View Single Post
      02-04-2013, 09:37 AM   #13
TC Kline Racing
BimmerPost Supporting Vendor
TC Kline Racing's Avatar
United_States
7
Rep
330
Posts


 
Drives: Many BMW's & Porsche's
Join Date: Mar 2012
Location: Columbus, OH & Santa Barbara, CA

iTrader: (0)

Quote:
Originally Posted by pits200 View Post
Really, all the m3 guys seem to have the rear a half inch lower than the front. Being I'm an xi would that change anything?

Thanks
Quote:
Originally Posted by DSC_OFF View Post
Yea ignore the guy who has proven history building successful race cars lol. Perhaps we should survey the experts here with highest post counts.

OP if you're going to do this right and get a corner balance prior to alignment, the heights of all 4 corners will change anyway. Set it to what you like, looks good and is practical enough to get by. Racers will tell you rake, as long as not aggressive, won't make a huge impact. Getting it balanced is where it's at.
Quote:
Originally Posted by DSC_OFF View Post
Nobody cares because nobody asked what looks good you fool. Read the original post.




OP asked about dynamic weight shifting and brake bias and TCK addressed just that. However your opinion of what looks cool is about as least technical as it can get and you answered a question nobody asked. Instead of advising others to consider where others are coming from, you should simply learn to read; the question was right there to begin with.
Quote:
Originally Posted by pits200 View Post
Well to be honest TCK didn't really address much. I was hoping for a slightly more detailed answer as to why we want a positive rake when it creates more understeer in this condition. Also, I'm an xi, wouldn't I benefit from a little more front turn in with a negative rake?
Quote:
Originally Posted by DSC_OFF View Post
While I can't speak for TCK, I think they assumed you wanted rake for the aggressive stance. So I'm guessing 3/4" would be the max you could go without feeling any negligible effects.

But I agree with your intuition on the more rake you have, the more the car would understeer as it would tend to nose dive more. I'll let the xi owners chime in but is the car's weight distribution any different than a non-xi model? If not, I would imagine whatever works on a rwd should work for xi. If the xi is more front heavy, then you probably want to go with less rake.

But like I said end of day, if you're willing to spend the $$$, a corner balance would yield the appropriate height for best handling (ie it'll take the guesswork out of how to set the rake). Set the overall height to what you like, and the corner balance would then tweak each corner separately (and you may see variances of up to 1/2" between corners).
Ok, a lot of information here so I will try and address everything.

First, let's determine where we are taking ride height measurements from. We measure from the rocker panel to the ground, not from the fender. So, at the very front of the rocker panel just where the front wheel well meets the rocker is where we take the front measurement. Then, we take the rear measurement where the rear wheel well and the rocker meet. This may add to the confusion, as we all may be picturing ride heights based on where we measure.

OP, your question seemed more like a 'performance' or 'technical' question as opposed to aesthetics. DSC_OFF is correct (thanks for the backing, btw) that we have done extensive testing on the street and on the track, and this is how we recommend you set your ride height if you want your car to perform. We set our cars up for function, not form. If you are looking for a 'stance' look, I have nothing more to offer, but if you want the car to function and perform well, then set the front ride height where you want, and then raise the rear 3/4" higher than the front. That is your base setting, and then you can corner balance from there.

You mentioned you don't want your car to 'nose dive' under braking......how hard are you braking on the street? That question just seemed more like a track related question

Just so you are aware, the car will actually understeer more as you lower the rear end, until you hit the bump stops. Once you hit the bump stops in the rear the car will oversteer again. So as you raise the rear end, the car will want to oversteer more and understeer less.

This set-up will be the same between an xi and non-xi, it does not change.

If you want your car to 'perform' on the street and track, this is the race/street proven set-up (assuming your are running the proper suspension and spring rates) based on the hours and hours of testing that we have done with our E90 both on the track and off.

The simple answer was 3/4" rake, but hopefully this explanation helps.

If you have any more questions, please let me know