[turugara]

Originally Posted by jippii ensio

That would get the understeer worse.

Not really. With the amount of torque 335's generate, having the right tire/suspension/driver would mean you would be able to steer the car more with your throttle. A thicker rear bar isn't necessary on a RWD car.

[RupertPupkin]

I understand that is the typical result but that is not the case with the e90/e92. I hope Harold chimes in here.

Originally Posted by jippii ensio

That would get the understeer worse.

[jippii ensio]

Originally Posted by turugara

Not really. With the amount of torque 335's generate, having the right tire/suspension/driver would mean you would be able to steer the car more with your throttle. A thicker rear bar isn't necessary on a RWD car.

He has 328 with lot less torque.

Many on this forum are complaining about even 335i understeering with stock tires and suspension. I'm sure that it can be helped with "right" tire/suspension/driver, though as you said. I'd be hesitant in changing the driver myself though

[nitehawk]

Originally Posted by jippii ensio

Yes, removing front sway would be the easy and cheap way to get better balance, and to reduce understeer by increasing the mechanical grip in the front.

More grip, yes, but at the expense of greater body roll.

[e679]

Originally Posted by sle39lvr

I want to talk about rear sways for the most part.

I have a non-sport E90 328i (pre LCI) and reloem.com states me rear sway as:
13mm - 33556764425

After months of research on this board, it seems like no ones knows if the ZSP has thicker sway bars or not. If anyone who reads this knows, please state...

I put 18" stock staggered wheels, and planning to get coilovers and want to go slightly lower than sports package height. (sports package is .6" lower and I want to go around 1").

Ultimately, I do want m3 control arms up front, but DO NOT WANT to touch the front sway bar. If anything, I would go skinnier up front. My last fwd car, I ran with a thicker sway in the back and no sway up front, feel was 100 better.

So down to the question:
After putting 18", I can tell car understeers even more (probably due to wider tires in the back). I want to put a thicker sway in the back to have the car feel neutral. Popular solution here seems like the M3 rear sway, which I think will be too much for me. Will be harsh in the back in straight line and stories about snap-oversteer scares me.

M3 rear sway is 20mm?
H&R also makes a 20mm one.

Is there anything in between 13mm - 20mm?

Thanks in advance.

What about Eibach? It has a 15mm rsb. I think they are adjustable? Right?

[sle39lvr]

Originally Posted by e679

What about Eibach? It has a 15mm rsb. I think they are adjustable? Right?

Would that be too close to stock?

[e90pilot]

Not really. I've got 15mm Dinan bar and it makes a pretty measurable difference. I get easily get the car up on 3 wheels now and I got lots of wheel spin when the car is on an uneven surface. 335s will get wheel spin during hard cornering and acceleration.

[cvc 22349a]

Originally Posted by e90pilot

Not really. I've got 15mm Dinan bar and it makes a pretty measurable difference. I get easily get the car up on 3 wheels now and I got lots of wheel spin when the car is on an uneven surface. 335s will get wheel spin during hard cornering and acceleration.

What does Dinan do for bushings w/their rear roll bar? Poly?

[HP Autosport]

Originally Posted by jippii ensio

That would get the understeer worse.

Yes and no, but in the case of E36/E46 and now the E82/E9x BMW's a stiffer front bar actually reduces understeer. How? By reducing roll induced postive camber changes. A larger front bar reduces body roll and keeps the outside front tire more upgright in a turn and when a tire is more upgright and not riding on its sidewall, you have more traction!

[e90pilot]

Originally Posted by cvc 22349a

What does Dinan do for bushings w/their rear roll bar? Poly?

I'm not too sure but it looks like its just rubber.

[e679]

Originally Posted by e90pilot

Not really. I've got 15mm Dinan bar and it makes a pretty measurable difference. I get easily get the car up on 3 wheels now and I got lots of wheel spin when the car is on an uneven surface. 335s will get wheel spin during hard cornering and acceleration.

Is it possible that they have different stiffness even they have the same thickness? Bcuz of the material maybe?

I have Whiteline Sway in mind also (20MM) but they are adjustable. Anyone have them installed?

[HP Autosport]

Originally Posted by e679

Is it possible that they have different stiffness even they have the same thickness? Bcuz of the material maybe?

I have Whiteline Sway in mind also (20MM) but they are adjustable. Anyone have them installed?

Yes, it is possible. Besides material, lever arm length, number of curves and solid vs hollow can all contribute to the rate.

[Mavus]

Originally Posted by sle39lvr

I want to talk about rear sways for the most part.

I have a non-sport E90 328i (pre LCI) and reloem.com states me rear sway as:
13mm - 33556764425

After months of research on this board, it seems like no ones knows if the ZSP has thicker sway bars or not. If anyone who reads this knows, please state...

I put 18" stock staggered wheels, and planning to get coilovers and want to go slightly lower than sports package height. (sports package is .6" lower and I want to go around 1").

