E9X Need help with alignment on a 335XI w/ kW v3, M3 RCA, Megan Racing Adjustable Rear Camber Arm

[zmon1300]

Need help with some alignment specs. 2010 335XI lowered on KW v3. Just installed rear m3 control arms and Megan racing adjustable rear camber arms. What specs should I get the car aligned to? Shop did factory specs at first and the car was unbearable. Back end feels super wobbly and when doing a WOT pull, the back end kicks out like a rwd car. Never had this issue before. Rear end slides around if i hit a bump mid-turn also, feels VERY unstable. Ill list my exact suspension specs:

KW v3 coilovers lowered about 1.5" (just enough to get rid of the wheel gap)
TRW M3 rear Control Arm
Megan Racing Adjustable Rear Camber Arm
Apex Arc8 18x9.5 square set
Michelin Pilot Super Sports 245-35-18 all around

 

[MattGu40]

Following.. got simillar setup and i am about to install Toe arms too.

any fitment issues in the front ? tire rubbing on sway bar ? im Pre LCI with 235s in the front Apex 9'' probably different offset

 

[Rob09msport]

Need help with some alignment specs. 2010 335XI lowered on KW v3. Just installed rear m3 control arms and Megan racing adjustable rear camber arms. What specs should I get the car aligned to? Shop did factory specs at first and the car was unbearable. Back end feels super wobbly and when doing a WOT pull, the back end kicks out like a rwd car. Never had this issue before. Rear end slides around if i hit a bump mid-turn also, feels VERY unstable. Ill list my exact suspension specs:

KW v3 coilovers lowered about 1.5" (just enough to get rid of the wheel gap)
TRW M3 rear Control Arm
Megan Racing Adjustable Rear Camber Arm
Apex Arc8 18x9.5 square set
Michelin Pilot Super Sports 245-35-18 all around

Do you have stock bushings and usually people do m3 specs with whatever camber they want. Rear should be .06 to .13 toe in and same in front. Toe will have largest effect on stability

 

[zmon1300]

Shop got the car re-aligned. Heard the camber should be -2 to -2.5 all around? Attached is the printout. Thoughts?

 

[Rob09msport]

Rear is fine but front needs more camber if you want dial out understeer, but you have alot of caster which gives dynamic camber

 

[zmon1300]

Do you have stock bushings and usually people do m3 specs with whatever camber they want. Rear should be .06 to .13 toe in and same in front. Toe will have largest effect on stability

stock bushings. thinking about getting it adjusted again to make camber -2 or -2.5 all around. steering wheel still has about 1/2 play in it before it really starts turning. thoughts?

 

[Rob09msport]

Thats your bushings a little more toe in the front will alleviate that but true fix is new arms, i rec the m3 upgrades i can take my pinky and move my steering wheel a mm and it translates to my tires their is 0 play.

 

[Rob09msport]

You also don't want go over 1.8 tops 2 in rear as it will start hurting straight line traction

 

[zmon1300]

Thats your bushings a little more toe in the front will alleviate that but true fix is new arms, i rec the m3 upgrades i can take my pinky and move my steering wheel a mm and it translates to my tires their is 0 play.

Are you referring to the m3 front control arms? I have an XI so only the rear m3 arms are PNP, which is what i have installed along with megan racing adjustable camber arms to control the tire wear in the rear.

 

[fmorelli]

@barry@3DM

Filippo

 

[barry@3DM]

Need help with some alignment specs. 2010 335XI lowered on KW v3. Just installed rear m3 control arms and Megan racing adjustable rear camber arms. What specs should I get the car aligned to? Shop did factory specs at first and the car was unbearable. Back end feels super wobbly and when doing a WOT pull, the back end kicks out like a rwd car. Never had this issue before. Rear end slides around if i hit a bump mid-turn also, feels VERY unstable. Ill list my exact suspension specs:

KW v3 coilovers lowered about 1.5" (just enough to get rid of the wheel gap)
TRW M3 rear Control Arm
Megan Racing Adjustable Rear Camber Arm
Apex Arc8 18x9.5 square set
Michelin Pilot Super Sports 245-35-18 all around

Sounds like your concern is the backend all over the place during WOT acceleration. I'm trying to figure out your timeline... So you had the KWs on the car for a while and the car was fine with OEM linkages and factory alignment settings. Then you changed the rear control and camber arms, had it re-aligned to the factory settings and the back end was all over the place. Now it looks like you have it re-aligned with what appears to be less toe in on the rear than factory settings. So is the back end still all over the place? Did it get worse or better?

