Suspension Upgrades - Best Bang for Buck?

[Olgeezer1]

Also trying for some improvement on a budget. Switching runflats for squared 225/40/18 max.perf.summers on factory #263 wheels as step one. Thinking step 2 will be Bilstein HD's with stock MSport springs. After that maybe the subframe bushings or inserts if I feel the need. Car is not driven hard, maybe 1 autoX/ 1 lapping day per season.

[dcaron9999]

I track my car, and even with 255/35R18 ZII tires in the front and -3* camber, my 135i still understeers in tighter corners on the track when lapping.

Originally Posted by 128Convertibleguy

...not McPherson strut cars. Based on recently adding a 32mm Hotchkis front bar to my 128i i can report that, in this case, it reduced understeer. And that's with no rear bar at all...

Based on this, do you recommend I install the thicker E93/M3 FSB over the E92/M3 FSB? (I would rather stick with OE parts, and remain as stealthy as possible.

Originally Posted by 128Convertibleguy

...personally I'm coming to a conclusion that, on a 1 series, for cornering grip, camber trumps most things up front. Limiting roll seems particularly important if you run static camber less negative than -1 degree.

On stock dampers and linear M springs, do you still recommend a thicker FSB with camber plates and front camber set to -3*? Im also considering Adjustable Toe arms (probably Megan Racing) in the rear, as I have a higher ratio 3.46FD Quaife LSD in the rear, putting more strain on the rear suspension and toe.

[3002 tii]

Originally Posted by dcaron9999

I track my car, and even with 255/35R18 ZII tires in the front and -3* camber, my 135i still understeers in tighter corners on the track when lapping.



Based on this, do you recommend I install the thicker E93/M3 FSB over the E92/M3 FSB? (I would rather stick with OE parts, and remain as stealthy as possible.


On stock dampers and linear M springs, do you still recommend a thicker FSB with camber plates and front camber set to -3*? Im also considering Adjustable Toe arms (probably Megan Racing) in the rear, as I have a higher ratio 3.46FD Quaife LSD in the rear, putting more strain on the rear suspension and toe.

Thicker front sway will increase spring rate and only add to your understeer issues. If anything you'll want a thicker rear sway or find another way to stiffen up the rear (relative to front, see Kgolf's thread). But if you're looking for stealth, your best bet is to continue to play with tire pressures and change your toe settings (more toe out front, less toe in rear) although that'll suck for a daily as you'll go through tires so quickly. And again, I've said this before but if you can't commit to a full track setup, you're going to have to work with what you have, take a different line, trailbrake through the turns, etc. You may have simply reached near the limit of the car.

Lastly I don't recall what pads you're using these days but make sure they are same compound front and rear. If you're one of those folks that runs a staggered pad setup where the front bites harder, then that could definitely contribute to understeer.

I'll just also add, you're going to have a tough time really making this car handle the way you like without spending serious money. It's not a momentum car so it'll never handle like a Miata but considering it puts down the same kind of power as V8's, I would almost view the car's understeer pretty good all things considering lol.

[dcaron9999]

The reviews on the stiffer FSB's on the 1-series are so mixed. Some say understeer is reduced, some say it is increased ... I know the ideal and more costly option is a spring/damper or coilover upgrade ...

Still experimenting with tire pressure. Latest alignment specs are 1/32" toe out with -3.2* camber in the front, and -3/32" toe in with -1.8* camber in the rear.

Im not totally thrilled by my XP10 pads, and ready to try something else to eliminate the brake fade ...

[TheSt|G]

Originally Posted by dcaron9999

The reviews on the stiffer FSB's on the 1-series are so mixed. Some say understeer is reduced, some say it is increased ... I know the ideal and more costly option is a spring/damper or coilover upgrade ...

Still experimenting with tire pressure. Latest alignment specs are 1/32" toe out with -3.2* camber in the front, and -3/32" toe in with -1.8* camber in the rear.

