Tricky Spring Question

[Shackleton]

Don't know if anyone can really help but here goes;

I had to uprate the front springs on my '73 RRC when I dumped the Td5 in. I got a bargain set of springs a local specialist had taken off something else when the owner wanted a lift (I think). They're blue and they've lifted the front end probably +1". They're also stiff as a horny fella.

Prob is there was only the front springs (and dunno if they were even front springs).

So over the last 2 years my rear springs have taken a hammering and the truck's been seriously bouncy to the rear. It toasted the rears AND the seals in the Boge unit which made matters worse. It's gone so far that it has now bounced the N/S upper shock bushes into non existence - literally. Time to do something.

Prob is I don't have any idea what the front springs are and can't afford a full set of 4.

I need the tail to come back up level with the front and obviously stop bouncing. God knows what state my shocks are in. I have a replacement Boge unit too which I'm hoping has some life in it.

So any suggestions about how to match a set of springs? Charts are no good 'cause I have an unknown quantity to begin with. From what I've read Terrafirma are the way to go. But which ones are going to be the right rate and the right height? Any help would be amazing, maybe a steer to a supplier who knows what they're talking about.

BTW I'd regularly carry watersports equipment but on the most packed day I doubt I'd carry more than 80kg's of equip and then maybe 2 mates. I never really tow but do a fair amount on the beach / dunes / rocks and usually have to do a couple of hours of motorway and then B roads to get there. I need to get rich an stick air in it don't I.

One last thing - am I right to assume that replacing my worn or obliterated bushes with Polybushes is the way to go?

George

PS If I had any money I'd go buy a full susp. kit and be done... but that's not going to happen!

[Turbocharger]

George,

Start simple - what does the back end weigh? Assume it's symmetric both sides and you can work out a range of springs which will give you a sensible ride height (long, soft springs or short, stiff springs). Then pick the one in the middle that will give you a natural frequency between 1Hz (smooth, comfortable, roly poly on the road) up to 2Hz (more crashy but better handling). Ideally, calculate/measure/guess the front end's frequency and go slightly lower for the back end, but you can sort it out with damping so that's not critical (ha!) to be honest.

[nicks90]

or go the simple route and chuck some red/white springs on the back - police spec heavy duty range rover rears. It'll lift hte back slightly and give you a bit more load carrying ability with a degree of safety.

[TheRecklessEngineer]

Don't go polybush! Standard bushes last much longer and put up with much more abuse.

[Shackleton]

Thanks guys,

@Turbocharger; #1. What the hell you talkin' 'bout? How do I find out what the back end weighs? I appreciate that a spring will have a frequency but should I be borrowing a tuning fork? You've given me light at the end of the tunnel in showing that this stuff can be sorted with some educated guessing but... well... HUH?

@Nick; heard of those, are they still made?

G

[landkeeper]

i'd also just get a set of red and white and throw them in and see , paddocks do them for pennies , i'd also throw the boge unit away before you start orrible things

http://www.paddockspares.com/pp/RANGE_ROVER_1986-1994/Suspension/Coil_spring_-_h%2Fduty_rear_-_RHD_%28Red%2Fwhite_stripe%29_to_GA464553.html

[Shackleton]

Sounds great for the price and if you guys say they're decent springs. The Paddocks site says '86-'94 though. Won't they be too short for a standard early bus let alone one thats already +1" at the front?

I'm getting all hairdresser now but I'd like it to sit totally level, it used to be higher at the back and I hated it. It's gone the other extreme now. I just want it to sit like a late RRC, albeit higher.

[forkrentfitter]

length wise they should be right,if not use a 1"spacer under the spring seat axle end.

[nicks90]

they`re plenty long enough. 17.5" freelength and 170lbs/inch if memory serves.

[landkeeper]

here go off buy the cheapest land rover genuine springs you can find fit them and see if they do your job if not use them as a datum and work from there using this

http://members.shaw.ca/jbarge/springinfo.html

[simonr]

You could use the following link to measure / calculate the rate of your current springs: http://forums.lr4x4.com/index.php?showtopic=10057

You probably have a publig weighbridge somewhere near you (we have two within 20 miles) which gives you the weight of each axle to drive across it.

