Suspension questions - trying to improve

[jmz135]

Hi all - I'm having some [issues] with my rear suspension and I want to improve the suspension in a way that doesn't waste my money.

I recently bought new wider wheels as well as ditched RFTs for some continental extremecontact DW tires.

After breaking in the tires for 150 miles or so I went for a hard drive through some mountain roads over the weekend. The rear-end now feels extremely floaty/squirmey. I did notice this before, but it was not nearly this pronounced.

I attributed the feeling to the RFTs before, but now I'm thinking it wasn't really the tires before causing the feeling. I did some research on this sub-forum over the last week and saw many mentions of sub frame bushings being a weak link in our suspension, which becomes more noticeable as you upgrade other parts of the car.

While I'm willing to spend some money, I did not want to spend $1k+ for an install, so I went ahead and purchased some whiteline inserts (should arrive this week).

I'm hoping this improves the issues I'm feeling. My question to you all - is there anything else that is causing this lack of firmness in the rear end as I'm cornering? Or is it only the bushings? Is there any other good bang for buck improvement I can do for a reasonable amount of money ($4-500)?

Ones I'm considering:
M3 Front Sway Bar
M3 control arms

Side note - I also have a set of ST coilovers waiting to be installed next weekend.

[128Convertibleguy]

The inserts will help. There is some debate over exactly how much more the bushings do, some people saying the difference is large, some not. It depends on a lot of things, not least the state of your bushings.

The front bar will likely help, by simultaneously putting more of the cornering load on the front, and making it better able to handle it.

The coilovers will be a mixed bag. Stiffer springs will, as you say, make any weaknesses worse. Better shocks will make things better. Where it all will fall out is difficult to say. One reason I kept stock springs and upgraded the shocks to Koni FSDs.

Suspension is complicated. It all interacts, and many times a change can have counter-intuitive results. Setups right for one person may not be good for others. The bushings and the RFTs are such weak points that it's relatively easy to get better results than stock. Past that, you're in murky waters.

[chris82]

Originally Posted by jmz135

Hi all - I'm having some [issues] with my rear suspension and I want to improve the suspension in a way that doesn't waste my money.

I recently bought new wider wheels as well as ditched RFTs for some continental extremecontact DW tires.

After breaking in the tires for 150 miles or so I went for a hard drive through some mountain roads over the weekend. The rear-end now feels extremely floaty/squirmey. I did notice this before, but it was not nearly this pronounced.

I attributed the feeling to the RFTs before, but now I'm thinking it wasn't really the tires before causing the feeling. I did some research on this sub-forum over the last week and saw many mentions of sub frame bushings being a weak link in our suspension, which becomes more noticeable as you upgrade other parts of the car.

While I'm willing to spend some money, I did not want to spend $1k+ for an install, so I went ahead and purchased some whiteline inserts (should arrive this week).

I'm hoping this improves the issues I'm feeling. My question to you all - is there anything else that is causing this lack of firmness in the rear end as I'm cornering? Or is it only the bushings? Is there any other good bang for buck improvement I can do for a reasonable amount of money ($4-500)?

Ones I'm considering:
M3 Front Sway Bar
M3 control arms

Side note - I also have a set of ST coilovers waiting to be installed next weekend.

Look into the rear upper shock mount. Dinan sells one as does Rogue Engineering and Powerflex. I have the Powerflex Black ones on mine, although I can't tell what it did specifically as I had my shocks and lower mount replaced back there too at the same time.

The Dinan ones are $99 a pair. I read that they also increase shock travel by 1cm.

They seem to be worth it: http://www.1addicts.com/forums/showp...42&postcount=1

Specifically: "Well - here's the mini review - the Dinan rear shock mounts did work. They firmed up the rear so the bounce is gone, and the car now feels much more under control and balanced. There's no noise or harshness - the ride is actually more comfortable. Definitely recommended."

If your installing coils anyway, I'd jump on it, sounds like it will be worth it.

