Under steer

Malinois · 06-14-2010, 12:49 PM

Hi guys, i'm new to this forum and new to the 1 series car. I just bought a 2011 135i, M pkg and DCT. So far i love it.

I've noticed a lot of you change the front sway bar, does this help with under steer?

Thanks

sodara · 06-14-2010, 01:11 PM

It reduces body roll, which helps with loss of camber change during hard-cornering.
So...

It's a good remedy for under-steer.

btw. how do like that 7speed dct?

GaryS · 06-14-2010, 01:13 PM

I dunno, but according to Wikipedia, with MacPherson struts "the wheel tends to lean with the body, leading to understeer."

BrokenVert · 06-14-2010, 01:17 PM

What happens during hard cornering is the top of the wheel leans away from the corner. This is called a positive camber situation and that positive camber means that weight comes off of the contact patch of the tire...this causes a loss of grip. The body leaning and rolling puts more strain on the wheel causing it to lean more which leads to more positive camber...that is what an antiroll bar/sway bar prevents. It stops the positive camber situation by keeping more of the rubber on the road

Malinois · 06-14-2010, 01:27 PM

Quote:

Originally Posted by sodara

It reduces body roll, which helps with loss of camber change during hard-cornering.
So...

It's a good remedy for under-steer.

btw. how do like that 7speed dct?

The tranny is unbelievable, i went to BMW to buy 6 speed manuel, the sales guy says "you should try the DCT".... SOLD! No human being can shift that fast or smooth. You don't even have to let of the gas.

Malinois · 06-14-2010, 01:30 PM

So it would definetly be the front sway bar? When i do this i want to get it right.
Thanks again.

BrokenVert · 06-14-2010, 01:52 PM

Quote:

Originally Posted by Malinois

So it would definetly be the front sway bar? When i do this i want to get it right.
Thanks again.

Front and rear will both help. But at the very least do the front.

GaryS · 06-14-2010, 01:52 PM

Yes, front bar. The consensus is you should leave the rear bar stock unless you also add a limited slip diff.

BrokenVert · 06-14-2010, 01:54 PM

Quote:

Originally Posted by GaryS

Yes, front bar. The consensus is you should leave the rear bar stock unless you also add a limited slip diff.

Yes I can undertand that consensus. It will keep the rear a bit more planted with stock springs/shocks

bradford · 06-14-2010, 01:57 PM

Quote:

Originally Posted by GaryS

Yes, front bar. The consensus is you should leave the rear bar stock unless you also add a limited slip diff.

I wouldn't say that's a consensus.

GaryS · 06-14-2010, 02:06 PM

Quote:

Originally Posted by bradford

I wouldn't say that's a consensus.

Well then explain. I'm just repeating what I read here; so I think the argument for a stiffer rear bar even without LSD needs to be made.

...adding: You have me almost talked into subframe bushings, so my question about rear bar is more than academic.

arrutled · 06-14-2010, 02:29 PM

Quote:

Originally Posted by GaryS

Well then explain. I'm just repeating what I read here; so I think the argument for a stiffer rear bar even without LSD needs to be made.

...adding: You have me almost talked into subframe bushings, so my question about rear bar is more than academic.

after I installed my rear subframe bushings I can see how one could believe in a little more rotation in the rear. I just dont want to drop the subframe again, lol.

GaryS · 06-14-2010, 02:48 PM

Quote:

Originally Posted by arrutled

after I installed my rear subframe bushings I can see how one could believe in a little more rotation in the rear. I just dont want to drop the subframe again, lol.

Exactly. I would hate to do subframe bushings and then find out I should have done the ARB too.

Anyway, the OP asked about understeer, and even I know a rear bar is a common solution for that. I've just seen so many people here say they lost too much traction with the M3 rear bar. I also remember that BMW originally included a stiffer rear bar in the 3-series Performance Suspension and then switched it to a stiffer front bar. The 1-series Performance Suspension also uses the stock 135i rear bar. And there were also some posts here about two racing teams that removed the rear bars from their 135's and got faster times. So that is where I got a consensus from.

JB135MDCT · 06-14-2010, 03:15 PM

Quote:

Originally Posted by GaryS

Exactly. I would hate to do subframe bushings and then find out I should have done the ARB too.

Anyway, the OP asked about understeer, and even I know a rear bar is a common solution for that. I've just seen so many people here say they lost too much traction with the M3 rear bar. I also remember that BMW originally included a stiffer rear bar in the 3-series Performance Suspension and then switched it to a stiffer front bar. The 1-series Performance Suspension also uses the stock 135i rear bar. And there were also some posts here about two racing teams that removed the rear bars from their 135's and got faster times. So that is where I got a consensus from.

If 135 gets faster with no Rear ARB, does this mean the chassis in general has balance issues? Do we loose a degree of freedoom for tunning the rear end? If I remove my rear ARB and keep stock front ARB, will I get faster times?

ianc · 06-14-2010, 06:01 PM

Quote:

after I installed my rear subframe bushing

Hey, didn't you promise us a DIY on that?

ianc

cpt97m3 · 06-14-2010, 09:16 PM

Quote:

Originally Posted by GaryS

Yes, front bar. The consensus is you should leave the rear bar stock unless you also add a limited slip diff.

I have a Hotchkiss front bar, and it does help the handling. I added a rear H&R bar, and it was slower at the AutoX. While it probably handled better, it was very difficult to put down power, and I got a lot of wheelspin. With the OE rear bar, it had no trouble, so the corner exit speed was higher. So my subframe has been off the car twice now.

