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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Apr-12-2017, 09:33:35 PM   #31
albino09
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Default Re: Aftermarket front sway bar: worth it?

If you want to improve handling to your taste, without significantly affecting ride comfort, sway bars are the way to go. Sway bars are basically the handling band-aid to soft, street compliant suspensions.

If you're looking for a flatter behavior in the corner and you're already planning on some aftermarket springs (as mentioned in the original post), the next logical step is a sway bar.
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Old Wed, Apr-12-2017, 11:17:18 PM   #32
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Default Re: Aftermarket front sway bar: worth it?

After a nine month hiatus I was back at my most frequented track and beat my previous PR by about 2 sec... while I was trying to relearn the track. Only changes to car were front sway, fixed back seats, and crappier, skinnier tires, as well as driver mod (3 track days at other tracks). Not sure how much the front sway contributed to times, but it did definitely inspire more confidence, as the car felt much more balanced. This made me feel much safer on track.



Quote:
Originally Posted by Obioban View Post
I don't understand why less body roll ("cornering flatter") is considered an upgrade

Mid corner do you want more or less negative camber on your outside wheel? Overall, do you prefer a car with solid axles or independent suspension?

Unless you're running out of travel, I don't see flatter as better... and if you are, there's probably other places you should be looking to address that.
I got less body roll with Hotchkis front sway. But my tires also stopped rolling over to the outside sidewall, and the car feels much more balanced.
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Old Thu, Apr-13-2017, 12:03:15 AM   #33
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Default Re: Aftermarket front sway bar: worth it?

Quote:
Originally Posted by Obioban View Post
I don't understand why less body roll ("cornering flatter") is considered an upgrade

Mid corner do you want more or less negative camber on your outside wheel? Overall, do you prefer a car with solid axles or independent suspension?

Unless you're running out of travel, I don't see flatter as better... and if you are, there's probably other places you should be looking to address that.
Quote:
Originally Posted by EricSMG View Post
Totally agreed, but I didn't want to go there. I've never had any interest in eliminating roll - it certainly doesn't hold the car back.
Since we don't have double wishbone suspension, doesn't our camber become more *positive* with suspension travel? I could see the merit to limiting that.
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Old Thu, Apr-13-2017, 12:36:30 AM   #34
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Default Re: Aftermarket front sway bar: worth it?

Quote:
Originally Posted by terraphantm View Post
Since we don't have double wishbone suspension, doesn't our camber become more *positive* with suspension travel? I could see the merit to limiting that.
Yes, with McPherson there's no camber gain so it's tougher to keep the tire flat with the ground when the body rolls. This requires more static camber which reduces braking and straight line traction. If you can reduce body roll to an extent, you should also be able to get away with a bit less static camber.

In my experience, even with 9k / 11k spring rates, going from stock sways to a front Hotchkis bar on medium setting made a positive improvement in turn-in response and a reduction in understeer with STICKY tires. However, I had some 400 treadwear tires on the car at one point, and with that setup I felt that the front bar actually increased understeer. It felt better with the bar on the soft setting.

This makes sense to me, and is sort of equivalent to the idea of matching your overall spring rate to the available grip. Less tire grip should be matched with softer rates. Same as running lower rates and softer damping in rain conditions. The 9k/11k rates are already stiff enough to only really work properly with a good tire.

Side note, and in my opinion and experience, stiff swaybars on a driven axle are usually a bad idea as they can reduce traction coming out of a turn unless you have a proper LSD. Lets say you add a super stiff rear bar to an E46. When the car squats coming out of a turn, the outside suspension compresses or "raises up". Since the stiff swaybar essentially links the left and right rear suspension together, the inside rear suspension also "picks up" and you end up with a tire that has very little load. Our LSD doesn't lock immediately so you'll end up with inside wheel spin until the diff locks. If you had a proper clutch type race diff (and not a Quaife-style ATB), you likely wouldn't have this issue. With a softer rear bar, the tires are more independent and the inside tire would be less likely to spin. Supposedly this is one of the main reasons that modern McLaren road cars don't use swaybars. They also don't have LSDs either, probably for the same reason.
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Old Thu, Apr-13-2017, 12:59:50 AM   #35
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Default Re: Aftermarket front sway bar: worth it?

Quote:
Originally Posted by terraphantm View Post
Since we don't have double wishbone suspension, doesn't our camber become more *positive* with suspension travel? I could see the merit to limiting that.
Depends on your ride height and if you've changed the geometry.

Stock it goes negative for a while, then flattens, then goes more positive.

If you've lowered the car too much, and haven't corrected the geometry, you will be in the positive part of the camber curve. But, I assume anyone with their car that low doesn't care about handling...

positive camber at droop:

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Old Thu, Apr-13-2017, 02:10:50 AM   #36
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Default Re: Aftermarket front sway bar: worth it?

Quote:
Originally Posted by terraphantm View Post
Since we don't have double wishbone suspension, doesn't our camber become more *positive* with suspension travel? I could see the merit to limiting that.
Perhaps, but I personally don't have any issues with the stock level of roll. I think it's pretty flat already, extremely stable, very grippy and, feels natural behind the wheel.

People just seem overly obsessed with eliminating body roll.

Edit - I don't think it's accurate to say that a MacPherson = no camber gain. If we think about this logically - imagine an infinitely long control arm. The strut would lay flat as the suspension compressed without the outer ball joint getting any closer to the chassis. This means camber gain. So, there must be a point where the control arm is long enough such that the the strut lays flat faster than the outer ball joint moves closer to the chassis and I suspect this is the case with the 46M.

