fitting e46 sport coil springs on e85

E

Erenbl

Member
I want to buy sport coil springs for my 2003 z4 but they don't sell them in my country.So will e46 sport coil springs fit on my 2003 z4?
 
Even if they physically fit in the E85 mounts, they could be longer/shorter than needed. But the biggest hurdle is they are designed for a car with different weights etc. You may even find that fitting E46 springs has the effect of raising an E85
 
Spring rates for any car are not set by the actual poundage of the spring but by the frequency of the spring when installed, if you fit 300lb springs to a London bus they would be soft as a sponge, yet fit the same springs to a Westfield and they would appear rock hard, so the fitted rate is not the actual poundage per inch of the spring but how it reacts to the loads applied to it.

To calculate the springs frequency you need to know the weight applied by the car to each spring, the leverage ratio of the suspension arms that act upon it and the weight of the unsprung components such as wheel, tyre, brakes, hubs and carriers etc.

once you calculate this you end up with a frequency, expressed in imperial terms as CPM, or cycles per minute, the frequency front to back will also be different, usually higher at the rear as this prevents the suspension developing a resonance which sees the front and rear pitching up and down in series of bounces that could lead to a crash, fitting a set of springs for one car to a different one means the springs will very probably not be matched or the correct length for the installed ride height or suspension deflection.

Put simply, unless you know how to calculate the rates don't guess!
 
Artful-Bodger said:
Spring rates for any car are not set by the actual poundage of the spring but by the frequency of the spring when installed, if you fit 300lb springs to a London bus they would be soft as a sponge, yet fit the same springs to a Westfield and they would appear rock hard, so the fitted rate is not the actual poundage per inch of the spring but how it reacts to the loads applied to it.

To calculate the springs frequency you need to know the weight applied by the car to each spring, the leverage ratio of the suspension arms that act upon it and the weight of the unsprung components such as wheel, tyre, brakes, hubs and carriers etc.

once you calculate this you end up with a frequency, expressed in imperial terms as CPM, or cycles per minute, the frequency front to back will also be different, usually higher at the rear as this prevents the suspension developing a resonance which sees the front and rear pitching up and down in series of bounces that could lead to a crash, fitting a set of springs for one car to a different one means the springs will very probably not be matched or the correct length for the installed ride height or suspension deflection.

Put simply, unless you know how to calculate the rates don't guess!
Click to expand...

+1 WHAT HE SAID :thumbsup:
 
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