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M3 Track: Racing and DE Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start!


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Old Mon, Dec-02-2019, 02:01:08 AM   #1
eacmen
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Default Managing Understeer with Aero

We recently bought a track car from a fellow forum member:


2004 AW E46 M3 Track Car
https://r.tapatalk.com/shareLink/top...ink_source=app


This is our first car with aero. Our previous M3 had very confidence inspiring steering. Turn in was direct and predictable. We havenít had the chance to take this new car out on track yet, but even at 75mph on the highway the steering seems loose.

Curious if others are running the BW race wing and front splitter combo and any advice on managing the understeer? Obviously taking out some wing angle, but anything else? Do the spring rates look correct (500F/750R)?
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Old Mon, Dec-02-2019, 02:37:42 AM   #2
CrookedCommie
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Default Re: Managing Understeer with Aero

Pretty sure I've seen that car at Putnam. Spring rates are way too low for aero. How's the alignment look?
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Old Mon, Dec-02-2019, 02:56:42 AM   #3
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Default Re: Managing Understeer with Aero

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Originally Posted by CrookedCommie View Post
Pretty sure I've seen that car at Putnam. Spring rates are way too low for aero. How's the alignment look?


Yeah car came from Indiana. Not sure on alignment, my shop is going to set it up like my previous car, which I loved.

What spring rates would you recommend? Not sure the ohlins will handle more spring. The car as it sits now is heavier than my previous car and I had 650F/750R with no aero.

Would a heavier spring in the rear help with front end grip?
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Old Mon, Dec-02-2019, 03:05:10 AM   #4
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Default Re: Managing Understeer with Aero

I have no experience with aero spring rate - my car is on 700/800 with slicks and no aero. I think James Clay discussed aero rate in the spring rate thread in this subforum, but 500/750 seems way too low. If the steering seems loose - it might be alignment.
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Old Mon, Dec-02-2019, 03:13:05 AM   #5
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Default Re: Managing Understeer with Aero

Putting stiffer springs on the front will make it understeer more. Iíd recommend trying softer front and/or stiffer rear springs.

Look at the flat ride thread. I fought a similar issue with understeer. ABS ended up being the problem - car wasnít behaving nicely in bumpy braking zones. Iíve installed softer front springs...much improved results. Now Iíve dialed in less rebound/compression on the front axle and more in the rear. Iíll test it again Dec14/15 if the weather will cooperate. I think Iím well on the path to a balanced car once again.

I think the next step is to increase the rear springs rates.


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Old Mon, Dec-02-2019, 03:36:48 AM   #6
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Default Re: Managing Understeer with Aero

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Originally Posted by bigjae1976 View Post
Putting stiffer springs on the front will make it understeer more. Iíd recommend trying softer front and/or stiffer rear springs.

Look at the flat ride thread. I fought a similar issue with understeer. ABS ended up being the problem - car wasnít behaving nicely in bumpy braking zones. Iíve installed softer front springs...much improved results. Now Iíve dialed in less rebound/compression on the front axle and more in the rear. Iíll test it again Dec14/15 if the weather will cooperate. I think Iím well on the path to a balanced car once again.

I think the next step is to increase the rear springs rates.


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Been following flat ride thread for a while. The 500/750 combo is much closer to flat ride than what I had before. Maybe more rear spring will help.

Might have to swap in the JRZ RS2 to run more spring. Was hoping to try out the Ohlins as Iíve heard great things.

Anyone know what the Max spring rate is for the ohlin r&t Kit?
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Old Mon, Dec-02-2019, 04:22:50 AM   #7
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Default Re: Managing Understeer with Aero

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Originally Posted by eacmen View Post
Been following flat ride thread for a while. The 500/750 combo is much closer to flat ride than what I had before. Maybe more rear spring will help.

Might have to swap in the JRZ RS2 to run more spring. Was hoping to try out the Ohlins as Iíve heard great things.

Anyone know what the Max spring rate is for the ohlin r&t Kit?
I think they recommend 20-25% from what the kit comes with (400 f / 628 r). So you are basically at the upper end with your current setup.

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Old Tue, Dec-03-2019, 05:07:18 PM   #8
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Default Re: Managing Understeer with Aero

"Steering seems loose"

What do you currently have the alignment set to, and when was the last time you set it? Does the problem go away with the wing removed?

Since it's a new-to-you car, I would spend more time zeroing in on the issue rather than just throwing stronger springs at it. (That's at least my take on the context of the thread)

It could need aero balance and stiff springs to back it up, but it could also very well be that it's got an un-even amount of toe on tires that still have mold-release which is making it feel weird on the highway.
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Old Tue, Dec-03-2019, 09:26:29 PM   #9
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Default Re: Managing Understeer with Aero

Quote:
Originally Posted by eacmen View Post
Been following flat ride thread for a while. The 500/750 combo is much closer to flat ride than what I had before. Maybe more rear spring will help.

Might have to swap in the JRZ RS2 to run more spring. Was hoping to try out the Ohlins as Iíve heard great things.

Anyone know what the Max spring rate is for the ohlin r&t Kit?
You could have the Ohlins shocks revalved to match your cars corner weights and get them valved for whatever spring rates you wanted. I'll likely be doing that next winter, as my corner rates and spring rates are getting pretty finalized and the shocks are coming up on 50,000 miles anyway...

But, to answer the question, Ohlins says the shocks can handle up to a 25% deviation from stock. Stock spring rates are 400 front, 628 rear.
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Old Tue, Dec-03-2019, 09:37:31 PM   #10
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Default Re: Managing Understeer with Aero

Thanks everyone.

BTW Bimmerworld recommends 2-3 degreeAoA to start.

Also doesnít help to be driving on rs4s when itís 45 degrees outside.

Going to bring the car in for some major service in the next week or two, will have them set the alignment to our previous specs and see how the car does.

Also doing sunroof delete, Rod bearings, fuel starvation kit, etc

Then bringing it down to get roll bar welded in.

Hopefully we can gain some confidence with the car before hitting the track in March. Right now it just feels like itís going to lose control. Could just be all in my head tho, trying to get back behind the wheel after crashing.
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Discussing Managing Understeer with Aero in the M3 Track: Racing and DE Forum - Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)