E90Post
 


TireRack
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > Snap oversteer following understeer on xi?



Reply
 
Thread Tools Search this Thread
      06-09-2008, 08:36 AM   #1
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Snap oversteer following understeer on xi?

Hey,
I had an autocross this weekend with BMWCCA and I certainly continue to learn. At the end of the day I dropped three seconds off my time and was pretty competitive with the better street tire cars. But something really weird happened to me on one of the runs.

Towards the end of the course there was a big sweeper left turn going into a short chicane left right left followed by a straight. I took it a bit quicker on the sweeper this run so as to allow myself to just hold the throttle on the chicane. So I came into the chicane at a good speed, hit left, right, and then felt a bit of understeer and tried to correct by gently rolling off the throttle and the car jerked side to side and then sent me the OTHER way, tossing me off course...

Was this just some freak occurrence that's never happened to anyone? Am I that bad a driver? That happening really confused me.... I mean, I felt that that run the tires were really biting....I don't know if this was caused by me just not being used to the friction from those tire temps or something? Let me know what you guys think.

Thanks,
Dave

EDIT: Some details: Bridgestone Potenza RE-01R 245/45/17 all around, 37 psi rear, 39 psi front, stock suspension all around (until thursday!!!), 85?F ambient temp, 100 octane race fuel
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 11:34 AM   #2
ttdmac
Second Lieutenant
 
Drives: E92 335i - Blk Saph/Coral Red
Join Date: May 2005
Location: Indianapolis

Posts: 201
iTrader: (1)

I haven't driven a XI to the edge so I'm not sure how they would react, however it sounds like lift oversteer.

Lifting the throttle and shifting too much weight forward, especially when the car is rotating could increase the likelihood of the rear snapping around when it loses adhesion.

I would have thought that in a XI, you'd want to add throttle when you push to try and get the front to bite.
ttdmac is offline   United_States
0
Reply With Quote
      06-09-2008, 11:41 AM   #3
sayemthree
Brigadier General
 
sayemthree's Avatar
 
Drives: bmw
Join Date: Aug 2007
Location: usa

Posts: 4,845
iTrader: (0)

sounds like lift throttle oversteer to me also.
sayemthree is offline  
0
Reply With Quote
      06-09-2008, 11:43 AM   #4
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Oh....that's a very obvious answer isn't it....doh! Well is there any particular suspension/tire adjustment that will lessen the effect of lift off oversteer? Because I know for a fact that if I lifted off at all, it was a minute adjustment and I made absolutely sure to roll off.
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 11:46 AM   #5
KL2DC
Moderator
 
KL2DC's Avatar
 
Drives: E90 328i, E85 Z4 3.0i
Join Date: Jan 2006
Location: DC Metro

Posts: 17,753
iTrader: (22)

Garage List
2011 E90 328i  [0.00]
2006 E85 Z4 3.0i  [0.00]
Send a message via MSN to KL2DC
Was your DSC/DTC on by any chance?
__________________

Official DC Metro Registry - Current, New & Prospective Area Members Roll Call!
KL2DC is offline   United_States
0
Reply With Quote
      06-09-2008, 11:48 AM   #6
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
no my DSC/DTC was off, I leave it on in the morning and shut if off for the afternoon.
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 11:50 AM   #7
S4to335
Brigadier General
 
Drives: 95 Audi S6
Join Date: Jan 2007
Location: San Jose, CA

Posts: 4,377
iTrader: (5)

Garage List
off throttle oversteer.
__________________

Car is now gone .... :-(
S4to335 is offline   United_States
0
Reply With Quote
      06-09-2008, 11:54 AM   #8
ttdmac
Second Lieutenant
 
Drives: E92 335i - Blk Saph/Coral Red
Join Date: May 2005
Location: Indianapolis

Posts: 201
iTrader: (1)

Ok, if the throttle change was minor perhapst trying a different entry speed into the chicane might help or trail brake through it and see if that will give you more bite in the front so you can power through with more throttle.
ttdmac is offline   United_States
0
Reply With Quote
      06-09-2008, 11:56 AM   #9
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Quote:
Originally Posted by ttdmac View Post
Ok, if the throttle change was minor perhapst trying a different entry speed into the chicane might help or trail brake through it and see if that will give you more bite in the front so you can power through with more throttle.
I'll certainly try that next time. I wasn't trying any fancy braking this go, really just teaching myself good positioning and smooth inputs and the like.
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 11:57 AM   #10
ttdmac
Second Lieutenant
 
Drives: E92 335i - Blk Saph/Coral Red
Join Date: May 2005
Location: Indianapolis

Posts: 201
iTrader: (1)

Slow in, fast out is 90% the better way to approach a turn that makes you push on exit.
ttdmac is offline   United_States
0
Reply With Quote
      06-09-2008, 12:35 PM   #11
S4to335
Brigadier General
 
Drives: 95 Audi S6
Join Date: Jan 2007
Location: San Jose, CA

Posts: 4,377
iTrader: (5)

Garage List
Quote:
Originally Posted by ttdmac View Post
Slow in, fast out is 90% the better way to approach a turn that makes you push on exit.
In autox he might try to play with left foot braking...

