[smarean]

Need some basic advice here...

Newbie autocrosser, I've been out 4 times now (3 times last year, once this year). Switched from the stock runflats to Michelin PS2's this year, but otherwise completely stock E92 2009 335i (sport package, steptronic, 18" wheels -- anything else you need to know?).

I was running the cold tire pressure at 35 for the fronts and 39 for the rears (3 PSI higher than the factory recommended settings of 32/36).

My impression (from in the car, and from watching other 335i's on the course) is that the 335i has A LOT more body roll than the M3 (which is to be expected, for sure). I feel like I'm just plowing through corners with major understeer, having to slow down much more than feels necessary in order to turn effectively.

BTW, I think the accelerating and braking are great. Of course, I have the DTC turned off. On a side note, I do think the PS2's were easier/faster to recover from the backend sliding than the stock Bridgestone runflats were last year (or maybe I'm just driving better now?).

So my questions are...
- Is it my driving? Should I just slow down more for the corners?
- Is it the tire pressure? In another post, someone said they ran cold pressures of 45 front / 42 rear. Should I go higher in general? Should the front be higher than the rear?
- Is it just the stock 335i? And if it is, then what are the mods that would be the biggest bang for the buck for tight autocross cornering?
- Or maybe I'm just completely missing the point and you have other advice... feel free... :-)

Thanks!

[CJ421]

Welcome!

I agree with you that the stock brakes are fine. I've changed the brake fluid to Total high-temp fluid but other than that run pretty much stock including pads. Never had a problem.

- Is it my driving? Should I just slow down more for the corners?

It's important to keep the car balanced so if that means slowing down, yes. You shouldn't be fighting the car; the car talks to you just like a human being but in a different language. It will tell you when it agrees with your inputs. The smoothness of your inputs goes a long way.

Do you have an instructor in the car with you?

- Is it the tire pressure? In another post, someone said they ran cold pressures of 45 front / 42 rear. Should I go higher in general? Should the front be higher than the rear?

Those pressures sound very high to me but I don't autocross. For my HPDE events I run stock tire pressures cold and then about 34/38 hot. I would always start with the pressures listed on your driver's door.

- Is it just the stock 335i? And if it is, then what are the mods that would be the biggest bang for the buck for tight autocross cornering?

Is it just the stock 335i - yes and no. If someone else can get in the car and drive faster than you, then the car's not the issue.

That said the cheapest way to go about changing handling is the tire pressures. Experiment pumping the front up some, that will improve turn-in responsiveness. I would only change one at a time e.g. change the front pressures but leave the back alone. Tire pressures won't make a night-and-day difference but hey, it's a $0 mod.

The next way to improve handling is to get a good alignment. Do you know your alignment specs?

The PS2s were a good choice in tire; they were stock on some BMW M cars for a while. Michelin Pilot Super Sport is the next step up from those, I just personally put those on my car and am blown away by the grip (coming from Hankook V12s). They are just awesome for high performance driving. Many cars at the track this past weekend were running them, some owners on their second and third sets - only praise coming from the owners.

Next after that you could consider new springs and dampers. Forget sway bars, etc - dampers/springs are 80-85% of the suspension equation (in terms of bang-for-the-buck difference). Koni Yellows/Sports & stiffer springs like H&R Sports or Eibach Pros (for a more modest drop) are an economical choice; after that there's AST 4150s/Swift springs - just as examples. The stock 335i dampers are severely underpowered and get overwhelmed by even small turns; they are certainly not helping you in autocross, as heavy as the 335i is. You'll be surprised at just how much of a difference a good damper and spring combo can make.

So in short...
-Driving habits first (do you have an instructor?)
-Tire pressures (small difference but $0)
-Alignment (please post your specs)
-Tires (if your PS2s are still good I'd wait till you wear them out)
-Dampers/springs - by far will make the biggest difference in your car's handling ability

[smarean]

Thanks for the quick reply and all the useful advice! Here's some responses to points you brought up...

You shouldn't be fighting the car

Yeah, sounds like I need to slow down. It feels like I'm trying to drive it beyond its limits. Which is frustrating, because it feels like the cornering capability does not match the accelerating/braking capability. But frustrating or not, I need to listen to the car and maximize what it can do.

Do you have an instructor in the car with you?

This last time out, I opted to not have an instructor to see how I did on my own. I agree. I still need an instructor. Next time...

If someone else can get in the car and drive faster than you

I'm sure that's the case. ;-)

Experiment pumping the front up some, that will improve turn-in responsiveness.

That's what I was thinking.

