AST Suspension

[B.Watts]

if only alternate parts were provided free of charge on these test and tune days

You have an adjustable bar set at full stiff, right? It takes a couple minutes to go softer. See if the car gets better...if it does, go softer again. If it gets worse, consider buying a stiffer bar. If you really have no idea how much roll stiffness you need, get something like the GC tubular front bar that has a large range of adjustment.

[Danny318]

You have an adjustable bar set at full stiff, right? It takes a couple minutes to go softer. See if the car gets better...if it does, go softer again. If it gets worse, consider buying a stiffer bar. If you really have no idea how much roll stiffness you need, get something like the GC tubular front bar that has a large range of adjustment.

no i have a non adjustable bar off of a 328is. 25.5mm.

[Danny318]

but im on the lookout for a larger adjustable bar, i guess that is what i need.

[Alan Coles]

You loaded the car with weight on one side, so you introduced ROLL into the equation. These cars do generally roll at a greater rate than the camber gain, which would account for you seeing less camber reading on the side of the car onto which you placed the weight...
I promise you that as the suspension goes through it's range of motion, under compression, the wheel gains camber relative to the chassis. However, it doesn't gain camber at a rate quick enough to keep up with the roll you introduced so you lose camber relative to the ground...

Sorry Bryan, guess I didn't take enough time to write that. Leave tomorrow morning for the Canadian Nationals and still tying up loose ends.

I'm aware that the suspension itself does not lose camber through it's normal range of travel, and that the overall camber loss is due to the chassis roll introduced by additional weight (either static - me, or dynamic - cornering) and the rate of camber loss from body roll being greater than the rate of camber gain from suspension travel. While understanding where the loss is occurring determines how one addresses it, my point was simply that there is an overall camber loss from adding weight to one side or the other such as in cornering.

...Keep in mind that you've added weight to the car which effects a lot of things rather than just the alignment. Your CoG, weight balance, ride heights, etc, all change. It's not the same thing as measuring the camber gain of the suspension as you put it through it's range of motion...

That's why I set my vehicles up with the driver in the car. Anything else ignores these very real factors. Once the base-line is set with static measurements/settings, it's then time to test on the track and/or skid-pad to adjust for all the various dynamics that come into play. My budget doesn't allow, and I'm not sophisticated enough in my setups to go beyond that or to get into custom parts.

Just wanted to illustrate, very quickly and simply, that there is an overall "total" camber loss when one side of the front-end on an E36/E46 compresses. Because of this, it is very important to recognize that the E36/E46 chassis requires more front roll-bar than many other chassis and what works for a Porsche, Honda, Ford, etc., isn't directly transferable to an E36/E46. Each has it's own geometry and dynamics to deal with.

Regards, Alan

[B.Watts]

no i have a non adjustable bar off of a 328is. 25.5mm.

Oh...you posted that you had the exact same setup as epj and he mentioned that he has a 1" bar set to full stiff. Therein lies my confusion.

[Danny318]

Oh...you posted that you had the exact same setup as epj and he mentioned that he has a 1" bar set to full stiff. Therein lies my confusion.

yes, that was an inaccurate post by me. sorry bout that.

[STirish]

Just wanted to illustrate, very quickly and simply, that there is an overall "total" camber loss when one side of the front-end on an E36/E46 compresses. Because of this, it is very important to recognize that the E36/E46 chassis requires more front roll-bar than many other chassis and what works for a Porsche, Honda, Ford, etc., isn't directly transferable to an E36/E46. Each has it's own geometry and dynamics to deal with.

Regards, Alan

This may need to be qualified a little bit. Once the roll is controlled with stiffer (much stiffer) springs and sways, then you can mostly use text book suspension tuning. For example, softening a sway or spring usually shifts grip to that end of the car.

Rob

[murph1379]

Because of this, it is very important to recognize that the E36/E46 chassis requires more front roll-bar than many other chassis

Like the $1200 40mm bmw motorsports bar?

[Danny318]

Well I changed my front bar to a 23mm from the 25.5mm and from what i can tell on the street so far, it seems like it will understeer less.

[Alan Coles]

Well I changed my front bar to a 23mm from the 25.5mm and from what i can tell on the street so far, it seems like it will understeer less.

Danny, I trust that's a typo and you switched to a 28mm front bar not a 23mm. If so than that's good.

If it's not a typo and going to a smaller bar (25.5mm to 23mm) increased your front grip then I'd suspect there is a setup/component problem someplace in the overall mix.

Regards, Alan

[Danny318]

Danny, I trust that's a typo and you switched to a 28mm front bar not a 23mm. If so than that's good.

If it's not a typo and going to a smaller bar (25.5mm to 23mm) increased your front grip then I'd suspect there is a setup/component problem someplace in the overall mix.

