[thatryan]

Want to order new sway bars, front and rear.

Few things I have read online mention you need to drop sub frame, and in front you need to support the engine with something like an "underhood engine support".

Anyone done this? Anyone recommend one?

Secondly, do you need to replace the linkage or anything else when upgrading bars?

[thatryan]

Actually searching more, I cannot see anyone has done these themselves?? Has anyone tried replacing these at home? Or am I crazy? lol

[rubber_ducky]

I'm an F80 guy so take that for what it's worth, but on F80s, you do need to drop the rear subframe. Not a small amount of work. The front is much simpler.

I've never heard of having to support the engine (on any car), when changing sways. That sounds downright crazy to me.

No need to replace linkages unless you're using an adjustable bar. And even then I isn't a requirement always. You'll likely need new bushings though as the bar diameter is likely different vs the stock bar.

[stxf30]

I think info may have been crossed during your searches. No need to support the engine. That is only if you are dropping the FRONT subframe, which is not necessary for this job.

[thatryan]

Originally Posted by stxf30

I think info may have been crossed during your searches. No need to support the engine. That is only if you are dropping the FRONT subframe, which is not necessary for this job.

Are you sure, on an f30? I have seen two install sheets now saying subframe has to drop. One for Dinan and one for AFE.

[Liquidpaper]

Originally Posted by thatryan

Are you sure, on an f30? I have seen two install sheets now saying subframe has to drop. One for Dinan and one for AFE.

I did the sways on my M235i. On all F series (not including F8X) you need to drop both subframes, as you've researched.

It's a huge pain in the ass (and expensive) but it makes the a bigger difference (with respect to handling) than anything else.

One bit of advice though - I wouldn't do the rear sway (or any sways) unless you put in a LSD. Otherwise you'll have traction issues in the rear.

[thatryan]

Could you elaborate a bit more on traction loss please?

[Liquidpaper]

Originally Posted by thatryan

Could you elaborate a bit more on traction loss please?

Putting a thicker sway bar decreases the independence of the suspension. This is good in that it stiffens the body of the car up on cornering, but bad in that it translates that motion into compression of the bar (which is essentially a spring) which may decrease contact of the inside wheel with the road on hard corners. Also causes problems on bumpy and/or uneven roads.

If you don't have a LSD, as you know the wheel with less grip will dictate the maximum amount of torque the car can get to the pavement - there is no system to force torque to the wheel with more grip. With a stiffer sway in the rear, you will restrict suspension Independence which will cause this to happen more often.

As most BMWs do not have mechanical LSDs anymore, that is (in part) why the rear sway is so thin - maximize road contact at the cost of body control. Now, you do have some torque vectoring coming from the eLSD system, but that system can only do so much and is overwhelmed relatively easily.

Hope that helps.

[Polo08816]

Originally Posted by Liquidpaper

Putting a thicker sway bar decreases the independence of the suspension. This is good in that it stiffens the body of the car up on cornering, but bad in that it translates that motion into compression of the bar (which is essentially a spring) which may decrease contact of the inside wheel with the road on hard corners. Also causes problems on bumpy and/or uneven roads.

If you don't have a LSD, as you know the wheel with less grip will dictate the maximum amount of torque the car can get to the pavement - there is no system to force torque to the wheel with more grip. With a stiffer sway in the rear, you will restrict suspension Independence which will cause this to happen more often.

As most BMWs do not have mechanical LSDs anymore, that is (in part) why the rear sway is so thin - maximize road contact at the cost of body control. Now, you do have some torque vectoring coming from the eLSD system, but that system can only do so much and is overwhelmed relatively easily.

Hope that helps.

This + 10000000 times!

Most driveway mechanics don't understand this and think that to reduce body roll, they should install the stiffest roll bars available with no consequences.

Suspension tuning is all about compromises.

[thatryan]

Originally Posted by Liquidpaper

Putting a thicker sway bar decreases the independence of the suspension. This is good in that it stiffens the body of the car up on cornering, but bad in that it translates that motion into compression of the bar (which is essentially a spring) which may decrease contact of the inside wheel with the road on hard corners. Also causes problems on bumpy and/or uneven roads.

If you don't have a LSD, as you know the wheel with less grip will dictate the maximum amount of torque the car can get to the pavement - there is no system to force torque to the wheel with more grip. With a stiffer sway in the rear, you will restrict suspension Independence which will cause this to happen more often.

As most BMWs do not have mechanical LSDs anymore, that is (in part) why the rear sway is so thin - maximize road contact at the cost of body control. Now, you do have some torque vectoring coming from the eLSD system, but that system can only do so much and is overwhelmed relatively easily.

Hope that helps.

Perfect explanation, thank you.
I kinda assumed this car had a posi rear end lol my bad!

[Liquidpaper]

Originally Posted by thatryan

Perfect explanation, thank you.
I kinda assumed this car had a posi rear end lol my bad!

Getting a posi rear end is a very worthy (and expensive) upgrade. I think much of the reason normal BMWs don't drive like M cars is because they don't have a locking rear end. It was by far the best thing I did to my car.

[thatryan]

Originally Posted by Liquidpaper

Getting a posi rear end is a very worthy (and expensive) upgrade. I think much of the reason normal BMWs don't drive like M cars is because they don't have a locking rear end. It was by far the best thing I did to my car.

Did you get the BMW M one?

[Liquidpaper]

Originally Posted by thatryan

Did you get the BMW M one?

No, I had a custom clutch-type differential with a 3.46 final drive (stock on 235i is 3.08) built by Diffsonline - Dan Fitzgerald. It was very expensive (and probably overkill) but made the biggest difference in how the car drives.

[thatryan]

Nice!

Is the BMW drop in one decent?

[Liquidpaper]

Originally Posted by thatryan

Nice!

Is the BMW drop in one decent?

It's fine from what I've heard. Any locking diff is better than an open one. And you can get one for a pretty reasonable price these days.

[thatryan]

Originally Posted by Liquidpaper

It's fine from what I've heard. Any locking diff is better than an open one. And you can get one for a pretty reasonable price these days.

Meaning a non-BMW one? Is there a better option for decent price?

[Liquidpaper]

Originally Posted by thatryan

Meaning a non-BMW one? Is there a better option for decent price?

You can get the M Performance diff for a reasonable price.