[krahooligan]

Hey e90post,

can I install new springs on a stock OEM suspension and get better handling or do I need to get coilovers?
kind of on a tight budget, so coilovers may be out of the question until spring.

[ammar23]

As far as I know the only reason to get new springs without new suspension is going for a lowered look... But it'll cost you ride quality for sure.

I may be wrong anyways

[krahooligan]

Originally Posted by ammar23

As far as I know the only reason to get new springs without new suspension is going for a lowered look... But it'll cost you ride quality for sure.

I may be wrong anyways

no im pretty sure your right. I don't know anything about suspension.

[justpete]

Originally Posted by krahooligan

Hey e90post,

can I install new springs on a stock OEM suspension and get better handling or do I need to get coilovers?
kind of on a tight budget, so coilovers may be out of the question until spring.

What kind of handling improvement are you looking for? Sounds like a dumb question but different aspects of weight transfer appear at higher speeds and faster transitions. This leads to a progression of changes that can get costly when stepping up from one set of mods to another but isn't exactly cheap to do all at once.

[krahooligan]

Originally Posted by justpete

What kind of handling improvement are you looking for? Sounds like a dumb question but different aspects of weight transfer appear at higher speeds and faster transitions. This leads to a progression of changes that can get costly when stepping up from one set of mods to another but isn't exactly cheap to do all at once.

less roll in corners, about an inch lower ride height. im trying to avoid the harsh and bumpy ride that I feel in so many of my friends cars with coilovers.
so basically looking for something that Is track friendly, but also decent for daily driving.

[justpete]

Originally Posted by krahooligan

less roll in corners, about an inch lower ride height. im trying to avoid the harsh and bumpy ride that I feel in so many of my friends cars with coilovers.
so basically looking for something that Is track friendly, but also decent for daily driving.

Understood. That's a tough compromise to reach, that's for sure, but understandable. I initially swapped out the stock sport suspension at 900 miles for the BMW Performance suspension and it made a huge improvement. Much less bouncy, tighter, less roll, another half inch of drop. It was perfect for the street as far as I was concerned and I think it still is. It'd be about an inch drop from stock, flattens cornering quite a bit, and drops right in.

Not cheap but it's a factory tuned suspension that avoids trying to mix and match parts to get a decent improvement especially if you're not DIYing it.

Your tires are going to make a difference. The chassis bushings are compliant enough to make the ride reasonable on stiff sidewall RFTs. Ride is going to be vastly different between tires. Most think it'll be better on non-RFTs but this isn't necessarily true.

For instance Pirelli P-Zero RFTs weigh within a pound of non-RFTs and have a sidewall stiffness not that much different from non-RFTs yet they have excellent traction for an RFT. These are now only used as winter tires since they got swapped out for Toyo R1R tires on the same rim diameter and with an aspect ratio that yields the same rolling diameter for use on the track. The Pirellis are a staggered setup but the Toyos are 255/35 square. The difference is the Pirellis make using the phone in the car a bit of a problem on rough stretches of freeway whereas the Toyos make it impossible because they're non-RFTs with a much stiffer sidewall. But then they're designed that way for track handling.

[krahooligan]

Originally Posted by justpete

Understood. That's a tough compromise to reach, that's for sure, but understandable. I initially swapped out the stock sport suspension at 900 miles for the BMW Performance suspension and it made a huge improvement. Much less bouncy, tighter, less roll, another half inch of drop. It was perfect for the street as far as I was concerned and I think it still is. It'd be about an inch drop from stock, flattens cornering quite a bit, and drops right in.

Not cheap but it's a factory tuned suspension that avoids trying to mix and match parts to get a decent improvement especially if you're not DIYing it.

Your tires are going to make a difference. The chassis bushings are compliant enough to make the ride reasonable on stiff sidewall RFTs. Ride is going to be vastly different between tires. Most think it'll be better on non-RFTs but this isn't necessarily true.

For instance Pirelli P-Zero RFTs weigh within a pound of non-RFTs and have a sidewall stiffness not that much different from non-RFTs yet they have excellent traction for an RFT. These are now only used as winter tires since they got swapped out for Toyo R1R tires on the same rim diameter and with an aspect ratio that yields the same rolling diameter for use on the track. The Pirellis are a staggered setup but the Toyos are 255/35 square. The difference is the Pirellis make using the phone in the car a bit of a problem on rough stretches of freeway whereas the Toyos make it impossible because they're non-RFTs with a much stiffer sidewall. But then they're designed that way for track handling.

thanks man! ill definitely look into that BMW PE suspension. im not really to concerned about how loud the tires are...they cant be that loud can they? also, would sway bars be a good idea to purchase? its all an idea right now, but im saving up for rims, tires and suspension.