[jmz135]

Originally Posted by 128Convertibleguy

The inserts will help. There is some debate over exactly how much more the bushings do, some people saying the difference is large, some not. It depends on a lot of things, not least the state of your bushings.

The front bar will likely help, by simultaneously putting more of the cornering load on the front, and making it better able to handle it.

The coilovers will be a mixed bag. Stiffer springs will, as you say, make any weaknesses worse. Better shocks will make things better. Where it all will fall out is difficult to say. One reason I kept stock springs and upgraded the shocks to Koni FSDs.

Suspension is complicated. It all interacts, and many times a change can have counter-intuitive results. Setups right for one person may not be good for others. The bushings and the RFTs are such weak points that it's relatively easy to get better results than stock. Past that, you're in murky waters.

Thanks for the feedback! I figure if the inserts even improve it by 50% compared to actually replacing the bushings it is worth it as they are so cheap and comparatively easy to install. I don't plan on seriously tracking my car where I'm trying to shave off seconds, I just want to get to what I consider "good enough".

I'm trying to do some more research regarding the FSB - seems to have mixed reviews on this forum. It's an attractive option because it's fairly cheap and I can do the install easily myself.

I'll be installing the coils and inserts this coming weekend and I'll be able to report back on my experience.

[jmz135]

Originally Posted by Chrisar82

Look into the rear upper shock mount. Dinan sells one as does Rogue Engineering and Powerflex. I have the Powerflex Black ones on mine, although I can't tell what it did specifically as I had my shocks and lower mount replaced back there too at the same time.

The Dinan ones are $99 a pair. I read that they also increase shock travel by 1cm.

They seem to be worth it: http://www.1addicts.com/forums/showp...42&postcount=1

Specifically: "Well - here's the mini review - the Dinan rear shock mounts did work. They firmed up the rear so the bounce is gone, and the car now feels much more under control and balanced. There's no noise or harshness - the ride is actually more comfortable. Definitely recommended."

If your installing coils anyway, I'd jump on it, sounds like it will be worth it.

Thanks for the tip - I hadn't come across the shock mount in any other threads yet. So it is the piece that connects the shock to the frame? It actually looks like it is $84 on Dinan's website right now. Like you said, if I had them when I was installing coils I will already have the relevant pieces off the car...

[128Convertibleguy]

Originally Posted by jmz135

I'm trying to do some more research regarding the FSB - seems to have mixed reviews on this forum.

You do have to research this for yourself. Take note of who is basing their opinion on actual experience, and who on their concept of the theory. Simplified theories about front bars usually apply to race cars, and often not to McPherson strut cars.

[jmz135]

Originally Posted by 128Convertibleguy

You do have to research this for yourself. Take note of who is basing their opinion on actual experience, and who on their concept of the theory. Simplified theories about front bars usually apply to race cars, and often not to McPherson strut cars.

I'm trying to figure out if what I'm feeling is car body roll, or just too much subframe movement in the rear. It is hard to tell.

[Rob Daman]

After installing inserts you'll notice a significant difference

[dcaron9999]

If the rear subframe inserts are as effective as the M3 bushings I installed as a DIY, this will be all you need to keep your rear end planted.

[Kgolf31]

The E82 in stock form are very under sprung and dampened as OEM. With that being said, doing subframe inserts/bushings will help eliminate a second dampening mass in the rear...

Right now you're trying to dampen the spring, and a soft bushing. Eliminate the soft bushing the car will be much more complaint.

[jmz135]

Good to know - I'm hoping the coilovers + subframe inserts will solve my problems. Down the road I will probably do a fsb...

[tracer bullet]

Originally Posted by jmz135

Good to know - I'm hoping the coilovers + subframe inserts will solve my problems. Down the road I will probably do a fsb...

Probably way down the road if at all. Your first 2 items on the list will be much more noticeable.

[chris82]

Originally Posted by jmz135

Thanks for the tip - I hadn't come across the shock mount in any other threads yet. So it is the piece that connects the shock to the frame? It actually looks like it is $84 on Dinan's website right now. Like you said, if I had them when I was installing coils I will already have the relevant pieces off the car...