The "backend all over the place" can be a result of the following things: Like @Rob09msport said, toe in on the rear tires will have the biggest effect. Dampers play a big factor as well, if they are too stiff that can cause problems. Too much camber can cause it too but you have to have a lot of camber for that to be a problem. Rear Camber in the -1 deg to -3 deg range isn't going to be drastically noticeable and an unlikely cause.

 

[Rob09msport]

Are you referring to the m3 front control arms? I have an XI so only the rear m3 arms are PNP, which is what i have installed along with megan racing adjustable camber arms to control the tire wear in the rear.

Your right sorry what about super pro arms honestly it's really just wanting new bushings to get rid of play

 

[zmon1300]

Sounds like your concern is the backend all over the place during WOT acceleration. I'm trying to figure out your timeline... So you had the KWs on the car for a while and the car was fine with OEM linkages and factory alignment settings. Then you changed the rear control and camber arms, had it re-aligned to the factory settings and the back end was all over the place. Now it looks like you have it re-aligned with what appears to be less toe in on the rear than factory settings. So is the back end still all over the place? Did it get worse or better?

The "backend all over the place" can be a result of the following things: Like @Rob09msport said, toe in on the rear tires will have the biggest effect. Dampers play a big factor as well, if they are too stiff that can cause problems. Too much camber can cause it too but you have to have a lot of camber for that to be a problem. Rear Camber in the -1 deg to -3 deg range isn't going to be drastically noticeable and an unlikely cause.

Right. So kW v3s on for about 1.5 yrs on stock arms with factory alignment specs. I would go thru rear tires every 2 months. Had alot of inner tire wear, very uneven but the car on WOT would stay straight. Then got m3 CA & Megan Racing Camber Arm installed and aligned to factory spec, and back end was wobbly and kicking out like a rwd on WOT. Then shop readjusted alignment (pic posted of alignment printout) and car is driving straight on normal throttle. Haven't gotten time to do WOT yet, but will do that shortly and report back. It still doesn't feel as tight as I would like it to be. Still have about 1/2 inch play in the steering wheel before car starts actually turning.

 

[Rob09msport]

That's why at current point i think more front toe and or new bushings in your arms or new arms your rear toe was way off which caused instability at first now with your alignment settings you currently have wot should feel fine.

 

[barry@3DM]

Right. So kW v3s on for about 1.5 yrs on stock arms with factory alignment specs. I would go thru rear tires every 2 months. Had alot of inner tire wear, very uneven but the car on WOT would stay straight. Then got m3 CA & Megan Racing Camber Arm installed and aligned to factory spec, and back end was wobbly and kicking out like a rwd on WOT. Then shop readjusted alignment (pic posted of alignment printout) and car is driving straight on normal throttle. Haven't gotten time to do WOT yet, but will do that shortly and report back. It still doesn't feel as tight as I would like it to be. Still have about 1/2 inch play in the steering wheel before car starts actually turning.

Still trying to get this straight. Before the rear arm replacement you had factory alignment settings, there was no play in the steering and WOT acceleration was stable. You then replaced the rear control arm and rear upper camber arm, had it aligned to the same factory specs as before, then there was play in the front steering and WOT acceleration made the back end get loose.

I'm Trying to figure out how you got play in the front steering when nothing was changed up front. Curious to hear how WOT acceleration is with new alignment in rear with less toe in.

 

[Rob09msport]

Still trying to get this straight. Before the rear arm replacement you had factory alignment settings, there was no play in the steering and WOT acceleration was stable. You then replaced the rear control arm and rear upper camber arm, had it aligned to the same factory specs as before, then there was play in the front steering and WOT acceleration made the back end get loose.

I'm Trying to figure out how you got play in the front steering when nothing was changed up front. Curious to hear how WOT acceleration is with new alignment in rear with less toe in.

