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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > Does lowering the front too much cause "push?"



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      03-05-2008, 12:48 PM   #1
sambonator
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Smile Does lowering the front too much cause "push?"

I've been playing with my coilovers, and it seems like I get more "push" (understeer) when I lower the front, particularly on slower speed, hard turns.

Is it better the raise the front to reduce this? I'm running my street wheels/tires and haven't tested with my track setup yet...

Thanks in advance!
Sam
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      03-05-2008, 02:32 PM   #2
leftcoastman
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I would think the opposite. Having the rake with the front lower would transfer more weight forward, reducing understeer.

Have you tried trail braking those slower turns? It works wonders on this car.
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      03-05-2008, 03:46 PM   #3
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It's hard to say... But logic would dictate that if there is less weight on the rear, that it would break traction first.

However, when you lower the fronts, a lot of things change and if the front becomes "stiffer" in anyway, like if it was riding on bump stops, then it would push / understeer. A lot of your suspension geometry is in the front as well and the lowering could affect that and cause you to lose some dynamic negative camber and traction.

I don't think it's easy to just say yes or no, but it's going to depend a lot on your setup and the settings that you are at.
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      03-05-2008, 07:06 PM   #4
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Hmmm sounds like I have to experiment...
Another question...is there such a thing as too much negative camber on the front, and can that cause you to lose traction in the front/push/understeer?

I just set up my TEIN coilovers in the front for max negative camber, and was wondering if there could be too much neg. camber...?

Also, without going to the big alignment shop with their expensive machines... is there any way to measure toe in/out, camber and caster on the car at home?

Thank you in advance, and thanks for your answers Leftcoastman and Chowbow!
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      03-06-2008, 02:24 AM   #5
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I know some guys who go to the track and run -4 degrees of camber... A lot of cars won't even allow for that much. I guess if your rubber isn't sticky enough, you could run TOO much... where you're still running on the insides of the tire as you don't lean the car over enough to get a full contact patch.

There are guys who can do a killer alignment with strings at home, but I have no idea how to set it up and do a DIY alignment... Probably a bunch of info on the net though.
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      03-06-2008, 07:33 AM   #6
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I do reverse rake and run max front negative camber on my TCK plates. I don't think you can run too much camber in the front with most street/track plates. All preference imo.
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      03-06-2008, 10:12 AM   #7
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Quote:
Originally Posted by leftcoastman View Post
I would think the opposite. Having the rake with the front lower would transfer more weight forward, reducing understeer.

Have you tried trail braking those slower turns? It works wonders on this car.
Yep...should be the opposite
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      03-08-2008, 12:26 PM   #8
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To generate more front end bite, you would need to raise the front end or lower the rear.
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      03-08-2008, 01:45 PM   #9
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Quote:
Originally Posted by leftcoastman View Post
I would think the opposite. Having the rake with the front lower would transfer more weight forward, reducing understeer.

Have you tried trail braking those slower turns? It works wonders on this car.
A big +1

Sambonator: This is really the last thing you would like to do. You want to have that 50/50 weight distribution if you can which means equal drop for of the OEM setup front and rear or close to it.

I upload a flow chart in this thread so you can use which is one the best ones I have ever found.

http://www.e90post.com/forums/showthread.php?t=113596

I would try more tire pressure in the front as it very effective if you gone thru the list and nothing seems to help.

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      03-08-2008, 02:45 PM   #10
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Thanks Orb! As far as front-end "push", its strange, but it just seemed like I got more push than stock when doing a real tight turn (like a U turn) at slow speed. The push is very noticeable if I accelerate with full-lock steering input. Fronts seemed like it used to grab better stock.

It could just be the tighter springs and less travel available? The front was lowered considerably by the installation of the coilovers. In fact I raised it up because I didn't like the low-rider look of the front (most of the top of the tire covered up by the fender). At speed handling feels fairly neutral (testing in a big parking lot late at night up to a 4 wheel drift ). I didn't want to get too crazy in the parking lot though so testing was limited .
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      03-08-2008, 02:45 PM   #11
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I would do a cornerweighting with you in the car..trying to get the diagonals to match as much as possible. RF + LR weight = LF + RR weight.
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      03-08-2008, 10:26 PM   #12
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Quote:
Originally Posted by S4to335 View Post
I would do a cornerweighting with you in the car..trying to get the diagonals to match as much as possible. RF + LR weight = LF + RR weight.
Are there shops that can do corner-weightings? I saw some DIYs using bathroom scales, but don't feel good about the setup they suggest... and I dont want to pay $1000-$2000 for a complete home unit .
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