E46 BMW Social Directory E46 FAQ 3-Series Discussion Forums BMW Photo Gallery BMW 3-Series Technical Information E46 Fanatics - The Ultimate BMW Resource BMW Vendors General E46 Forum The Tire Rack's Tire Wheel Forum Forced Induction Forum The Off-Topic The E46 BMW Showroom For Sale, For Trade or Wanting to Buy

Welcome to the E46Fanatics forums. E46Fanatics is the premiere website for BMW 3 series owners around the world with interactive forums, a geographical enthusiast directory, photo galleries, and technical information for BMW enthusiasts.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

Go Back   E46Fanatics > Tuning & Tech > Motorsports & Track Forum

Motorsports & Track Forum
From Auto-X to Trackday to Racing and Professional Motorsports this is the place to discuss making BMWs fast

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 06-22-2015, 09:55 PM   #1
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Suggestions on how to improve rotation (non-M)?

Hi, what are some upgrades I can add to my 330Ci to improve turn in, rotation, and decrease understeer?

I am running non-staggered 255/35/18 Federal RS-R with a wider track up front (18x9.5 ET22 front, 18x9.5 ET33 rear).

Alignment settings are: -3 camber front, -2 camber rear and just about factory toe-in settings in the rear.

At the track, I ran 32psi hot up front and 34psi hot rear and played around with coilover dampening to try and get the car more balanced, but I ended up having to trail brake to get the car to turn in the way I want it to. Through slower sweepers, the car would push really badly on turn in.

I am thinking about upgrading to a thicker rear sway bar but also looking for other suggestions.
alexisthemovie is offline   Reply With Quote
Ads by Google

Guests, get your FREE E46Fanatics.com membership to remove this ad.
Old 06-22-2015, 09:57 PM   #2
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Here's a video from this past weekend.

alexisthemovie is offline   Reply With Quote
Old 06-23-2015, 12:33 AM   #3
Rob43
Hates Low RPM !
 
Rob43's Avatar
 
Join Date: Oct 2009
Location: Richmond VA
Posts: 6,045
My Ride: 03 331Ci 5spd R1200R
It's late so I'll comment more tomorrow, but in short I believe this can be fixed with a F&R set of Hotchkis sway bars & a revised tire pressure plan. A set of offset Fcab's like the OE Z4M units for added positive caster wouldn't hurt either.



Rob43
__________________



Rob #43 ITS/ITR/STU, BMW 325I, STU LAP RECORD
SUMMIT POINT WV 1:24:229 S.C.C.A.
(DynoDynamics https:vimeo.com/8486878 Dyno Video)
"Chance Favors The Prepared Mind"

Need Help With Your Nitrous Ambitions ?.....PM ME
Quote:
Originally Posted by RacerX View Post
Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
Rob43 is online now   Reply With Quote
Old 06-23-2015, 04:24 PM   #4
Rob43
Hates Low RPM !
 
Rob43's Avatar
 
Join Date: Oct 2009
Location: Richmond VA
Posts: 6,045
My Ride: 03 331Ci 5spd R1200R
I'll start by saying I don't know the Federal RS-R tires, I'm sure they're a good high perf. summer street tire but I'd ask you to consider some form of dedicated track wheel/tire setup. There are certainly many good choices in this area, I'd give great consideration to the Toyo RA1 because of their long-ish lasting tread life (they get faster as they wear out) & the fact that they work well in the rain if you ever get any.

As to tire pressures, I'd want you to come off the track with a Hot temp of 38 to 40 PSI. Most competion tires work best at that PSI, but adjust accordingly.

I'd buy the Hotchkis F&R bars and start with both set on the full soft setting, then as you feel them out I'd start by stiffening the rear bar settings to address your issue.


Rob43
__________________



Rob #43 ITS/ITR/STU, BMW 325I, STU LAP RECORD
SUMMIT POINT WV 1:24:229 S.C.C.A.
(DynoDynamics https:vimeo.com/8486878 Dyno Video)
"Chance Favors The Prepared Mind"

Need Help With Your Nitrous Ambitions ?.....PM ME
Quote:
Originally Posted by RacerX View Post
Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
Rob43 is online now   Reply With Quote
Old 06-23-2015, 06:46 PM   #5
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Quote:
Originally Posted by Rob43 View Post
I'll start by saying I don't know the Federal RS-R tires, I'm sure they're a good high perf. summer street tire but I'd ask you to consider some form of dedicated track wheel/tire setup. There are certainly many good choices in this area, I'd give great consideration to the Toyo RA1 because of their long-ish lasting tread life (they get faster as they wear out) & the fact that they work well in the rain if you ever get any.

As to tire pressures, I'd want you to come off the track with a Hot temp of 38 to 40 PSI. Most competion tires work best at that PSI, but adjust accordingly.

I'd buy the Hotchkis F&R bars and start with both set on the full soft setting, then as you feel them out I'd start by stiffening the rear bar settings to address your issue.


Rob43
I'm using street tires because I'm planning to run in Redline and Global's time attack events later on this year in the Enthusiast class. Therefore, an RA1 is out of consideration (besides, there are better tires than RA1 in the same class).

I'll look into the Hotchkis bars. They're less than half a mile from my shop so seems quite convenient. Thank you for the recommendation.
alexisthemovie is offline   Reply With Quote
Old 06-24-2015, 12:37 AM   #6
e46techtuner
Registered User
 
Join Date: Jun 2005
Location: USA
Posts: 741
My Ride: 2000 328i
Looks like you have the tire size, psi and track width dialed for oversteer. You can try stiffening the rear more with a sway bar as suggested. Also, you can turn up the dampening and/or get stiffer springs for the rear as well.

How are the sidewalls on those tires? With a 140 treadwear they should have pretty good turn-in, once warm. You want the tire to fit pretty square on the wheel. A 9.5" seems pretty wide for a 255 but then again, I don't have experience with these tires to know how wide they run.

Was this DE or timed GTA? I usually do NASA TT events but I might head out to GTA events in the future just to experience other tracks. Unfortunately, my TTE car is classed in Limited for GTA just because its gutted.
__________________
e46techtuner is offline   Reply With Quote
Old 06-24-2015, 05:40 AM   #7
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Quote:
Originally Posted by e46techtuner View Post
Looks like you have the tire size, psi and track width dialed for oversteer. You can try stiffening the rear more with a sway bar as suggested. Also, you can turn up the dampening and/or get stiffer springs for the rear as well.

How are the sidewalls on those tires? With a 140 treadwear they should have pretty good turn-in, once warm. You want the tire to fit pretty square on the wheel. A 9.5" seems pretty wide for a 255 but then again, I don't have experience with these tires to know how wide they run.

Was this DE or timed GTA? I usually do NASA TT events but I might head out to GTA events in the future just to experience other tracks. Unfortunately, my TTE car is classed in Limited for GTA just because its gutted.
The sidewall is stiff and it's perfect on a 9.5" wide tire. I have experience with most commonly used street tires (RS3, Z1SS, 595RSR, Achilles 123S, etc) and choose whatever is cheap for most DE's (eg. this past weekend).

I think as long as you have a dashboard and glovebox, you can run Enthusiast or Street. The main limiting factors are tires and aero. For Enthusiast class, you must run a cat and can't have a chassis mounted splitter. Street class allows almost anything, but limits you in tire width and treadwear rating.

If all goes well, I plan to go FI and compete for Enthusiast class at Super Lap Battle.
alexisthemovie is offline   Reply With Quote
Old 06-24-2015, 07:04 AM   #8
RudyT
Registered User
 
Join Date: Apr 2012
Location: Cincinnati
Posts: 128
My Ride: 2001 330i
What suspension are you on? I'm surprised at the suggestions of stiffening up the rear bar, I'm running full stiff in the front, as are most of the SE46 guys.
__________________
RudyT is offline   Reply With Quote
Old 06-24-2015, 03:45 PM   #9
Rob43
Hates Low RPM !
 
Rob43's Avatar
 
Join Date: Oct 2009
Location: Richmond VA
Posts: 6,045
My Ride: 03 331Ci 5spd R1200R
Quote:
Originally Posted by RudyT View Post
What suspension are you on? I'm surprised at the suggestions of stiffening up the rear bar, I'm running full stiff in the front, as are most of the SE46 guys.
You have to understand that the OP is Not running the high dollar SE46 suspension that you have.

Different setups = different recommendations.......



Rob43
__________________



Rob #43 ITS/ITR/STU, BMW 325I, STU LAP RECORD
SUMMIT POINT WV 1:24:229 S.C.C.A.
(DynoDynamics https:vimeo.com/8486878 Dyno Video)
"Chance Favors The Prepared Mind"

Need Help With Your Nitrous Ambitions ?.....PM ME
Quote:
Originally Posted by RacerX View Post
Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
Rob43 is online now   Reply With Quote
Old 06-24-2015, 04:47 PM   #10
RudyT
Registered User
 
Join Date: Apr 2012
Location: Cincinnati
Posts: 128
My Ride: 2001 330i
Quote:
Originally Posted by Rob43 View Post
You have to understand that the OP is Not running the high dollar SE46 suspension that you have.

Different setups = different recommendations.......