Im not totally thrilled by my XP10 pads, and ready to try something else to eliminate the brake fade ...

BBK would make a much bigger improvement than the minor differences between pads.

[dcaron9999]

Originally Posted by TheSt|G

BBK would make a much bigger improvement than the minor differences between pads.

Wish I could afford it, and I could say I will commit to keeping the 135i for years to come.

[Kgolf31]

Originally Posted by 3002 tii

Thicker front sway will increase spring rate and only add to your understeer issues. If anything you'll want a thicker rear sway or find another way to stiffen up the rear (relative to front, see Kgolf's thread). But if you're looking for stealth, your best bet is to continue to play with tire pressures and change your toe settings (more toe out front, less toe in rear) although that'll suck for a daily as you'll go through tires so quickly. And again, I've said this before but if you can't commit to a full track setup, you're going to have to work with what you have, take a different line, trailbrake through the turns, etc. You may have simply reached near the limit of the car.

Lastly I don't recall what pads you're using these days but make sure they are same compound front and rear. If you're one of those folks that runs a staggered pad setup where the front bites harder, then that could definitely contribute to understeer.

I'll just also add, you're going to have a tough time really making this car handle the way you like without spending serious money. It's not a momentum car so it'll never handle like a Miata but considering it puts down the same kind of power as V8's, I would almost view the car's understeer pretty good all things considering lol.

Yea. So I think I've found the go-to setup for my car as of now. It is PERFECT in the way I want to to handle.

I had a multi-national champion drive my car Sunday and he said the setup is exactly how it likes it. I have to rotating on power oversteer and front end grip is perfect.

Of course, I'm pretty stupid with my alignments, so YMMV.

Front:
Camber: -3.6*
Toe: 0 with maybe a bit of toe out

Rear:
Camber: -2*
Toe: 1/8th total toe

So, after much debate, and people telling me (and convincing myself) that BMWs do not need a rear bar....I bought a rear bar and installed it. It is a UUC 19mm 2 way adjustable. Probably one of the thicker bars offered for our cars.

I have it right now on the stiffer of the 2 settings, and realistically the other setting probably isn't that much different.

Instead of trying to play stupid with tire pressures, trying to get the car to rotate, I am finally able to run correct rear pressures. I should note that the care REALLY likes to trailbrake, it really secures the front down

Front: 34 PSI Hot
Rear: 32-33 PSI Hot.

Rollover is way past the arrows on the front, and rear is at the top of the arrows.

I am also able to run correct suspension settings. Before I had to run crazy front rebound/compression to try and get the rear to "stiffen" up and rotate.

So, from past where I was around 6/12 clicks on compression and high rebound, I'm not 2 clicks up on compression and lower rebound up front. As well, I'm able to run correct rear rebound in the rear instead of turning them up to max attempting once again to get the rear to rotate.

Yes, I did lose "some" stability in a slalom...but by turning the suspension I have re-secured the rear down for the most part and I drive around the minor issue.

First event with the rear bar. Low grip surface.

You can see the car "bouncing". I ran too stiff of suspension and that was probably some issues with too much oversteer.

So my event on Sunday. Very, very high grip surface and on concrete. Probably the worst case scenario for push

My co-driver Andrew who took alot more speed through the slalom and curvewalloms

And a comparison.

So in summary. I eat my words saying these cars only need a FSB, because I don't think that is the case anymore after my experiments.

[3002 tii]

Originally Posted by dcaron9999

The reviews on the stiffer FSB's on the 1-series are so mixed. Some say understeer is reduced, some say it is increased ... I know the ideal and more costly option is a spring/damper or coilover upgrade ...

Still experimenting with tire pressure. Latest alignment specs are 1/32" toe out with -3.2* camber in the front, and -3/32" toe in with -1.8* camber in the rear.

Im not totally thrilled by my XP10 pads, and ready to try something else to eliminate the brake fade ...