Regards, Alan

No typo. I got so many people telling me that I probably had too much spring rate/sway bar in the front compared to the rear and that less bar in the front would help the understeer issue. I had a 23 bar laying around so I tossed that in there. I havnt had time to give it a proper testing, but so far it seems good.....why do you think its not possible ?

[Danny318]

what do you mean 'setup/component problem' ?

[=BA=]

This may need to be qualified a little bit. Once the roll is controlled with stiffer (much stiffer) springs and sways, then you can mostly use text book suspension tuning. For example, softening a sway or spring usually shifts grip to that end of the car.

Rob

+1

The larger/stiffer front bar theory works for relatively soft suspention systems like you often see on the boards here, ie with 500-600 lbs springs.

We in the EU seem to have smoother tracks. We drive with springs in the range of 1100-1200 lb in front and 600-700 lb rear (on coil over) and then you'll see that roll is not really a problem. Stiffening your front bar then is more likely to promote understeer, a lot of people drive with stock bars, or only go aftermarket for the sake of adjustability. With so much roll stiffness coming from the springs alone you would have to go very thick on your bars anyway and have rock solid mounting / droplinks for the swaybar to make a noticable effect.

I for example have Eibach bars on my E36 M3 streetcar but have stock bars on my E36 M3 racecar. I'd rather spend the money for swaybars on a better shock.

[Danny318]

well I had a lot of people tell me front springs + that bar was too stiff and thats why it was understeering. Also had lots of other people tell me too soft in the front.

[=BA=]

A larger front bar can help reduce understeer because it will reduce roll and keep the vehicle in a better part of the camber curve so to say, as stated above in some posts.

On the other hand if front roll stiffness is too big compared to the rear it will shift weight faster.

You have to find some way in the middle. That's why it's called tuning.

The bar itself is only a small part in the total picture. There can be various solutions for your problem, ie add a bit of rake, stiffen up the rear bar,a touch more front negative camber, less negative camber in the rear, slightly higher tirepressure in the rear etc etc.

That is, if it's a technical problem. It can be your own driving style as well.

Discussing thing like this over a message board is always hard because you usually don't get to see the total picture.

[Danny318]

Yeah I hear what you're saying there. I've done a few things, each thing is helping.

Do you think adding some wheel spacers to the front only would help? Just guessing.

[raoke]

Would there be any issues running a stiffer setting in the rear?

How about running very stiff settings on the street?

I'm at +4/+5 atm but will probably do +4/+6 tomorrow before trying out +6 up front.

[Danny318]

I run like +9 and +10 f/r it feels too bouncy on the soft settings, like there is not enough sshock for the spring rate.

[Alan Coles]

well I had a lot of people tell me front springs + that bar was too stiff and thats why it was understeering. Also had lots of other people tell me too soft in the front.

Danny, you can always find plenty of people to tell you something is X and just as many people to it's Y, especially on an internet forum. If you listen to everyone then you'll get absolutely nowhere because you'll continually be going around in circles. You need to be very discriminating in whose advice you take. Look for people with proven results.

No typo. I got so many people telling me that I probably had too much spring rate/sway bar in the front compared to the rear and that less bar in the front would help the understeer issue. I had a 23 bar laying around so I tossed that in there. I havnt had time to give it a proper testing, but so far it seems good.....why do you think its not possible ?

The reason I suggest it's incorrect is that it is 100% opposite to what the most successful competitors have found after years of testing, data-logging, and competing. As I said above proven results are what you're looking for, not theory or generalizations, etc. Unless you go to very high spring rates (way too high for your mostly street application in New England) than you need to address the camber curve problem with a larger than stock front sway-bar. That is the setup that has been tested and proven to be successful. If you wish to ignore it and try to re-invent the wheel or to try to follow every piece of advice that has you going back and forth than I'm afraid you'll be very busy and likely not very happy.

what do you mean 'setup/component problem' ?

What I mean is that with AST4100's @ 500F/625R or so and a stock rear sway-bar, going to a smaller front bar can only reduce understeer if you've got a problem component someplace or the alignment/camber/toe/etc., is out of whack. If everything were put together properly and setup properly, going to a smaller front bar with that setup will increase understeer.

While I agree with =BA='s assessments for the track completely, I don't feel they're applicable to your street driven car that spends it's time on New England roads. Those roads are a world away from the roads in Georgia, Florida, Texas, California, etc., forget about the velvet smooth roads and tacks in Europe.

As =BA= and others have alluded to, each setup needs to start with a proper understanding of what the working environment is going to be (street/track, moderate to rough surfaces, 500#F/625#R springs, etc.). Once that is determined then one takes the specific vehicle (E36) and applies the appropriate fixes to it. For an E36 in these parameters, the fix is a larger, not smaller front bar.

