[Bspreen]

I've got a loaded '06 325xi that sees a lot of Tail of the Dragon miles and soon to be occasional track use.
Its now hit about 97k miles and the rear shocks are in need of replacement. I talked to a local BMW specialist and discussed getting upgraded rear shocks because of how I drive.
My concern is that will not be enough to satisfy my handling needs, as the car already feels a little soft and floaty on country roads.

Handling wise I'd like to:
- Eliminate front end push/washout
- reduce body roll
- make the car rotate more readily (under liftoff/braking or power)

There seems to be a lot of debate about weather you should upgrade the front or rear bar, replace the suspension and even more debate about the effects of doing so. I wouldn't mind lowering the car if it would help. And I am not very concerned about ride quality. (I'm used to much worse)

I was hoping to get some input on what to do with the car from some people that have done this before.

Wheels: 19x8.5
Tires: Continental Extreme Contact DWS 235/35/r19

[CJ421]

Front end push is you over-driving the car; it's physics telling you to slow down. The car doesn't push if you stay within the grip limits of the tires; believe it or not you'll probably go through the corner quicker by going a tick 'slower'. The car will run cooler and your tires and brakes will last longer as well.

That said there's little denying your car is in need of a suspension overhaul and potentially a few other items if you're at 97K and haven't done much in the way of replacing parts. Suspension especially is a wear and tear item.

The most important upgrade overall would be tires. It's the only part of the car in normal contact with the road. I recommend some Michelin Pilot Super Sports. These tires are what BMW is including on its M cars. I upgraded my street setup to them a few years back and used to track them on HPDE's. Outstanding grip levels for a street tire and very good in the wet. They're also quiet and last a long time.

Next have your undercarriage inspected - look for signs of leaks around the control arms and for any worn bushings. Replace an entire arm instead of just the bushings.

For suspension (dampers/springs), what is the budget? Suspension is the last component to cheap out on.

P.S. a suspension with a poor ride is a poorly designed suspension. No exceptions.

[justpete]

Originally Posted by CJ421

P.S. a suspension with a poor ride is a poorly designed suspension. No exceptions.

No argument with anything but this. Race car suspensions for instance are nowhere near a quality ride. If you want your car to handle like one you need to be prepared for a ride like one. No exceptions. But if you're talking about street suspensions only then yeah you're right but the handling will be severely compromised. I see it at the track all the time.

[thakid22]

A few thoughts here...
DWS will make the car feel soft and mushy and increase roll and dive on their own.
The super soft sidewalls kill handling precision. DWS have good grip, really better than good. However micro steering response sucks. The first few degrees of steering wheel turn are slow, soft and relatively imprecise. On center steering feel leaves much to be desired. Some people care, others don't.

You upgraded to 19s which somewhat negate the soft side wall issue... Somewhat. They are still relatively soft.

Let me ask a question. How do you know the rear shocks are worn out? Leaking, noise, roughness, or bounce?
Know that all non M3 E90 are afflicted by a certain amount of rear bounce. So don't let bounce/rubberyness back there make you think the shocks are dead.

@97k miles, I would not replace just the rear. Do all four. You will definitely be able to notice new rears paired with 100k old front struts. The feeling will be one of disharmony between the front and rear axles, producing a lack of solidity in regards to feel. Stock spring/shock combos are tuned to have the car traverse bumps as a whole so the chassis acts as a unit rather than two axles attached to the same car. Stock E90 suspension is only average in this regard brand new. Worn/new shocks paired together will only lessen this important area of perceived ride quality.

Moving on...
Buy 4 replacements, if you feel you need new shocks.
Buy Dinan rear strut mounts to go on the rear shocks if you hate the rear bounce native to the E90 non M3 models. it will be cured.

Easiest way to cure the under steer is via tire pressure tweaks. 40 front and 35 rear will be a good starting point. Then reset Tpms.
Right away your car will be more lively and rotatable around the twisties. The increased front pressure will reduce dive, roll, and steering feel at the same time. Best of all this is
free and immediate. You can do this on new or old shocks.

[Bspreen]

Thanks for the reply.

Originally Posted by CJ421

Front end push is you over-driving the car
For suspension (dampers/springs), what is the budget? Suspension is the last component to cheap out on.
P.S. a suspension with a poor ride is a poorly designed suspension. No exceptions.