That's the beauty of suspension tuning, it's more art than science and not every driver responds the same way. I personally link a hint of understeer on track since I'm forced to rely more on my inputs to rotate the car rather than the hardware. This helps me approach and recognize the car's limit.

Are you running XP10 on all 4 corners? Buy the FSB, and see how you like it. Install is really easy and worst case you sell it, those things go fast here so reselling should not be a problem.

[TheSt|G]

Originally Posted by dcaron9999

Wish I could afford it, and I could say I will commit to keeping the 135i for years to come.

Yeah you and me both.

[dcaron9999]

Originally Posted by Kgolf31

Yea. So I think I've found the go-to setup for my car as of now. It is PERFECT in the way I want to to handle.

I had a multi-national champion drive my car Sunday and he said the setup is exactly how it likes it. I have to rotating on power oversteer and front end grip is perfect.

Front: Camber: -3.6*, Toe: 0 with maybe a bit of toe out

Rear: Camber: -2*, Toe: 1/8th total toe

Do you think the alignment setup for autocross and lapping should be the same? Based on tire surface pyrometer readings, all four tires exibit different heat patterns across the tread. The two track I visit frequently are driven counterclockwise, with several high speed left turns. So the right side tires, especially the right front gets more wear. I cant help but wonder if I get as much braking force out of the front tires with that much camber, as the outside edge is not in complete contact with the pavement in a straight line.

Originally Posted by Kgolf31

So, after much debate, and people telling me (and convincing myself) that BMWs do not need a rear bar....I bought a rear bar and installed it..

Contrary to my stock 135i suspension, you are using stiffer springs and better dampers, do feel the need to do the Front Sway bar as well? I thought a FSB was only worthwhile combining with stock M sport suspension ...

Originally Posted by Kgolf31

I should note that the care REALLY likes to trailbrake, it really secures the front down

Agreed, I use trailbraking in long high speed turns all the time.

Originally Posted by Kgolf31

So, from past where I was around 6/12 clicks on compression and high rebound, I'm not 2 clicks up on compression and lower rebound up front. As well, I'm able to run correct rear rebound in the rear instead of turning ...
So in summary. I eat my words saying these cars only need a FSB, because I don't think that is the case anymore after my experiments.them up to max attempting once again to get the rear to rotate.

Sound like stiffening up the rear lateral movement helped with your particular aftermarket suspension setup and use (auto-X) of the car.

[dcaron9999]

Originally Posted by 3002 tii

Are you running XP10 on all 4 corners

Yes for now, but should be getting a BETA set of the front and rear PFC08 pads for my 135i in 1-2 weeks

Originally Posted by 3002 tii

Buy the FSB, and see how you like it. Install is really easy and worst case you sell it, those things go fast here so reselling should not be a problem.

Good point, but market is smaller in Canada , and international shipping and brokerage fees would not make it worthwhile.

Also debating if the E93/M3 FSB is enough on its won, or both the FSB and RSB would be better matched with my Quaife LSD ...

[128Convertibleguy]

Originally Posted by dcaron9999

I track my car, and even with 255/35R18 ZII tires in the front and -3* camber, my 135i still understeers in tighter corners on the track when lapping.

Based on this, do you recommend I install the thicker E93/M3 FSB over the E92/M3 FSB? (I would rather stick with OE parts, and remain as stealthy as possible.

I just don't know. I have stock front springs, and about -.5 camber.

I don't claim my experience is valid for -3 degrees, and stiff front springs. But I suspect understeer on a 1 series is very camber dependent, particularly with the limited sized front tires we have to run. I also suspect certain tires like more negative camber than others, too.

My stock setup was a small front bar and no rear bar. Changing to the 32mm front, still with no rear, clearly reduced understeer. Simplistic weight transfer theory says that's backward, but simplistic weight transfer theory doesn't apply for my specific situation.

