steve_d Posted September 16, 2008 Share Posted September 16, 2008 Have now driven the Dakar for the first time (to and from SVA test). What made me thing RR police spec Red/White springs would be OK I don't know or I could have just been swayed by the fact they were only £10.58 each. Anyway they seem to be much too hard. The SVA test showed that it weighs 984Kg (2169lb) at the front and 784 (1728lb) at the rear. It is on polybushes and +2" De Carbon shocks all round. Can anyone suggest a suitable spring or some tech info on how to choose the right rate etc.? Many thanks Steve Quote Link to comment Share on other sites More sharing options...
Hamish Grundy Posted September 16, 2008 Share Posted September 16, 2008 hi steve, id go for standard rr springs, i have an 88 tomcat and i use them for comping and it gives a nice ride. hamish Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted September 16, 2008 Share Posted September 16, 2008 Don't guess, you have the weights for yours so work out whats best via Trevs (LR90) spring calculator on his website Nige Quote Link to comment Share on other sites More sharing options...
clbarclay Posted September 17, 2008 Share Posted September 17, 2008 There is some useful info in this link for selecting spring rates. http://www.pirate4x4.com/tech/billavista/coilovers/Part_1/ Quote Link to comment Share on other sites More sharing options...
steve_d Posted September 17, 2008 Author Share Posted September 17, 2008 Not sure how relevant the billavista link is as it seems to cover just coilovers. The calculator link from LR90's site does not work for me. Can someone confirm if it is just me? Steve Quote Link to comment Share on other sites More sharing options...
clbarclay Posted September 17, 2008 Share Posted September 17, 2008 The billavista page is based on coil overs but the spring theory in it is the same for coil overs as non coil overs, you just don't have to worry about the angle/position of the spring with a typical LR setup as they are directly above the axle. The spring rate calculator within it is setup for dual rate springs, but if your only after single rate springs then the formula in the main article should be easy enough to apply. Quote Link to comment Share on other sites More sharing options...
LR90 Posted September 18, 2008 Share Posted September 18, 2008 Not sure how relevant the billavista link is as it seems to cover just coilovers.The calculator link from LR90's site does not work for me. Can someone confirm if it is just me? Steve Sorry Steve, one of my routers died a few days back and I still haven't had the chance to put everything back in order after a hasty rejig. But HFH is right you've got the info (nice and light too ), so best to use it. Prob something like 170s in the front and 150s rear but I'll try and get the site back on line this weekend so you can try the options. Quote Link to comment Share on other sites More sharing options...
simonr Posted September 19, 2008 Share Posted September 19, 2008 The way to calculate spring rates and lengths is this. When you go over a bump, the effective weight on the spring increases. How much obviously depends on the application and speed. As a rule of thumb, use about 1.8 x to 1.9 x. For soft springing about 1.7x Say you want a 2" lift - that gives you a separation between the axle and bump stop of say 4". The compression of the spring to give you the 4" separation is due to the weight of the vehicle and the rate of the spring must be such that 4" worth of compression is at least 0.8 of the vehicle weight. So, say for example a wheel has 1000lbs sitting on it. in that 4" it needs to 'absorb' 800Lbs. you therefore need a spring with a rate of 800 / 4 = 200Lb/in With the vehicle sat on the bump stops, there is usually about 7" of separation between the top and bottom spring mounts. So, at 4" stationary height, the spring is 11" long Therefore the 1000lb needs to be 'absorbed' by the first part of the travel. Your spring is 200lb/in so 1000 / 200 = 5" Therefore to give reasonable handling, and a 2" lift you need a spring with a rate of 200lb/in and a free length of 11" + 5" = 16" Obviously, you need to do a bit of measuring to see what the separation of the spring hangers is and how much separation on the bump stops you want - but this will give you a quantitative way of determining the actual rate and length you need. From this, you can see what dual rate springs do. The first part of the spring travel is soft - which means to support the static weight of the vehicle there is a lot of compression, giving you lon extended travel. The second part of the compression is harder, reducing the separation of the bump stop and axle required to absorb the bumps. You can therefore run less lift for a given extension without constantly hitting the bump stops. Likewise, helper springs, compressible and hydraulic bump stops just increase the rate for the last part of the travel to achieve the same end. If you are hitting the bump stops, your suspension is not doing it's job and it will loose you traction. The last thing to remember is that £10 springs, even where badged as a given colour code, are rarely actually the Land Rover specified length and rate. The only springs I've found that are accurate apart from genuine ones are from OME. To calculate the rate of a spring, I posted a formula here: http://forums.lr4x4.com/index.php?showtopi...;hl=spring+rate Si Quote Link to comment Share on other sites More sharing options...
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