I thought he always had play in the front and did these upgrades then got squirrelly now he fixed that but would still like to improve the vague steering.

 

[barry@3DM]

I thought he always had play in the front and did these upgrades then got squirrelly now he fixed that but would still like to improve the vague steering.

Yeah, I dunno, not sure.

In post #6 he mentions play in steering for first time but no idea if that was there already or if that came after the rear arm mods.

Then in post #13 he says: Before mods WOT good. After mods with factory alignment WOT wobbly and all over the place. Then he got re-aligned with less toe in and says... "Haven't gotten time to do WOT yet, but will do that shortly and report back."

I'm curious to know if steering play came after the rear linkage mods because that seems odd. Then curious to see if back end is more planted with less toe in on WOT. If so that also seems odd.

 

[barry@3DM]

The rear e90 suspension is very complex. On earlier BMW suspensions designs you could toss in some solid joints and be fine. On the standard e90 tossing in a solid joint or two greatly effects the toe curves.

This is the rear suspension toe curve for the standard e90. Red is static, green is when hitting the brakes, blue is when cornering. Unfortunately BMW didn't publish the toe curve under acceleration.

I've measured the static toe curve (red) and got the same result. Unfortunately measuring dynamic toe curve is very difficult. I'm still in the process of that.

There are 12 pivot points on each side of the rear e90 suspension. (e46 has 5 for reference) The standard e90 has mostly rubber joints whereas the e90 M3 has mostly solid joints. Because of this the e90 M3 has a totally different toe arm geometry. (as well as other geometry changes for the other linkages).

I'm curious to about @zmon1300 issues because I'm curious about the toe curve under acceleration.

 

[Rob09msport]

You seem like you have awesome grasp on our suspension so figure you would be person to ask. Do you recommend rtab upgrade or the ecs arm? That is the one item I have left stock besides my arbs . Also what do you recommend as good dual purpose spring rate I currently am 440f 700r but 6 inch front 8 inch rear, I want to go inch longer on each because I am at the limit for how high my gc collars can adjust and I fear 6 inch may be able to bind in some situations. The car feels great but it is on the firm side for front like I get scared goons bend rim on expansion joints in poor condition lol. 90 percent of time it rides better than stock it just would be nice to increase comfort a little if it won't sacrifice the performance I finally achieved. Sorry for thread jack

 

[barry@3DM]

You seem like you have awesome grasp on our suspension so figure you would be person to ask. Do you recommend rtab upgrade or the ecs arm? That is the one item I have left stock besides my arbs . Also what do you recommend as good dual purpose spring rate I currently am 440f 700r but 6 inch front 8 inch rear, I want to go inch longer on each because I am at the limit for how high my gc collars can adjust and I fear 6 inch may be able to bind in some situations. The car feels great but it is on the firm side for front like I get scared goons bend rim on expansion joints in poor condition lol. 90 percent of time it rides better than stock it just would be nice to increase comfort a little if it won't sacrifice the performance I finally achieved. Sorry for thread jack

@Rob09msport... I would recommend an RTAB bushing upgrade and NOT replacing the whole arm. The rear trailing arm is built to be a failure point and bend in the case of an accident and not puncture the gas tank. It is sufficiently strong enough to take any loads you put on it. (unless you have drag tires and are launching at a drag strip)

Those spring rates are pretty good. Pinpoint springs rates depend on your tires, wheels, driving style, intended use, etc. You definitely want to put a taller spring up front. What kind of spring do you have?

Lets say you have a typical "race" style spring that is 2.5" in diameter. Assuming your car is stockish weight, that means you have roughly 850 lbs on each front wheel. A 440 lb/in spring will compress approximately 2 inches at ride height. Depending on what kind of spring you have a typical race spring of that dimension has a travel of 3.8ish inches before coil bind. So that means you have about 1.8 inches of travel before it coil binds under bump. The other thing to remember is that a linear spring is not linear all the way to coil bind. As the spring gets closer to coil bind the rate ramps up very quickly. (some coils bottom before others causing this) In other words its linear for most of its range but not the last .5" or so.

In a nutshell you want to try to get as long of a spring as possible up front.

Hope this helps.
Barry