If you jack up the front on one side until the spring is loose - you can measure the length of the unloaded spring.

That will let you identify what you have on the front.

Si

[Turbocharger]

As Si says, there's a number of ways to find the corner weights of your car. Your local garage probably has a roller brake tester - that'll give you the weight on each wheel individually if you know how to read it (most garages don't, but a 'pass or fail' for the brake test is all they need to know). The free length is easily measured with a tape measure if you jack it up, and you can figure the spring rate by measuring the length of the spring with your (now) known corner weight resting on it. The frequency bit is just maths then...

(Or go for a known solution. I've got red&whites on the front of my Ninety, seems to work out ok but I don't know how much the back end of a RR weighs in comparison to a Tdi and some alu wings...)

[vinny]

Ive a pair of yellow hd discovery springs sitting in the shed your welcome to try out?

[mickeyw]

Don't go polybush! Standard bushes last much longer and put up with much more abuse.

Seems to me these have gone a bit Marmite these days!

I have only good things to say about Polybushes. They have far outlasted any standard bushes on my Ninety. Been in place for well over ten years.

I have the stiffer red bushes at the axle ends of all arms, and the blue softer ones at the chassis end. Also red ones in the Panhard rod. All are original and not any sign of wear anywhere, this vehicle gets a fair amount of off-roading too.

There - that's my 2p on that subject.

Springs - my 1990 RRC has heavy duty Iron Man yellow springs. These are Discovery spec, so intended for cars without the Boge strut (mine's toasted too ). I have 4 LPG tanks on board, so some extra weight in the back. IIRC the rears were meant to be +40% and the front +20% spring rates. It sits perfectly level and gives a pleasant ride with De Carbon shocks.

HTH

[gazelle]

Once you have got your weights LR90's spring calculator may be useful (or not!)

Coupled with this spring spec reference

Martin

[Shackleton]

Thanks guys

@Mickey, thing is though my 1973 is a taller truck than your 1990.Damn cause I was excited about the yellow springs just up the road with Vinny. Prob a good idea to give 'em a try anyway.

The RR has started giving a vibration (intermittent) this evening, coming from the back end. I hope it's just road surface imperfections coming through the shock onto the chassis. If not I've messed up my diff or prop shaft.

About the bushes. I used to be quite the expert on them from back in my Mini days. The only cogent thing I'd read against them (apart from the potential for a harsher ride) was that their memory wasn't as long lived as standard bushes. As in they'd get flat spots on the load bearing side where the weight was constantly sat on them.

Now I'm worse off than before I asked cause there's such mixed opinion on them.

[Aragorn]

If your going to change the springs, you need to buy a known quantity.

If you stick another set of random springs on, and its still not right, then you've no idea what to look for in terms of rate/length etc.

Personally, i'd start with a set of the police spec red/white rears, and remove the boge strut, and go from there.

[Shackleton]

Folks thanks for all the help on this, thought I'd post the outcome for future generations cause swapping springs front to back with only one set of compressors and no air wrench is seriously lame.

I got a set of red and whites as suggested.

They didn't raise the back to level with the front.

Put them on the front and all is pretty much even. The other springs I have that are unidentified are almost certainly Bearmach HD units. They're blue, as in they're actually painted blue all over and have a fairly heavy guage by comparison to the red and whites. They're in the 17" length range but I don't have a precise measurement.

Red and whites are 17" something too.

Managed to fit a new Boge unit too (read salvage new). Unbelievable. I could cycle my old unit with no resistance and I couldn't cycle the replacement at all. Hopefully it lasts a long time, it shouldn't have to work too hard with those springs at the back. Oh and the Boge balljoint sleeves are a bitch to tighten.Couldn't LR have made the bolt flanges a little deeper so you could get a grip on them with some sort of decent tool???