Advice on 318iS suspesion setup

[LN_318iS]

Hi guys, one of my first posts here. I'm here to get some advice for my new suspension setup on my 318iS. I'm doing a complete restoration of the car itself. Now i need to start thinking ahead what i want for now. I'm not going 'full race mode' because i still want it to be 'driveable' on normal roads. More like 'spirited country lane driving'. PU bushes or not, heavier ARB's, strutbrace, which springs en dampers, M3 (E30 or E36) control arm bushes, ... Plz help me out Normally i'm putting in a M50b25... Something to take into account i guess?

Ps: Sorry for the grammar. English is not my first language. Belgian here

[Brianmoooore]

Welcome to the zone! Your grammar is better than many on here.
Just had part of your discussion very recently: http://www.e30zone.net/modules.php?name ... c&t=274514
For springs, either Eibech or H&R -35mm, and dampers, Bilstein B4 for UK roads, or possibly B6/B8 if in Europe.

[TurtleDesignTech]

Welcome to the zone! Your grammar is better than many on here.
Just had part of your discussion very recently: http://www.e30zone.net/modules.php?name ... c&t=274514
For springs, either Eibech or H&R -35mm, and dampers, Bilstein B4 for UK roads, or possibly B6/B8 if in Europe.

Does the combining stiffer -35mm springs (H&R) with OE replacement B4 shocks, have any affect on the longevity of the shocks?

[Topblag]

I'd go for the eibach springs, not as harsh when driving sensibly.

[rob420]

Welcome to the zone! Your grammar is better than many on here.
Just had part of your discussion very recently: http://www.e30zone.net/modules.php?name ... c&t=274514
For springs, either Eibech or H&R -35mm, and dampers, Bilstein B4 for UK roads, or possibly B6/B8 if in Europe.

I am in a very similar position to OP, have an '89 318i which is almost finished with its m50 conversion. I am going to be upgrading springs, shocks and bushings. I already know I am going to be going with rubber bushes all around (not a fan of the ride with poly bushes). Not so sure on springs/shocks though.


You say to go for the springs with around 35mm drop, would these then be something like H&R sports? I was looking at those but have heard lots about how the spring rate is quite soft for the lowering, causing them to hit bump stops quite a bit on rough roads (lots around where I live), just wondering if that is actually a problem? Maybe H&R OE sports could be better? (similar spring rate but higher ride height)


Otherwise I have also heard H&R race can be good at solving this, but I am then worried about suspension geometry, mostly with the front control arms being past parallel to the ground. Not sure if this is a problem or if it can be fixed with maybe using thicker spring pads to raise it a little, but have only seen decent size pads available for the rear.


Shocks depend on what springs are used so if anybody has any experience with spring setups, any advice would be greatly appreciated!

[TurtleDesignTech]

Welcome to the zone! Your grammar is better than many on here.
Just had part of your discussion very recently: http://www.e30zone.net/modules.php?name ... c&t=274514
For springs, either Eibech or H&R -35mm, and dampers, Bilstein B4 for UK roads, or possibly B6/B8 if in Europe.

I am in a very similar position to OP, have an '89 318i which is almost finished with its m50 conversion. I am going to be upgrading springs, shocks and bushings. I already know I am going to be going with rubber bushes all around (not a fan of the ride with poly bushes). Not so sure on springs/shocks though.


You say to go for the springs with around 35mm drop, would these then be something like H&R sports? I was looking at those but have heard lots about how the spring rate is quite soft for the lowering, causing them to hit bump stops quite a bit on rough roads (lots around where I live), just wondering if that is actually a problem? Maybe H&R OE sports could be better? (similar spring rate but higher ride height)


Otherwise I have also heard H&R race can be good at solving this, but I am then worried about suspension geometry, mostly with the front control arms being past parallel to the ground. Not sure if this is a problem or if it can be fixed with maybe using thicker spring pads to raise it a little, but have only seen decent size pads available for the rear.


Shocks depend on what springs are used so if anybody has any experience with spring setups, any advice would be greatly appreciated!

I have been doing research for some time as I need to refresh the shocks and springs on my 316i.

From what I understand so far:

Anything more than 35mm drop will ruin the suspension geometry.

Therefore, as I care about suspension geometry this narrows the choice of springs to: H&R Sports, Eibach or H&R OE Sports.

Spring rates copied from some other forum:

Spring---------------------Front(lb/in.)------------------Rear(lb/in.)

Stock 325i*-----------------------106-------------------------245

Stock 325is*----------------------118-------------------------265

H&R OE Sport---------------------180-------------------------380

H&R Sport-------------------------180------------------------380

Eibach Pro-Kit--------------------114 linear --------------------------280 - 326 progressive

As you can see the H&R sports/OE sports have and 80% increase in spring rate compared to stock 325i/s springs.

After some further research about suspension geometry and eventually stumbling on MotoIQ's website; it appears logical to that if you are lowing a car you HAVE to INCREASE the spring rate.

The higher the spring rate, the more force required for the car to reach the bump stops.

Essentially, you need the higher spring rate to compensate for lowering the car as the springs are now shorter.

Furthermore, the high spring rate should in theory stop the car from having as much body roll in corners, or loading up all the way to the point of sitting on the bump stop mid corner, effectively give you and infinite spring rate. While this might "feel sporty" it actually ruining the handling of your car.

That leaves you with the choice of H&R Sports vs H&R OE Sports. H&R Sports can be found for £120 on eBay for all 4 corners.