Rob43
I'm running Koni Yellows on H&R springs that's why I was curious what his setup was. Mine is ok, but needs another degree of camber from the current -2.0
__________________
RudyT is offline   Reply With Quote
Old 06-24-2015, 04:58 PM   #11
Rob43
Hates Low RPM !
 
Rob43's Avatar
 
Join Date: Oct 2009
Location: Richmond VA
Posts: 6,045
My Ride: 03 331Ci 5spd R1200R
My mistake, I though you were running the Spec E46 suspension system which uses a reasonable high F&R spring rate not to mention excellent dampers.


Rob43
__________________



Rob #43 ITS/ITR/STU, BMW 325I, STU LAP RECORD
SUMMIT POINT WV 1:24:229 S.C.C.A.
(DynoDynamics https:vimeo.com/8486878 Dyno Video)
"Chance Favors The Prepared Mind"

Need Help With Your Nitrous Ambitions ?.....PM ME
Quote:
Originally Posted by RacerX View Post
Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
Rob43 is online now   Reply With Quote
Old 06-25-2015, 12:00 AM   #12
badfast
Registered User
 
Join Date: Feb 2008
Location: San Jose, CA
Posts: 621
My Ride: A Car
From the video it looks like you are cranking on the wheel quite aggressively and giving a lot of steering input. Combine too much steering and too much brake and you have your entry understeer problem.

Also, do you have an lsd? If not I would be careful about going with too big of a bar. You may find yourself getting wheelspin.
badfast is offline   Reply With Quote
Old 06-25-2015, 06:10 AM   #13
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Quote:
Originally Posted by RudyT View Post
What suspension are you on? I'm surprised at the suggestions of stiffening up the rear bar, I'm running full stiff in the front, as are most of the SE46 guys.
Single adjustable coilover, can't go with anything too crazy or my car won't class where I want to compete.

Quote:
Originally Posted by badfast View Post
From the video it looks like you are cranking on the wheel quite aggressively and giving a lot of steering input. Combine too much steering and too much brake and you have your entry understeer problem.

Also, do you have an lsd? If not I would be careful about going with too big of a bar. You may find yourself getting wheelspin.
This was merely one lap of the entire day, but anyways whether or not my driving style is the issue (in this case, it's not), I should be able to tailor the characteristics of the car to match the way I drive.

At this moment, no LSD, however I will be going with the full M3 rear end once I go FI. I think you're correct about excess wheelspin with too much bar. Personally I prefer to look at alternative solutions (coilover, alignment, and tire pressure micro adjustments) to find the best balance.
alexisthemovie is offline   Reply With Quote
Old 06-25-2015, 09:34 AM   #14
Mark506
Registered User
 
Join Date: Jun 2015
Location: Pittsburgh
Posts: 9
My Ride: turns in early
Badfast has a good point about steering input. Glanced over the video slightly. Seems like you're pushing hard into the corner, what about exit? Increasing rear sway bar would help, but would have more focus on mid corner/exit rather than entry.

In your situation, I would first try addressing the front for any changes rather than rear. Lowering ride height, if possible, would take away slight stability but help with grip in entry. I know you said you "can't do anything crazy", but softer springs upfront would also help.

Not sure how often you track, but it might be a smart investment to get a tire temperature prob (try eBay). I think many overlook how much genuine information you can pull from checking tire temps (outside/middle/inside) immediately after a run which can tell you if you're running too much/too little pressure/camber/etc. A little more info can be found here: http://www.fluke.com/fluke/uses/comu.../racetracktemp
__________________
Driver for GMS
Twitter: @MA506

Last edited by Mark506; 06-25-2015 at 12:14 PM.
Mark506 is offline   Reply With Quote
Old 06-25-2015, 10:14 AM   #15
RudyT
Registered User
 
Join Date: Apr 2012
Location: Cincinnati
Posts: 128
My Ride: 2001 330i
Quote:
Originally Posted by alexisthemovie View Post
Single adjustable coilover, can't go with anything too crazy or my car won't class where I want to compete..
What coilovers, what's your spring rates, and ride height?

These cars tend to push, so you need to drive accordingly. I find trail breaking to help out, and sometimes you need to be patient when getting back on the throttle. I've been trying to get more grip out of the front with a stiffer front bar, more camber, and proper tire pressure. If I had coilovers and linear springs I would also increase spring rates and increase stiffness compression and rebound accordingly. You have a lot of variables here, so you need to play with them.