BTW, longodj, I have considerable experience on track with AWD cars. I have tracked them from late 1997 until probably early 2007. I dont know what you could have done...it is apparent that you upset the car...without being in the car with you at the time..it is hard to tell what might be done to lessen it in the future.
Attached Images
     
__________________

Car is now gone .... :-(
S4to335 is offline   United_States
0
Reply With Quote
      06-09-2008, 01:08 PM   #12
nicknaz
Brigadier General
 
Drives: 2012 Z4 35i
Join Date: May 2008
Location: San Diego CA

Posts: 4,036
iTrader: (0)

i'm guessing you were understeering because you tried to carry way too much entry speed into the corner and also had a lot of steering (the wheel was turned a lot) right before you lifted.. when you lifted you unloaded the rear, front tires started to grip as you scrubbed off speed, and then because you still had the steering turned, the car suddenly changed direction in the way the front wheels were turned

hard to say without being in there with you, but perhaps you could try to lower your entry speeds, finish braking earlier and use a neutral throttle at turn in

i found this approach was best when tracking my WRX.

also have you considered using stock tires for now? IMHO its easier to learn with less sticky tires because the traction limit is reached at a lower speed, making it easier to figure out what is going on and correcting it
nicknaz is offline   United_States
0
Reply With Quote
      06-09-2008, 05:10 PM   #13
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Quote:
Originally Posted by S4to335 View Post
In autox he might try to play with left foot braking...

BTW, longodj, I have considerable experience on track with AWD cars. I have tracked them from late 1997 until probably early 2007. I dont know what you could have done...it is apparent that you upset the car...without being in the car with you at the time..it is hard to tell what might be done to lessen it in the future.
S4to335 I don't doubt your experience at all. I really hope I didn't insult you in the other thread....I really did assume your knowledge of driving and was basically offering my redundant knowledge...
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 05:15 PM   #14
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Quote:
Originally Posted by Nick Nazareno View Post
i'm guessing you were understeering because you tried to carry way too much entry speed into the corner and also had a lot of steering (the wheel was turned a lot) right before you lifted.. when you lifted you unloaded the rear, front tires started to grip as you scrubbed off speed, and then because you still had the steering turned, the car suddenly changed direction in the way the front wheels were turned

hard to say without being in there with you, but perhaps you could try to lower your entry speeds, finish braking earlier and use a neutral throttle at turn in

i found this approach was best when tracking my WRX.

also have you considered using stock tires for now? IMHO its easier to learn with less sticky tires because the traction limit is reached at a lower speed, making it easier to figure out what is going on and correcting it
I agree with your interpretation, I think that is exactly what happened. I'm not sure if I was going too fast or what it was, I was certainly trying to go slower in the second half of the day (which my best time was on my final run of the day...my "slowest" run). I certainly agree with the too much steering bit, I've been trying to get over that in autocross..

I ran my first few autocrosses on stock tires and I might try doing half a day with and half without in the future or something, but I found that the RE-01Rs are street-like enough that they provide the squeally feedback I really need while providing the performance advantage of a sticky tire.

Thanks for the input everyone.
longodj is offline   United_States
0
Reply With Quote
      06-09-2008, 10:43 PM   #15
sayemthree
Brigadier General
 
sayemthree's Avatar
 
Drives: bmw
Join Date: Aug 2007
Location: usa

Posts: 4,845
iTrader: (0)

tire pressures?
too much late trail braking
snapping off the brakes suddenly
more practice being smooth at the limit

I too have some decent track experience with AWD cars. in fact I took my wifes 535ixT wagon out once - it was a blast. gave a Caymen a run for his money till she yelled at me for being hard on her brakes.

S4to335i - nice collection of Audisa!!! I also tracked my wifes S4 Avant at quite a few events, both Audi club and CCA.
sayemthree is offline  
0
Reply With Quote
      06-10-2008, 09:50 AM   #16
S4to335
Brigadier General
 
Drives: 95 Audi S6
Join Date: Jan 2007
Location: San Jose, CA

Posts: 4,377
iTrader: (5)

Garage List
Quote:
Originally Posted by longodj View Post
S4to335 I don't doubt your experience at all. I really hope I didn't insult you in the other thread....I really did assume your knowledge of driving and was basically offering my redundant knowledge...

