pcw64 Posted September 5, 2017 Report Share Posted September 5, 2017 I have just removed my rear spring on my 1974 TR6 and discovered the free length is 290mm with 10 coils and the manual states the it should be 278mm with 6 3/4 coils.Have i the wrong springs fitted or are they uprated ?Thanks Paul Quote Link to post Share on other sites
astontr6 Posted September 5, 2017 Report Share Posted September 5, 2017 I have just removed my rear spring on my 1974 TR6 and discovered the free length is 290mm with 10 coils and the manual states the it should be 278mm with 6 3/4 coils.Have i the wrong springs fitted or are they uprated ?Thanks Paul Hi Paul! What colour paint stripes are on these springs? Bruce. Quote Link to post Share on other sites
pcw64 Posted September 6, 2017 Author Report Share Posted September 6, 2017 Hi Bruce,They were a bit rusty but it did look like there were 2 red stripes.Thanks Paul Quote Link to post Share on other sites
Peter Cobbold Posted September 6, 2017 Report Share Posted September 6, 2017 (edited) More coils would make a spring softer, not uprated, if the wire diameter is identical. Think of the spring straightened out to make a torsion bar- the longer one will twist easier. The wire diameter is critical and has to be measured with precision. Formula for coil spring stiffness is here: http://www.tribology-abc.com/calculators/t14_1.htm Peter Edited September 6, 2017 by Peter Cobbold Quote Link to post Share on other sites
astontr6 Posted September 6, 2017 Report Share Posted September 6, 2017 Hi Bruce,They were a bit rusty but it did look like there were 2 red stripes.Thanks Paul Hi Paul! Looking at my old SAH book, it does not show Red/Red only Red/Yellow rated at 510 lbs/ins, fitted length 8.45". I do not know if this is any help to you? Standard TR6 springs are shown as Green/White rated at 354lbs/ins, fitted length 8.841"! Bruce. Quote Link to post Share on other sites
pcw64 Posted September 6, 2017 Author Report Share Posted September 6, 2017 Hi Bruce & Peter.Thanks for your reply's,the thickness of the spring is 1/2 inch so the mystery thickens,If i fit new springs and they are shorter then what i have it will mean that the car will be to low.Thanks Paul Quote Link to post Share on other sites
Peter Cobbold Posted September 6, 2017 Report Share Posted September 6, 2017 Hi Bruce & Peter.Thanks for your reply's,the thickness of the spring is 1/2 inch so the mystery thickens,If i fit new springs and they are shorter then what i have it will mean that the car will be to low.Thanks Paul Paul, Depends upon how stiff the shorter springs are compared with present ones.New ones could be so stiff they dont compress much so the running height could be higher What are you hoping to improve? Peter Quote Link to post Share on other sites
pcw64 Posted September 7, 2017 Author Report Share Posted September 7, 2017 Hi Peter.I think that my car may be sitting a bit low as the distance between the bottom of the chassis and the floor is 5 inches and i think that it should be 6 inches.Seeing that i am replacing the drive shafts at the moment i thought i would remove,clean,paint & measure the springs and i was surprised to see that the free length was 290 mm and the new Moss & Rimmer rear springs are 278mm so i was wondering what springs that was fitted as i would like to lift that car up an inch.Thanks Paul Quote Link to post Share on other sites
pcw64 Posted September 7, 2017 Author Report Share Posted September 7, 2017 I think i have cracked it,Looking on Rimmers web site the standard springs they have for sell are 295mm long and have the same number of coils as mine,so i have lost 5 mm but i can live with that.Paul Quote Link to post Share on other sites
astontr6 Posted September 7, 2017 Report Share Posted September 7, 2017 I think i have cracked it,Looking on Rimmers web site the standard springs they have for sell are 295mm long and have the same number of coils as mine,so i have lost 5 mm but i can live with that.Paul Hi Paul! If you replace these springs make sure that you replace them with springs that are rated at 400 lbs/ins minimum or you will suffer from spring wind up which quickly leads sagging rear end. I still see many TR6s suffering from this problem! Triumph uprated the springs more than 3 times during its production life because of this problem! I doubt that your springs are original? Bruce. Quote Link to post Share on other sites