OE Sports seem to me to be quite hard to come across in Europe. The only place you can pick them up is the dealer and they are considerably more expensive.

Then comes the discussion of shocks.

Bilstein B4 vs B6 vs B8.

B6 and B8 have the same valving. B8 have huge bumpstops to comply to Germany TUV regulations. The B8's are supposedly to be used when "lowering". By Germany law, the car has to keep the springs in place when jacked up. Hence the longer bumpstops, to supposedly stop the spring falling of the perch. I have no idea if this is a real issue or not.

From my research I concluded, probably best just to use B6's with the largest spring pads and opt for B6 or B4's.

Hence we come to my questions earlier.

All I have managed to find out is that "supposedly" as B4's have stock valving and you are using shorter springs, you could be in theory over working the shock, therefore affecting it's longevity. At least this is what some people claim on other forums I have read. I have no idea though, if this is true or not.

If it does not affect longevity, it would appear to me the most logical set up is similar to what Brian said:

UK roads - B4 + H&R Sports
Europe - B6 + H& Sports

[rob420]

I have been doing research for some time as I need to refresh the shocks and springs on my 316i.

From what I understand so far:

Anything more than 35mm drop will ruin the suspension geometry.

Therefore, as I care about suspension geometry this narrows the choice of springs to: H&R Sports, Eibach or H&R OE Sports.

Spring rates copied from some other forum:

Spring---------------------Front(lb/in.)------------------Rear(lb/in.)

Stock 325i*-----------------------106-------------------------245

Stock 325is*----------------------118-------------------------265

H&R OE Sport---------------------180-------------------------380

H&R Sport-------------------------180------------------------380

Eibach Pro-Kit--------------------114 linear --------------------------280 - 326 progressive

As you can see the H&R sports/OE sports have and 80% increase in spring rate compared to stock 325i/s springs.

After some further research about suspension geometry and eventually stumbling on MotoIQ's website; it appears logical to that if you are lowing a car you HAVE to INCREASE the spring rate.

The higher the spring rate, the more force required for the car to reach the bump stops.

Essentially, you need the higher spring rate to compensate for lowering the car as the springs are now shorter.

Furthermore, the high spring rate should in theory stop the car from having as much body roll in corners, or loading up all the way to the point of sitting on the bump stop mid corner, effectively give you and infinite spring rate. While this might "feel sporty" it actually ruining the handling of your car.

That leaves you with the choice of H&R Sports vs H&R OE Sports. H&R Sports can be found for £120 on eBay for all 4 corners.

OE Sports seem to me to be quite hard to come across in Europe. The only place you can pick them up is the dealer and they are considerably more expensive.

Then comes the discussion of shocks.

Bilstein B4 vs B6 vs B8.

B6 and B8 have the same valving. B8 have huge bumpstops to comply to Germany TUV regulations. The B8's are supposedly to be used when "lowering". By Germany law, the car has to keep the springs in place when jacked up. Hence the longer bumpstops, to supposedly stop the spring falling of the perch. I have no idea if this is a real issue or not.

From my research I concluded, probably best just to use B6's with the largest spring pads and opt for B6 or B4's.

Hence we come to my questions earlier.

All I have managed to find out is that "supposedly" as B4's have stock valving and you are using shorter springs, you could be in theory over working the shock, therefore affecting it's longevity. At least this is what some people claim on other forums I have read. I have no idea though, if this is true or not.

If it does not affect longevity, it would appear to me the most logical set up is similar to what Brian said:

UK roads - B4 + H&R Sports
Europe - B6 + H& Sports

My thinking is the same as yours, I want good geometry and a decent amount of suspension travel due to the rough roads around where I live. I have heard of H&R sports being too soft for their ride height, causing issues with cars hitting their bump stops on rough roads. Not sure if this is true though so I'm wondering if anybody has any input on this?

I am considering H&R OE sports for the same spring rate but a little extra suspension travel. Only problem is most reviews of them I've found seem to end with "too high or too soft, swapped to h&r race which were perfect". This is not helpful for me as I would rather the suspension works as intended rather than just dropping as low and stiff as you can go. Looking from a technical point, due to the static compression of soft springs, you get a bit more grip from softer springs as they expand faster and with more force than stiffer springs when encountering bumps/dips in the road.

I would probably match these with Bilstein HD (not sure what the equivalents are in different parts of the world) or some sort of Koni shocks if I can find them for a good price.

[LN_318iS]

Thanks for the info, guys! But my iS is (normally) going to run a m50b25 engine. So technically the front springs should have a higher spring rate to be perfect?

[TurtleDesignTech]

Thanks for the info, guys! But my iS is (normally) going to run a m50b25 engine. So technically the front springs should have a higher spring rate to be perfect?

In that case I would buy springs advertised for a 325i, as the M20 engine weighs nearly the same as the M50.

The 325i advertised springs should have a higher front spring rate compared to 316i/318is springs, to compensate for the extra nose weight. This would be the most ideal solution.

The wiki mentions upgrading to 51mm front struts to deal with the extra weight. Means you can run the larger 51mm front dampers as well. Basically everything for a 325i.

[Brianmoooore]

iS should already have 51mm struts.

[LN_318iS]

iS should already have 51mm struts.

Correct!

[reggid]

shocks screw up the ride not the springs (unless you lower the car with soft springs aka eibach)

if i was doing a mild setup id look for koni and H&R been down the eibach billy rd

new OE or lemforder rubber bushes, slighty bigger antiroll bar(s) (adjustable type to dial in the balance) with OE bushes