[Daily_Driver]

The suspension on my 2007 E92 (coupe) 328i (MT) is at 75,000 miles and needs to be refreshed. This is a daily driver (60 mile/day commute) with NO plans for track time (although I have spent way too much time on a track). I run a square 17" setup with both RFT (summer) and non-RFT (winter).

I am considering the B12 Bilstein Pro-Kit. The sticky at the top indicates that the spring rates are the same as my 'BMW Sport Suspension' and that seems to be confirmed by those that have tried the pro-kit.

These are 'progressive' springs, meaning that while the initial travel in the spring may be similar to stock, they get progressively stiffer. Can someone explain why i might prefer 'progressive' springs over 'linear' springs for a daily driver? I get that they will make small bumps more tolerable (a good thing for a commuter car) but do 'progressives' have unusual traits as they become compressed?

[CJ421]

You stated it - a progressive spring is preferred for street use because its soft initial rate allows it to compress more vs. a linear spring (w/ a similar avg. rate) for the same bump; that extra travel allows the illusion the progressive setup is soaking up bumps ('comfortable ride') since the car body moves less - because the suspension is traveling more.

Linear spring use requires a damper with a well-designed compression stroke to be comfortable e.g. not harsh.

I'd have a hard time making up a reason for you to spend extra for a setup with a linear rate.

[D's Bimmer]

Originally Posted by CJ421

You stated it - a progressive spring is preferred for street use because its soft initial rate allows it to compress more vs. a linear spring (w/ a similar avg. rate) for the same bump; that extra travel allows the illusion the progressive setup is soaking up bumps ('comfortable ride') since the car body moves less - because the suspension is traveling more.

Linear spring use requires a damper with a well-designed compression stroke to be comfortable e.g. not harsh.

I'd have a hard time making up a reason for you to spend extra for a setup with a linear rate.

I agree. I ended up going with the Bilstein B12 setup for my daily driver.

[cvc 22349a]

[QUOTE=Daily_Driver;15390482]The suspension on my 2007 E92 (coupe) 328i (MT) is at 75,000 miles and needs to be refreshed. This is a daily driver (60 mile/day commute) with NO plans for track time (although I have spent way too much time on a track). I run a square 17" setup with both RFT (summer) and non-RFT (winter).

I am considering the B12 Bilstein Pro-Kit. The sticky at the top indicates that the spring rates are the same as my 'BMW Sport Suspension' and that seems to be confirmed by those that have tried the pro-kit.

These are 'progressive' springs, meaning that while the initial travel in the spring may be similar to stock, they get progressively stiffer. Can someone explain why i might prefer 'progressive' springs over 'linear' springs for a daily driver? I get that they will make small bumps more tolerable (a good thing for a commuter car) but do 'progressives' have unusual traits as they become compressed?[/QUOTE]

Not unusual but will roll more initially then set in turns but may not be that noticeable since they also lower the car. Never read anyone being unhappy with those springs for a DD.

[cvc 22349a]

Originally Posted by D's Bimmer

I agree. I ended up going with the Bilstein B12 setup for my daily driver.

Pls post a review after you've had them installed for a bit. Intriguing spring/shock combo.

[jjellyneck]

How much might a slightly stiffer sway bar in front mitigate the "set in" or initial roll in hard cornering? OK....I'll do a search

[KKelly]

My only experience with a progressive spring was riding in an Audi and an E34 M5. Candidly, I hated them. I thought both cars porpoised quite a bit. I am sure that it was deficient shock valving for the spring but I just prefer an immediate response.

[mlifxs]

op thanks for this question.

that b12 kit keeps getting mentioned on this subforum...interesting

[mike-y]

Originally Posted by KKelly

My only experience with a progressive spring was riding in an Audi and an E34 M5. Candidly, I hated them. I thought both cars porpoised quite a bit. I am sure that it was deficient shock valving for the spring but I just prefer an immediate response.

My track car with high linear rates and custom valve konis porpoises like a mofo on uneven pavement. stiff suspensions tend to do that, since they are less likely to soak up small bumps. it really depends on how the damper is tuned though, as long as the rates are reasonable, you can get a good ride with the proper damper, regardless of the type of spring (linear/progressive).

KW V1-V3 have progressive rates and people don't complain about porpoising with those.

[KKelly]

Originally Posted by mike-y

My track car with high linear rates and custom valve konis porpoises like a mofo on uneven pavement. stiff suspensions tend to do that, since they are less likely to soak up small bumps. it really depends on how the damper is tuned though, as long as the rates are reasonable, you can get a good ride with the proper damper, regardless of the type of spring (linear/progressive).

KW V1-V3 have progressive rates and people don't complain about porpoising with those.

I understand as I drive the M3 on the street. It is a matter of degree I guess. I was driving my M3 last week and the chassis just felt active to me. A couple of clicks more on rebound and while stiffer it is a lot more controlled. When I say porpoising I mean it kind of oscillates more than it needs to. I am sure a kit designed to go together eliminates a lot of that.