[justpete]

Originally Posted by krahooligan

thanks man! ill definitely look into that BMW PE suspension. im not really to concerned about how loud the tires are...they cant be that loud can they? also, would sway bars be a good idea to purchase? its all an idea right now, but im saving up for rims, tires and suspension.

Neither tire was loud or became loud with wear, not a big concern though so I may just not have noticed, sorry.

The PE comes with a new front bar, you'll likely want to leave the rear bar stock. A stiffer rear bar will create the sensation of crisper turn-in but it adds to the risk of lifting the inner rear wheel in aggressive situations or at the very least increasing the chance of spin causing the e-diff function to react and pulse the inside rear brake to steer torque to the outer wheel since the car runs an open differential. The stock rear bar will minimize this and keep the rear tires on the road. Crisper turn-in can be achieved with M3 front control arms, spherical bearings in the LFCA, and camber plates, etc. The ride quality suffers as does the steering sensitivity for street use though. As usual YMMV.

If you keep the rolling diameter the same as stock with the new wheels and tires the only thing to watch out for is interference with the front strut if the new rims and tires are too wide.

[krahooligan]

Originally Posted by justpete

Neither tire was loud or became loud with wear, not a big concern though so I may just not have noticed, sorry.

The PE comes with a new front bar, you'll likely want to leave the rear bar stock. A stiffer rear bar will create the sensation of crisper turn-in but it adds to the risk of lifting the inner rear wheel in aggressive situations or at the very least increasing the chance of spin causing the e-diff function to react and pulse the inside rear brake to steer torque to the outer wheel since the car runs an open differential. The stock rear bar will minimize this and keep the rear tires on the road. Crisper turn-in can be achieved with M3 front control arms, spherical bearings in the LFCA, and camber plates, etc. The ride quality suffers as does the steering sensitivity for street use though. As usual YMMV.

If you keep the rolling diameter the same as stock with the new wheels and tires the only thing to watch out for is interference with the front strut if the new rims and tires are too wide.

would spacers clear up the interference with the front strut?
I have so much to learn about suspension....

[justpete]

Originally Posted by krahooligan

would spacers clear up the interference with the front strut?
I have so much to learn about suspension....

They will but if you need them then you need to have the fenders rolled and likely pulled. Increasing camber can help with clearances to the fender/bumper but will decrease clearance to the strut.

[cdgatti]

Here is a popular and recommended order of improvement - go as far as you need to:

1. Change to good non-rft tires
2. Bilstein B12 kit (eibach springs and bilstein B8)
3. M3 front control arms
4. M3 rear subframe bushings
5. e93 M3 front sway bar
6. LSD (for 335) and M3 rear sway bar

[koches]

Originally Posted by cdgatti

Here is a popular and recommended order of improvement - go as far as you need to:

1. Change to good non-rft tires
2. Bilstein B12 kit (eibach springs and bilstein B8)
3. M3 front control arms
4. M3 rear subframe bushings
5. e93 M3 front sway bar
6. LSD (for 335) and M3 rear sway bar

What about non 335s, such as my 330xi?

[andrey_gta]

Coils give you fresh shocks - those make things nice with the stiffer springs

[cdgatti]

Originally Posted by koches

What about non 335s, such as my 330xi?

non 335 do not need the LSD. There isn't enough power with the lower power cars to worry about spinning the inside wheel.

[The HACK]

Originally Posted by cdgatti

non 335 do not need the LSD. There isn't enough power with the lower power cars to worry about spinning the inside wheel.

That's a stupid statement. Even my lowly E46 323Ci could use an LSD, there were plenty of "inside wheel" spin at two of the slower corners at Buttonwillow, Button Hook and Star Mazda.

And the 323Ci only made 170HP. On a good day.

The right answer would have been, no, the 330Xi would need a limited slip up front, limited slip in the rear, and a central locking diff, otherwise it'll send power to the wheel that doesn't have traction, because it splits the power 2 ways (front and rear) between two open diffs.

[justpete]

Originally Posted by cdgatti

non 335 do not need the LSD. There isn't enough power with the lower power cars to worry about spinning the inside wheel.

Huh. Funny thing, a clutch type LSD helped me lose over four seconds a lap at MSRC. And yes it was the LSD since it was the only change. Its elimination of inside wheel spin, well except at two of the apexes in the double chicane at MSR Cresson, was obvious as was the sensation that it was helping push the car through corners as opposed to the e-diff always kinda lagging it through the corners.

And it's not just on the track, the car is vastly better handling on the street.