Winter driving dynamics.

[Audi4kq]

As a newer B6 owner I was curious of what people have done to make their cars more 'flickable' on snow packed roads.
This chassis is unfamiliar territory for me as I'm used to the older pre-electronic Audis where there was no ABS (or one could override) and you more or less steered with transferring body weight to overcome the overhanging 5cyl that always wanted to plow. That feeling of snapping through corners never leaves ya, even though it may not be the fastest way through said corner.

These days I'm working with an '03 A4 manual 1.8t Sport suspension, Malone tuned with studded Hakka 9's. Great car, leaps and bounds in refinement over the older chassis' but not nearly as fun to drive on snow, IMO.
First thing I generally do when I get in my car and snow is on the road is turn off the ESP which obviously helps with the 'power steering' but not so much the brakes.
Is there a way to turn off the ABS in order to lock up the wheels in a controlled brake slide, transfer weight and then power through a corner? The ABS system is doing its job well (too well), but I'd rather not have it think for me.
What are other options out there? Maybe a thicker rear sway? Currently I'm having a bit more understeer than I'd like. :)

Curious to hear your thoughts!

[EuroxS4]

Engine past the front axle always equals understeer. You can disable the abs by disconnecting the whole unit.

[kwilson]

Definitely get a thicker rear (and front) swaybar. I have a set of H-Sport sways that totally transform the handling. A bit of added throttle will bring the rear out around any corner in the snow. Adding some countersteer while keeping on the gas lets me drift in complete control. So much fun.

[EuroxS4]

Definitely get a thicker rear (and front) swaybar. I have a set of H-Sport sways that totally transform the handling. A bit of added throttle will bring the rear out around any corner in the snow. Adding some countersteer while keeping on the gas lets me drift in complete control. So much fun.

Thicker rear sway yes but not front. Most install b7 rs4 rear way.

[kwilson]

Thicker rear sway yes but not front. Most install b7 rs4 rear way.

Gotta disagree with you here. I've driven plenty of B5 and B6 chassis cars with just the larger rear bar. The added front bar makes it so much more balanced while not taking away any of the benefits of the rear bar

[EuroxS4]

Gotta disagree with you here. I've driven plenty of B5 and B6 chassis cars with just the larger rear bar. The added front bar makes it so much more balanced while not taking away any of the benefits of the rear bar

Adding stiffer front sway will increase understeer. These cars have plenty of understeer as it is because the engine hangs out over the front axle. Any weight past the front axle always = understeer. You want stiffer in the rear not the front but I guess everyone has a different feel. Easier to rotate the car with a stiffer rear sway only.

[JoshDub]

I miss the abs kill switch from my 90 20VQ. Thicker rear sway is the go to for toss ability. You can also do 4:1 center diff mod. My S5 was way more tossable than my B6 but the extra power probably helped.

[Kevin C]

I added a RS4 bar and the improvement was great. The only issue was it was a bit too tail happy in the rain on the on / off ramps. I found out when traffic slowed and I went from steady to decelerate on a tight ramp and the tail kicked out. It didn't take much to get into lift throttle oversteer so I added a bit more front bar. The H&R front bar pairs up pretty well with the RS4 rear while it doesn't feel as quick as just the RS4 bar in the back, it does feel better on high speed corners.

Weight distribution is a factor in under vs over steer, so is roll coupling since it controls the dynamic load distribution. Since a tires friction factor is non linear if you start with a balanced cornering weight transfer and more weight in the front, you get understeer. Add more force to the rear outer tire with a stiffer rear bar and it puts the that tire into a different range of friction factor and you can even out the handling. Keep adding roll coupling to the back and you will get oversteer regardless of weight distribution.

The non linear friction factor of tires is what makes chassis tuning possible.

To the OP. the 18mm rear bar on the sport suspension is way, way too light. The S4 at 20mm or the RS4 22 mm bar is a much better match. From the factory the RS4 also had a higher rate front bar. For a daily driver in a rainy area I went with a 22mm rear bar a the H&R front. 034 makes a 25.4mm rear bar. If you get that one consider beefing up the bar mounts since they are know to break off. Lots of people run just the 034 rear bar.

The later B7 manual tranny got a better power distribution with 60 Rear 40 front (vs 50/50). I could see that being a lot more fun and making throttle over steer more fun you can also add in a rear limited slip. You can also move the battery to the back.

I would start with more rear bar. No idea on the ABS and I don't see enough snow to have ever thought about it.

[old guy]

My thoughts on front/rear sway bars: Clicky-1 and clicky-2

[Mike Tries]

Engine past the front axle always equals understeer. You can disable the abs by disconnecting the whole unit.

Or do what I did and wait for the ABS computer to quit on its own and never come back on again... :-)

[Mike Tries]

Also, this is probably one of the best threads I've read in a while... just making a car more fun in the snow! I, too, have noticed that the car likes to resist fun slides. Easy tweaks to make that better would be fun to try.

Thanks for posting!

[Fast4esT]

I cannot comment on snow performance as the car goes into winter storage but I replaced my RS4 rear sway bar with Hotchkiss front and rear bars and the car is much more stable in corners now, flatter and faster.

[Audi4kq]

Wow, lots of good ideas here guys, thanks! Sounds like the general consensus will be to add a beefier rear sway...I'll put out a feeler for an RS4 one and see how I like it. I'm sure for the snow it will be a major improvement and then come next season I can re-evaluate the road manners and maybe beef up the front a little too. One step at a time.

