Spring rates !?!

[beggse]

So I'm looking at a set of coilovers, either D2 or BC's.. Anyway, what would be a suitable spring rate... Chasis is a 320i sedan (australia) with an M20B25 swap..

[Vivek]

Basically whatever you want. With what you've given us, theres nothing anyone can really tell you.

[beggse]

Okay well I'm sure that most people would have added the rates and such that they are running as a measure, basically looking for some advice/experience as to what works well for some with similar swap setups... -_-

[jlevie]

Is the goal performance, or appearance? Is the car a daily driver, or a race car?

[E30_fiend]

The rates those kits come with, 8k front and 8k rear, are pretty streetable. If I were to get them, I would rather have 12k front and 14k rear. But that's just me and I like a hard spring rate.


Taylor

[bmwguy325is]

Back up whatever springs you get with good shocks

[Vivek]

Okay well I'm sure that most people would have added the rates and such that they are running as a measure, basically looking for some advice/experience as to what works well for some with similar swap setups... -_-

Mine are like 500 front and 300 rear. Yes it's a bad combo (sigs a photoshop, it's a couple inches higher than that) but it rides acceptably and handles good for what it is.

[Ant_e30]

beggse i'd go for BC over D2, just hear a lot better things about BC.

spring rates it tough to guess. I am thinking of going 9k / 11k or there abouts. But i want to ride low with tight fitting wheels so i will need hard suspension. It depends what you want.

also you can generally go +/- 2kg with your shocks on your coilovers. So say you go for the standard 8k / 8k or even 8k / 10k, you could change springs later and go up to 10 / 12 or down to 6 / 8 without issues.

[Madhatter]

Mine are like 500 front and 300 rear. Yes it's a bad combo (sigs a photoshop, it's a couple inches higher than that) but it rides acceptably and handles good for what it is.

why the hell would you run such a low spring rate in the rear? you realise that the motion ratio of the rear is different than the front too right? so comparing them together, a 300lb spring in the rear equates to much softer suspension than in the front. Running such a huge difference, just doesn't make any sense at all, especially given the split is higher in the rear for this very reason.

OP, sounds like you have the exact same car as me :) D2 is rubbish with loads of problems, BC coils are basically made in the same factory but with better valving and quality control. They aren't up to the standard of a KW or something, but they aren't bad for what they are. If you are getting them in AUS, couple of things though. The spring lengths are the same up to 8kg, if you go stiffer than 8kg, the spring increases in length again which equates to nearly 40mm ride height difference. So if you want to go really low, you might struggle to get it down there if you go stiffer.

Im prretty happy with the 6kg/8kg split ive got on mine, Ive got the preload wound right off, any further and the springs wouldn't be captive anymore. Im running the shocks on about 10-12 for the street too, so coupled together it's pretty firm, but can handle the really shitty roads we have out here, especially since im running on 17's too.

Are you running thicker swaybars at all? If not, i reckon the 6kg/8kg split is a pretty good starting point. You can play around with the preload on the springs (ie, wind up the bottom spring perch to compress the spring) and crank up the shocks to get it pretty stiff, then if you still want a little more have a look at increasing the size of the swaybars to give you a little more. Otherwise, you can have springs made out here pretty cheap, rears run to about $160 the pair while the fronts are a little cheaper. So if you find the spring rates to be off, it's not a massive amount to have them remade.

You know you have to cut the strut tubes down and weld the coilovers to them though right? they aren't a simple bolt in swap.

[wakdog]

beggse i'd go for BC over D2, just hear a lot better things about BC.

K-sport, D2, BC, HSD, Megan Racing and a few other cheap coilover brands all come out of the same factory, as far as I am aware though BC are the easiest to get through to about custom spring rates.

Im running approx 8kg/12kg with my GE coilover setup but I cant really comment on how it rides due to the fact im running on billy sports pretty much on bumpstops until my IX billys arrive....

[Vivek]

why the hell would you run such a low spring rate in the rear? you realise that the motion ratio of the rear is different than the front too right? so comparing them together, a 300lb spring in the rear equates to much softer suspension than in the front. Running such a huge difference, just doesn't make any sense at all, especially given the split is higher in the rear for this very reason.

Simple...that's what JOMs are (according to someone in the thread). I didn't pick the rates. I'm looking for some ~600-700# rear springs atm but I have other things to deal with also.

[E30_fiend]

Simple...that's what JOMs are (according to someone in the thread). I didn't pick the rates. I'm looking for some ~600-700# rear springs atm but I have other things to deal with also.

Stephen, on here, is selling some 625lb 5_ rear springs


Taylor