Ultimately, I do want m3 control arms up front, but DO NOT WANT to touch the front sway bar. If anything, I would go skinnier up front. My last fwd car, I ran with a thicker sway in the back and no sway up front, feel was 100 better.

So down to the question:
After putting 18", I can tell car understeers even more (probably due to wider tires in the back). I want to put a thicker sway in the back to have the car feel neutral. Popular solution here seems like the M3 rear sway, which I think will be too much for me. Will be harsh in the back in straight line and stories about snap-oversteer scares me.

M3 rear sway is 20mm?
H&R also makes a 20mm one.

Is there anything in between 13mm - 20mm?

Thanks in advance.

I installed OEM Perf Susp Kit V2 with the thicker front sway bar and the handling improved significantly, turn-in, understeer decreased, less roll, batter damping, faster cornering speeds, etc. I also run PS2 ZP. I am a happy camper...it transformed the car. Now the next step is LSD and then wider 245f 265r PSS tires. Can't wait!

[Midnight Magic]

I only replaced the front sway bar with the M3 e93 and the car feels great. I've taken 90degree turns going approx 30mph and had no understeer. I do have the M3 links front and back with coilovers.

[cvc 22349a]

Originally Posted by Sleepy330i

I installed OEM Perf Susp Kit V2 with the thicker front sway bar and the handling improved significantly, turn-in, understeer decreased, less roll, batter damping, faster cornering speeds, etc. I also run PS2 ZP. I am a happy camper...it transformed the car. Now the next step is LSD and then wider 245f 265r PSS tires. Can't wait!

The PS front sway bar is the same size as your oe sport sway bar; it just has two additional kinks/curvature to it. Not sure how much, if any, roll resistance it adds. The PS springs and dampers sure do improve handling

[e679]

Originally Posted by HP Autowerks

Yes, it is possible. Besides material, lever arm length, number of curves and solid vs hollow can all contribute to the rate.

To make thing more complicated. The sways bar stiffness should also match the spring rate?

[HP Autosport]

Originally Posted by e679

To make thing more complicated. The sways bar stiffness should also match the spring rate?

Yes, you are correct.

We would typically tune with spring rates first, then use anti roll bar or bars at the very end to balance the handling or make fine balance adjustments. Remember, larger/stiffer isn't better. Lifting the inside tire off of the ground in a turn may look cool, but it's the the fastest.

If you can't alter spring rates, a larger than stock bar or bars or adjustable ones will have to do.

[CJ421]

Originally Posted by e679

To make thing more complicated. The sways bar stiffness should also match the spring rate?

Keep in mind it is possible to make these cars too stiff in turns. Sways are more of a tuning tool; I consider the sway bar diameter to be at the mercy of the damper/spring combo. Install good dampers and matching springs first, then see if the car is performing as you want. If not match the sway bar to how much more stiff you want the car. Your car already has sway bars now so ... remember that too. I would go with stiffer springs before I changed the sway bars (assuming you have dampers to match).

That said the M3 bars are noticeably stiffer than stock sport pkg. Only upgrade the front one, the rear is unnecessary since we are not FWD.

Keep in mind that none of this will increase the maximum possible grip of your car ... it's just altering how the load transfer happens. Best way to get more grip is to get better tires.

Edit: Harold beat me to it.

[cvc 22349a]

Originally Posted by CJ421

Keep in mind it is possible to make these cars too stiff in turns. Sways are more of a tuning tool; I consider the sway bar diameter to be at the mercy of the damper/spring combo. Install good dampers and matching springs first, then see if the car is performing as you want. If not match the sway bar to how much more stiff you want the car. Your car already has sway bars now so ... remember that too. I would go with stiffer springs before I changed the sway bars (assuming you have dampers to match).

That said the M3 bars are noticeably stiffer than stock sport pkg. Only upgrade the front one, the rear is unnecessary since we are not FWD.

Keep in mind that none of this will increase the maximum possible grip of your car ... it's just altering how the load transfer happens. Best way to get more grip is to get better tires.

Edit: Harold beat me to it.

Do you find the rear M3 sway bar to be too rigid for your car at the track?

[cdgatti]

Originally Posted by Sleepy330i

I installed OEM Perf Susp Kit V2 with the thicker front sway bar and the handling improved significantly, turn-in, understeer decreased, less roll, batter damping, faster cornering speeds, etc. I also run PS2 ZP. I am a happy camper...it transformed the car. Now the next step is LSD and then wider 245f 265r PSS tires. Can't wait!

How has the ride quality changed? Could the car still be used to comfortably carry passengers?

[sle39lvr]

I really don't understand how putting just a front sway bar reduces understeer. Doesn't make sense to me.

I was thinking, with a decent set of coil-overs, trying the M3 rear first. Then if it's too twitchy, put the M3 front since it's cheaper and easier to replace compared to back. I am hoping that just the M3 rear bar would be "FUN"..

[tomtom11]

i got the rear M3 bar and love it on my 335XI