JoshDub, what's this center diff mod you speak of?

[EuroxS4]

Wow, lots of good ideas here guys, thanks! Sounds like the general consensus will be to add a beefier rear sway...I'll put out a feeler for an RS4 one and see how I like it. I'm sure for the snow it will be a major improvement and then come next season I can re-evaluate the road manners and maybe beef up the front a little too. One step at a time.

JoshDub, what's this center diff mod you speak of?

Torsion diff mod required removal of center diff from the transmission and you install different thickness shims into the diff, this will cause the center diff to transfer more power and torque to the rear wheels.

In my opinion, this modification is better suited if you track the car. Otherwise it will only benefit those and slide the ass end out if you drive it like you stole it which is how I drive all my cars.lol

[Audi4kq]

That makes sense, thanks EuroxS4. That's probably something I won't get into, but I remember way back adding the 'shim kit' to my mk2 gli to gain similar results in traction bias.

[Kevin C]

The center diff shim mod only changes the torque bias, it cant change the basic power split front to back. Torque bias is the torque ratio that the diff will handle before it starts to slip. The cavate is one end needs to start slipping for it to matter. If your in a corner the front tires are going slower than the rear (less distance traveled). As you give the motor throttle the internal friction in the diff increases, and it starts to act as a more like a locked diff. It does not "send" power to a low traction wheel, it just increases in friction with loading. This internal friction helps to prevent one end of the other from spinning faster than the other. As torque is applied friction increases and the ability for the center diff to account for different front to back speeds is diminished. This shows up as one end of the vehicle fighting the other (front wants to go slower, the back want to go faster).

In a low traction condition on end is going to win over the other. That's where things like friction coefficient curves spring rates sway bar coupling and weight distribution determine understeer or oversteer. The friction ratio on changes the locking percentage vs the input torque, not the balance. The later diffs that have a different gear reduction ratio from to back will put more power down to the back, making the AWD feel more like a RWD.

A typical scenario is the front wheels are slipping first and the extra bias can allow more power to be applied to also get the rears to slip. With the 40/60 split since more torque is being sent to the back it likely that the back wheels are losing traction before the front (or closer to losing traction).
As far as street use the extra locking might be OK but it can cause drivability issues. On my 02X the factory locking rate was a bit too aggressive and I got bucking when I pulled out into traffic (sharp turn, on the throttle). The first fix was stiffer motor mounts to keep the motor from flopping around, that made a signifigant improvement but was not a total cure. I had been running OEM gear box lube. Swapping to something a bit more slippery fixed the issue. This is a case of the factory locking rate being to aggressive. A modified center diff can get you into the same issue but possibly worse.

It took me a while to figure out the root cause was the diff itself and that running Motul gear lube would fix the issue. I still have a set of factory RS4 motor mounts installed. That was an expensive experiment.

Short story? Be careful modding the center diff and it helps to understand how it works. The 40/60 split center diff that came in some 0A3's in on my wish list of mods.

https://www.audizine.com/forum/showt...B7-S4s-and-RS4

[Audi4kq]

Thanks for those details Kevin...a lot of great info there!

[walky_talky20]

I definitely agree with Kevin. A higher torque-bias-ratio on your center diff can definitely help with the "not getting stuck" factor, which is cool. However, transferring more torque around, and doing so more aggressively can make the car behave much differently. The most likely behavior being more oversteer on throttle input. This would have the potential to make the car more rowdy to drive. I'd probably only try this on a car with working ESP.

[Audi4kq]

We were experiencing a January thaw out here but we're back to full winter again, hooray!

Since last post, I ended up getting an RS4 RSB installed, thanks for that Todd. With the ESP off again the RSB has really has transformed the way the car moves on snow and ice, it's so much more fun to drive! It was pretty amazing the difference and actually took a bit to get used to but most of my understeering is now gone. I can still push corners but the majority of the time it just wants to swing the ass end which is exactly what I was looking for.

Thanks for the suggestions fellas!

[Mike Tries]

Yeah, I don't think it snows in my part of Pennsylvania anymore.

[Turbo510]

My A4 has seen snow only once, as far as I know. Going up the mountain to the ski resort town of Big Bear, to join family at a lodge, I took a little traveled two-lane with lots of twisty turns. Just after passing the 8,000-foot summit of the road, I lost all power to the wheels; the engine just revved like it was in neutral. Coasted to a snowy turnout, then found I had no cell-service nor a jacket. So then started a long cold walk until reaching an emergency call box. More to the story but the problem turned out to be a front drive shaft spline had stripped, due to someone not installing the 'C' clip correctly.

[EuroxS4]

My A4 has seen snow only once, as far as I know. Going up the mountain to the ski resort town of Big Bear, to join family at a lodge, I took a little traveled two-lane with lots of twisty turns. Just after passing the 8,000-foot summit of the road, I lost all power to the wheels; the engine just revved like it was in neutral. Coasted to a snowy turnout, then found I had no cell-service nor a jacket. So then started a long cold walk until reaching an emergency call box. More to the story but the problem turned out to be a front drive shaft spline had stripped, due to someone not installing the 'C' clip correctly.

Pretty common failure with reman axles, or cheap axles as well. I rather use used factory axles and CV's rather than some other garbage. I also never let anyone rebuild an axle/cv other than myself.