Will driving style, etc., affect this? Yes. Bob Tunnell, Terrry Fair, etc., have already shown with National wins what the proper setup is to achieve the fastest times. So that leaves you with two choices, adjust the setup to the style and go slower or adjust the style to the setup and go faster. It's really that simple.

Once a person gets a lot of experience driving competitively and gets good at it and at setting up their car then there is plenty of room for improvement to be had by fine-tuning the setting to your style, but not until one is at least well started on that journey.

Regards, Alan

[STirish]

What I mean is that with AST4100's @ 500F/625R or so and a stock rear sway-bar, going to a smaller front bar can only reduce understeer if you've got a problem component someplace or the alignment/camber/toe/etc., is out of whack. If everything were put together properly and setup properly, going to a smaller front bar with that setup will increase understeer.

Regards, Alan

Alan, according to my skid pad findings with very similar spring rates/bars, I'm not sure you are giving out correct advice. Either way, I do agree with your point of individuals testing for themselves.

Rob

[Danny318]

Thanks for all of that Alan, I have a track day at NHIS next thursday where I'll be able to see what the smaller front bar is actually doing. If it understeers more well it only took a few minutes to change it out and now I'll know to go find a bigger bar.

[Alan Coles]

Alan, according to my skid pad findings with very similar spring rates/bars, I'm not sure you are giving out correct advice. Either way, I do agree with your point of individuals testing for themselves.
Rob

Rob, as I mentioned above, I'm basing this more on the results the Bob Tunnell, Vic Stasis, Terry Fair, etc. It's quite possible that if your overall setting are significantly different from theirs that a smaller front bar might reduce under-steer. Would it make the car faster is another question.

These guys are the competitors who have won the most National titles running an E36 recently. They've tested most of the probable setups and all arrived at a fairly similar "range" of optimal settings. IIRC, it goes roughly like this:

Sway-bars:
Front sway-bar = 28mm (or 27mm)
Rear sway-bar = 22mm (or 21-20mm)
Typically with a split of 5-6mm up front. To further widen the front/rear gap, most run the front between mid-stiff and full-stiff while running the rear between mid-stiff and full-soft depending on the course and conditions. Some people do run both ends full stiff, but then you're just really back to the 28mm/22mm setup.

Spring rates:
Front = 500# - 600#
Rear = 600# - 700#
Typically with a split of 75-100 lbs. more in the rear

Camber:
Front = -3.5 to -4.0
Rear = -2.0 to -3.5
Typically with a split of 0.75-1.0 more negative camber in front

Toe:
Front = 0" to 1/8" (or slightly more) toe-out total
Rear = 1/8" to 1/4"+ toe-in total

Caster usually at or close to the maximum available.

This is what's been producing the best results. So it's what I've used as my base point as well. I am a firm believer in using the best current competitors setups as a starting point on any tuning exercises.

We've not had the time to do any significant testing with the new AST4100's due to our getting the engine re-build finished just before the season started and then having to do a rebuild mid-season. Just haven't had the time to do anything other than run the above setup and do a little fine tuning. On most courses that are reasonably open my co-driver has been able to set FTD and often by a good margin. Last weekend his FTD time was 1:35.034 with the next closest competitor running a 1:40.670. That's a difference of 5.6+ seconds. You have to go back to 12th position to get someone within 5.7 seconds of 2nd fastest. The car has been data-logged at 1.54 g's lateral on cold road-racing tires (1st turn in an autoslalom on BFG R1's).

I sold my previous setup to very competent professional racer-car driver who autoslaloms his E36 M3 with us from time to time and will always be very close to FTD given a competitive car. The main difference between his car and mine with my last-years setup on it is that he's still running the stock front bar. His car under-steers noticeably more than mine did with the larger front bar. It's not bad at all, just noticeably more, which ends up being slightly slower.

Hopefully, we'll be able to get some actual testing done with proper data-logging after the season is over.

Thanks for all of that Alan, I have a track day at NHIS next thursday where I'll be able to see what the smaller front bar is actually doing. If it understeers more well it only took a few minutes to change it out and now I'll know to go find a bigger bar.

Good idea Danny. Take your larger bar (the 328i 25.5mm one) with you so that if you do feel you're understeering more you could swap them and have a side-by-side test.


Regards, Alan

[Danny318]

Alright we'll see. I wonder what is up with my car. I have m3 offset control arm bushings and control arms....is that not good?

[Danny318]

my camber maxes out at about -3.3 with ~6 of castor (max)...Vorshlag says they can get > -4 camber with the same plates

Why ?

[=BA=]

Might be due to the shock tower arches. Usually there is a bit of that 'coating' in there, once you scrape that off you usually get some more.

Also it depends on your ridehight as well. Lowering the shock 60mm over stock or so already gives you a degree of extra negative camber without even adjusting the topmounts.