Quote:
Originally Posted by JJZ4MR
I am doing my 2nd autocross one week from today. It's in Brooksville FL on an old runway. This post has not been active for 3 years. Is anyone else using a Z4M for autocross, or HAS used in the past On the first one 3 months ago, there was another Z4MR driven by an experienced driver. He finished 5 seconds better than my best run. I went into it pretty unknowledgeable. Just watched a few videos and read up on apexing ( didn't really know anything about it ) Took my first 2 of 4 runs with an instructor, first one is mandatory, second one by choice, 2 different instructors. Did a run with an instructor at the beginning of the first run. He had a MIATA and he whipped that car around at the brink of losing control. He was in complete control of it's limits. That's what I want. First thing I bought for the car was a new set of Bridgestone Potenza RE-71's. Spent more than I thought I wanted to, based on advise from this forum. I want to control my car a the edge of it's limitations. I do realize that at 3200#, this is not a prototypical autocross car. I know this car has limitations. I don't care about points, plan on doing an autocross every other month or so. Want to move on to HPDE once I have a full understanding of my cars abilities and become a better driver in general. I think driving at Sebring being my goal. I'd like some advice on a few things in general, not Z4M specific. I'd like to use good autocross driving habits, instead of just steering my car around the coarse.
1) Left foot braking
2) Keeping my hands at 9/3 position on the wheel
3) Backsiding cones
4) Trail braking
5) Figuring proper tire inflation
I have read some things about all of these, but don't fully understand them.
I have just installed Vibra Technics MM and Rogue Engineering TM and would like to continue adding any suspension parts that my 11 year old car with 56K should have for longevity and improved handling. I have looked into :
1) Strut brace
2) Sway bar F/R
3) RTAB
4) FCAB
5) FCA
6) Subframe poly - I've seen 8 piece sets that claim ease of installation
Any particular Manufacture to go with or stay away from for these parts.
Any help on these questions would be greatly appreciated
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If it was a titanium silver Z4MR you ran against that was probably Carl Waghenfor. He's a decent driver so he's a good benchmark to compare yourself to. He runs a lot more FAST events than I do so you'll get more comparison points tracking to his times. I won't try to comment on the suspension parts since my car is a 3.0si and the suspensions are different. On the autoX questions, here's my $0.02:
1) Left foot braking - My first BMW was an E36 with an auto trans so I learned left foot braking auto crossing that car and have been doing it since. That's just what feels natural to me now. In theory not having to move your right foot back and forth to accelerate and brake cuts a few tenths time. That's the upside of it. The downside is it is very easy to over brake. It's a conscious effort to keep my left foot off the brakes and just lift off the throttle when only a slight slowing is needed. I know several SCCA national champions that left foot brake and I know several that don't. Really a personal choice, and there is a definite learning curve. I wouldn't think about trying it for a while. Too many other things you need to get to be 2nd nature before LFB will really make any difference.
2) Keeping my hands at 9/3 position on the wheel - If an autocross course is designed correctly and you keep up enough speed you rarely need to do any hand over hand stuff to manuever. Keeping your hands a 3 & 9 gives you the most flexibility in steering the car.
3) Backsiding cones - Generally the fast way around an autocross course is to get the car pointed at the next element before you've left the one you're at. In a slalom that means you've already got the car pointed to go around the next cone as you're going by the cone you're at. I posted up a digram that shows the difference. On the right you can see that you should be passing the cone on the rear corner or "backsiding" the cone.
4) Trail braking - This is not releasing fully off the brakes before you're passed your turn in point. It's an advanced technique that can help the car rotate if done correctly. If done incorrectly it will help the car rotate a lot, more commonly called a "spin". Like left foot braking, there's a lot to be learning and a lot of time to be gained before you need to worry about this.
5) Figuring proper tire inflation - This can be a key element in autocross, but you need to get to where you can run consistent times before you can see the results from adjusting pressures. Best bet is to find someone experienced running same tires on the same car and run what they're running for now. On the RE71s I was running 30 psi front and 31 psi rear. Fronts are 245/40 x 18, rears are 265/35 x 18. I'm on Hankook RS-4s currently and running much higher pressures. I believe Carl runs 2 psi higher than me. I'm not convinced that's optimal for his car but it's where he feels comfortable. He's on wider rims so where's he's at may actually be good. He just hasn't tried going down until grip goes away to see if there's anything to be gained there.