Originally Posted by dcaron9999

On stock dampers and linear M springs, do you still recommend a thicker FSB with camber plates and front camber set to -3*? Im also considering Adjustable Toe arms (probably Megan Racing) in the rear, as I have a higher ratio 3.46FD Quaife LSD in the rear, putting more strain on the rear suspension and toe.

As others have said, it's a tricky business. Racers set bars more by trial and error than great theory. The real answer to all your questions is to try things at the track.

From the late, great, Carroll Smith. "If all this makes it seem like we're not going to have much time for drinking beer and chasing girls, you've got it right."

Yeah, it's expensive, too. Such is racing. People who put more time and money into it tend to go faster. I expect that's a big part of why Montoya didn't do so well at NASCAR, and Michael Andretti failed at F1.

[Kgolf31]

Originally Posted by dcaron9999

Do you think the alignment setup for autocross and lapping should be the same? Based on tire surface pyrometer readings, all four tires exibit different heat patterns across the tread. The two track I visit frequently are driven counterclockwise, with several high speed left turns. So the right tires, especially the front gets more wear. I cant help but wonder if I get as much braking force out of the front tires with that much camber, as the outside edge is not in complete contact with the pavement in a straight line.


I'm already 4/32nds through my Z2s and my wear is pretty much constant through the width of the tire (it isn't wanting to fall over on one side when standing upright). I think my alignment transfers over well from autocross to track, since you still need front end camber and rear camber for corner speed. On a typical track, you should see tire readings increase from outside in, if camber is correct. If you're seeing the hotest readings on the outside, you probably don't have enough camber. You will probably decrease contact patch with more camber during a braking zone...but my tires load up fairly well for autocross braking:

This photo is right at the end from braking at about 50 mph. It is hard to tell, but most of the tire is on the ground:



Contrary to my stock 135i suspension, you are using stiffer springs and better dampers, do feel the need to do the Front Sway bar as well? I thought a FSB was only worthwhile combining with stock M sport suspension ...

Yes, A FSB is critical IMO to excellent turn in. From the words of my co-drive this past weekend:

As well, the FSB helps the car keep its camber curve while in a high G load. There are multiple other factors that have to do with turn in (like caster) but a front bar makes a HUGE difference, IMO

Agreed, I use trailbraking in long high speed turns all the time.


Sound like stiffening up the rear lateral movement helped with your particular aftermarket suspension setup and use (auto-X) of the car.

I think a rear bar would be beneficial for track as well. Of course I can dial my dampers to meet certain grip requirements (like bumpy, non grippy surface versus smooth, grippy surface) but from my testing so far you either need:

1. Less rear camber, which I didn't want to do because of my rear tire clearance
2. Lower front ride height, or higher rear ride height
3. No aftermarket front sway bar
4. Add a rear swaybar

I can go on and on, but a rear bar was the most economical solution

Comments in Red.

[dcaron9999]

Thanks for your input Kyle!

Originally Posted by Kgolf31

On a typical track, you should see tire readings increase from outside in, if camber is correct. If you're seeing the hotest readings on the outside, you probably don't have enough camber.

Im actually seeing a hotter inside edge by about 25 to 45* F (10 to 15*C).

Originally Posted by Kgolf31

You will probably decrease contact patch with more camber during a braking zone...but my tires load up fairly well for autocross braking. This photo is right at the end from braking at about 50 mph. It is hard to tell, but most of the tire is on the ground

If you can ever get a GOPRO pointed at your lower front tire area and contact patch, this would somewhat demonstrate if the ZII tires really deforms, squats down, and full width of tire patch is laid down during hard braking.

Originally Posted by Kgolf31

Yes, A FSB is critical IMO to excellent turn in. From the words of my co-drive this past weekend:The car was much better than the last time I drove it. The turn-in is by far the highlight feature... it's very positive and the steering does a good job of communicating that to you.