I didnt take it as such. From the factory these cars, IMHO, push pretty badly. You can adjust that stuff a bit with tire pressures...but it becomes a chase to find the correct set up as tires heat up. I have autocrossed my 335i only once..but I have lots of experience autocrossing a 2000 Audi S4....actually got third place for the year in 2000 in CSP class in SF Region...with 17 autocrosses attended that year. Anyway, the hard part about autocrossing an AWD car is to get the car to rotate. RWD cars can do this easily. My friend Corey, who now has a 335i..but doesnt autox anymore... spent tons of hours trying to dial in the ability to get the his S4 to rotate...with power. I think this snap oversteer that you encountered was the result of you having understeer..trying to correct for that..and going overboard the other direction. I have spun out in autocross events before.. I know how touchy it can be..especially if you run late in the day and happen to find the marbles/pebbles...I am thinking that these two things could have contributed to your snap oversteer.

Anyway, that is my 2 cents worth.

Some pictures from 1903...actually 1999 (red A4) and 2000 (blue S4)

Attached Images
  
__________________

Car is now gone .... :-(

Last edited by S4to335; 06-10-2008 at 10:56 AM.
S4to335 is offline   United_States
0
Reply With Quote
      06-10-2008, 10:53 AM   #17
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Thanks for the response, and nice pics! I agree with your interpretation as well I have a lot to work on for either this weekend or next depending on if I want to travel an hour or not...
longodj is offline   United_States
0
Reply With Quote
      06-10-2008, 12:30 PM   #18
nicknaz
Brigadier General
 
Drives: 2012 Z4 35i
Join Date: May 2008
Location: San Diego CA

Posts: 4,036
iTrader: (0)

slightly off topic, but for what its worth, i use to do a handful of autoX events per year and last year i switched to doing HPDE instead. i find that it is a lot more time efficient. both autoX and hpde use 1 weekend day, but in an autoX you get like 10-12min of actual driving time but in hpde you get anywhere from 80 to 110min of driving. on a $/min driving basis, hpde is also a better value.

you are in rochester? perhaps you can do events at the glen or poconos east
nicknaz is offline   United_States
0
Reply With Quote
      06-10-2008, 01:59 PM   #19
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Hey,
I actually do both. There aren't HPDE events every weekend and even if they are, they are extremely expensive for me. Also, they teach different things I think. Autocross really gets you to act quickly and really be careful about throttle and braking etc. At least so far, it has been a good precursor to HPDE. This year I'm aiming for 4-5 HPDEs and >10 Autocrosses.
longodj is offline   United_States
0
Reply With Quote
      06-10-2008, 02:03 PM   #20
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Oh and also...in autocross let's say you get 10 min per day at $25 per day that's 2.5 $/min....in HPDE let's say you get 100 min of driving for $250 per day...that's still 2.5 $/min....so really they are equivalent but you're able to do 10 autocrosses on 10 different courses on 10 different days instead of one HPDE on one course. Don't get me wrong I love both, but they have different purposes I think. In terms of adrenaline rush HPDE certainly wins out, but there's also no real competition involved (at my level).
longodj is offline   United_States
0
Reply With Quote
      06-10-2008, 04:18 PM   #21
nicknaz
Brigadier General
 
Drives: 2012 Z4 35i
Join Date: May 2008
Location: San Diego CA

Posts: 4,036
iTrader: (0)

maybe its different out east.. here in norcal i find that it is possible to do at least 1 HPDE per month, and those are multiple day events, so its possible to get a crap load of seat time in. i hear you on the cost, so i only do average 1 HPDE day per month.

and there are so many technical roads around here its like.. free autoX all the time.. tons of 30mph-60mph roads all to yourself
nicknaz is offline   United_States
0
Reply With Quote
      06-10-2008, 04:53 PM   #22
longodj
Major
 
longodj's Avatar
 
Drives: 135i
Join Date: Jun 2007
Location: Rochester, NY

Posts: 1,288
iTrader: (3)

Garage List
2007 335xi  [0.00]
1974 VW Beetle  [0.00]
Send a message via AIM to longodj
Quote:
Originally Posted by Nick Nazareno View Post
maybe its different out east.. here in norcal i find that it is possible to do at least 1 HPDE per month, and those are multiple day events, so its possible to get a crap load of seat time in. i hear you on the cost, so i only do average 1 HPDE day per month.

and there are so many technical roads around here its like.. free autoX all the time.. tons of 30mph-60mph roads all to yourself
lol....we have....highways?.....maybe some city traffic....

back home in jersey there are tons of twistys but nothing fun up in rochester
longodj is offline   United_States
0
Reply With Quote
Reply

Bookmarks

Tags
autocross, bmwcca, racing, snap oversteer, understeer

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 Off
Forum Jump


All times are GMT -5. The time now is 09:08 PM.




e90post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST