesting that you fitted the JRW front springs. I have a set to fit from them and queried the free length as it was different to the manual.
The answer to the query was that there are quite a few different specifications for the front springs and that the one they are selling is one size fits all model. However the spec for the spring sold is not entirely clear as the stock was inherited from a previous supplier.
The free length as supplied is 15/5" whereas specified length on the V8 is 17" (according to the haynes manual) If it sits a little higher at the front (in fact even if it sat at the same height) it suggests to me that the spring rate of the original springs.
How much higher than before do you think the front sits? Have you measured it against the specified ride height in the manual?
The answer to the query was that there are quite a few different specifications for the front springs and that the one they are selling is one size fits all model. However the spec for the spring sold is not entirely clear as the stock was inherited from a previous supplier.
The free length as supplied is 15/5" whereas specified length on the V8 is 17" (according to the haynes manual) If it sits a little higher at the front (in fact even if it sat at the same height) it suggests to me that the spring rate of the original springs.
How much higher than before do you think the front sits? Have you measured it against the specified ride height in the manual?
theshadeoflordstokes
New Member
JRW were not my first choice but Ian Wilson (Rover Classics) had sold out.
Yes the new springs are shorter, however, with my bodyweight (ca. 80kg) I was able to compress the old spring by about an inch - I couldn't compress the new spring at all. So you are correct, the rate of the new spring is greater.
The previous ride height was not a good guide as it was leaning towards the driver's side.
Tell me where you would like me to measure the ride height at the front and I will measure it later today.
Yes the new springs are shorter, however, with my bodyweight (ca. 80kg) I was able to compress the old spring by about an inch - I couldn't compress the new spring at all. So you are correct, the rate of the new spring is greater.
The previous ride height was not a good guide as it was leaning towards the driver's side.
Tell me where you would like me to measure the ride height at the front and I will measure it later today.
The Haynes manual specifies it as 331mm from the ground to the centre of the bottom suspension arm mounting bolt on the chassis. This is with standard wheels which give 294mm from centre of hub to ground. (It's actually specified as 294mm + 37mm +/- 6mm)
I tried standing on the replacement spring and was able to compress from 15.5" to 14.25" with my svelte 95kg! This gives an approximate spring rate of 170lb per inch. (210/1.25 = 168). This matches the rate of the original springs that Ron related in an earlier post and suggest the car should sit lower. I do have a friend with a hydraulic press to perhaps later I will pay a visit with the bathroom scales and try and get a better measurement.
My wife measured for me and was surprised as normally when I ask for assistance it is with brake bleeding, she asked if we can do spring measuring more often as it much quicker!
I tried standing on the replacement spring and was able to compress from 15.5" to 14.25" with my svelte 95kg! This gives an approximate spring rate of 170lb per inch. (210/1.25 = 168). This matches the rate of the original springs that Ron related in an earlier post and suggest the car should sit lower. I do have a friend with a hydraulic press to perhaps later I will pay a visit with the bathroom scales and try and get a better measurement.
My wife measured for me and was surprised as normally when I ask for assistance it is with brake bleeding, she asked if we can do spring measuring more often as it much quicker!
theshadeoflordstokes
New Member
Good point.
The ramp was lowered so that the car's weight was taken on a prop placed under the vertical arm. Then the shock absorber was disconnected and the car raised again.
The ramp was lowered so that the car's weight was taken on a prop placed under the vertical arm. Then the shock absorber was disconnected and the car raised again.
theshadeoflordstokes
New Member
To answer the question regarding currrent ride height:
The height to the center of the bottom link mounting is 330mm.
However, this is with wheel centre to the ground distance of 285mm (65% profile tyres) so the springs are a tad stiffer than standard.
The height to the center of the bottom link mounting is 330mm.
However, this is with wheel centre to the ground distance of 285mm (65% profile tyres) so the springs are a tad stiffer than standard.