Yes, it's the piece on the top of the rear shocks that mount them to the car.

What you have stock, you can see all the rubber pieces in there; no good:


You ideally want to isolate the damper to do all the work of absorbing the bumps and imperfections of the road, not the body or frame of the car

*But please do your research to make sure they will work with your coils

[Kgolf31]

I re-used my stock shock mounts on my TC Coilovers, so as long as they can accept OE I'm assuming you "should" be okay

[jmz135]

Originally Posted by Kgolf31

I re-used my stock shock mounts on my TC Coilovers, so as long as they can accept OE I'm assuming you "should" be okay

I don't think that the ST kit I purchased came with shock mounts, which means they can be used with OEM, so I assume replacement ones will work unless they are different than the stock ones, which is unlikely.

[CAVU]

I removed the runflats, installed the rear subframe inserts, then the BMW performance suspension. The inserts helped some, but the rear tires are still not as planted as I would like. Next step for me would be the 1M/M3 rear subframe bushings.

[jmz135]

Originally Posted by CAVU

I removed the runflats, installed the rear subframe inserts, then the BMW performance suspension. The inserts helped some, but the rear tires still are not as planted as I would like. Next step for me would be the 1M/M3 rear subframe bushings.

Yea I mean it sounds like this is recommended by just about everyone, it's just tough stomaching a $900 labor cost for $100 hardware.

[128Convertibleguy]

Originally Posted by jmz135

Yea I mean it sounds like this is recommended by just about everyone, it's just tough stomaching a $900 labor cost for $100 hardware.

The inserts are good, the bushings are better. Whether the difference is worth the labor cost (or the labor time and effort) is strictly a matter of taste. It wasn't worth it for me. I have the Powerflex black (race) inserts, which I believe are the stiffest available. For a track car, the bushings are the clear choice.

Still, the inserts won't work if the surrounding bushings are worn out. On my 30K 3 year old car, they weren't. Limiting their movement will no doubt extend their life.

[jmz135]

Originally Posted by 128Convertibleguy

The inserts are good, the bushings are better. Whether the difference is worth the labor cost (or the labor time and effort) is strictly a matter of taste. It wasn't worth it for me. I have the Powerflex black (race) inserts, which I believe are the stiffest available. For a track car, the bushings are the clear choice.

Still, the inserts won't work if the surrounding bushings are worn out. On my 30K 3 year old car, they weren't. Limiting their movement will no doubt extend their life.

Yea that makes sense. My car has 37k miles so I'm hoping the bushings are still in decent shape and the inserts will be enough!

[HP Autosport]

You will need to figure out which deflection you are feeling the most then address it. There are just too many things with the E8x none-M suspension that can use improvements.

[jmz135]

Originally Posted by HP Autosport

You will need to figure out which deflection you are feeling the most then address it. There are just too many things with the E8x none-M suspension that can use improvements.

That's the plan - but I honestly am fairly new to the performance car game and though I can tell when something is off I can't always tell what part of the car is causing it. I understand that there are probably more than a couple weak points on this car's suspension, but I'm just trying to identify a few good suspension mods that will give me good bang for my buck and improve some of the weakest points.

[Overpar56]

Here's my seat of the pants review once I ditched the RFTs:

1) RFTS have stiff sidewalls and the rear end wiggle wasn't that noticeable but the TC light came on fast. No bite on the OEM RFTs and the rear end would wash away pretty easy.
2) switched to Michelin PSS and more pronounced wiggle butt. Tires do grip more so less TC light flashing on.

If you think of it when you come out of a turn and feed the throttle, what will happen? Rear end will break away and TC will come on or rear end will stick with the better tires. Since you're on the throttle, weight will start shifting rearward and load up the backside while your turning and shift the weight into the turn. Tires stick and suspension starts giving it up.

Yeah, my next mod will be new bushings and maybe a suspension tweak. The ass end of our cars are pretty loose.