Do you know your alignment specs?

What's an alignment spec, and how do I figure mine out? :-)

The PS2s were a good choice in tire; they were stock on some BMW M cars for a while. Michelin Pilot Super Sport is the next step up from those

OK, my mistake. I thought PS2 was the nickname for Pilot Super Sport. Guess it's not. ;-) I have Pilot Super Sports. I agree, the grip is amazing. ;-)

you could consider new springs and dampers

Glad to know there is something I can do that doesn't sound like an outrageous investment. Thanks for all the specific recommendations.

[will.c]

Not an expert, but I got a few comments that could perhaps be helpful.

First you can try is tire pressure modulation. The optimal tire pressure (bias) really depends on the tire/track conditions. But there are general rule of thumb within a small window. Of course, if you go outside of this window, you will lose traction both ways, e.g. way to high or way too low will deform the tire in a way that you will lose contact patch area, therefore lose grip.

Now in between those extremes, starting from the very low end, I believe you will gain traction as the pressure goes higher, but only up to a certain point. Again the reason is, in this low pressure region, the higher the pressure, the higher the resistance of tire deformation under hard cornering, hence increase in tire contact patch area. (High pressure = high grip)

On the other hand, in the higher pressure region, as the pressure becomes too high, the tires will become too stiff and bounce around the (uneven) track surface. This phenomenon would be similar to how dampers would be adjusted for track conditions; the more irregular the track surface, the softer they need to be so that they don't bounce around everywhere and lose traction. (High pressure = low grip)

To complicate things further, there are good and bad tire deformations. The above mentioned is the bad case. A good deformation is when the tire flattens ever so slightly under load and increases the overall contact patch area. This is another example of high pressure = low grip.

Having said the above to massively confuse you, I believe that the factory recommended tire pressures (32/36 in your case) typically are more optimized for comfort rather than max grip, allowing more deformation than we'd like at the track/autoX. Therefore, as you increase from here, you would most likely gain grip, but again, not going over that threshold.

If I were you, I'd start from 36/36 or maybe even 40/36, and take the first few sessions as trial and error and react according to observations.

If you still find your car pushing, then I'd look into a square setup next.

(Experts, please correct me if I'm wrong.)

[turugara]

Originally Posted by wonho

If I were you, I'd start from 36/36 or maybe even 40/36, and take the first few sessions as trial and error and react according to observations.

The starting point depends a lot on the day, how long the course is, your driving. I know for the tires that I run, Hankook RS-3's, they feel best when they are around 38-39 HOT.

Starting 40/36 COLD may not be optimal. But then again, I'm talking from road course experience so I'd imagine on a much shorter, one lap auto-x course may be different from my knowledge base.

[vwong]

Originally Posted by smarean

So my questions are...
- Is it my driving? Should I just slow down more for the corners?

Since you mentioned that this was your 4th autox event, I would think that it's mostly because you were over-driving the car. Most beginners I've met over the years have the tendency to push the car around the corners. This not only makes you slower, but also increase tire wear on the outside shoulders. Most corners in an autox course are slow anyways, and they're pretty much all connected one after another. So if you mess up on the first corner, the subsequent corners will be messed up too, and that adds to more frustration on yourself. Slow down more in the corners to get faster lap times. Having an instructor will definitely help improve your driving.

Originally Posted by smarean

- Is it the tire pressure? In another post, someone said they ran cold pressures of 45 front / 42 rear. Should I go higher in general? Should the front be higher than the rear?

Not sure if you got those tire pressures from my posts. Those are the pressures I normally run in an autox. This is to prevent the tires rolling over too much. And the reason for higher front pressures is because a stock suspension does not provide enough negative camber, therefore the front tire tends to wear quicker on the shoulders. If I had more negative camber up front, I would probably run the same tire pressures all around.

Originally Posted by smarean

- Is it just the stock 335i? And if it is, then what are the mods that would be the biggest bang for the buck for tight autocross cornering?

Almost all modern cars are designed to understeer from the factory because it's easier and safer for most drivers to regain control from a panic situation. However, the alignment (like the other poster has mentioned) can be adjusted to provide a little better handling characteristics.

With all that said, I think the best thing for you to do is get as much seat time as you can. And while doing so, have an instructor to help you out. This will speed up your progress. When you get to the point where your lap times are dropping (without doing any mods to your car) and are competitive with other drivers, then you can consider other changes to your car.

[vwong]

Originally Posted by turugara

The starting point depends a lot on the day, how long the course is, your driving. I know for the tires that I run, Hankook RS-3's, they feel best when they are around 38-39 HOT.

