Parabolic springs

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jungleMTbiker

Parabolic springs

Post by jungleMTbiker » Sun May 11, 2014 10:29 pm

Some time ago I fitted a set of parabolic springs to my '67 SIIa station wagon. I forget who made them, but I bought them from a UK based supplier. They were the cheapest parabolics I could find at the time. I've been happy with them, the ride is nice, and ride quality and articulation are both much improved over the well-worn original type springs that were fitted before. At the front are 2 leaf sets, and at the rear, 3 leaf sets.

Recently I decided to fit a set of parabolics to my '62 SIIa. This time I found that the price for the Rocky Mountain brand springs had come down, and that once I figured in shipping to PNG, I could actually get the RM's for less than I paid for the cheaper ones I had bought last time. Again I went with 2 leaf front springs and 3 leaf rears.

The RM website says: "fitting these springs, you should expect an increase of about 1" in lift." Given that my springs were well and truly knackered, I imagined that I might gain 2" in lift. Imagine my surprise when I fitted the rear springs and ended up with around 5" increase! At the front I gained maybe 3". But 5 at the rear? And these feel much stiffer than the ones on the back of my '67. This doesn't bother me as the '62 is the one I am more likely to use to pull a trailer or to carry heavier loads.

Has anybody else used Rocky Mountain parabolics and had similar results? I had not intended to build a car crushing monster truck out of the '62, but that said, I am getting used to it, and of the two trucks, the '62 is definitely the one I would have picked to build into something that looks like it came out of a Hot Wheels packet.
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surfermick

Re: Parabolic springs

Post by surfermick » Mon May 12, 2014 7:06 am

not tried them as i havnt yet found a Lnad rover but ive been reading for a couple of years about thois stuff and have read about the stiff ride on parabolics. so its just the rm's that are stiff?
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TJRL
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Re: Parabolic springs

Post by TJRL » Mon May 12, 2014 4:21 pm

When I had my 1960 SII SWB SW renovated I had parabolic fitted. As the vehicle was a wreck I cannot comment on how much higher the new springs made it, but over the last 2 years they have settled down a bit perhaps an inch or so.
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1997 MT350 (with 500e) - Sold 2014 :(
1999 MT350 (With 604e) - Sold 2018 :( :(
2014 F800 GT
2015 R1200RT LE
1960 SII Land Rover SWB SW

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TDIPower
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Location: Sheffield

Re: Parabolic springs

Post by TDIPower » Mon May 12, 2014 5:55 pm

If you have a copy of the OLD Haynes or LR workshop manual it will give you the specs of distance from chassis to bump stop on the axle. One thing a lot of people forget to do is preload the bushes before you tighten up the shackle bolts.
It has been a long time since I did this so it is either you load the vehicle to a set weight on each axle then tighten the shackles or you load it to a set clearance and then tighten the shackles. Obviously this is for OEM springs but would still be worth doing if by the weight method or an adapted version of the clearance.
It means that when you have an empty landy the bushes would be twisting the rubber say clock wise from the neutral point. Loaded to the pre load weight the bushes would be neutral, load it more and they will twist counter clock wise.
This is more important if you do a reasonable amount of offroad work as you will be twisting the rubber in the bushes beyond limit and they will tear out if you do not pre load (due to the travel in the springs).

When you say you have a 5" lift at the rear and 3" at the front I presume this is with the shocks removed as they will limit the travel you have (the MOD series LR were fitted with check straps on the rear axles to limit the drop when air lifted etc) otherwise you run the risk of the prop shaft pulling apart. Also with that much lift you should check the angles of your universal joints.

Pete
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jungleMTbiker

Re: Parabolic springs

Post by jungleMTbiker » Mon May 12, 2014 10:22 pm

Yes, I was aware of the fact that original type shocks wouldn;t be long enough so I went with the recommended longer travel ProComp shocks.

Thanks for the bushing pre-load info--I normally work on motorcycles, so it would not have occurred to me to preload the bushes. Now that you mention it, though, I'll slacken the shackle bolts, load a bunch of firewood in the back and then tighten the shackle bolts again.

Andrew
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surfermick

Re: Parabolic springs

Post by surfermick » Tue May 13, 2014 7:24 am

im becoming very excited reading this, hope i find a landy soon :D :D :D
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jungleMTbiker

Re: Parabolic springs

Post by jungleMTbiker » Tue May 13, 2014 10:43 am

I gave away a very late production SIIa 109" a few days ago--it had a 3 litre (186 ci) Holden 6 cylinder in it that was locked up from sitting, had a broken front spring and broken front axle shaft. No rust to speak of, I had last driven it 7 or 8 years ago, shortly before I got my first 88". I gave it to a co-worker of mine who has big plans for it. If it hadn't been on the other side of the world from you, Surfer, it might have been a decent project, though it sounds like you want one that is already well-sorted.
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surfermick

Re: Parabolic springs

Post by surfermick » Tue May 13, 2014 4:58 pm

thanks Jungle, you are right,due to my heavy business load i want something that has been largely set up already. but as always with old machines its a role of the dice after that ;)
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TDIPower
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Re: Parabolic springs

Post by TDIPower » Tue May 13, 2014 9:16 pm

ProComp are a pretty good shock, Ive had them on the 110 for 14yrs. Although I did have a rear shock rip itself to bits they used to have a lifetime warranty but Im not sure now.
I was a bit miffed with the 1st set which were classed as 'standard' replacements for the 110, they were 1" shorter than standard. So the replacements I fitted are +2" on the rear and +1" on the fronts. With that on full articulation the springs are just at the point of dislocation.

You do need to pre load the front end as well, I ended up with 3 spare wheels on the bonnet and both my parents sat on the front bumper to get to the right clearance!

I always found when I had a 109 that a couple of bags of sand in the back right over the axle made a nice ride.
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jungleMTbiker

Re: Parabolic springs

Post by jungleMTbiker » Tue May 20, 2014 10:52 am

I have discovered that with the RM springs, I need to go a little longer on my front shackles--now I have the standard 3 3/8" (measured centre of one hole to the centre of the other) length shackles and the "military wrap" portion of the spring is only 1/8" from the chassis. I've read that I can go up to 5" on the shackle length without negative effects (the military shackles are longer yet), so I'm thinking I may just make up a set about 4 3/8 or 4 1/2" long and see how they do. with all the springs installed the front end is still a bit lower than the rear and I'd like to level it out a bit.

Having radial tyres on all around has made a big difference in ride quality--I'll have to put together some before and after pics.

Oh and by the way, I have fitted 245/75 x 16 tyres on a set of SIIa 109 rims (all the rims are dated 1969), and they DO fit, though the somewhat aggressive mud tread that I went with does rub against the spring just a little bit on the front when the steering is all the way to one side or the other.
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