I spend a large amount of time tracking 911s so I may have unrealistic expectations for the car.
I Definitely agree with a lot of your points. I get the feeling I'm over-driving the car but I can tell that there is room to improve it. There is definitely room to improve over a stock non sport 325xi

As for tires I am a huge fan of MPSS(never had them last long though) I ended up with the DWS because I had purchased this car to be a winter warrior initially, but it has grown on me very fast. The DWS are actually very good for an all season tire with good snow traction.

Going to do the suspension overhaul soon, which is why I thought I'd figure this out now.

As for the budget, the car was only 11,300. Ideally I'd like to go with a more cost effective solution and not spend half the value of the car on suspension.
I think there is a general misconception people have that stiff=better handling. I was just mentioning that I didn't mind a worse ride because I spend so much time in track cars

Thanks for the response

[Bspreen]

[QUOTE=thakid22;17763985
Buy Dinan rear strut mounts to go on the rear shocks if you hate the rear bounce native to the E90 non M3 models. it will be cured.
[/QUOTE]
The tires can be replaced easily. I did notice the lack of on center steering feel and response.
And what prompted this post was actually the driver side rear shock just lost all its fluid the other day.
The suggestion to replace on the the rear shocks struck me as a bit unusual. Certainly would like to eliminate that rear end bounce somewhat. So I'll look into some of your suggestions.
I've always been very into driving and car control but this is my first serious foray into modification

[thakid22]

Originally Posted by Hubris

The tires can be replaced easily. I did notice the lack of on center steering feel and response.
And what prompted this post was actually the driver side rear shock just lost all its fluid the other day.
The suggestion to replace on the the rear shocks struck me as a bit unusual. Certainly would like to eliminate that rear end bounce somewhat. So I'll look into some of your suggestions.
I've always been very into driving and car control but this is my first serious foray into modification

Oh. Leaking. Yeah, it has gotta be replaced then...
I can't reiterate enough. Get the Dinan rear mounts. They are just 99 bucks and completely eliminate the rear bounce. You are already gonna have to remove the shocks so that is the perfect time. You will not retreat it. I wish someone had told me about the Dinans when I first got my 330i. That bounce irritated me to no ends. Curing it was the best thing I did for my ride.

On another note, why did BMW think that was appropriate in the first place. I guess they thought the rear end bounce added "character." The E36 did this too sometimes. But on those cars the entire car (front and rear together) would have a little hop that was indeed sporty, over some surfaces. The E90 on the other hand is just comical with that rear only bounce.

[CJ421]

Yes the rear upper shock mounts (RSM's) are wear and tear items. Replace them with harder versions - I don't know about the Dinan ones mentioned above but I believe Powerflex sells some as well. Perhaps look on Turner's site for others (or better yet, call them). What happens is that when the rear hits a bump, the RSM's will move first - then the dampers will come into play. So even with the greatest suspension, if you have soft RSM's, it's compromising your suspension.

Replace all of the dampers at the same time. KW V1 is a good kit if you're on a budget, or for a bit more, the Ground Control coilover kit is a good upgrade.

Adding some negative front camber does a lot for handling and will help grip in turns. I like the Ground Control ones. They use Aurora bearings and have excellent machining quality. I think they are available for XI, but verify.

So:
--Michelin PSS tires
--KW V1 (or other damper/spring combo)
--Replace any bushings/arms that require replacement re: my first post in this thread
--Stiffer RSM's
--Camber plates
--New alignment (more camber in front; -1.5 to -2 deg)

...and you'll have a very different car.

[Bspreen]

Originally Posted by CJ421

Yes the rear upper shock mounts (RSM's) are wear and tear items. Replace them with harder versions - I don't know about the Dinan ones mentioned above but I believe Powerflex sells some as well. Perhaps look on Turner's site for others (or better yet, call them). What happens is that when the rear hits a bump, the RSM's will move first - then the dampers will come into play. So even with the greatest suspension, if you have soft RSM's, it's compromising your suspension.

Replace all of the dampers at the same time. KW V1 is a good kit if you're on a budget, or for a bit more, the Ground Control coilover kit is a good upgrade.

Adding some negative front camber does a lot for handling and will help grip in turns. I like the Ground Control ones. They use Aurora bearings and have excellent machining quality. I think they are available for XI, but verify.

So:
--Michelin PSS tires
--KW V1 (or other damper/spring combo)
--Replace any bushings/arms that require replacement re: my first post in this thread
--Stiffer RSM's
--Camber plates
--New alignment (more camber in front; -1.5 to -2 deg)

...and you'll have a very different car.

Thats a pretty good list! I was doing a little research and was coming to similar conclusions. I just cant seem to find the Dinan rears