HotBits coilovers

above are 16 inch straight spring
 
Th stiffest 14" Eibach barrel springs I can find advertised is 4.5Kg/mm, this has a stroke of 244mm. The 12" come in 5.8Kg/mm and 6.3Kg/mm, this has a stroke of 205mm. Do you have a link to the springs you are looking at?



On my SG, while stationary on level ground, the springs support 365Kg on each front corner and 325Kg on each rear corner. An Sf will probably be a bit lighter, especially on front, but depends on mods ect.


While the car is sitting stationary, 6Kg/mm springs on front will compress 365/6=60mm. This is about 30% of your shock travel, I think rally you want about 1/3 for rally, so you're about right. If your car is much lighter then my SG maybe consider 1 step lighter rate. Low speed 4wding you want the car to sit closer to 50% of shock travel, hence softer springs. Keep in mind if your car is sitting at 30% shock stroke it will be higher then 2" lift. If you wind down the preload adjustment to lower car, the springs won't extend to full shock adjustment and you will need helper springs to maintain preload. The part of the stroke where the helper springs extend is wasted stroke IMO as they take negligible load.



4.5Kg/mm springs on rear will compress 325/4.5=72mm. Which is also about 30% of shock stroke. So about right again.



So springs are about right for what most people like for rally. Providing there are ones long enough in those rate.



I briefly drove my car with 55Kg and 45Kg springs and personally I thought they were good on tarmac, but destroyed grip as soon as the gravel road got rough. But I'm not a rally driver and wasn't on rally roads, just corrugations.
 
Oh straight springs...


The issue with straight springs is they bend under compression and rub on the shock housing.
kWpdNz5l.jpg
 
thanks redxs for the explanation. very valuable.


the 'safari spec' usually runs a stiffer spring than regular gravel spec due to rougher conditions.


targeted suspension lift was 2.5fr and 3.0rr. tires should give another 1 in maybe 1.5



barrel springs not an option would have to go for straight, as below


1600.300.0250S and 1600.300.0350S
 
On my SG with 210mm stroke front, full droop on the front has the wheel centres 590mm bellow the wheel arch. With 60mm compression under static load as calculated above you will have 530mm gap from wheel centre to wheel arch. This is 93mm of lift over the stock spec of 437mm gap. An approximate calculation as I am guessing your cars weight ect, but well over 2.5 inch lift front.


My rears full droop with 300mm stroke shocks is 595mm wheel centre to wheel arch. With only 72mm compression you end up with 523mm centre to wheel arch. Which is 88mm of lift over the stock 435mm.


If you want the heavy spring rates and only 2.5f and 3r lift you may need to consider shorter springs and helper springs.



Once you wear in the straight non-barrel springs they will permanently bend and constantly rub on the housing every single second that you are driving.
 
thanks again red xs!


if i factor in the current decision on stroke lengths as below and took in the spring advice from local guru. would the below solution make sense?


rr. 270 shaft not 300.
difference of 88 less 30 is 58
target is 75mm less 58 is 17
so housing is 17mm too short?



fr 230 shaft not 210.
difference of 93 plus 20 is 113
target is 63 mm less 113 is -50
so housing is 50mm too tall
 
I would definitely take the longest strokes available, because as long as a wheel is in contact, it gives you steering and traction. I tried straight springs so did RedXS...don't go this route ! If you want stiffer tuning, it is also possible to add some pressure in the canisters (nitrogen or very dry air) or change for more viscous shock oil. Well, its up to you to try and find whats best for your needs !
 
im hoping i have captured the recommended strokes in the above, will be using pillow ball top hats...


would two springs of the same poundage also cause the same bending problem?
 
Yes ! When you put two springs on top of each other, they have to be two times harder to get the same rate as a single spring.

If you read the thread from the beginning, its all explained :iconwink:
 
Rear: With 270mm stroke and 45Kg 16" springs work apart from not being barrel springs. 17mm too short doesn't matter as you can preload the springs up 17mm. It's removing preload to get negative preload that would be an issue.


Front: You need softer springs for the the static weight of the car to compress the long travel coilovers enough to only have 2.5" lift. If the front corners of your car weigh 365Kg each and you want to compress the total wheel drop (Wheel centre to wheel arch) from 590mm to 500m (2.5" lift) the max spring rate would be 365/(590-500)=4Kg/mm. If your car can get more wheel drop then mine or is lighter then mine you will need even softer spring rates.


Are people with those stiff 60Kg springs using helper springs? (Like the small red spring in my above pic)
 
Swifts do long stiff barrel springs: https://swiftsprings.wpengine.com/products/standard-coilover-springs/


If you use helper springs you will be able to get full travel with stiffer springs. The helper springs extend at a very soft rate to maintain some preload under full extension. That way the main heavy duty spring isn't actually traveling the full stroke. I don't really see the purpose to full extension if it's only the helper maintaining preload, but people do this so maybe there is a purpose I don't understand. They do allow you to use stiff springs, have high stroke figures without large lift.



Front: A Swift 14" 325lb Barrel spring with helper spring would work. The main spring would be compressed 63mm under static load and there's another 132mm of spring stroke available. This is more then enough as your shock should compress about another 80mm from static extension.



Rear: Could try Swift 16" 250lb barrel spring with helper.


It will take serious forces to get full compression out of these springs, definitely not designed for low speed 4wding lol


Make sure your Hotbits housing has plenty of threading on them to allow for the long length of the helpers stacked onto the long springs.
 
red xs


i hear you but pls clarify one more thing.


in the below


Front: You need softer springs for the the static weight of the car to compress the long travel coilovers enough to only have 2.5" lift. If the front corners of your car weigh 365Kg each and you want to compress the total wheel drop (Wheel centre to wheel arch) from 590mm to 500m (2.5" lift) the max spring rate would be 365/(590-500)=4Kg/mm. If your car can get more wheel drop then mine or is lighter then mine you will need even softer spring rates.


if the strut housing length was 50mm shorter therefore droop would be 540mm (and not 590) then only 40mm static sag would be required to get to 500mm which wld be a 2.5 lift.
 
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60kg springs are being used with no helpers nor tenders.


yes im pretty shocked as well.


F= MA... the A must be quite a bit!!
 
16" Swift barrel springs are 4" ID (vs 3" for the Eibachs) and will rub a lot in the wheel arch at full droop.
 
If your housing was somehow 50mm shorter that would work.



Those other cars mustn't be getting much wheel drop from static. Which isn't really needed for rally stuff. Would you know how much stroke and how much lift they have?



If Swifts are 4" ID then don't use them. My Eibachs have a slight rub in the rear on full droop.
 
traditionally from all the wrc events the cars ran the highest ride height in the safari.


i hear you on the low static sag. topping out is very annoying. i have that issue on my daily that i lifted via stiffer springs.
 
Cool video!! I couldn't watch all of it, got a lot on today, but the first 5 min was excellent. I love how easily the silver Foz with the Hotbits does it!! That's yours jf1sf5?
 
Yes !

And it gets more and more difficult as the video plays...
 
Suspension travel makes grip plus lots going on in center and diffs there.
 
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