[PanSid]

Which is the best springs for E92 320i coupe?

Eibach sportline,H&R sport or Hartge?

[cvc 22349a]

Originally Posted by PanSid

Which is the best springs for E92 320i coupe?

Eibach sportline,H&R sport or Hartge?

Best is subjective. You have to do the research and decide.

[PanSid]

What are the positive and what negatives of each spring?

[mike-y]

Originally Posted by KKelly

When I say porpoising I mean it kind of oscillates more than it needs to.

ah, that would indicate a damper that isn't strong enough to control the high spring rate. My track car does follow the bumps more than my E90 (600lb springs on a 2200 lbs car), but it does not oscillate more than once after initial compression. It's very controlled because of the revalved shocks.

[shadow191]

Progressive is better for a streetcar IMO. Better small bump absorption and less likely to bottom out. Most cheaper coilovers are linear, BC is linear. I run BC's on my other car and it was blowing through the travel so I had to swap to higher rate springs. Now it's very rough over small bumps. I have V3's on the BMW and it feels much more compliant.

[CALWATERBOY]

Originally Posted by CJ421

You stated it - a progressive spring is preferred for street use because its soft initial rate allows it to compress more vs. a linear spring (w/ a similar avg. rate) for the same bump; that extra travel allows the illusion the progressive setup is soaking up bumps ('comfortable ride') since the car body moves less - because the suspension is traveling more.

Linear spring use requires a damper with a well-designed compression stroke to be comfortable e.g. not harsh.

I'd have a hard time making up a reason for you to spend extra for a setup with a linear rate.

Better handling. Ride's mildly firmer @ low speed [read: small bumps]. Better at higher speeds. Exquisite in twisties. Hasn't the buildup to high resistance progressives have - they have a >AHEM< linear response.

[solishe]

Originally Posted by D's Bimmer

I agree. I ended up going with the Bilstein B12 setup for my daily driver.

Hi. I'm very curious to know the part number of the Eibach springs you receive with the B12 kit. I called Bilstein USA and got part numbers for front and rear springs included in the kit, then I called Eibach USA and they recognized one set of part numbers but not the other. They made it seem like B12 kit came with European part numbers (designed for their roads). Anyway, as I have B8 dampers I may look to buy the B12 kit springs but I would need part numbers. I don't want to assume its the standard USA Eibach Pro Kit part number. This on top of the fact I've heard some say Eibach pro springs are progressive and others say they are linear just adds to the confusion. The Eibach rep I spoke with said they are linear and he even gave me the linear rates. Soooo....yeah, any spring part numbers you see would be awesome!

[jjellyneck]

^ what are the Eibach spring rates that he stated?

[mlifxs]

Originally Posted by solishe

Hi. I'm very curious to know the part number of the Eibach springs you receive with the B12 kit. I called Bilstein USA and got part numbers for front and rear springs included in the kit, then I called Eibach USA and they recognized one set of part numbers but not the other. They made it seem like B12 kit came with European part numbers (designed for their roads). Anyway, as I have B8 dampers I may look to buy the B12 kit springs but I would need part numbers. I don't want to assume its the standard USA Eibach Pro Kit part number. This on top of the fact I've heard some say Eibach pro springs are progressive and others say they are linear just adds to the confusion. The Eibach rep I spoke with said they are linear and he even gave me the linear rates. Soooo....yeah, any spring part numbers you see would be awesome!

same here on the eibach spring rates, Called them around end of the year, asked about spring rates for 2085 and 2092. rep gave the same rates for both and said they were linear....meanwhile, as you suggest, places like Turner describe the springs in the b12 kit as progressive...eibach also describes springs for the f30 as progressive, on the US website.

[cvc 22349a]

Originally Posted by mlifxs

same here on the eibach spring rates, Called them around end of the year, asked about spring rates for 2085 and 2092. rep gave the same rates for both and said they were linear....meanwhile, as you suggest, places like Turner describe the springs in the b12 kit as progressive...eibach also describes springs for the f30 as progressive, on the US website.

If they're Eibach pro kit springs, they're progressive and of similar rate as oem zsp unless they've changed in the last 7 years.

[solishe]

Originally Posted by cvc 22349a

If they're Eibach pro kit springs, they're progressive and of similar rate as oem zsp unless they've changed in the last 7 years.

Exactly why I'm confused. Rep told me linear for the 2092 pro kit.....either way I'm just curious to know what spring part numbers are in the B12 kit. I'm wondering if Europe uses progressive for the road situation out there and Eibach USA uses linear?? I got the vibe from Bilstein that the B12 is kitted overseas. Leading me to wonder which springs are in this kit (as I read the B8s were valved particularly for the springs in that kit).

[solishe]

Originally Posted by jjellyneck

^ what are the Eibach spring rates that he stated?

The same values as on this forum's spring rate sticky.

Front: 148 lb/in
Rear: 456 lb/in