Waldi Posted September 7, 2017 Report Share Posted September 7, 2017 Hi Paul, The number of coils alone does not give you the full answer. If you measure the wire diameter, preferably with a caliper, like 12.45 mm, and the coil mean diameter and number of FREE (active) coils, you can calculate the springrate. Use the formula Peter has provided via the link. Then, if you have the free length, compressed length (in the car, car on the ground) and the calculated spring rate of your existing spring, you can calculate the expected lenght of a new spring of which you now springrate and free length for the same load (force). Alternatively, you can buy shims to put on your existing spring, they will increase the ride hight, not the springrate (how far your suspension moves). Regards, Waldi Quote Link to post Share on other sites
pcw64 Posted September 7, 2017 Author Report Share Posted September 7, 2017 Thanks you all for your help & advise but it seems that i have standard springs from Rimmers at 358 lbs,the car rides well and don`t bottom out even with 2 up and a boot full of luggage so i might buy some up rated springs later when i have some spare cash and experiment.Thanks Paul Quote Link to post Share on other sites
Peter Cobbold Posted September 7, 2017 Report Share Posted September 7, 2017 Thanks you all for your help & advise but it seems that i have standard springs from Rimmers at 358 lbs,the car rides well and don`t bottom out even with 2 up and a boot full of luggage so i might buy some up rated springs later when i have some spare cash and experiment.Thanks Paul Paul, Rimmers sell polyurethane spring shims. They fit between the trailing arm and spring base and will raise the ride height by their thickness, moreorless. Easy to fit. Using stiffer springs can make potholes a trial. I went that route and regret it nowadays. Peter Quote Link to post Share on other sites
pcw64 Posted September 7, 2017 Author Report Share Posted September 7, 2017 Hi Peter,By adding the shims does it change the camber?Thanks Paul Quote Link to post Share on other sites
Peter Cobbold Posted September 7, 2017 Report Share Posted September 7, 2017 Hi Peter,By adding the shims does it change the camber?Thanks Paul Paul, The trailing arm will be at a slightly steeper angle to the ground because the chassis rides a bit higher. That will add a bit of toe-out that can, if need be, be taken out with the bracket shims. I dont think the small reduction in negative camber will need correcting, and its trickier to do. I would fit the shims and see what it feels like. I fitted shims and made no adjustments ...but the suspension is lowered and the t/a is nearer horizontal so I can't be sure yours wont need re-aligning. Peter Quote Link to post Share on other sites
pcw64 Posted September 8, 2017 Author Report Share Posted September 8, 2017 Hi Peter,I think i will buy thicker spring collars and see how i get on.Thanks for your advice.Paul Quote Link to post Share on other sites
Peter Cobbold Posted February 14, 2018 Report Share Posted February 14, 2018 Hi Peter.I think that my car may be sitting a bit low as the distance between the bottom of the chassis and the floor is 5 inches and i think that it should be 6 inches.Seeing that i am replacing the drive shafts at the moment i thought i would remove,clean,paint & measure the springs and i was surprised to see that the free length was 290 mm and the new Moss & Rimmer rear springs are 278mm so i was wondering what springs that was fitted as i would like to lift that car up an inch.Thanks Paul Paul, The free length doesnt tell you how mcuh it will compress when loaded. Your springs must have a lower rate than Moss's.So they compress more and lower the ride height. If the ride/handling is good, then try fitting a PU shim under the rear spring to lift it a bit. That will not upset the front-rear spring rate balance. A 1cm shim will lift the rear roughly 1.5cm. Peter Quote Link to post Share on other sites
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