What toe alignment settings are you running? I think 0 toe in front and .20 total toe out back is the best for a street driven car. You can add toe out if it's track only, or set it up with your camber plates so when you increase camber, it will add toe out.
__________________

Last edited by RudyT; 06-25-2015 at 10:27 AM.
RudyT is offline   Reply With Quote
Old 06-25-2015, 04:30 PM   #16
badfast
Registered User
 
Join Date: Feb 2008
Location: San Jose, CA
Posts: 621
My Ride: A Car
Quote:
Originally Posted by alexisthemovie View Post
Single adjustable coilover, can't go with anything too crazy or my car won't class where I want to compete.



This was merely one lap of the entire day, but anyways whether or not my driving style is the issue (in this case, it's not), I should be able to tailor the characteristics of the car to match the way I drive.
Sure.

Just curious why you don't think your driving style could be an issue?

Quote:
At this moment, no LSD, however I will be going with the full M3 rear end once I go FI. I think you're correct about excess wheelspin with too much bar. Personally I prefer to look at alternative solutions (coilover, alignment, and tire pressure micro adjustments) to find the best balance.
Springs would be a good option. Do you know your spring rates?
badfast is offline   Reply With Quote
Old 07-01-2015, 09:03 AM   #17
SoloII///M
Registered User
 
Join Date: Mar 2005
Location: Columbia, MD
Posts: 618
My Ride: Many
The steering inputs are definitely part of the issue. You're giving the car very quick and choppy inputs and with a soft suspension it cannot react to the weight transfer fast enough and you're overwhelming the front tires.

I don't know what the rates of the H+R springs are, but I'm guessing they're not much higher than stock, which even with 3 degrees of front camber is going to cause the front of the car to roll too much and ultimately will lead to understeer, particularly on corner entry. Combine that with a reduced ride height and you've lowered the front roll center to the point that the front spring rate is lower still. I really don't like a big rear bar on any BMW, but understand it's easier to bolt on bars than it is to switch to adjustable coilovers. At the very least you need a big front bar.

Have you tried increasing the rebound damping of the rear shocks to free it up on corner entry?

With a stock open differential the car will rotate fantastically on corner entry. It will be corner exit that won't be as good as with an LSD. Most BMW LSDs are set up with higher ramp angles on deceleration to try to mimic an open differential for this reason. The lower ramp angles are on the acceleration side to improve how the car puts power down.
__________________
John V
'02 330Ci - Megasquirt 3 tuned by PFTuning.com, M50 manifold, Kromer Kraft headers, Motons, widebody, etc.
SoloII///M is online now   Reply With Quote
Old 07-02-2015, 04:41 AM   #18
alexisthemovie
Registered User
 
Join Date: Jul 2014
Location: Los Angeles
Posts: 103
My Ride: BMW
Thanks for the suggestions guys. I will try to drive smoother next time. I'm used to driving S2000's and lighter/stiffer cars.

Spring rates: Front: 10 kg/mm & Rear: 14 kg/mm

I'll be switching to Swift springs in the rear (non progressive).

Running .14 total toe in rear. Might try to dial it out closer to 0. I'm driving the same track on 7/18 in the different direction, but hopefully I can test the changes.
alexisthemovie is offline   Reply With Quote
Old 07-02-2015, 05:36 AM   #19
SoloII///M
Registered User
 
Join Date: Mar 2005
Location: Columbia, MD
Posts: 618
My Ride: Many
Your front spring rate is really soft, especially if you don't have a large front bar and you're only running 3 degrees negative camber up front. Make the front end work better and you will have fewer problems with understeer. Start with a big front bar and take some of the rear toe-in out of the car. I wouldn't personally go stiffer in the rear.

Depending how your shocks are valved you might not be able to up the spring rate.
__________________
John V
'02 330Ci - Megasquirt 3 tuned by PFTuning.com, M50 manifold, Kromer Kraft headers, Motons, widebody, etc.
SoloII///M is online now   Reply With Quote
Old 07-02-2015, 10:05 AM   #20
RudyT
Registered User
 
Join Date: Apr 2012
Location: Cincinnati
Posts: 128
My Ride: 2001 330i
Quote:
Originally Posted by SoloII///M View Post
Your front spring rate is really soft, especially if you don't have a large front bar and you're only running 3 degrees negative camber up front. Make the front end work better and you will have fewer problems with understeer. Start with a big front bar and take some of the rear toe-in out of the car. I wouldn't personally go stiffer in the rear.

Depending how your shocks are valved you might not be able to up the spring rate.
I'd be careful how much toe you take out of the rear. IIRC without sufficient toe in you'll introduce oversteer because of the rear suspension changes during power down.
__________________
RudyT is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Censor is ON





All times are GMT -5. The time now is 09:18 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
(c) 1999 - 2011 performanceIX Inc - privacy policy - terms of use