Assuming there is some camber gain, the real question is, then, does the camber gain outpace the camber loss due to body roll, a 'net' negative camber gain even at maximum lean? This is probably carefully calibrated in a car like this. Also consider that a high caster levels, such as we have, turning causes negative camber gain.

I remember reading about this topic some time ago... I'll see if I can find the article.
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Old Thu, Apr-13-2017, 04:09:11 PM   #37
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Default Re: Aftermarket front sway bar: worth it?

Quote:
Originally Posted by zaharias View Post
My car came with B6s/oem springs from the previous owner. I liked the handling very much, but i hated sometimes how it reacted on rough surfaces and potholes + i wanted to lower it a bit.

So i got from a friend a used AC Schnitzer suspension (shocks & springs) with ground control street camber plates. Definately much comfier ride but a tad more body roll compared to the B6s.

I was thinking of upgrading just the front to keep the comfort ride of the schnitzer suspension and just to reduce a bit the body roll.



Is it worth it adding just a front? Does it make a big difference over handling/roll/comfort?



I saw EricSMGs post and got me into thinking cause i dont want a firmer ride.

The roll bars only do anything when the relative ride height from the left to ride sides are displaced from each other. In other words, it doesn't add to the spring rates of the car, so hitting a bump with both sides of the car should be just as comfortable as before. Still, it harshens the car in general, you're essentially making the wheels less independently suspended. If you hit a pothole with one wheel the other side will feel it more as well

Quote:
Originally Posted by SQ13 View Post
After a nine month hiatus I was back at my most frequented track and beat my previous PR by about 2 sec... while I was trying to relearn the track. Only changes to car were front sway, fixed back seats, and crappier, skinnier tires, as well as driver mod (3 track days at other tracks). Not sure how much the front sway contributed to times, but it did definitely inspire more confidence, as the car felt much more balanced. This made me feel much safer on track.



https://youtu.be/H2tjT67RufY



https://youtu.be/8QwEMcD3iM0



I got less body roll with Hotchkis front sway. But my tires also stopped rolling over to the outside sidewall, and the car feels much more balanced.


About that last part... the outside front wheel develops more negative camber in compression, no? That would mean that less body roll doesn't necessarily mean the car doesn't roll onto the sidewall as much I think?

If you're just trying to reduce body roll for whatever reason, obviously a bigger bar will do that, but I think the main benefit of using aftermarket sway bars is the adjustability. You can adjust the balance of the cars weight transfer from side to side at both ends of the car, but in the end you want to use the smallest bar you can work with ..?
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Old Thu, Apr-13-2017, 05:32:33 PM   #38
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Default Re: Aftermarket front sway bar: worth it?

After some Google searching it is clear that, if properly designed, a MacP setup will definitely gain negative camber during bump, until a point, and then start to lose it. There are numerous youtube videos of animated 2D drawings that show this. Further, there are camber gain graphs posted for MacP cars like STis, etc.... all showing a fair amount of negative gain for the first couple inches of travel. Further, I found one article that showed the MacP gaining as much negative camber as the SLA for the first two inches - this was specific to the Mazda 626 but illustrates how effect the MacP can be if designed right.

From what I can tell, the basic principle is that negative camber gain is dictated by the angle between the strut and the LCA. Once the angle reach 90* camber loss begins.
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Old Thu, Apr-13-2017, 07:18:38 PM   #39
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Default Aftermarket front sway bar: worth it?

Quote:
Originally Posted by BTB View Post
About that last part... the outside front wheel develops more negative camber in compression, no? That would mean that less body roll doesn't necessarily mean the car doesn't roll onto the sidewall as much I think?

If you're just trying to reduce body roll for whatever reason, obviously a bigger bar will do that, but I think the main benefit of using aftermarket sway bars is the adjustability. You can adjust the balance of the cars weight transfer from side to side at both ends of the car, but in the end you want to use the smallest bar you can work with ..?
I dunno man. Physics is like the Russian language to me. If it is true that there is a negative, then positive camber gain with the suspension, I would guess the soft front springs have something to do with it. Maybe stiffer springs would reduce tire roll.

With stock bar:
https://mohflo.photoreflect.com/stor...31&po=31&pc=77

Edit:
Stock


Hotchkis


PSS10s with front spring rate ~350
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Old Thu, Apr-13-2017, 11:07:24 PM   #40
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Default Aftermarket front sway bar: worth it?

Quote:
Originally Posted by SQ13 View Post
I dunno man. Physics is like the Russian language to me. If it is true that there is a negative, then positive camber gain with the suspension, I would guess the soft front springs have something to do with it. Maybe stiffer springs would reduce tire roll.

With stock bar:
https://mohflo.photoreflect.com/stor...31&po=31&pc=77

Edit:
Stock


Hotchkis


PSS10s with front spring rate ~350


Haha agreed I'm no expert. Suspension geometry and tuning is pretty damn complicated. Im not sure what the resulting relative camber would be of the outside wheel (relative to the ground) in each case, but the way I see it, the car with a looser bar rolls more, which would seem to result in more 'rolling into the tire sidewall' but at the same time, more roll means the suspension on that side is in bump which develops more negative camber, working against that effect. Overall I'd think it depends on what the rate of camber change is compared to the roll generated.

I really gotta finish reading and rereading my Carroll smith books lol..
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Discussing Aftermarket front sway bar: worth it? in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)