Starting 40/36 COLD may not be optimal. But then again, I'm talking from road course experience so I'd imagine on a much shorter, one lap auto-x course may be different from my knowledge base.

Yup, tire pressures for road course are different from autox. I do both autox and tracks, and I always set my tire pressures accordingly. For autox, I run high pressures (45/40 f/r cold), but for track, I target 38/35 hot.

[mrbillytalent]

I'm wathcing this thread, its full of great imformation. I'm running my e90 335 in its first autox event next weekend, and I'm afraid of its increase in power and weight from my e46 323. Only one way to find out!

[will.c]

Originally Posted by turugara

The starting point depends a lot on the day, how long the course is, your driving. I know for the tires that I run, Hankook RS-3's, they feel best when they are around 38-39 HOT.

Starting 40/36 COLD may not be optimal. But then again, I'm talking from road course experience so I'd imagine on a much shorter, one lap auto-x course may be different from my knowledge base.

Same here. No auto X exp. I guestimated that the temp increase is not as big as you'd see on road courses, if much at all. Maybe start 38/34 "cold" or something.

As for me, I feel a sweet spot around 34/35 hot with my Star Specs.

[CJ421]

Originally Posted by smarean

Yeah, sounds like I need to slow down. It feels like I'm trying to drive it beyond its limits. Which is frustrating, because it feels like the cornering capability does not match the accelerating/braking capability. But frustrating or not, I need to listen to the car and maximize what it can do.

What's an alignment spec, and how do I figure mine out? :-)

Yes definitely start with slowing down ... learn proper technique w/ an instructor and speed will come naturally. I agree that newer drivers tend to overdrive their car and think it's fast but you're wasting a lot of energy and time. A good driver will maximize available grip without exceeding the limit. Because they are not overdriving the car, it uses less energy; brakes are cooler, tire temps are cooler, and it's just more balanced.

The Friction Circle will help you visualize this:
http://www.caranddriver.com/features...riction-circle

Alignment spec - that's your camber and toe settings. You should have been provided a sheet last time you got an alignment stating what those were set to - those are the specs.

[NoTempoLimitN54]

I'm running my first autocross in over 20 years this Sunday at the AutoClub Speedway in CA. Stock E92 335i 6MT with ZSP and 19" ZCP style wheels. Michelin Pilot Sport 235/35 PS2 front, 265/30 PSS rear.

I drive my car on Mulholland Drive every morning. What I've noticed so far: The 335i has a bit more body roll than my M Sport II E39. This is due to the small (13mm) rear sway bar. The staggered tire sizes don't help either. But I haven't been troubled by understeer -unless- I get heavy into the throttle too early in the turn.

The simple driving adaptation to understeer is: Turn in later into the turn with more trail braking. When you're doing it right it will feel like the car is "pivoting" slightly under you. Don't dip into the throttle until you can at least see the apex, even better have one of your front tires nearly on top of the apex.

Also, the Steptronic probably doesn't help because it reduces your engine braking to the rear wheels (torque converter). More engine braking helps reduce understeer because it makes the rear tires work harder. Are you downshifting going into turns?

I would be interested in hearing what tire pressures you guys have run with stock ZSP suspension. Obviously less pressure in the back with stock ZSP would work, but how much bias?

Also, what do you guys think of running DTC vs. traction control full off? I was thinking of doing my practice run with DTC and seeing how that responds. If it intervenes too much I can turn it full off.

[vwong]

Originally Posted by NoTempoLimitN54

Also, what do you guys think of running DTC vs. traction control full off? I was thinking of doing my practice run with DTC and seeing how that responds. If it intervenes too much I can turn it full off.

I run with all electronic nannies off.

[GRIP]

I never raced my E92 335i, but I have been racing and autocrossing since 2003 in a prepped honda accord until 2005, and then an EVO IX MR stock/modified till 2010, then a stock EVO X MR till the end of 2010, and now another stock EVO IX MR. The 335i's biggest problem is that it's soft. I don't agree with slowing down too much because yes it is true that sometimes you have to slow down to go faster, but that's only if you are over driving the car, not if you just aren't driving it correctly.

First turn all the traction controls off completely. The next thing I'd suggest is to learn how to control the car. Don't be afraid to get the car unsettled because that's the only way you're going to get it to rotate. Use the car's weight transfer to help turn the car, then use the steering wheel, and the gas to modulate the oversteer. Now you don't want the car drifting every turn and always being at opposite lock, but tossing the car in, and letting the rear slide a bit through a turn is a lot faster than slowing all the way down to the point that the front tires can handle it.