If I ever do an LSD, I'd likely put the rear bar back on. I still have stock springs and shocks.

arrutled · 06-15-2010, 06:52 AM

[QUOTE=ianc;7497631]

Quote:

after I installed my rear subframe bushing[/qote]

Hey, didn't you promise us a DIY on that?

ianc

http://www.1addicts.com/forums/showt...frame+bushings

Thats all your gonna get. Taking apart the subframe is easy, nuts and bolts. just dont forget about the brake lines

BrokenVert · 06-15-2010, 07:07 AM

Quote:

Originally Posted by cpt97m3

I have a Hotchkiss front bar, and it does help the handling. I added a rear H&R bar, and it was slower at the AutoX. While it probably handled better, it was very difficult to put down power, and I got a lot of wheelspin. With the OE rear bar, it had no trouble, so the corner exit speed was higher. So my subframe has been off the car twice now.

If I ever do an LSD, I'd likely put the rear bar back on. I still have stock springs and shocks.

You need to drop the subframe inorder to add a swaybar?!

GaryS · 06-15-2010, 07:33 AM

Quote:

Originally Posted by BrokenVert

You need to drop the subframe inorder to add a swaybar?!

Yes, for the rear bar.

I'll just add for the OP that the M3 front control arms kit combined with front swaybar kit is a very popular approach for reducing understeer.

http://www.hpashop.com/product.sc?pr...categoryId=119
http://www.hpashop.com/product.sc?pr...categoryId=119

cpt97m3 · 06-15-2010, 09:34 PM

Quote:

Originally Posted by BrokenVert

You need to drop the subframe inorder to add a swaybar?!

Yeah, for the rear of the 135. Front is easy though.

jeremydgreat · 06-16-2010, 01:33 AM

Quote:

Originally Posted by GaryS

Well then explain. I'm just repeating what I read here; so I think the argument for a stiffer rear bar even without LSD needs to be made.

...adding: You have me almost talked into subframe bushings, so my question about rear bar is more than academic.

That's what I gather from reading the forums too. That people are doing the front bar only.

bradford · 06-16-2010, 01:57 PM

Quote:

Originally Posted by jeremydgreat

That's what I gather from reading the forums too. That people are doing the front bar only.

People are doing the front bar only because it's cheap.

You can do the rear bar (within reason - bigger is not always better) too but you need to drop the subframe. = big labor $$$ or big PITA if you're doing it yourself. And if you're in there you're nuts if you don't do the subframe bushings = additional $ and PITA.

So faced with the above, most people just spend a couple hundo on the front bar and call the job done. YMMV.

06-14-2010, 12:49 PM	#1
Malinois Enlisted Member 6 Rep 39 Posts Drives: 2011 135i M Pkg, DCT Join Date: Jun 2010 Location: Vancouver BC iTrader: (0)	Under steer Hi guys, i'm new to this forum and new to the 1 series car. I just bought a 2011 135i, M pkg and DCT. So far i love it. I've noticed a lot of you change the front sway bar, does this help with under steer? Thanks
	Appreciate 0 Tweet Quote

06-14-2010, 01:11 PM	#2
sodara Private 12 Rep 77 Posts Drives: 135i Join Date: Sep 2009 Location: Minnesota iTrader: (0)	It reduces body roll, which helps with loss of camber change during hard-cornering. So... It's a good remedy for under-steer. btw. how do like that 7speed dct?
	Appreciate 0 Quote

06-14-2010, 01:13 PM	#3
GaryS Colonel 37 Rep 2,084 Posts Drives: 2009 135i 6MT Join Date: Feb 2010 Location: Maryland iTrader: (0) Garage List 2009 135i [6.50]	I dunno, but according to Wikipedia, with MacPherson struts "the wheel tends to lean with the body, leading to understeer."
	Appreciate 0 Quote

06-14-2010, 01:17 PM	#4
BrokenVert Resident Kerbalnaut 477 Rep 10,703 Posts Drives: Topless Brute/Hybrid Boogaloo Join Date: Apr 2009 Location: Fahrvergnügen/NY iTrader: (0)	What happens during hard cornering is the top of the wheel leans away from the corner. This is called a positive camber situation and that positive camber means that weight comes off of the contact patch of the tire...this causes a loss of grip. The body leaning and rolling puts more strain on the wheel causing it to lean more which leads to more positive camber...that is what an antiroll bar/sway bar prevents. It stops the positive camber situation by keeping more of the rubber on the road __________________
	Appreciate 0 Quote

06-14-2010, 01:30 PM	#6
Malinois Enlisted Member 6 Rep 39 Posts Drives: 2011 135i M Pkg, DCT Join Date: Jun 2010 Location: Vancouver BC iTrader: (0)	So it would definetly be the front sway bar? When i do this i want to get it right. Thanks again. Last edited by Malinois; 06-14-2010 at 01:42 PM..
	Appreciate 0 Quote

06-14-2010, 01:52 PM	#8
GaryS Colonel 37 Rep 2,084 Posts Drives: 2009 135i 6MT Join Date: Feb 2010 Location: Maryland iTrader: (0) Garage List 2009 135i [6.50]	Yes, front bar. The consensus is you should leave the rear bar stock unless you also add a limited slip diff.
	Appreciate 0 Quote