As well, the FSB helps the car keep its camber curve while in a high G load. There are multiple other factors that have to do with turn in (like caster) but a front bar makes a HUGE difference, IMO

Happy to hear that the FSB has helped turn in, and not affected your understeer. This is high on my to do list. Im also hesitant if I should get the RSB, now that I have a Quaife 3.46 LSD. Some run with the Rear Sway Bar completely disconnected to have the rear end lean and put down better traction...

Your use case seems to indicate that stiffening the rear lateral movement helped with your particular aftermarket suspension setup for autocross + lapping.

Originally Posted by Kgolf31

1. Less rear camber, which I didn't want to do because of my rear tire clearance
2. Lower front ride height, or higher rear ride height
3. No aftermarket front sway bar
4. Add a rear swaybar
I can go on and on, but a rear bar was the most economical solution

So with the above, you are trying to induce oversteer, and you are happy with the front end grip, correct?

[Hops128i]

Originally Posted by ian48

As far as staged goes, I would say go with the rear subframe bushing swap first. If you have two jacks and some stands, it is a job that is doable in a day. Doing it yourself will save you a lot of money. They literally transform the back end. I'm sure you have already read other peoples experiences though.
As far as anything after that it's really up to you.

Do you need an alignment after the bushing swap? And is it worth doing on a stock suspension?

[ian48]

Originally Posted by Hops128i

Do you need an alignment after the bushing swap? And is it worth doing on a stock suspension?

You don't need to do an alignment after the bushing swap. Well some people do but it's dependent on which method you use for the removal.
It is completely worth it on a stock car. That is the only mod I have at the moment and it really does change the car completely. I don't think anyone who has raved about how good of a mod this is, is exaggerating. And it's an easy diy if you have two jacks handy.

[Hops128i]

Originally Posted by ian48

You don't need to do an alignment after the bushing swap. Well some people do but it's dependent on which method you use for the removal.

That great! What method could require an alignment. I'm thinking of going to press route for getting the old ones out, and installing the inserts, or those yellow powerflex... but not sure.

[ian48]

Originally Posted by Hops128i

That great! What method could require an alignment. I'm thinking of going to press route for getting the old ones out, and installing the inserts, or those yellow powerflex... but not sure.

If you use that method then you don't need to do an alignment. That is also the much faster way to do it. Other method is to remove the subframe completely.

[wjk_glynn]

Originally Posted by 3002 tii

...Buy the FSB, and see how you like it. Install is really easy and worst case you sell it, those things go fast here so reselling should not be a problem.

That's an interesting point, maybe worth a few hundred bucks of experimentation.

How would one do a before & after measurement (as opposed to subjective feel) of understeer when adding the FSB, without access to complicated stuff like steering angle vs. yaw rate sensors and the like?

The emphasis is on measurement...

Karl.

[3002 tii]

Originally Posted by wjk_glynn

That's an interesting point, maybe worth a few hundred bucks of experimentation.

How would one do a before & after measurement (as opposed to subjective feel) of understeer when adding the FSB, without access to complicated stuff like steering angle vs. yaw rate sensors and the like?

The emphasis is on measurement...

Karl.

Easiest would be lap times, if this is for measuring improvement on street then it'd sort of moot since there's nothing to be gained. If it subjectively feels better on street that would be good enough for me.

[uberschnell]

Not sure why it's not mentioned more, but first mod should be the rear subframe bushings. You can do them economically with two piece urethane bushings (no special tool needed). DIY this can be a sub $250 job.

Eventually, most everyone doing serious suspension upgrades makes their way to the bushings, but it should be first.

With as much movement as the rear stock bushings allow I don't think you can truly assess any suspension changes. Start with a solid foundation then build up.

[Suprgnat]

Originally Posted by uberschnell

first mod should be the rear subframe bushings.

With as much movement as the rear stock bushings allow I don't think you can truly assess any suspension changes. Start with a solid foundation then build up.

This.