Try to drive the car on the rear wheels if that makes sense. The biggest thing is learning to control the car once it gets out of shape. Autocrossing is different from road racing in that sometimes you have to manhandle the car to get the fastest time out of it. It's not always about being super smooth. It depends on the course layout. If you are plowing a lot though, you need to look at your driving style before you just assume you are carrying too much speed.

Good luck at the next event!

[Kcyrusm]

I am not an experienced autocrosser by any means, and have only completed 3 so far, but I just wanted some input on my tire pressure experience. After reading the posts in here, I am way off what people are using, lol...

First off, I drive a 335is and the tire pressure recommendations on the door sill are 33/41 on 225/255's. I guess due to the heavier weight of the 'is'? I'm still running the stock Pilot Sport rft that came with the car, and was blaming my stock tires until I started seeing better times coming out of the same cars. BTW, running traction control fully off.

I set my pressures cold to 36/45 and began my day. Well, after learning the course and learning not to overdrive my car so much, I started shaving lots of time off. Here's the thing, I didn't bother to check my tire pressures as my tires heated up (especially in the fun runs at the end) and I had my best times at the end of those fun runs shaving off another 6/10 of a second.

Out of curiosity and realizing my hadn't checked my pressures in the back to back fun runs, I pulled out my tire gauge. 40/49 f/r. These had my car handling exactly how I wanted. Minimized some of the understeer (which I'm sure a lot had to do with my better lines and not over driving the tires) and let my rear end rotate when I needed it to, in mid-turn with some throttle input.

Was this tire pressure setup crazy??? Should I set these pressures cold next time and start releasing air to keep the same pressures as my tires warm? It was 45 degrees F by the end of the day.

I noticed some of you are running more pressure in the front than rear?

[gary88]

When I first started autocrossing with my 335i I was plowing and understeering like crazy, which was a result of me just simply going too fast. Spot your braking points early, always look ahead, and be smooth in your movements. The 335i is a heavy car for autocross, but if you keep good momentum through turns it's very good.

For tire pressure I usually run 42f/40r, if you're running on a hot day remember your PSI will increase a little once the tires get up to temperature.

[Kcyrusm]

Why run more pressure in the front tires than the rear like that on a staggered setup? Doesnt that induce more understeer?

[GTM_Challenge]

I learned early on autoxing that you can't overdrive the car and expect fast times - especially a heavy car such as a BMW.

The best advice I was ever given was the come into a corner faster, brake less, and get on the throttle later - just let the chassis and tires take the grip around the corner. I dropped a massive amount of time.

Coming into autox from a largely track background, my mentality had always been to set the car into the turn and get back on the throttle as soon as possible. With autox, I couldn't do that. When I first started I became very frustrated until a very experienced autocrosser noticed how I was driving - I was somehow able to get a supercharged s2000 I was co-driving to understeer. Imagine that. He gave me the advice I posted above and man, did it make a huge difference.

Before messing with tire pressures, id modify my driving to see if it helps at all. When you change too many variables, you never know exactly what fixed the issue - and then you don't learn for the next time you have a handling issue.

[NoTempoLimitN54]

After the understeer that I experienced at that autocross, plus the wear pattern on my front tires, I'm convinced I need more negative camber in the front.

The 335i is heavy and has a lot of power. It reminds me (but nowhere near as bad) of when I used to watch Fox body Mustangs autocross in the early '90's. Heavy car, lots of power, crude suspension and terrible weight distribution F-R. These guys would always end up plowing right off the edge of the corners, front tires turned all the way to the right/left, car going straight ahead.

335i is not as bad due to sophisticated suspension and good weight distribution. But the combination of soft springs and small sway bars (intended for the run flats that I'm not running) makes it roll too much, and then the understeer sets in.

My front tires are nearly $600 for a set and have plenty of tread life left in the center but are quite worn on the shoulder. I had noticed this wear when I bought the car (I guess the PO was an enthusiastic driver too). The wear got worse after the autocross.

So I'm going to take care of the alignment issue first before I run any more events. I might even do M3 front control arms. I'd rather spend $$$ on that than on front tires at half their tread life because they're corded on the shoulder.

Here's my tire/wheel config:

FR: 8.5J x 19 ET 40 / 235/35R-19 Michelin Pilot Sport PS2
RR: 9.5J x 19 ET 45 / 265/25R-19 Michelin Pilot SuperSport

BTW, wear pattern looks good on the rear.