Spring rates and coilovers

Adam · 08-10-2011, 09:41 PM

Hi,
In the quest at the moment for some coilovers for my e87 hatch and I\'m finding it hard to work out spring rates.
Basically I have come from in the past a 7kg front and 5kg rear on a Subaru forester and was happy with the ride. Now when I look for the 1er I get spring rates of 8kg fronts and 10kg rear, which to me scream out \"harsh ride\"

So, who has coils (hatch owners if possible) and what are your rates? And how do you find them - harshness...

Also does anyone know what the stock spring rates are for m-tech as I\'m happy with this comfort.

Thanks
Adam

tracer bullet · 08-11-2011, 03:02 PM

Something I found when looking at springs on my last car (I swapped my setup out several times and still mod the suspension section of that forum) is that you have to take leverage into account. It's not all about the spring rate but also where it is located in relation to any pivot points for the suspension and etc. If 135i springs are closer in than the Forester, higher spring rates might only really make things equivalent. Think how much easier it is to cut something thick with a pair of scissors by placing it down at the hinge as opposed to the tip.

Really need to know the current OE spring rates to see how coilovers compare. You might draw a conclusion if say the Forester coilovers were 3x over stock, that a 135i coilover also at 3x over stock might be equivalent.

Even then it's only ballpark, the strut stiffness (resistance to movement for damping the spring) plays a big part, soft springs with stiff struts while being more than willing to lean through a long corner will still feel stiff over little impacts from the road and snappy steering inputs.

Suspension geometry, car weights, etc. also factor in a ton. A spring rate of X will feel a lot different on a Hummer than it will on an Elise (assuming all else is equal) so again a 135i to Forester comparison is not apples to apples.

Anyhow.... don't read too much into printed rates, need to see what people think and try some out for yourself if you can (and even then you may have to take their comments with a grain of salt as you don't know what their baseline is)!!!

Adam · 08-11-2011, 09:12 PM

Thanks for that detailed reply. Yes I understand that different cars need/have different setups, and this is why I was asking to see what other people are running. I'm not saying that I need the same setup, that is just were I have come from.

I would also like to know the stock spring rates to gauge what would be a good set up. I know this will only be a ballpark idea, but it's better to have this knowledge than none. Haha

08-10-2011, 09:41 PM	#1
Adam I say no to mods... my car tells me otherwise :( 3 Rep 22 Posts Drives: 120 Join Date: Jul 2011 Location: Perth WA iTrader: (0)	Spring rates and coilovers Hi, In the quest at the moment for some coilovers for my e87 hatch and I\'m finding it hard to work out spring rates. Basically I have come from in the past a 7kg front and 5kg rear on a Subaru forester and was happy with the ride. Now when I look for the 1er I get spring rates of 8kg fronts and 10kg rear, which to me scream out \"harsh ride\" So, who has coils (hatch owners if possible) and what are your rates? And how do you find them - harshness... Also does anyone know what the stock spring rates are for m-tech as I\'m happy with this comfort. Thanks Adam
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08-11-2011, 03:02 PM	#2
tracer bullet Brigadier General 2461 Rep 3,591 Posts Drives: '11 135i , '15 X3 35i Join Date: May 2011 Location: Saint Paul, MN iTrader: (1)	Something I found when looking at springs on my last car (I swapped my setup out several times and still mod the suspension section of that forum) is that you have to take leverage into account. It's not all about the spring rate but also where it is located in relation to any pivot points for the suspension and etc. If 135i springs are closer in than the Forester, higher spring rates might only really make things equivalent. Think how much easier it is to cut something thick with a pair of scissors by placing it down at the hinge as opposed to the tip. Really need to know the current OE spring rates to see how coilovers compare. You might draw a conclusion if say the Forester coilovers were 3x over stock, that a 135i coilover also at 3x over stock might be equivalent. Even then it's only ballpark, the strut stiffness (resistance to movement for damping the spring) plays a big part, soft springs with stiff struts while being more than willing to lean through a long corner will still feel stiff over little impacts from the road and snappy steering inputs. Suspension geometry, car weights, etc. also factor in a ton. A spring rate of X will feel a lot different on a Hummer than it will on an Elise (assuming all else is equal) so again a 135i to Forester comparison is not apples to apples. Anyhow.... don't read too much into printed rates, need to see what people think and try some out for yourself if you can (and even then you may have to take their comments with a grain of salt as you don't know what their baseline is)!!!
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08-11-2011, 09:12 PM	#3
Adam I say no to mods... my car tells me otherwise :( 3 Rep 22 Posts Drives: 120 Join Date: Jul 2011 Location: Perth WA iTrader: (0)	Thanks for that detailed reply. Yes I understand that different cars need/have different setups, and this is why I was asking to see what other people are running. I'm not saying that I need the same setup, that is just were I have come from. I would also like to know the stock spring rates to gauge what would be a good set up. I know this will only be a ballpark idea, but it's better to have this knowledge than none. Haha
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